PRIZE ESSAY. 
VISION, AND SOME OF ITS ANOMALIES, 
AS REVEALED BY 
THE OPHTHALMOSCOPE. 
BY 
MONTROSE A. PALLEN M.D.. 
OF ST. LOUIS, MISSOURI. 
Dux hominum medicus eat. 
EXTRACTED FROM TIIE 
TRANSACTIONS OF THE AMERICAN MEDICAL ASSOCIATION. 
PHILADELPHIA: 
COLLINS, PRINTER, 705 LODGE ALLEY. 
1858. PRIZE ESSAY. PRIZE ESSAY. 
VISION, AND SOME OF ITS ANOMALIES, 
AS REVEALED BY 
THE OPHTHALMOSCOPE. 
BY 
MONTROSE A. PALLEN, M.D., 
OP ST. LOUIS, MISSOURI. 
Dux hominum medicus est. 
EXTRACTED FROM THE 
TRANSACTIONS OF THE AMERICAN MEDICAL ASSOCIATION. 
PHILADELPHIA: 
COLLINS, PRINTER, TO5 LODGE ALLEY. 
1858. TO 
JOHN H. WATTERS, A.M., 31.D., 
PROFESSOR OF PHYSIOLOGY AND MEDICAL JURISPRUDENCE IN THE SAINT LOUIS 
MEDICAL COLLEGE. 
Dear Doctor : 
Saint Louis, May 19, 1858. 
Accept this, the first dedication I have ever proffered, 
as an humble acknowledgment of your disinterested and 
self-sacrificing friendship, and as a recognition of your 
untiring zeal for the promotion of science. 
Sincerely yours, 
MONTROSE A. r ALLEN. PRIZE E S S A Y. 
VISION, AMt SOME OF ITS ANOMALIES, AS RE- 
VEALED BY THE OPHTHALMOSCOPE. 
The following essay purports to consider two subjects, which 
are intimately connected: viz., the anatomy and physiology of the 
parts concerned in vision, and some of the derangements attending 
it. For the purpose of better illustrating these latter, the late dis- 
coveries effected by the ophthalmoscope will be entertained. 
That branch of science which treats of the nature and laws of 
vision, is called optics, and is generally considered in three points 
of view, viz:— 
A. Perspective Vision, which treats of the apparent size of objects, 
from the theory of the laws of the straight lined motion of 
light. 
B. Catoptric Vision, which embodies the laws of the reflection of 
light, embracing always the principle, that the angle of inci- 
dence is equal to that of reflection. 
C. Dioptric Vision, signifying the power of-seeing through trans- 
parent media, involving the laws of refraction, which embraces 
the principle of the bending of light as it passes from a rarer 
to a denser medium, or vice versa. 
The two former have so slight a connection with our task, that 
it is needless to discuss the formulae involving their demonstratiok:' 
But as the third division enters very materially into the explana- 
tion of the modus operandi of vision, it is deemed advisable to enter 
into its discussion, when, further on, the subject will be brought up 
in its proper place. 
The eye is the most complete of all optical apparatus, and, 
although it is perfected in man, he is not the sole possessor of 4 
prize essay: 
this “ window of the soul,” for many of the lower animals, the 
invertebrata as well as the vertebrata, are endowed with the sense 
of vision. 
As we propose to take a rapid and cursory glance of the optical 
apparatus of the invertebrates, it may not be amiss or foreign to 
the subject, to sketch the various groups of the invertebrates, with 
regard to the structure of the visual apparatus. The vertebrate 
mammals are represented by man, whose eye will be more fully 
described, both as regards its anatomy and its physiology. 
Before entering into any details concerning the invertebrata, we 
will give Siebold and Stannius’1 
CLASSIFICATION OF TIIE INVERTEBRATE ANIMALS. 
The invertebrate animals are organized after various types, the 
limits of which are not always clearly defined. There is, therefore, 
a greater number of classes among them than among the verte- 
brates. But, as the details of their organization are but yet imper- 
fectly known, they have not been classified in a natural manner. 
There are among them many intermediate forms, which make it 
difficult to decide upon the exact limits of various groups. The 
following division, however, from the lowest to the highest forms 
of organization, appears at present the best. 
ANIMALIA INVERTEBRATA. 
INVERTEBRATE ANIMALS. 
Brain, spinal cord, and vertebrate column, absent. 
• First Group.—Protozoa. 
Animals in which the different systems of organs are not dis- 
tinctly separated, and whose irregular form and simple organization 
are reducible to the type of a cell. 
Class I. Infusoria. 
“ II. llliizopoda. 
Second Group.—Zoophyta. 
Animals of regular form, and whose organs are arranged in a 
ray-like manner around a centre, or a longitudinal axis; the cen- 
1 Anatomy of the Invertebrata, by C. Th. v. Siebold. Translated from the Ger- 
man by Waldo I. Burnett, M. D. THE OPHTHALMOSCOPE. 
5 
tral masses of the nervous system forming a ring, which encircles 
the oesophagus. 
Class ITT. Polypi. 
“ IY. Acalephce. 
“ Y. Echinodermata. 
Third Group.—Vermes. 
Animals with an elongated symmetrical body, and whose organs 
are arranged along a longitudinal axis; so that right and left, 
dorsal and ventral aspects may be indicated. The central nervous 
mass consists of a cervical ganglion, with or without a chain of 
abdominal ganglia. 
Class VI. Ilelminih.es. 
“ VII. Turhellarii. 
“ VIII. Rotatorii. 
“ IX. Annulati. 
Animals of varied form, and whose bodies are surrounded by a 
fleshy mantle. The central nervous mass consists of ganglia, some 
of which surround the oesophagus, and others, connected by nerv- 
ous filaments, are scattered through the body. 
Fourth Group.—Mollpsca. 
Class X. Acephala. 
“ XI. Cephalophora. 
“ XII. Cephalopoda. 
Fifth Group.—Akthbopoda. 
Animals having a perfectly symmetrical form and articulated 
organ of locomotion. The central masses of the nervous system 
of a ring of ganglia surrounding the oesophagus, from which pro- 
ceeds a chain of abdominal ganglia. 
Class XIII. Crustacea. 
“ XIY. Arachnida 
“ XY. Insecta. 
Having premised the above classification, we propose to enter 
upon the visional apparatus of the Invertebrata, and will begin 
with the Protozoa. 
Most of the Infusoria and Bhizopoda have simple red pigment 
spots, capable only of distinguishing light from darkness, and 6 
PRIZE ESSAY: 
which, without a special optical apparatus, accomplish the object 
by the whole surface of the body. Ehrenberg1 presumed the pig- 
ment spot to be an eye, but it has no connection with a nervous 
spot or expansion, and contains no refractive media. 
Of the second group (the Zoophytes), but few of the Polypi have 
organs of vision: their sensibility to light is perceived by the 
whole body. The Syncoryne and Coryne2 have four red organs cor- 
responding to ocular globes; and, the organ seen at the base of 
the six arms of the Eleutheria dichotoma, contains refractive media, 
viz., the cornea, crystalline lens, and aqueous humor. 
Of the Acalephce, the Cteniphora3 is the only order having an 
organ corresponding to the eye: the organ in question has been 
considered by many as also performing the functions of audition. 
Of the Echinodermata4 there are none which possess an eye. 
Of the third group, or Vermes, the Ilelminthes5 possess no eye: 
the Turbellnria6 have on the anterior extremity a light refracting 
body, containing a cornea, which corresponds to an eye: the Rota- 
torn7 have single or double eye-specks upon the neck, and some- 
times upon the forehead: these specks are covered by a cornea, and 
are situated upon the cerebral ganglion, and also connected with 
it by nervous filaments. The Annulati8 are without eye-specks. 
Among the Acalephce, an order of the fourth group, organs of 
vision are very common, and occupy a large portion of the borders 
of the mantle, or are situated upon the external orifices of the 
longer or shorter mantle-tubes. These eyes contain a cornea, 
aqueous humor, sclerotica, greenish or bluish iris, and retina. 
Most of the Cephalophorcd possess organs of vision, and are seldom 
more than two in number. These eyes contain a cornea, sclerotica, 
iris, choroid, retina, and optic nerve. 
The Cephalopoda10 have very highly developed eyes which are dis- 
proportionately large: they are quite similar to those of the verte- 
brata. These eyes are composed of a cornea, aqueous humor, iris, 
1 Abhand’l. d. Berliner Akad., 1831, p. 12 ; also, Die Infusionthierchen, p. 491. 
2 Dumortier, Mem. sur. l’Anat. et la Physiol, d. Polypiers, p. 41. 
3 Milne-Edwards, Annal. d. Sc. Nat., pp. 206, 211. 
4 Valentin, Monograph. Zoophyta, p. 198. 
5 Muller, Zool. Danica., tab. LVIII. figs. 16, 17. 
6 Siebold, Anat. of Invertebrat., loc. cit., p. 135. 
7 Khrenberg, loc. cit., and Siebold, loc. cit., p. 145. 
8 Cuvier, Mem. sur les Thalides, p. 12. 
9 Swammerdamm, Bibel der Nat., p. 47, tab. IV. figs. 5, 8. 
10 Mayer, Analekt, f. vergleich. Anat. lift. i. p. 52. THE OPHTHALMOSCOPE. 
7 
crystalline lens, vitreous body, choroid, retina and optic nerve. 
Among those of the fifth group, or the Anthropodia, the Crustacea1 
most generally possess eyes, which exist in various grades of de- 
velopment. One form of these eyes, which ik the lowest order, is 
known as Simple; they are composed of a cornea anterior to a 
refracting lens, surrounded by a layer of brown, blue, red or black 
pigment; at the most convex point of the lens, the optic nerve pene- 
trates. Another form of these eyes is the Compound Unfaceted,2 
which consist of numerous eyes covered by a common cornea. Still 
another form is the Compound Faceted,3 which is composed of very 
numerous tetragonal or hexagonal facets, behind each of which is a 
conical or prismatic lens, fitted in the vitreous body, and connected 
with a filament of the optic nerve. The Arachnoida34 always pos- 
sess simple eyes (stemmata), which are analogous to the simple 
eyes of the Crustacea. They are formed of a cornea, lens and 
vitreous body surrounded by a retina, which is enveloped by a 
pigmentary membrane corresponding to the choroid. The Insecta5 
possess simple and compound eyes. The simple eyes (Ocelli, Stem- 
mata) are composed of a cornea, either convex, elliptical, or sphe- 
roidal, a spherical or cylindrical lens, a pigmentary membrane cor- 
responding to the choroid, and an optic nerve. These simple 
eyes are sometimes situated so contiguous to the brain, that the 
optic nerve is but a mere scale. The compound eye0 is composed 
of single eyes whose cornete are quadrangular or hexagonal, all of 
which are covered by one common faceted cornea. Behind each 
cornea, instead of a lens, there is a transparent pyramid whose 
apex is directed inwards, and received into a cup-shaped body cor- 
responding to the vitreous humor, which is again enveloped by an 
expansion of the optic nerve, constituting the retiua. Each pyra- 
midal lens is enveloped by its own choroid. 
As regards the differences in the Anatomy of the eyes of Verte- 
brate mammals, their general forms are so slightly varied from 
that of man, that a mere glance at some of the peculiarities will 
suffice. 
J Muller, Zur vergleich. Physiol, d. Gesiehtsinnes, p. 307. 
2 Tiedemann, Zeitsch. f. Physiol., p. 97. 
3 Milne-Edwards, Hist. Crust., t. i. p. 117. 
4 Latreille, Regne animate, iv. p. 207, 1829. 
5 Marcel de Serres, Mem. sur les Yeux comp, et les Yeux lisses d’Ins. 
6 Will, Beitriig. zur anat. d. zusammengesetzen augen mit facettirt, Hornhaut, 
1840. 8 
prize essay: 
With carnivorous mammals, one of the most remarkable addi- 
tions to the eye, is a strong retractor muscle, shaped like a hollow 
cone, with its apex attached to the bottom of the orbit, and with 
its marginal base inserted into the sclerotic, which it embraces, 
being under the recti muscles. Its use is to draw the eye within 
the orbit, giving it a very peculiar expression of hollowness, ob- 
served in the carnivora when enraged. 
With birds and fishes there exist some peculiarities which we 
will cursorily notice. Fish are unprovided with eyelids; and, 
there is but little independent motion of the ball. Near the optic 
nerve between the layers of the choroid, is a gelatinous red struc- 
ture, denominated the choroid gland, the use of which is unknown. 
Fish most generally are devoid of ciliary processes and bodies; but 
there is a rudimentary structure very similar to the ciliary bodies 
and corresponding to the pecten of birds. 
With regard to birds, a sketch of the optic apparatus of the com- 
mon owl (strix bubo) will explain the pecten, and the curious me- 
chanism of the third eyelid, or membrana nictitans. The general shape 
of the eye is that of a bell, which arises from the disposition of a 
series of quadrangular osseous plates, convex on their inner aspect, 
which overlap, and are accurately fitted to each other. The firmness 
and rigidity thus communicated to the exterior casing containing the 
refractive media, prevent their pressure throwing the eye into a 
globular form. The ciliary body extends over the whole of this 
portion of the surface. The pecten is a curious quadrangular fold 
of the choroid, which projects into the vitreous body (in some birds 
it is attached to the lens), and is rather short and folded upon it- 
self, very similar to a' lady’s fan. Its use is as yet a mooted ques- 
tion. The yellow spot of Soemmering in the human retina is a 
rudiment of the pecten. 
At the back of the globe, two muscles, originating from the 
sclerotica, are curved superiorly and inferiorly around the optic 
nerve. The superior and larger, the Qaadratus, is attached near the 
margin of the sclerotic, its fibres converging to a narrow tendon, 
perforated through its whole length like the hem of an apron. The 
inferior and smaller muscle, from its shape called the Pyramidalis, 
is inserted in an opposite part of the circumference; its fibres con- 
verge and are attached to a long round tendon, which passes 
through the hem or loops of the Quadratus, thence turning over 
the edge of the broad part of the sclerotic, is continued over the 
bell-shaped surface, where it passes through several filiform loops THE OPHTHALMOSCOPE. 
9 
or pulleys, which keep it applied to the concavity, and around a 
bony projection from the surface. 
It is attached near the cornea, to the membrana nictitans, an 
elastic fold of the conjunctiva, which constitutes the third or wink- 
ing eyelid. From the modus operandi of these muscles, the sweep- 
ing action of the membrane is readily understood, as it is moved 
with incredible rapidity over the ball, and as rapidly rebounds 
owing to the elasticity of its structure. The membrane is of a 
milky hue, and has for an object the cleansing of the ball from hy- 
persecretions and foreign substances. The haw of quadrupeds is 
the analogue of the membrana nictitans; this haw is frequently 
forced out of the orbit toward the inner canthus, by the pressure of 
the globe upon it, as it is unprovided with muscles. In the human 
eye there is a rudimentary winking membrane, which is a small 
crescentic fold of conjunctiva situated at the inner canthus behind 
the lachrymal caruncle. 
Having thus cursorily glanced at the Invertebrata, as well as a 
few of the Yertebrata, with'regard to the optical apparatus, we will, 
according to the proposed plan, sketch the Anatomy of Vision as it 
is typified in Man, the highest of mammals, by remarking the de- 
tails of structure of the ocular globe proper. 
The eye, as seen in man, is composed of four distinct parts. 
I. The wall or tunics, constituting the protective parts. 
II. The adjunct portions for its perfection as an optical instru- 
ment. 
III. The dioptric apparatus or refractive media. 
IY. The visional or specially sensitive parts. The protective 
parts of the apparatus are the Sclerotic and the Cornea. 
The sclerotic is a strong, fibrous, dense and white membrane, 
thicker posteriorly than anteriorly, where it presents the appear- 
ance of a truncated sphere of one-fifth, and ha-s a bevelled edge for 
the reception of the cornea in a manner very similar to the fitting 
of a watch crystal in its case. Posteriorly, and a little to the inter- 
nal side of the axis of the ball, it is perforated by the optic nerve. 
No nerves have as yet been traced into its substance, although 
many, together with bloodvessels, pass through it. The outer sur- 
face is rough and firm for the attachment of muscles, but every- 
where else is perfectly smooth; the inner surface is of a light brown 
color, and roughened from the presence of the membrana fusca, a 
delicate areolar membrane through which branches of the ciliary 10 
PRIZE ESSAY: 
nerves and vessels pass in an oblique manner. The texture of the 
sclerotic is similar to that of tendon, viz., of longitudinal and trans- 
verse fibres interlaced at right angles with each other. The cornea, 
which is one of the dioptric media as well as a protective part of 
the eye, is circular, occupying the anterior fifth of the eye, and re- 
sembling the segment of a smaller sphere adapted to a larger one. 
Its anterior border surface is convex, and its posterior one con- 
cave. The cornea has properly but one layer; all others mentioned 
by anatomists, being produced by boiling water and other re agents 
acting upon its chondrin. Bloodvessels do not exist in the cornea 
proper, its nutrition being carried on by endosmosis and exosmo- 
sis ; its structure is of stratified bundles of fibres, analogous to 
those of the areolar tissue, and between which, there exists an 
amorphous, solid, and transparent matter. Anterior to the cornea 
is the conjunctiva, erroneously presumed by some to be the first 
layer of the cornea; it consists simply of stratified tessellated epi- 
thelium, and is continuous with the conjunctiva scleroticm, and 
wants only its cellulo-vascular basis. Behind the cornea is a very 
solid amorphous membrane, covered by a pavement epithelium 
which is called the membrane of Demours or Descemet, a continua- 
tion of which is carried over the iris. Schlemm has traced branches 
from the ciliary nerves into this membrane. 
The adjunct parts for the perfection of the eye, as an optical in- 
strument, are: the Iris, which serves as a diaphragm, to prevent 
the passage of too much light, and to correct the aberration of 
sphericity; the Pigment, which serves for the absorption of light, 
and the Choroid, which is but a continuation backwards of the iris. 
The Iris is a disk or circular membrane placed behind the cor- 
nea, and anterior to the crystalline lens, dividing what are called 
the chambers of the eye into two unequal portions, the anterior 
being larger than the posterior. The pupil is a circular opening or 
perforation, situated rather to the inner and upper part of the iris; 
it presents a free border, known as the pupillary margin. The an- 
terior face of the iris, carpeted by the same epithelium as that of 
the membrane of Descemet, presents a number of radiating fibres, 
of a streaked whitish tendinous character; they diverge from or 
converge to the pupil at about -gV of an English inch from the pu- 
pillary margin, constituting what is known as the larger or outer 
ring, between which, however, and the pupillary margin they are 
concentrically arranged, constituting the smaller or inner ring. The 
fibres of the rings are non-striated muscular, and by their contrac- THE OPHTHALMOSCOPE. 
11 
tion produce the changes in the size of the pupil; the outer ones 
contracting producing dilatation, whereas the inner ones doing like- 
wise, produce contraction. The posterior border of the iris is cov- 
ered by the uvea, or an aggregation of pigment granules with 
nuclei and without cell-walls. This side of the iris, unlike the an- 
terior, wants epithelium, and is continuous with the choroid, by the 
annulus albidus or ciliary ligament, or more properly the tensor or 
circular muscle of the choroid, which has been proven by Br'uke to 
be of the non-striated class of muscles ; but of this when we speak 
of the choroid. The iris is very abundantly supplied with blood- 
vessels and nerves. The arteries are the long posterior ciliaries, 
branches from the short posterior ciliaries, ramifying in the ciliary 
processes, and branches from the anterior ciliaries. There are 
veins which run parallel or correspond to the posterior ciliaries 
(arteries), whilst the veins corresponding to the anterior ciliaries, 
commuuicate with the sinus circularis iridis, or canal of Fontana, 
which is lodged in a groove parallel to the junction of the inner 
surface of the sclerotica with the cornea, where the ciliary ligament 
is inserted, and is of sufficient size to permit the passage of a hair 
within its calibre. The different bloodvessels form a very free 
anastomosis at the circumference of the iris, whence branches pro- 
ceed to the pupillary margin, near which another finer vascular 
network is formed, whence capillary loops go to the pupillary mar- 
gin. The long posterior ciliaries enter the sclerotic at a greater 
distance from the optic nerve than do the short ones, and then pro- 
ceed in a line corresponding to the equator of the eye, upon the 
outer surface of the choroid, on the nasal and temporal sides, where 
about -4- of an inch from the ciliary processes of the iris upon the 
temporal side, less upon the nasal, they divide at a very acute 
angle into the upper and lower branches. They all inosculate in 
the annulus albidus, whence their ramifications extend to the above 
described, first vascular circle. The ciliary nerves or nerves of the 
iris, from twelve to fifteen in number, arise from the nasal branch 
of the fifth pair, and especially the anterior portion of the ophthal- 
mic ganglion, unite into two bundles, pierce the sclerotic near the 
entrance of the optic nerve, and pass forward on the outside of the 
choroid, to be distributed to the tensor muscle of the choroid, or 
annulus albidus, whence they ramify in the muscular fibres of the 
iris. The fibrillae of the ciliary nerves, which preside over the 
circular muscle of the iris, arise from the third nerve, whilst those 
governing the radiating muscle, come from the spinal and the sym- 
pathetic of the neck. 12 
prize essay: 
The functions of the iris are to measure the quantity of luminous 
rays necessary to vision: for in a glare of light the pupil is con- 
tracted, and in obscurity it is dilated; undoubtedly showing that 
these functions are governed by the reflex-motor and automatic 
system of nerves. The iris also serves to correct the aberration of 
sphericity. The color of the iris depends upon pigment cells 
deposited in front and behind the membrane, and the presence of 
pigment deposits within its substance. The uvea is a quantity of 
pigment contained under a thin transparent membrane covering 
the posterior face of the iris; and, as its quantity is increased so is 
the tint deepened. The pigment cells of the iris as well as of the 
choroid are for the most part polyhedral in figure, generally hexa- 
gonal, and joined together like Mosaic work; others are spheroidal, 
particularly those of the uvea: in Albinos they contain no colored 
granules. The contents of these cells are minute brown or black 
granules, either spheroidal or elliptical, measuring in their greatest 
diameter from ttoott to sioanr of an inch, and after having escaped 
from the cell-membrane, they exhibit a peculiar molecular move- 
ment. Chemically this black or brown matter is insoluble either 
in hot or cold water, alcohol, acetic or diluted mineral acids, fixed 
or volatile oils. Oxide of iron, chloride of sodium, lime and its 
phosphates are obtainable from its ashes. 
The function of the pigment is evidently and obviously intended 
to absorb redundant light, hence Albinos bear but indifferently 
well the superabundance of light, and see better at night than 
during the daytime. 
The choroid is a very delicate membrane which carpets the pos- 
terior portion of the eye, and lies between the sclerotic and retina. 
Penetrated posteriorly by the optic nerve it extends thence to the 
tensor muscle or annulus albidus, and to the anterior portion of the 
hyaloid membrane, where it becomes plicated or thrown into folds 
around the margin of the crystalline lens. It is composed of a 
multitude of very small arterial and venous ramifications, connected 
by very fine areolar tissue, cells, lamellae, and pigment granules. 
It is connected outwardly with the sclerotic by a thin areolar tissue 
interspersed with irregular shaped pigment cells, called the arach- 
noidea oculi or lamina fusca, and inwardly to the membrana Jacobi 
retinae. The arteries come from the short ciliaries of the ophthalmic, 
piercing the* sclerotic near the optic nerve, and are some twenty or 
thirty in number, which divide into branches parallel to the equator 
of the eye: they communicate and anastomose very freely, forming 13 
THE OPHTHALMOSCOPE. 
a network on the concavity of the venous layer, constituting what 
is known as the tunica Ruysckiana. The veins, from their whirl- 
like arrangement, are called vasa-vorlicosa, and converge to four 
nearly equidistant trunks, which empty into the ophthalmic vein, 
midway between the cornea and the optic nerve. The posterior 
ciliary veins pass out from the eye parallel to the entrance of the 
arteries. The pigment has been described above. The annulus 
albidus, or connection between the iris and choroid, is a flat, narrow 
band of a grayish substance, situated at the anterior end of the 
choroid, and serves to hold the retina and choroid around the 
vitreous body. According to Briicke it is formed of non-striated 
muscular fibres, converging from before backwards, and of circular 
fibres on a level with the union of the cornea to the sclerotic; the 
iris attaches itself to it by its greater circumference, a little behind 
the union of the cornea and sclerotic, upon a circular line which 
traces the separation between the anterior portions of the ciliary 
processes, and the internal face of the ciliary muscle or ligament: 
Graefe, of Berlin, has latterly discovered that some fibres bend for- 
ward to again cover the internal face of the ciliary ligament. Thus, 
whilst the areolar portions of the choroid appear to blend with 
the annulus albidus, its vascular portions, with large quantities of 
pigment, turn inwardly, posteriorly to the iris, anteriorly to the 
vitreous body, and as they approach the crystalline lens, are 
thrown into radiated folds called the ciliary processes, of which 
there are seventy in number, the whole of which is denominated 
the ciliary body, and is subdivided into a pars plicata, and a pars 
non-plicata. 
The dioptric apparatus, or refractive media, consist of the cornea 
above described, the aqueous humor, the crystalline lens and 
capsule, and the vitreous body. 
The aqueous humor is found in the anterior portion of the eye, 
immediately behind the membrane of Descemet, and anterior to the 
crystalline and folded ends of the ciliary processes: the iris divides 
it into two unequal compartments or chambers, viz: the anterior 
and posterior, which in the foetus are completely unconnected by 
an occlusion of the pupil, by the membrana pupillaris. In extra 
foetal life they are connected by means of the pupil; and, of the 
two chambers, the anterior is the larger. This fluid is composed 
of a small quantity of albumen, and of the various salts met with 
in the economy, particularly the chloride of sodium held in solution. 
It is secreted or formed from a membrane covering the posterior 14 
PRIZE ESSAY: 
wall of the iris and the anterior folds of the ciliary processes. The 
aqueous humor, when examined under the microscope, is found to 
contain only a few colorless cells; its form is somewhat of a menis- 
cus, and measures at its greatest antero-posterior diameter about 
X’T of an English inch. Its functions are those of refraction, which, 
in conjunction with the ellipsoidal cornea, the lens, and the vitreous 
body, serve to bring the light to a focus upon the retina. 
The crystalline lens is a double convex or lenticular body, placed 
between the aqueous humor and the vitreous body, at the reunion 
of the anterior third, with the two posterior thirds of the ocular 
globe. Its diameter is nine millimetres of an inch), and its 
thickness, corresponding to the axis of vision, is about half as 
much, five millimetres. The axis does not lie exactly in the centre 
of the eye, but slightly to the internal side, parallel with, or corre- 
sponding to the centre of the pupil and the axis of vision. The 
lens is more convex posteriorly than anteriorly; and its convexity 
is in an inverse ratio to the convexity of the cornea and the quan- 
tity of the aqueous humor. In density, degree of diaphanousness, 
color, and form, the crystalline lens presents marked changes in the 
different stages of life. Thus, in the foetus it is reddish in color, 
not perfectly diaphanous, easily broken down, and is spherical, 
whereas in adult life it is perfectly transparent, the posterior sur- 
face becomes more convex, and the substance is firmer and color- 
less; and, in old age, it assumes a slightly yellowish or amber 
colored tint (sometimes so insensibly increased as to terminate in a 
loss of transparency or cataract); it becomes flattened, and gradually 
increases in specific gravity and firmness. By its external margin 
it is in immediate contact with a membranous sac, the capsule, the 
character of which is quite different on its anterior and posterior 
margins. The anterior border is free, whilst the posterior is lodged 
in a depression in the vitreous humor, and is much thinner than 
the anterior one; the whole sac is an amorphous, homogeneous 
transparent substance, brittle and breaking like glass, and carpeted 
on its inner layer by epithelial cells, with very fine granular sphe- 
rical or oval nuclei. The tissue of the crystalline is composed of 
two sets of fibres, very regularly disposed above and by the side 
of each other, forming two distinct layers. The superficial ones 
are composed of nucleated fibres, forming a layer from x% to fV of 
a millimetre in thickness, upon the surface, and are disposed parallel 
to each other of a size from TdVir f° to9ou °f a millimetre, flattened, THE OPHTHALMOSCOPE. 
15 
with clear edges, and finely granulous within the interior, with 
spherical or oval nuclei of toW °f a millimetre in diameter. The 
other fibres are called dentelated, and are firmer, narrower, smaller, 
paler, and more transparent than the former, and without any 
granulations in the interior, with notched borders, whence the 
name. The aggregate of the above described fibres form concen- 
trated layers, easily separated when immersed in alcohol, and 
which are as a whole segmentated. The fibres pursue an antero- 
posterior direction ; and it is remarkable that they do not converge 
to points on the anterior and posterior margins, but form radiating 
clefts like an orange. After death, when the capsule is punctured, 
there flows a peculiar liquor, which, according to the best authori- 
ties, is altogether a post-mortem production, and is known as the 
liquor Morgagni. 
The canal of Petit is the name given to the space found between 
the ciliary and vitreous bodies, and which comprises the whole 
circumference of the lens; this canal does not in reality exist, but 
is made artificially, by the separation of the areolar tissue holding 
the parts together; this separation is made by the injection of air, 
which forms lead-like projections, united by bundles of tissue. 
Some authors suppose the canal of Petit to be a separation into 
two layers of the hyaloid, one going to the posterior border of the 
capsule of the lens, adhering to it and lining the fossa hyaloidea, 
and the other forming the ciliary zone, or zonula of Zinn (to be 
described), which is inserted into the circumference of the lens. 
What is known as the zonula of Zinn, or ciliary zone, is the hya- 
loid membrane for the breadth of about | of an inch, raised up into 
radiating folds, of a similar structure to the ciliary processes, into 
which it digitates and dovetails. 
The vitreous body or humor lies in the middle and posterior 
parts of the eye, behind the crystalline lens, concentric with, par- 
allel to, and within the retina. It is composed of a transparent 
semi-solid gelatinous substance, without either nerves or blood- 
vessels. It presents anteriorly a concavity, called the fossa hya- 
loidea, into which the larger or posterior segment of the lens is 
lodged; posteriorly it presents a convexity corresponding to the 
concavity of the retina. According to all anatomists, with the 
exception of some of the modern microscopical school, particularly 
M. Charles Robin, the vitreous humor is surrounded by a membrane 
of envelope, called the hyaloid; but, according to M. Robin, it is 16 
prize essay: 
surrounded posteriorly and laterally simply by the retina, and 
anteriorly by the posterior margin of the capsule of the lens, toge- 
ther with the ciliary processes in front. 
But, according to others, the vitreous humor is contained in a 
segmentary membrane, which (according to Hannover) may be 
discovered “by a careful maceration in chromic acid, to consist of 
about one hundred and eighty delicate septa like the pulp of an 
orange,” with the angles of the inclosed spaces in the direction of 
the axis of the eyeball, which do not meet, but leave a cylindrical 
portion for the passage of a branch of the arteria centralis retinae, 
called the arteria hyaloidea, and the canal through which it passes 
is called the hyaloid canal of Cloquet. In the foetus there is a vein 
corresponding to the artery, which conducts the blood from the 
posterior part of the capsule. Eobin considers this canal to be not 
in existence, that there is no reflexion of the membrane, and that 
the artery having no investing membrane penetrates the substance 
proper. He also maintains that the vitreous humor is a special 
organic substance, entirely amorphous, not even fibroid; the fluid 
of which slowly drains away, when separated from the eye, leaving 
behind an amorphous and heterogeneous matter. Bowman has 
confirmed Hannover’s experiments only in the foetus. Kolliker 
thinks that it is an analogous condition to the embryonic areolar 
tissue, which after foetal life completely disappears, and becomes a 
kind of more or less consistent mucus. The function of the vitre- 
ous body is the correction of prismatic refraction. 
The visional or specially sensitive parts are the retina and the 
optic nerve. 
The retina is the most internal of the tunics of the eye; it entirely 
embraces the vitreous body, and is situated between it and the 
choroid. Anteriorly it is limited by7, the ora serrata retinae, where 
it is somewhat thickened, and appears to end in a defined margin. 
Eobin, Bidder, and Valentin contend that it is continued over the 
inner surfaces of the ciliary processes, and connected to the hyaloid. 
Posteriorly it is connected with the papilla conica or colliculus of 
the optic nerve, which apparently it seems to constrict. Two lines 
exterior to the papilla, and in the centre of the visual axis, is found 
the macula flava seu lutea centralis: this, the yellow spot of Soem- 
mering (who first described it in 1791), is composed of a depression 
and a border. Soemmering thought this colorless depression to be 
.a canal, and hence named it foramen retinae centrales, but wrongly, as THE OPHTHALMOSCOPE. 
17 
there exists only the above-mentioned depression: the border or 
ring alone is colored, and is called the limbus luteus foraminis 
centralis. Continuous with the limbus and extending towards the 
papilla, the retina is thrown into a fold, which is known as the 
plica centralis retinae. 
The retina, in the living subject, is normally transparent, but 
becomes opaque, of a grayish white color, upon decomposition, or 
subjection to alcohol or nitric acid. Formerly, the retina was sup- 
posed to .consist of only three layers, viz: the membrane of Jacob, 
the medullary, and the vascular layers. The latest researches, how- 
ever, indicate five different sorts of substances, arranged in succes- 
sive strata. 
I. The layer of columnar bodies or stratum bacillorum. 
II. “ “ “ myelocytes “ stratum granulosum. 
III. “ “ “ corpuscles “ stratum gangliosum. 
IY. “ “ “ nerve-tubes “ stratum Jibrillosum 
Y. “ “ “ amorphous substance or membrana limitans. 
The stratum bacillorum is formed of small cylindrical bodies, 
arranged side by side, and vertically to the retina; they consist of 
a peculiarly clear substance, from the to of a millimetre 
in thickness. Two kinds of bodies can readily be distinguished in 
this stratum: the cylinders or columns proper (batonnet, French, 
stabschen, Germ.), which are transparent, flexible, and of a length 
varying from the to the -jof a millimetre; they are either 
single or geminated (twin-like), that is to say, curved in the manner 
of a horseshoe, with their free extremities on the same level; and 
fusiform (cones, French, zapfen, Germ.), which are about the size and 
form of small cylindrical epithelial cells; they are slightly enlarged 
in the middle, finely granulous, and have delicate filamentous pro- 
longations similar to the cylinder proper. 
The layer of myelocytes, or stratum granulosum, is composed of 
numberless nucleated, small, and regular cells, which are scattered 
about in an amorphous substance, very much like the gray matter 
of the brain. This gray matter is most abundant in the anterior 
portion of the second layer, which is the thickest of the whole of 
the five strata. 
The layer of corpuscles, or stratum gangliosum, is composed of 
ganglionic corpuscles, which send off filamentous prolongations, or 
cylinder axes, to the layer of myelocytes, and cylinders proper, to 
the continuation of some of the tubes of the optic nerve. 18 
PRIZE ESSAY: 
The layer of nerve-tubes, or stratum fibrillosum, is the spreading 
out of the optic nerve. The optic nerve at first sends out very 
delicate radiating fibrillae, interlacing with various plexuses, with 
elongated meshes, which continually diverge, and the spaces between 
them constantly undergo an increase. With regard to the termina- 
tion of this stratum, anatomists disagree. Valentin says that they 
end in loops upon the anterior margin of the retina. Hannover 
contends that they end by free extremities. Robin, who seems to 
have investigated this matter more thoroughly than any one else, 
says that they do not reach the anterior margin or fringed border, 
but terminate upon the whole surface of the retina, most probably 
in the ganglionic corpuscles. Some of them go directly to the 
yellow spot of Soemmering, and terminate at its periphery, where 
they surround it, forming two bundles or two quite large rolls, and 
which, in all probability, form thq plica or folds there visible. The 
depression in the yellow spot is owing to the absence of this layer: 
all of the other strata being there found. This layer is composed 
altogether of gray matter, and, what was latterly demonstrated by 
Todd and Bowman, was long ago suspected: viz., that none of the 
white substance of Schwann enters into the composition of the 
retina. 
Fifthly, there is found in the retina an amorphous substance, 
known as the membrana limitans, which is parallel and anterior to 
the stratum fibrillosum, and passes in front of the ciliary processes 
to the capsule of the crystalline lens, where it terminates in a circle. 
This is the only layer of the retina which is vascular, the central 
artery and vein ramifying throughout its extent. According to 
H. Muller, various fibres are detached from this membrane (fibres 
of Muller), to pass through the thickness of the other layers into 
the cylinders proper of the stratum bacillorum. 
The optic, or second cranial nerve, is one of special sense, and is 
entirely distributed to the eye. It springs from the superficial 
layer of the optic tract, which arises from the thalamus opticus1 cor- 
pora quadrigemina, and corpora geniculata. Leaving the under part of 
the thalamus, it makes a sudden bend forwards, and strikes obliquely 
across the inferior surface of the cerebral peduncle, assuming 
a flat ribbondike appearance. Before reaching the sella turcica, it 
assumes a more rounded form, where it decussates with its fellow, 
forming the chiasma or commissure, previously, however, having 
received an accession of fibres from the lamina cinerea, and having THE OPHTHALMOSCOPE. 
19 
ati adherence to the tuber cinereum. 11 The fibres of origin of the 
optic tract from the thalamus are derived partly from the superficial 
stratum, and partly from the interior of that body. According to 
Foville, this tract is also connected with the tcenia semi-circularise 
and with the termination of the gyrus fornicatus; and he states, 
further, that where the optic tract turns round the back of the tha- 
lamus and the cerebral peduncle, it receives other delicate fibres, 
which descend from the gray of those parts.” (Mayo, Outlines of 
Anatomy, p. 514.) The nerve, after leaving the commissure, passes 
through the foramen opticum of the sphenoid bone, being previously 
invested with a sheath from the dura mater, and passes, surrounded 
by the recti muscles, to, and then through the sclerotic and cho- 
roid tunics at the back of the eyeball. 
The nerve is composed of fasciculi of microscopical primitive 
fibrils, inclosed in a neurilemma, the whole being again incased in 
a larger neurilemma. As the nerve penetrates the sclerotic, the 
neurilemata of the fibres cease; hence the apparent constriction of 
the nerve at that place. About four lines from the sclerotic, the 
nerve is penetrated by a canal which transmits to and fro, the cen- 
tral artery and vein of the retina. 
With regard to the circulation of the eye, as well as its develop- 
ment, it would be foreign to our present purpose, and also would 
extend this essay to a most formidable length, were we to enter 
into it in a manner worthy of its importance; hence we must leave 
it untouched. We have thus sketched, almost superficially, the 
anatomy of the eye. Why we have so done, is readily apparent; 
and its bearing upon the physiology of vision is at once compre- 
hended. 
According to the proposed plan, the physiology of vision will 
now be sketched. 
Vision is a function of relative life, of which the eye is the ap- 
paratus, through which we perceive one of the qualities of physical 
bodies, denominated luminous. The perception of these luminous 
bodies is subject to the above mentioned laws of optics. Of these 
laws we propose to enter upon the demonstration of but one, viz: 
that of refraction. The facts that opaque bodies reflect light, and 
transparent bodies transmit it, are such as need no demonstration, 
and they are but secondary to our object; but, a ray of light enter- 
ing in an oblique manner, from one medium to another, the di- 
rection is changed, or rather the ray is bent either to or from the 
perpendicular, which phenomenon constitutes refraction. 20 
PRIZE ESSAY: 
Thus, if a ray passes from A perpendicularly to the surface of the 
piece of glass at B, it will pass to K in the right line ABIDE. 
But if the same ray be directed to the surface B obliquely, as from C, 
instead of passing through in a direction CB FII, it will be refracted 
to E, in a direction approaching the perpendicular A K. The ray of 
incidence is G G, and the angle G B A, made with the perpendicular 
A K, is denominated the angle of incidence. The refracted ray is 
B E, and the angle E B D is the angle of refraction. The ray 
from G to B, and refracted to E, is as much bent from the line of 
the refracted ray B E, as it was from the line G B FII. nence, 
Fig. l. 
it follows that a ray passing through a transparent medium hav- 
ing two surfaces on parallel planes, is refracted from its original 
course, and in passing out is bent parallel to the original line. 
Now, if a circle be described about a centre B, with any radius as 
B E, the arc D F measures the angle of incidence D B F, and the 
arc D E, that of the angle of refraction DBF. A line F /, brought 
from the point F' perpendicular to A B ID K is the sine of the 
angle of incidence, and the line D E is the sine of the angle of re- 
fraction EBB. Hence, it follows that the sine of the angle of in- 
cidence has the same ratio to the sine of the angle of refraction, it 
matters not in what degree of obliquity the incident ray G B is 
thrown upon the transparent medium. Dr. Arnot draws, after en- THE OPHTHALMOSCOPE. 
21 
tering very minutely into the details of a very long mathematical 
calculation, the following conclusions from the above theorem. 
“ If any ray of incidence passes from air obliquely into water, the 
sine of incidence is to that of refraction as 4 to 3; if it passes from 
air into glass, the proportion is as 2 to 3; and if from air into dia- 
mond it is as 5 to 2.” 
Having thus premised the phenomenon of refraction, its applica- 
tion to the study of vision is readily appreciated. The cognizance 
by the retina of an object, is the combined result of the impinging 
of rays of light upon the retina, and a sensation communicated to the 
brain by means of the optic nerve. These sensations are produced 
by colors and their refraction and reflection, all of which are sub- 
ject to the laws of light: they cause us besides to perceive certain 
characteristics in a mathematical order, such as situation, form, and 
size, subject to judgment and comparison, which apply the phe- 
nomena of reflection and refraction produced by these bodies. 
Hence it is, that errors of judgment produce deceitful appearances, 
which errors are induced by, either the manner in which the light 
is reflected, or . according to its intensity, or whether it strikes one 
or both eyes, or according to the conditions of the refractive media, 
their curvature, etc. etc. Were we dependent entirely upon judg- 
ment for the perception of bodies, we would frequently be deceived, 
but the sense of touch causes us specially to recognize the pecu- 
liarities to which vision is subjected. 
The phenomena of vision are, A, purely physical, beginning at 
the cornea and ceasing at the retina; and b, organic or specially 
sensitive, depending upon the properties of the nerve, which begin 
where the physical ones cease, and cease themselves in that portion 
of the brain which perceives. 
Every object sends off a cone of luminous rays, which so long as 
they pass through a medium of the same density, proceed in straight 
lines; but when they enter a denser medium undergo the refraction 
above demonstrated. Whether, as Newton and Descartes main- 
tained, light be a material substance emitted from luminous bodies, 
thence conveyed to the eye, thereby rendering them visible, or as 
Dr. Young considered it, to be undulations propagated through a 
fluid (the doctrine at present generally admitted), it matters not for 
our present purpose: its discussion rather belongs to the Secondary 
Mechanical Sciences, than to a brief essay upon vision. Whatever 
be the adopted theory, this light, before producing the desired 
effect, undergoes four successive refractions:— PRIZE ESSAY*. 
I. From the air or object A B to the cornea, which refracts it in 
consequence of its density and convexity. 
II. From the cornea C\ to the aqueous humor H, which causes 
it to be bent slightly to the perpendicular. 
Fig. 2. 
III. From the aqueous humor II to the denser and more convex 
crystalline lens 0, where it undergoes a new refraction, following 
the general law. 
IY. The last and chief refraction is from the denser medium the 
lens, to the rarer one the vitreous body. Thus, in the crystalline 
Fig. 3. 
lens, the ray b o is bent to the perpendicular o g prolonged, and 
passing through follows the direction o z, and in passing out ap- 
proaches the line b a; but it passes to the rarer medium, the vitreous 
body (Fig. 2, d), by which it is again bent from the perpendicular. THE OPHTHALMOSCOPE. 
23 
Thus (Fig. 2), if from the assumed points A B, light be emitted, the 
image will be formed upon the retina, JR, upon the points K L; 
the image thus produced is inverted, constituting one of the para- 
doxes of vision, of which hereafter. There are two circumstances 
which will prevent the perfection of the above mentioned image, 
were not the eye so perfectly adapted to its ends. Thus Spherical 
Aberration is corrected by the combination of the aqueous humor 
and the iris ; the former from its refrangibility, the latter acting as a 
stop or diaphragm, in such a manner that only the central portion of 
the crystalline is used. Chromatic Aberration is corrected or reme- 
died by the conjoint action of the crystalline and the vitreous body, 
the latter exercising the greater dispersive power, and also from its 
offering a concavity to the convexity of the lens. All of the re- 
fractive media conjoin to produce the image upon the retina, which 
is clear and precise if these media be correctly adapted, and if they 
be incorrectly placed, the image is indistinct and confused. The 
adaptiveness of the eye to distance, is one of the prerogatives of 
sight, and, as such, its mechanism is truly wonderful. The power 
by which it adapts itself to variations of distance, whether it be the 
small distance between the eye of the engraver and the steel, or the 
vast expanse of old ocean’s mightiness, has as yet been unexplained, 
at least in a satisfactory manner. Whatever be the distance of an 
object from us, it is a matter of no immediate perception, but is a 
judgment and inference drawn from our sensations. The elements 
upon which our judgment is based, are, the effort by which the two 
eyes are fixed upon the same object, and that by which one or the 
other eye is adjusted to distinct vision; and, the colors, forms, and 
volume of objects, as compared with each other’s appearance. The 
correct interpretation of the whole is gradually learnt by expe- 
rience, the rapidity and unconsciousness of which process are not 
more remarkable than the acquirement of speech and the capa- 
bility of reading. Having acquired the conception of the relation 
of position, or in other words, the ratiocinative faculty of vision, by 
what faculty then is this accomplished ? Brown1 denies touch, but 
advocates muscular sense, which is but another name, and is but the 
consciousness of an exertion of the various muscles by which we 
move our limbs; for our knowledge of the forms of bodies is 
acquired by the perception of the course of the fingers, following 
1 Brown, Lectures of the Philosophy of the Human Mind. 24 
their surfaces. Sir Charles Bell1 calls this consciousness of muscu- 
lar action a “sixth sense,” which Marshall Hall more fully devel- 
oped in his various writings upon the reflex-motor actions of the 
nervous system. The conclusion at last, is, that by the modifi- 
cations of touch, or by touch itself, the relation of position is 
readily comprehended, and that it is fundamentally and insepara- 
bly connected with our own actions in space. A doubt seems to 
have arisen as to the fact whether a person born blind, who pre- 
viously by touch could distinguish mathematical figures, a cube and 
a sphere for instance, on suddenly obtaining vision, would be able 
by this sense to recognize them. Locke8 denied the possibility of 
so doing, and with justice: he arrived at this conclusive point by 
reasoning, which has subsequently been proven by facts. Chesel- 
den relates the case of a lad born blind, who at the age of twelve 
years, was, by an operation for artificial pupil, restored to sight. 
This boy saw everything flat as in a picture, simply receiving the 
impression upon the retina, without being able to refer it, and it 
was for a long time before he had the power of judging, by vision, 
of the real distances and forms of objects around him. He was 
incapable of distinguishing a dog from a cat, until he touched 
them. Carpenter3 relates a similar instance, of a boy who pre- 
ferred to find his way (after being restored to sight), through his 
father’s house by touch, rather than by sight alone. 
Among the new-born of the lower animals, the capacity for 
estimating distance results from some immediate power, and they 
manifest, at an early moment, that which takes man a long time to 
acquire. They perform automatically or instinctively, these actions 
in obedience to internal impulses, without even the perception of 
their adaptiveness on the part of the being who is their agent. 
All of these impressions are called into play, by the action of 
external objects, or by changes in the individual organism. Now, 
whatever be the refraction undergone by the rays emanating from 
a luminous body, the spot where the image is pictured upon the 
retina, is determined by the prolongation of a ray which represents 
the centre of a cone, whence an inverted image is the result, vide 
Fig. 2, the point B is represented upon the retina at A, and the 
point A, at L. The angle formed by two central rays, G and D, 
PRIZE ESSAY: 
1 Bridgewater Treatise, p. 195. Phil. Transactions, 1826. PI. II. p. 167. 
2 Locke, On the Human Understanding. 
3 Carpenter, Principles of Human Physiology, p. 676, Am. ed. edited by F. G. 
Smith, M. D., Pliilada. THE OPHTHALMOSCOPE. 
25 
Fig. 4, is known as the visual angle, and it follows as a consequence 
that objects situated at various distances from the eye, project 
images of equal size, provided they subtend the same angle. Hence 
the estimate of the size of an object is partly dependent upon the 
Fig. 4. 
visual angle, and partly upon its distance, and the condition of the 
atmosphere. Thus if two objects, op, e/(Fig. 4), the former twice 
the length of the latter, are placed at the same distance from the 
(R) retina, it is obvious that the angle 0 X P is twice the size of 
the angle e xf. 
The faculty of the eye to accom- 
modate itself to distances is physi- 
cally owing to the displacement of 
the crystalline lens, through the 
action of the ciliary muscle {tensor 
ciliaris), and the erectile tissue of the 
ciliary processes. Although com- 
parative anatomy would tend to 
prove this statement, yet in the hu- 
man subject it has never been de- 
monstrated by observation. Among 
the predaceous birds (the strix bubo 
(common owl) above mentioned), 
distinguished for great range of vi- 
sion, there is a very firm attachment 
for the tensor ciliaris, in the osseous 
plates of the sclerotic. Another fact 
to go to prove this statement, is that 
Fig. 5. 
L, lens; P, junction with the assumed ca- 
nal of Petit; I, iris ; cor, cornea; con, 
conjunctiva; ch, choroid; m, the tensor 
ciliaris, showing a projection of the mus- 
cle and its connection with the lens. 26 
prize essay: 
with persons operated upon for cataract, there is an entire absence 
of the power of adapting the eye to distance. 
Hence, this adaptiveness in the curvature of the refractive media, 
such as the cornea, aqueous humor, lens, and vitreous body. The 
most frequent conditions of abnormal vision are short-sightedness, 
myopia, and long-sightedness, presbyopia. Myopia is dependent 
Fig. 6. 
upon a condition of the refractive media, whereby the rays of light 
are so influenced that they converge so much as to unite before 
reaching the retina. The diagram illustrates this condition as well 
as its remedy by a concave glass, shown by the dotted lines reach- 
ing the retina. The physical causes which produce this condition 
of vision, are either an excess of density and a too great prominence 
of the cornea, or a superabundance of the humors of the eye, or a 
too great density or convexity of the crystalline, or an enlargement 
or dulness of the pupil, or a preternatural density of the vitreous 
body, or an over-activity of the power inherent in the eye, of 
adapting itself to the seeing of near objects, etc. etc. Were we to 
enter into the discussion of any of the above conditions necessary 
to the production of myopia, it would cause this essay to be of a 
too great length; hence, we must unwillingly pass over them, re- 
gretting our inability, at present, to inquire into this most interest- 
ing branch of optics. 
Presbyopia is just the reverse of myopia, and is a confusion of 
vision, when near objects are looked at, while distant objects are 
distinctly seen. It is dependent upon a condition of the refractive 
media whereby the rays of light do not converge sufficiently soon, 
and hence do not reach the retina before coming to a focus. It is 
remedied (vide Fig. 7, dotted lines) by a convex lens, which pro- 
duces the convergence necessary to throw the image upon the 
retina, by bringing the rays into a focus at that point. THE OPHTHALMOSCOPE 
27 
Fig. 7. 
The concomitant causes of this affection are generally, flatness 
of the cornea, shortening of the axis of the anterior chamber, dimi- 
nution in the size of the pupil, and an apparent sinking of the 
. globe within the eye. The same remarks made concerning the 
discussion of the causes of myopia, are equally applicable to those 
of presbyopia 
There are many other abnormities of vision, resulting from de- 
fective refractive media, which for a w'ant of space cannot be 
described. Among them, however, there are two which we deem 
proper to notice, viz., astigmatism, and dyschromatopsia. Astig- 
matism (» privitive, and point) is a result of defective re- 
fraction in such a manner that the cornea and lens are so arranged, 
as to prevent the production of a focus, when the rays of light are 
presented in a vertical direction; and, when presented in a hori- 
zontal direction, a focus is produced. .Thus, if a straight black 
line be drawn upon a piece of white paper, and viewed horizon- 
tally, nothing abnormal appears; but if presented vertically, it 
seems to be double. In the Philosophical Transactions for 1801, Dr. 
Young, in his article on the Mechanism of the Eye, mentions that 
his own eye, “ in a state of relaxation, collects, to a focus on the 
retina, those rays which diverge vertically from an object at the 
distance of ten inches from the cornea, and the rays which diverge 
horizontally from an object at seven inches distance.” What, then, 
is the explanation of the above phenomenon? It appears to us to 
have been caused by the light falling upon the whole surface of 
the pupil, and not brought to one corresponding point, or focal 
spot within the eye, thereby producing two linear images at right 
angles to each other. And it is probable that in all astigmatics, the 
cornea is without the “ surface of revolution,” and that its curva- 
ture is less in the horizontal than in the vertical plane; that the 
lens has one or both surfaces cylindrical, and varies in symmetry 28 
PRIZE ESSAY: 
and density. In the case of Dr. Young, he considered himself to 
be affected with an “ obliquity of the cornea and crystalline lens, 
with respect to the visual axis.” 
Gerson1 relates the case of Prof. Fischer, of Berlin, who observed 
that, if a number of parallel lines were placed before him in a 
horizontal direction, he could distinctly count them at the distance 
of from fifteen to twenty inches, and when changed to a vertical 
position, they presented a confused appearance, until brought 
within five or six inches of the eye. Also, when Prof. F. looked 
at the bars of a window, in an upright position, the cross bars ap- 
peared longer than normally, and when he hung his head upon his 
shoulder, the upright bar assumed an elongated appearance. 
The most remarkable instance of the defect occurred in the no 
less celebrated personage than the distinguished Mr. Airy,2 the 
Astronomer Eoyal of Great Britain. The publication of this case 
led to the investigation of the subject, and the defect has been 
found not to be so uncommon as previously supposed. Dr. Hays,3 
of Philadelphia, details an account of a clergyman of that city, 
astigmatic in both eyes. Dr. Goode4 relates his own case. Dr. 
Hamilton* describes a case of double astigmatism. The writer of 
this paper was consulted by a negro for what he himself denomi- 
nated “ upside-down sight,” which, after a tedious and patient in- 
vestigation, proved to be astigmatism. This patient was unable to 
distinguish or reckon time by the hands of a clock, whenever it 
was at a full hour, and from that peculiarity he knew it was the 
full hour; the quarters, halves, and fractional halves, were very 
distinctly told. Up to his death, he suffered from the defect, being 
unable to procure a lens, which was concavo-cylindrical on one 
side, and plane upon the other. The action of such a lens is owing 
to the cylindrical shape, “ producing no convergency or divergency 
in parallel rays, incidental to the plane of the axis, whilst it con- 
verges or diverges rays in a plane at right angles to the axis, as a 
spherical surface of equal curvature would do.” As we cannot, or 
at least do not, feel disposed to enter into the rationale of astigma- 
1 G&rson, De Forma Cornese, p. 17. Gottingen, 1810. 
2 Transactions of the Cambridge Philosophical Society, vol. ii. p. 267, et seq. 
Cambridge, 1827. 
3 Lawrence, Diseases of the Eye, p. 669, edited by Isaac Hays, M. D. Philadel- 
phia, 1854. 
4 Cambridge Transactions, loc. cit. 
5 Monthly Journal of Medical Sciences, p. 711, April, 1848. THE OPHTHALMOSCOPE. 
29 
tism, we would omit anything more on the subject, as it can be 
found minutely detailed by Mr. Airy, in the Cambridge Philosophi- 
cal Transactions, vol. ii. 1827, and in Mackenzie’s work on the Eye. 
The second abnormal phenomenon is known as Dyschromatopsia 
(from Sv;, difficult, color, sight), or insensibility to cer- 
tain colors, the color-blindness of Sir David Brewster. Of late 
years, this affection has been very much investigated, and the pro- 
priety of such is readily appreciated, when we know that human 
life is at stake, and that many sad accidents have taken place on 
account of mistakes as to the color of railway and marine signals. 
Many instances are on record of individuals who were totally inca- 
pable of appreciating various colors, and of mistaking one color for 
another, such as orange for green, or vice versa. 
Dr. Darwin, the poet and botanist, could distinguish a cherry 
from the leaves only by its shape. There is another case of a family 
in York, England, who were similarly affected with regard to full 
reds and full greens. Dr. Dalton, the discoverer of the Atomic 
Theory, and distinguished chemist, was likewise similarly affected. 
This defect was not known to him until, one day, discussing with 
a friend concerning the nomenclature of the colors of the solar 
spectrum, Dalton was unable to distinguish red, and all of the others 
consisted simply of yellow and blue. When made aware of his 
defect, it is said that he consigned to the flames a large manuscript, 
the contents of which were unknown. Dalton knew of twenty 
persons similarly affected as he was. Twice, with different classes 
of twenty-five pupils, he explained the defect, and detected the same 
misfortune in two of them. Provost declared that five per cent, of 
the human race were color-blind. 
Dr. Wilson seems to doubt Provost’s numbers, if applied to such 
cases as Dalton’s, but admitted them with regard to blue and green; 
for out of 1154 persons examined in the city of Edinburgh 
alone:— 
1 in 55 confounded red with green. 
1 “ 60 “ brown “ 
1 « 46 “ blue “ 
The proportion with respect to blue and green was accidentally 
discovered, as it was unsought for. With regard to red and green, 
and brown and green, they are, according to Dr. Wilson, but 
“degrees of the same affection; all in the first category, red with 
green, must be added to those in the second, brown with green; 
and many of those in the second might appear in the first; but no 30 
PRIZE ESSAY: 
one was counted more than once.” Many cases have been related 
and detailed in various journals, books, and monographs, which 
were spurious, being diseases of the retina, and readily recognized 
by the ophthalmoscope; one such will hereafter be described. 
There are two great classes of the color-blind, which differ in 
degree and character. Mr. Seebeck has given the best classifica- 
tion, and as such we will quote it. Seebeck’s first class consists of 
those who differ considerably in the degree of their vision, yet 
agree very nearly in the confounding of the following colors. 
“1. Sky-blue, gray-blue, and gray-lilac. 
2. Lilac and bluish-gray. 
3. Bluish-green and imperfect violet. 
4. Crimson, dark green, and hair brown. 
5. Rose-red, green (rather blue than yellow) and gray. 
6. Pure light green, gray-brown, and flesh color. 
7. Intense orange, light yellowish-green, or brownish-green, and yellow-brown. 
8. Light orange and pure yellow.” 
Persons who come under this class, have generally a very im- 
perfect idea of all colors, but particularly confound red with green, 
which appears to be of a dull gray; they also give the latter appear- 
ance to blue. Yellow they distinguish the most perfectly, but still 
lack the acuteness of perception of the normal eye. 
Individuals of the second class have only an imperfect percep- 
tion of the least refrangible rays, which is not the case with those 
of the previous class. These persons also recognize yellow the 
best, distinguish red better, and blue not so well as those of the 
other class. They more particularly confound:— 
“1. Dark violet and dark blue. 
2. Crimson and violet. 
3. Rose-red, lilac, sky-blue, and gray (including lilac). 
4. Brick-red, rust-brown, and dark olive-green. 
5. Cinnabar-red and dark brown. 
6. Imperfect (somewhat yellowish) rose-red and pure gray. 
7. Flesh-red, gray-brown, and bluish-green. 
8. Dark carmine and blackish blue-green. 
9. Light orange, greenish-yellow, brownish-yellow, and pure yellow. 
10. Bright orange, yellow-brown, and grass-green.” 
In speaking of the vitreous body, we mentioned Hannover’s dis- 
covery of the segmentary disposition of that body, as revealed after 
a maceration in chromic acid. This discovery seems to have been 
totally neglected by all writers upon the subject of color-blindness, 
which, if properly reviewed, would explain the phenomenon, and 
suggest a remedy. The writer believes an explanation of the defect THE OPHTHALMOSCOPE. 
31 
of color-blindness can be made by the above mentioned segmentary 
arrangement of the vitreous body. Thus, we know the laws of the 
refraction of light, and the peculiar property which a triangular 
prism of glass possesses of refracting light, and of decomposing it 
into seven primary colors. For the knowledge of this fact, we are 
indebted to Sir Isaac Newton. He placed a prism opposite an ori- 
fice in a window-shutter, admitting a ray of light in a darkened 
room, and, as the result, the pure white light was found to be com- 
posed of seven brilliant colors, viz: violet, indigo, blue, green, yel- 
low, orange, and red. 
The solar spectrum with regard to each particular color is vivid 
only at particular parts, as they blend and mingle with each other 
in such a manner that it is difficult to say where each begins or 
ends. The violet rays bend most from their course, whereas the 
red ones are the least turned out; the other colors possess this 
property in the proportion as they are mentioned in the list. These 
seven colors were named primary, and considered as simple or 
homogeneous, particularly as they preserved their individuality 
when passed through another prism. Notwithstanding our incapa- 
bility of analyzing these rays, they can synthetically, some of them 
at least, be shown to be compound. For artists have demonstrated 
that red, blue, and yellow would form all 6f the tints of the pris- 
matic spectrum, and as no mixture would produce these colors, 
they were necessarily simple or homogeneous; and the others, viz: 
violet, indigo, green, and orange, as a natural consequence, were 
compound or heterogeneous. Every one is familiar with the ex- 
periment of Buffon, who showed that by steadfastly looking at a 
red, yellow, or blue spot, upon a black or white ground, a fringed 
border is recognized around each one of them, the tints of which 
are composed of three colors: thus, a green border is seen around 
the red spot, and green is composed of yellow and blue; a violet 
border is observed around the yellow spot, and violet is made up 
of blue and red; an orange border is perceived around the blue 
spot, and orange is a mixture of red and yellow. The experiments 
induced to explain the phenomena revealed by Buffon’s experi- 
ments remained unsatisfactory, until Mr. Hay, of Edinburgh, scien- 
tifically demonstrated them in his work on the Laius of Harmonious 
Coloring. Sir David Brewster, Dr. Neil Arnot, F. R. S., Professor 
Holmes, and many other scientific persons have concurred with the 
opinions advanced by Mr. Hay. The writer of this essay has fre- 
quently verified them : his procedure and results are the following, 32 
PRIZE ESSAY: 
corresponding almost in every particular with those of the learned 
gentleman of Edinburgh. A prism was fixed in a hole in a shutter 
admitting a ray of light in a darkened room, and the decomposed 
light thrown upon a screen. Each color was successively put to 
the test, and was found incapable of being divided into two. A 
hole then was made in the screen, corresponding to the centre of 
the red of the spectrum, and another in that of the blue, and these 
colors were allowed to fall on a second screen. By means of a 
second prism the red ray was directed to the spot where also the 
blue appeared, in which spot they combined to produce as pure and 
intense a violet as was seen upon the first screen. Red and yellow 
were subjected to the same experiments, and a beautiful orange 
sprang forth; yellow and blue thus treated produced the prismatic 
green. After the above experiments were performed, a simple ray 
wras thrown upon a compound color, and did not unite, for, as soon 
as red was thrown upon green, it vanished arid black resulted; thus 
it was with the whole series. In another course of experiments 
two spectra were used, the one behind and of course a little above 
the other, and the same results were adduced. Thus, by synthesis, 
it was clearly demonstrated that the three homogeneous colors, 
yellow, red, and blue, had an affinity for one another, which was 
wanting in violet, indigo, green, and orange; and, as a consequence, 
they could not be the same in every respect, save color and refrangi- 
bility. The three homogeneous colors, ■ yellow, red, and blue, are 
in a numerical ratio as follows: yellow 3, red 5, and blue 8; and 
when anytipaque body reflects these colors in such proportions, 
white is the result. In this condition they are in the active state, 
and each is neutralized by the relative effect of the others. These 
rays when in the passive state are absorbed, and black is the result. 
The effect is the same when transmitted through a transparent sub- 
stance, but are material or inherent in the first case, and impalpable 
or transient in the second. Hence, color solely depends upon the 
refractive or reflective power of bodies. The opinion at present 
most generally received is, that according to the disposition of the 
minute particles of various bodies, so is their power of reflecting 
and absorbing rays; and as is the reflection and the absorption so 
is the color, which is not of itself an inherent part of a body. Color, 
when produced by artificial light, such as by oil, candles, or gas- 
light, the rays of which are not so pure as those of the sun, is very 
apt to be deceptive, so much so that every one will mistake pale 
blue for green, or vice versa. THE OPHTHALMOSCOPE. 
33 
What, then, is color? Color is the reflection of the rays which 
the object does not absorb! A white color is the reflection of all 
the rays, a black their absorption. A poppy is red because it 
absorbs all the other rays of the prism and reflects red; but, if it 
be seen through the medium of a compound color, a green glass for 
instance, there is an interference of rays, and the brilliant poppy 
appears to be black. Numerous instances of these apparent para- 
doxes might be enumerated; but these, as well as the discussion 
of the heat and actinic rays of the prism, are necessarily crowded 
out for the want of space. 
Sir Isaac Newton discovered that different rays require different 
distances to bring them to a focus, or, in other words, that the 
momentum of each ray is different. The red is the soonest brought 
to a focus, and has the greatest momentum. It is on this account 
that in a fog the sun appears red, from the rays of this color pos- 
sessing the force or momentum to penetrate the dense atmosphere. 
White light has the regular recurrence of periodical movements 
at equal intervals (500,000,000,000,000) five hundred millions 
of millions in one second. Eed to produce its effect undergoes 
(482,000,000,000,000) four hundred and eighty-two millions of 
millions in gV part of a minute! Yellow, to produce its sensation, 
affects the eye in one second (542,000,000,000,000) five hundred 
and forty-two millions of millions of times. Violet, to do likewise, 
must vibrate in one second’s time (707,000,000,000,000) seven hun- 
dred and seven millions of millions of times. 
Of all modern investigators, Sir John Herschel seems to have 
arrived at the most correct data with regard to the length and 
rapidity of the various rays of the solar spectrum; he gives them 
as follows:— 
Colored rays. 
Length of luminous rays 
in parts of an inch. 
Number of undulations . 
in an inch. 
Number of undulations 
in a second. 
Red 
.0000256 
39180 
477 billions. 
Orange 
.0000240 
41610 
506 “ 
Yellow 
.0000227 
44000 
535 “ 
Green 
.0000211 
47460 
577 “ 
Blue 
.0000196 
51110 
622 “ 
Indigo 
.0000185 
54070 
658 “ 
Violet 
.0000174 
57490 
699 “ 
The relative intensity of the light of the various portions of the 
solar spectrum, according to the calculations of Frauenhofer, are 
numerically expressed as follows :— 34 
PRIZE ESSAY 
Violet from 5 to G 
Blue, dark (indigo) 31 
Blue of solar spectrum 170 
Green ............ 480 
Between orange and yellow 1000 
Orange ............ 640 
Red, middle ray .......... 94 
Red, extreme ray .......... 22 
Having cursorily glanced at the theory, and the facts of color, 
we are prepared to enter into an explanation of the phenomenon 
of color-blindness. Rejecting all opinions heretofore maintained, 
not as worthless, for many of them merit the most distinguished 
consideration, but as certainly not giving a very correct idea, the 
writer presumes the following:— 
A. That light is transmitted by undulations. 
B. That the different colored rays of the solar spectrum may be 
accounted for, by a difference in the frequency of recurrence 
in the vibrations. 
That light is transmitted by undulations, no one doubts, and its 
discussion here would be mal-apropos. With regard to proposi- 
tion B, the simple facts will be stated, not discussed. The diffrac- 
tion and interference of light present phenomena which go to prove 
it; such as Newton’s luminous rings, Grimaldi’s interior and exterior 
fringes, and the estimates above mentioned. 
Remembering Hannover’s discovery that the vitreous body is 
composed of a series of segments, the writer believes color blindness 
to be the result of an irregular prismatic refraction of light as it passes 
through that dioptric medium. What conditions combine to produce 
such an effect, physical research has as yet been unable to demon- 
strate, but a priori reasoning by exclusion tends to that effect. For 
there are bodies which will transmit one kind of color and reflect 
another, leaf gold for instance, which transmits yellow, but reflects 
green. Again, some substances only reflect the various rays, 
thereby producing color, when they are of a certain thickness, be- 
yond which they appear black. Most of the color-blind, and par- 
ticularly in such as Dr. Darwin, the segmentary arrangement of the 
vitreous body is such as to induce a decomposition of light, and to 
bring the focus of two colors, a simple red and compound green, 
upon the same spot of the retina, and as a consequence their mu- 
tual disappearance, as proven by the experiments above quoted by 
the writer upon harmonious coloring. Now, if all phenomena ex- THE OPHTHALMOSCOPE. 
35 
hibited with regard to that abnormal process of vision (or color- 
blindness), can be produced physically by a series of prisms, does 
it not follow (as no other series of lenses can bring about the same 
effects) that it is reasonable to suppose the impressions conveyed 
to the brain by means of such images upon the retina, are similarly 
produced by a similar series in the vitreous body? We emphati- 
cally answer in the affirmative! 
When we gaze upon the faultless beauty of the humble violet, the 
brilliant jonquil and the modest lily, we little suppose that billions 
of vibrations must take place before the proper image is formed 
upon the retina, and the sensation conveyed to the sensorium! 
What innumerable vibrations take place, when we look around 
and behold the various hues of all that exists in nature from the 
humblest pebble to the sublime snow-capped mountain! Yet, of 
all the millions of millions of vibrations, if one only should be lost, 
the color would be imperfect! 
It thus seems, without reapplying the laws of coloring in detail, 
that color-blindness is a purely physical result of a disarrangement 
of the vitrhous body, and that its remedy is the application of such 
substances, the wearing of various glasses for instance, such as 
light or deep orange, rose tinted, etc., with a certain amount of con- 
vexity or concavity, as the case might warrant, thereby preventing 
an interference of rays. We sincerely hope to see color-blindness 
as easily remedied, as either presbyopia or myopia. 
Besides the above mentioned phenomena of vision, there are 
others which are entirely subjective, that is, such as afford evidence 
of the action of the retina, and which are not dependent upon the 
influence of the external agency of light. The most remarkable of 
these subjective phenomena, are what are denominated by M. Serre 
(d’Uzes) Phosphines (&*(, light, and $alvttv, to cause to shine), and Druck- 
jiguren by Purkinje. These are luminous images which are pro- 
duced by pressure upon the ocular globe, whence a mechanical 
action upon the retina. The procedure of M. Serre consists in sud- 
denly and gently tapping either with the extremity of the finger or 
the head of a pencil (over the closed lids) the globe of the eye, 
which produces the luminous rings in question. 
The partial or entire absence of these rings, their indistinctness, 
or their segmentary appearance, is a precious source of diagnosis 
which permits us to recognize any threatening or actual lesion of 
the function of vision. The method of the writer to obtain the 
development of these phenomena, is to place the patient in a dark 36 
PRIZE ESSAY: 
room, and then proceed as M. Serre in the manner above described. 
The beneficial advantage which these pliosphenes offer to the sur- 
geon, is to enlighten him upon the state of the retina as regards 
the feasibility of an operation for artificial pupil, when adhesions 
or cataract totally obstruct the passage of any rays of light. M. 
Serre mentions four particular phosphines, viz: jugal, frontal, tem- 
poral, and nasal. To produce either of which the eye must be 
compressed upon the opposite side; thus, to produce the nasal, the 
temporal margin of the globe is pressed upon or tapped, and so on 
with the others. In the first degree of anaesthesia retinae, the jugal 
disappears; in the second, the frontal; in the third, the temporal; 
in the fourth, the nasal. When the latter is wanting, the others 
cannot be developed; but, in an inverse order, when the jugal is 
absent, the others remain; when the frontal is also absent, there 
still remain the other two; and when the temporal, is also absent, 
the nasal remains, the obliteration of which indicates a complete 
anaesthesia or loss of sensibility in the retina. When, after an active 
or other treatment, the phosphines begin to reappear, they do so in 
an inverse order to their disappearance; thus, the nasal being the 
last to disappear, is the first to reappear; then the temporal, frontal, 
and jugal. When the jugal phosphenic light is wanting, its absence 
indicates that the terminal portion of the retina alone is anaesthetic; 
the non-appearance of the frontal implies that a more distant por- 
tion is implicated; and the absence of the temporal and nasal ones, 
point out that a loss of sensibility has reached still more distant 
portions. The other subjective phenomena are of such physiolo- 
gical importance that space will not permit of their discussion; a 
mere mention will, have to suffice. 
A. Luminous appearances produced by the pulsations of the arteria centralis 
retinae. 
B. Phosphenic circles made apparent by a sudden lateral motion of the eyes. 
C. Vascular figure, and visible movement of the blood, presenting a luminous 
appearance in the field of vision. 
D. Electrical and galvanic productions of phosphenic circles. 
E. Spontaneous phosphenes. 
F. Narcotic and rotatory phosphenes. 
We now propose to entertain, in as concise a manner as possible, 
some few of the peculiarities of healthy vision. 
Vision is subject to two paradoxes; the first of which, upright 
or erect vision, or the seeing of objects upright by inverted images 
upon the retina. The second is the faculty of seeing single with two 
such images. THE OPHTHALMOSCOPE. 
37 
With regard to the solution of the cause of erect vision many 
theories have been advanced, which are as yet unsatisfactory. Kep- 
ler presumed that objects appeared erect, on account of the mind’s 
perception of the impulse of a ray on the lower part of the retina; 
and he thought this ray to be directed from a higher part of the 
object, and vice versa. The opinion most in vogue is that of Porter- 
field, sanctioned by Sir David Brewster and Mr. Keid, viz: that the 
mind never sees the picture painted upon the retina, and conse- 
quently never judges of the object. According to this law, all 
objects are seen in the direction of the perpendicular to a point of 
the retina, upon which any impression is made; hence, in seeing 
any object, in consequence of an immutable and known law, the 
sensation is traced by the mind back from the sensorium to the retina, 
and thence referred in consequence of the perpendicular lines to its 
proper place without the eye: or in the words of Carpenter, “as all 
the perpendiculars to the several points of the inner surface of a 
sphere meet in the centre, the line of direction of any object is 
identical with the prolonged radius of the sphere, drawn from the 
point at which its image is made upon the retina.” Volkman,1 upon 
a close examination, found this law to be optically incorrect, since 
the lines of direction cross each other at a spot a little posterior to 
the crystalline lens, and consequently falling at different angles on 
various points of the retina, no fixed and determined law can be 
promulgated concerning them. 
Miiller contends that erect vision consists only in the perception 
of the state of the retina itself, and not of any object placed anterior 
to it in the external world. He objects to the hypothesis of the 
“law of visible directions,” and denies that the retina has an out- 
ward action, since there is no possibly apparent reason why one 
direction should have the preference to another; and if each ulti- 
mate sensitive portion of the retina had the power of action beyond 
itself, there would be produced as many directions as radii could 
be drawn from it to the external world. To use Muller’s own 
words,2 “If we do see objects inverted (or rather if the picture on 
the retina be inverted), the only proof we can possibly have of it is 
that afforded by the study of the laws of optics ; and, if everything 
is seen reversed, the relative position of the objects remains un- 
changed. Hence, it is also that no discordance arises between the 
1 Volkman, On the Refractive Power of the Eye. 
2 Muller, On Erect Vision. 38 
prize essay: 
sensations of inverted vision and those of touch, which perceives 
everything in its erect position; for the images of all objects, even 
of our limbs, on the retina are equally inverted, and, therefore, 
maintain the same relative position. Even the image of our hands, 
when used in touch, is inverted.” 
The above quotation corresponds with the previously advanced 
ideas, by the writer, concerning the correlation of vision and touch. 
Now, it cannot positively be said that we perceive, or that the mind 
perceives, an image upon the retina; none but anatomists know it; 
for we are not conscious of its existence; we perceive, or we see hy 
means of this image. Having thus premised, all difficulty seems 
banished, if this distinction be borne in mind. Why then, it may 
be asked, do we perceive an object in the upright position, when 
the image upon the retina is inverted ? We see it in the upright 
position simply because it is inverted ! This inversion is the neces- 
sary means of our so seeing the object. 
Granting the above distinction, why is it that we do not judge of 
the object according to its sensible image ? This is readily answered, 
since we have no knowledge or notion of upright or inverted, except 
such as is based upon experience; and, whatever be our standard 
of up and down, the sensible representation of upright will be an 
image upon the lower side of the retina, and of doivnwards just the 
reverse. The experience taught by the education of the senses in 
man, is intuitive or instinctive in animals. It seems to us that 
the various perplexities have arisen in consequence of the phe- 
nomenon of erect vision being produced by inverted images, 
or cubical and pyramidal, by means of an image upon the con- 
cavity of a sphere, or the perception of the many tinted colors 
of the rainbow upon a black surface. V\Tell may the poet say :— 
“ There is a voiceless eloquence on earth, 
Telling of Him who gave her wonders birth : 
Whose hidden but supreme control 
Moves through the world an universal soul. 
The faculty of seeing objects single with two eyes, is very sin- 
gular, and has occasioned much discussion. The fact is, that we 
are incapable of receiving two impressions from two images, but 
that, under certain, particular, and peculiar circumstances, one im- 
pression is formed of two. Each eye judges of the position of all 
objects directly within the field of vision. Now, when the two 
eyes are directed to any object, their axes meet in it, the two retinae 
are opposite it, and all other points of the eye correspond mutu- THE OPHTHALMOSCOPE. 
39 
ally, in order to give the sensation of single vision. Therefore, 
when we look at a distant object, sufficiently far that the distance 
between the eyes becomes comparatively small, the two objects, 
being similar collections of forms, will coincide, if the correspond- 
ing points in both do likewise; this being the case, the double 
image of each object, falling upon corresponding points in the 
retina, becomes a single one. 
Single vision from two images upon the retina is consequently 
but the result of an optical law, and it is a fallacy and mistaken 
notion to call in the aid of habit and experience to aid in its expli- 
cation. For in ascribing single vision to experience, we necessarily 
infer an educational system of touch, or some such corresponding 
system, which is not true. Who would say that infants see every- 
thing double ? Certainly no one, yet to prove such a doctrine, 
children would have to learn by experience that which they possess 
per naturam, and which would take a long time to be cognizant of. 
Another objection to such a theory is the simple fact that persons 
born blind, when restored to sight, do not see double; the only abnor- 
mal deviations being a lack in the power of adaptiveness with 
regard to perspective, etc. If two objects do not exactly coincide, 
the stronger impression absorbs the weaker, and the object is seen 
single. The writer has frequently verified this, by looking through 
two colored glasses at the same time, blue and dark red, and look- 
ing at objects (although he has no defect of vision whatsoever), he 
sees them red or blue, according as one or the other is before the 
right eye, the other color being before the left eye. This plainly 
shows how completely the mind takes cognizance of one impression 
to an unconscious exclusion of the other, when this impression is 
communicated by one organ of sense, exclusive of its fellow. The 
above phenomena were discovered by accident, whilst observing 
an eclipse of the sun. Exciting some surprise in the writer’s mind, 
he prosecuted these experiments, and discovered, in every instance, 
that one eye was stronger than the other, or, in scientific application, 
that distinct impressions could be made upon one retina to the 
exclusion of the other. The conclusions drawn from these pheno- 
mena were such as to induce the following theory upon single vision: 
Impressions are made upon both eyes at separate times1 one following the 
other so rapidly that almost simultaneously an impression is conveyed 
by each to the sensorium, which reflects a double sensation, but one after 
another; and, in this manner, objects are seen singly, in consequence of a 
series, as it were, of sensations. prize essay: 
40 
The duration of an impression upon the retina varies. Mr. D’Arcy 
found that when a live coal was swung around a circle of 165 feet 
circumference, the impression remained a little longer than one 
seventh of a second upon the retina. Again, when a first impression 
is succeeded by a second in such rapidity that the latter runs into 
the other, the two, as it were, become one. This is readily demon- 
strated by whirling a piece of burning stick, which seems to be a 
complete circle of fire. 
That the phenomena of single vision cannot be explained by the 
peculiar decussation of the optic nerve at the chiasma hardly any 
one will deny, when the important experiments and discoveries of 
Prof. Wheatstone concerning the stereoscope are entertained. These 
discoveries go to show that the mental interpretation of sensory 
impressions is a modus operandi not to be explained by any struc- 
tural arrangements of the sensory apparatus, and that it is a process 
entirely foreign from any affection of the consciousness by such 
impressions. 
According to Prof. Wheatstone, the perception of distance or 
perspective, and the idea of solidity, are evidently produced by the 
combination of two pictures of a solid body taken from either eye, 
as from t\YO different points of sight. A singular and curious fact, 
which goes to prove this, is that a person with one eye, in viewing 
any solid body, is constantly moving his head from one side to the 
other; the result of which is, that he, by this means, gets with one 
eye the same effect that is obtained by two eyes with the head sta- 
tionary. These conclusions, concisely drawn from the opinions of 
Prof. Wheatstone, are not as fully elaborated as the writer would 
desire; any further explanation either of the stereoscope or pseudo- 
scope wouM be useless, as Prof. W. has two very learned and able 
articles upon them in the Philosophical Transactions for 1838 and 
1852. 
We now come to the consideration of the ophthalmoscope, and 
the revelations made by this most ingenious instrument. This 
discovery, as applied to the investigation of disease, is of modern 
date, and we owe it to Helmholtz, Professor of Physiology at 
Konigsberg, Prussia. Mackenzie, of Scotland, however, applied a 
rudimentary ophthalmoscope in the investigation of diseases within 
the eye, previous to 1840, of which the particulars will be given 
farther on. 
The power of seeing the interior of the eyes of such animals as 
the dog and the cat, which are deprived of pigmentum, depends, THE OPHTHALMOSCOPE. 
41 
not as many observers have supposed, upon nervous influence, but 
upon a reflection of the light from their eyes, which had passed 
therein from without. Prevost, in 1810, was the first to demon- 
strate this fact, and proved it by showing that no such effect was 
produced in a perfectly dark room. Gruithuisen1 came to the same 
results, and added that the phenomenon was in part owing to an 
extraordinary refraction of the crystalline lens: he examined the 
eyes of many animals, living and dead, and his experiments were 
confirmed by Tiedemann,1 Rudolph,1 Miiller,1 Esser,2 and Hassen- 
stein.3 
Hassenstein believed that the power of seeing within the eye was 
due to the muscular contraction of the globe in its antero-posterior 
diameter. Rudolphi considered that the eye should be turned in 
a certain direction in order that the phenomenon of oculoscopy 
might be made apparent. Beer4 was among the first to observe the 
phenomenon in man, in a case of iridemia or congenital absence of 
the iris, where the patient suffered from a tumor upon the retina, 
and he remarked, that in order to see within the eye of the patient, 
the observer should look into it parallel to the luminous rays which 
fall upon it. Briicke5 and Cumming6 both gave the same directions, 
in order that the interior of the eye might be seen, yet they never 
once sought to discover there any diseased condition by such a 
procedure; they merely advised it as a method in which the cham- 
bers of the eye could be illuminated. Their experiments were 
about the same ; and consisted in placing the subject in a darkened 
room, the observer holding a lamp or candle in one hand, and a 
screen in the other, the upper border of which is held upon a level 
with the flame, in such a manner as to prevent the rays of light 
from directly impinging upon his eyes: he looks over the top of 
the screen towards the pupil of the patient, who is some eight or 
ten feet in front of him, and who looks, as it were, out upon dark- 
ness. In this latter position the patient’s pupils present a brilliantly 
lighted appearance of reddish-yellow color, which immediately be- 
come black if turned towards the light. The rationale of this 
experiment will be explained a little farther on. In the early part 
1 Zur vergleichenden Pliysiologie des Gesichtsinns. Leipzig, 1826. 
2 Kastner’s Archiv. fiir die gesammte Naturlehre. Bd. viii. s. 399. 
3 De Luce ex quorundum animalium oculis prodeunte atque de tapeto lucido. 
4 Hecker’s Annalen, t. i. s. 378, 1839. 
5 Muller, Archiv. fiir Anatomie uud Physiologie, s. 225, 1847. 
6 Medico-Chirurgical Transactions, vol. xxix. p. 284. PRIZE ESSAY: 
of the eighteenth century, Mery1 having accidentally plunged a cat 
into water, very unexpectedly beheld the bottom of the eye, and 
distinctly saw the bloodvessels thereon. lie gave no explanation 
of the phenomenon, but reported the fact to the Academy of Sci- 
ences in Paris. In 1709, five years afterwards, La Hire2 and Lat- 
tere2 separately performed the same experiment, and both arrived 
at the same conclusion as to its explanation, viz., that we cannot 
see within the eye on account of the refractive power of the cornea 
and lens, whose normal refraction becomes neutralized by the action 
of the water, for the rays in passing out of the eye are divergent, 
but the water causes their convergence, and thus induces a focus to 
be brought upon the retina of the observer, and consequently an 
image there formed. 
Kussmaul,3 after having carefully studied the above described 
phenomena, repeated the experiments, and in 1845 published a 
monograph upon the subject. He demonstrated by dissection, that 
our inability to see the bottom of the eye is due to the refractive 
power of the cornea and lens. He took a sheep’s eye and removed 
the cornea, and was still unable to see the retina: he then removed 
the lens, when all was visible, the transparent retina appeared with 
its bloodvessels, the papilla of the optic nerve stood out in bold 
relief, and the bright shining choroid glistened behind. Here was 
positive proof that the lens as well as the cornea exerted its influ- 
ence upon the phenomenon in question, had we not previously 
known that the pupil still appears black after a successful operation 
for cataract. 
The rationale of the experiments of Brucke and Cumming, quoted 
above, was not given until 1851, when Helmholtz4 published his 
essay uporl the ophthalmoscope. This distinguished savan explained 
the black color of the pupil by purely optical rules. Thus, the 
retina is not only transparent, but also reflects light, at least some 
rays which impinge upon it: these rays, in passing out of the eye, 
traverse the same media through which they entered, and come to 
a focus at the point of departure of the incident rays. The eye of 
the observer is too feeble to project sufficient light to illuminate the 
1 Ann, de l’Acad. des Sciences, 1704. 
2 Ibid., 1709. 
3 Die Farbenerscheinungen im Grande des Menschliclien Auges, Heidelberg, 
1S45. 
4 Besclireibnngeines Augenspiegel zur Beobachtung der Netztliaut in lebenden 
Auge, Berlin, 1851. 43 
THE OPHTHALMOSCOPE. 
bottom of the eye explored, in order that the reflection there might 
throw an image upon the observer’s retina. 
From these propositions, the deduction is clear that, to see the 
retina of an individual, our own eye should, be the luminous point, 
but our eye is too feeble to project a sufficient quantity of light 
to illuminate the eye explored—and as a consequence, in looking 
into an eye by the aid of ordinary daylight, our head would inter- 
cept the rays of light, necessary to the illumination; hence, being 
in the shade, the pupil would naturally appear to be dark and 
black. If the eye, on the contrary, instead of regarding a lumi- 
nous point, is fixed, upon a distant object, the rays reflected from 
the retina do not come to a focus at the point of departure of the 
incident rays, but beyond it; and, as these rays proceed in almost 
parallel bundles, a person placed anterior to the eye of the subject 
of the experiment, may easily perceive a portion of these rays. 
This is the rationale of Briike’s and of Cumming’s experiments. 
These facts led to the invention (not discovery) of the Ophthal- 
moscope of Helmholtz; for, upon the authority of Mr. Wharton 
Jones, Mr. Babbage has the priority of discovery. Mr. B. showed 
him an instrument in 1847, for the purpose of looking into the eye. 
It was made of a plain mirror, with the amalgam removed in two 
or three small spots in the centre; it was fixed in a tube at such 
an angle, that the rays of light falling upon it through the side of 
the tube, were reflected into the eye to be examined, to which one 
end of the tube was turned. The surgeon looked through the clear 
spots in the centre of the mirror, at the other end. This ophthal- 
moscope of Mr. Babbage was but the original of those of Graefe, 
Coccius, Donders, and Epkeus, and Meyerstein, which are but 
modifications of Helmholtz’s. Helmholtz, although he introduced 
his ophthalmoscope four years later than did Mr. Babbage, is justly 
entitled to the distinction of being its inventor, as Mr. Babbage 
made no publication of his discovery. Reasoning upon the prin- 
ciples enunciated above, Helmholtz bethought himself of an arti- 
ficial method of overcoming the insufficient reflection of the retina, 
or at least to devise some plan whereby the reflection from the 
retina would be so great, that the eye of the observer could, by 
being in the focus of the reflected rays, or at the point of de- 
parture of the incident rays, observe the bottom of the eye to be 
explored. 
Yon Erlach, who wore spectacles, observed one day, whilst con- PRIZE ESSAY: 
versing with a friend, that the sunlight was reflected from a neigh- 
boring window, upon his spectacles, and thence reflected into his 
friend’s eye, very highly illuminating the pupil. He communicated 
this fact to Ruete and Helmholtz, and which undoubtedly led to 
the latter’s using plate-glass reflectors in the ophthalmoscope which 
he invented in 1851. This instrument consists of a metallic tube 
or cylinder, painted black upon the inner surface; it is bevelled at 
one end to an angle of 56° to its axis; the other end is perfectly 
square, containing an eye-piece, composed of a diaphragm placed 
anteriorly to a bi-concave lens. Attached to the bevelled edge is 
a reflector of four highly polished and parallel pieces of glass. 
The modus operandi of this eye-speculum is readily understood by 
referring to the annexed figure. The eye B looks into the eye G} 
Fig. 8. 
through E, consisting of a reflector, composed of four superposed 
glass plates, disposed at an angle of 56°, by which the light from 
A is reflected from it into the eye to be observed, C, in the same 
direction in which the observing eye looks. The eye B receives 
the reflected rays from (7, converging so much, that the refractive THE OPHTHALMOSCOPE. 
45 
powers of the cornea, lens, and vitreous body, are not sufficiently 
strong to counteract; consequently, they do not come to a focus 
upon the observer’s retina, thereby rendering him relatively 
myopic. To remedy this deficiency, Helmholtz introduced a bi- 
concave lens, which brings the rays to a focus upon the observer’s 
retina, thereby producing an image of the internal structures of the 
eye, G. 
Numerous ophthalmoscopes have been devised since the con- 
struction of Helmholtz’s. 
Ruete modified Helmholtz’s by employing, instead of plate glass, 
a concave mirror (looking-glass), ten inches focus, having a small 
orifice in the centre, through which the surgeon looks into the pa- 
tient’s eye; a bi-con vex lens is used to intensify the light. 
Coccius’s instrument is a plain mirror, with a hole in the centre, 
and the light is concentrated upon it before it is reflected into the 
eye. Whenever either the surgeon or patient is myopic, a bi-con- 
cave lens is substituted to remedy the defect. 
Graefe’s instrument is similar to the one claimed by the Greek 
surgeon, Anagnostakis, as his invention. It consists of a concave 
mirror, of about two and a half inches in diameter, with a hole in 
the centre, through which the observer looks, the posterior surface 
of which is covered by a coating of blackened sheet copper; a bi- 
convex lens is used as in Coccius’s. The writer, having read in 
Mackenzie’s work on Diseases of the Dije, something concerning the 
claim of Anagnostakis to this instrument, whilst in Berlin, in the 
summer of 1857, made inquiries concerning it, and upon the 
authority of M. Lebrich, chef de clinique of Graefe, he learned that 
early in 1853, Graefe showed to the Athenian an instrument, the 
counterpart of the one described by him as being his own inven- 
tion, the only difference being that Anagnostakis’s is slightly the 
larger. 
Ulrich’s is a similar one to Ruete’s, but more compactly ar- 
ranged. 
Rollin' and Nachet’s is nothing more than Helmholtz-’s, with 
the addition of a bi-convex lens to condense the'light, as it falls 
upon the reflector. 
Meyerstein’s is but a compact modification of Coccius’s. 
Zehender’s is quite like Ulrich’s, as is also Hasmer’s. 
Donders and Epkens’s instrument is a modification of Coccius’s, 
the light being intensified as in Follin and Nachet’s. 46 
prize essay: 
Desmarres’s ophthalmoscope consists of a concave mirror of 
about 10 inches focus, constructed of burnished steel, with two 
small holes near the circumference on a line corresponding with its 
equator: the object of these two holes, is that the surgeon may 
use indiscriminately either the right or left eye. A bi-convex lens 
is used as in the application of Coccius’s instrument. The writer 
prefers and uses Desmarres’s instrument on account of its sim- 
plicity, and non-liability to get out of order: he also adds to it, a 
bi-concave glass to remedy myopia, when any such patient is exa- 
mined (according to the method of Coccius). 
Dixon’s is upon the principle of Coccius, but is fixed in one of 
the rings of a spectacle frame: the other being balanced on the 
nose by a plane glass. 
Jager’s ophthalmoscope is said by many to be the most complete 
yet devised, but its complications are such, that when Desmarres’s 
can possibly be used, it is by far the more preferable. 
Thus having cursorily glanced at the various modifications of 
the ophthalmoscope without entering into their respective merits or 
demerits, it is deemed proper at once to enter into an account of 
the method of its use. As above stated, that of Desmarres is used 
by the writer, on account of its simplicity of construction and ap- 
plication : with it he proceeds as follows, always conducting the 
examination in a darkened room. The patient’s pupil is at first 
dilated1 by a solution of belladonna or atropia (neut. sulphat.); 
the writer prefers the atropine, and uses it in the proportion of 
one or two grains to the ounce of water. He places himself in 
front of the patient, seated preferably upon a music stool, as by so 
doing he can elevate or lower his position at will, which is a matter 
of no little importance. 
A jet of gas covered by a glass shade, or an oil lamp, is placed 
to the left2 of the patient upon a level with his eye, eight or nine 
inches from, and very slightly behind the head, in such a position 
as to have the eyes out of the immediate reflection of the light, and 
1 As to the dilatation of tlie pupil it is not necessary where the patient has an 
unusually large one, as in some cases of (so called) amaurosis. Frequently the 
healthy pupil is sufficiently large to allow of an ophthalmoscopical examination. 
2 With regard to the position of the light, whether it he to the left, or the right, 
or even above and behind the patient’s head, is simply a matter of habit or conve- 
nience to the surgeon. The writer places the light to the left on account of cus- 
tom, having first used the ophthalmoscope at the cliniques of the celebrated Des- 
rnarres, of Paris, where it is thus used. THE OPHTHALMOSCOPE. 
47 
in such a position as to receive the rays as propelled from the re- 
flector of the ophthalmoscope. The surgeon then places his ophthal- 
moscope before either his right or left eye, the other being closed, 
and looks through one of the minute openings near its circumfer- 
ence, and causes the reflected light to fall upon the eye to be ob- 
served ! A few manipulations with a bi-convex lens from 2| to 4 
inches focus will expose the internal arrangement of the eye. There 
are several important considerations to which attention must be 
given, before proceeding with the examination, viz., that the light 
be of sufficient intensity, that it be placed in a convenient position 
for the projection of the rays within the eye, that it be of varying 
intensity, and, that the patient be lower than the observer. Further 
on we will refer to the varying intensity of the light, as either the 
anterior or posterior portions of the inner eye are to be examined. 
After being properly arranged as regards position, light, etc., there 
still remain the greatest difficulties, viz., the bringing of the light 
to a focus so as to recognize the parts for which search is made. 
For the beginner this is extremely difficult: many and patient must 
be the sittings before he can acquire that degree of skill by which, 
at the first glance, he can immediately recognize the deep-seated 
structures, as there are certain very embarrassing obstacles to be 
overcome, such for instance as mistaking the image of the reflector 
for the papilla of the optic nerve. This obstacle with Desmarres’s 
ophthalmoscope is easily remedied, as the two small holes near the 
circumference of the reflector appear as two minute black specks, 
which move in the same direction as the instrument is moved by 
the observer. 
Another difficulty is the seeming impossibility of tracing the 
ramifications of any of the vessels, by neglecting to move the 
lens in an opposite direction from the point sought after. Again, 
the patient must keep his eye upon a fixed point, otherwise it 
is absolutely impossible to obtain the necessary reflection; and, 
all points to be examined should be placed as near as possible 
in a direct line corresponding to the axis of vision of the ob- 
server. Before introducing the lens, the reflection of the eye to be 
observed must be of a size corresponding to the reflector. The 
pupil 'at this stage presents a light yellowish-red color, like the 
tints of a summer’s sunset cloud. The lens is now placed before 
the patient’s eye, and, if properly adjusted, a most beautiful sight 
is revealed; but, if it be not properly adjusted, either the head of 
the observer, or the lens, or both must be moved slightly back- 48 
PRIZE ESSAY: 
wards or forwards, or laterally until a focus be obtained, when, if 
the eye examined be a healthy one, there will be displayed the 
OPHTHALMOSCOPICAL APPEARANCES OF THE NORMAL OR HEALTHY EYE.1 
The first thing sought for is the papilla of the optic nerve, as, 
from its peculiar characteristic appearances, it serves as a valuable 
landmark. In looking for the papilla it is well to trace the ves- 
sels, seen upon the reddish-white concavity of the retina, in the 
direction as they grow larger, when, a little below the equator and 
slightly within the axis of the eye, there will be seen a white shin- 
ing circular spot of about four lines diameter, resembling the full 
moon in a clear sky. This papilla, which is' nothing more than 
the termination of the optic nerve, slightly projects over the sur- 
rounding parts, thereby producing an apparent shading of the 
retina, but which truly is nothing more than the dark choroid seen 
shining through the transparent retina: this shading is known as 
the periphery of the papilla, and is generally surrounded by a slight 
grayish ring, composed of fine points of pigmentum resting upon 
the choroid. The dimensions of the papilla vary both in the liv- 
ing and the dead. Iluschke came to the conclusion after many 
autopsies of healthy eyes, that it never exceeded one line in diame- 
ter. The mean diameter of over fifteen hundred reported ophthal- 
moscopical examinations of the papilla, as seen through a bi-convex 
lens, is 8| lines. It frequently varies, more particularly with indi- 
viduals affected with myopia and presbyopia. With short sighted 
individuals, when examined without the lens, the papilla seems to 
occupy the whole range of sight, if the pupil have not previously 
been dilated with atropine: if the lens be introduced then all ap- 
pears just to the contrary, for the papilla appears much smaller 
than normal. In persons who are affected with presbyopia, the 
papilla without the lens seems very small, whereas the glass ap- 
pears really to magnify it. From these apparent anomalies, it fol- 
lows that in examining a short-sighted person, a lens decreasing in 
strength should be employed in a ratio as the myopia increases; 
and, with presbyopic individuals, the lens should be larger in pro- 
portion as the defect is more marked.2 
1 Vide Appendix, Figure I. 
2 Desmarres and Graefe advise the habitual use of the same lens in all exami- 
nations, as by it any abnormal appearance, however slight, can be the more readily 
appreciated, and the surgeon the more quickly see the necessity of using any other, 
such as the nature of the case might call for. THE OPHTHALMOSCOPE. 
49 
Springing from the papilla, but by no means always from its 
centre, is the arteria centralis retinae, which frequently divides into 
four branches, two ascending and two descending, which go to form 
capillary loops throughout the whole of the retina, and then anas- 
tomose with the veins of the same name, which run nearly parallel 
to the arteries, and which pass out where the arteries enter. (Vide 
Fig. I., Appendix.) The veins are somewhat larger than the arte- 
ries, slightly more tortuous, and of a darker color. In cases of 
congestion of the retina, the writer has been able to count the 
pulsations of the arteries. Surrounding the papilla of the optic 
nerve is the retina, a transparent membrane, furrowed by blood- 
vessels, presenting a tint varying from a deep red to a pale rose 
color, and forming a concavity presenting anteriorly. The retina 
is of itself perfectly transparent, and the varying tints depend upon 
the color of the individual; hence, the color of the choroid. The 
retina would not be at all recognizable, were there no bloodvessels 
furrowing its surface. In Albinos, there being a diminution or 
even a complete want of pigmentum of the choroid, the retina 
appears to be of a pale rose tint, whereas in persons of a very dark 
complexion, negroes for instance, it is of a deep red, owing to the 
greater deposition of pigmentum in the choroid: with all indivi- 
duals its color varies with the color of the skin. 
The vessels of the retina, decreasing from behind forwards, to- 
wards the ora serrata, are but the continuation of the artery and the 
commencement of the vein, described above as springing from and 
entering the papilla. They present the general characteristics of 
color, size, and tortuosity, as veins and arteries most frequently do, 
only the former are more numerous than the latter. The yellow 
spot of Soemmering, as seen by the ophthalmoscope, presents a bril- 
liant yellowish appearance, with a depression in the centre, and is 
always found in the centre of the visual axis. Desmarres, from 
ophthalmoscopical observations, denies the existence of the plica 
transversalis; but it nevertheless exists, and is no post-mortem forma- 
tion from shrinking of the retina. For, if the light be concentrated 
by a bi-con vex lens upon the reflector, previous to its being thrown 
in the eye, it then becomes sufficiently intense, and the plica pre- 
sents the same appearances as before described. 
The choroid is readily recognized through the transparent retina, 
and presents a series of irregular blackish radiating striae, arising 
from the circumference of the papilla of the optic nerve, and which 50 
PRIZE essay: 
pursue a direction in lines of unequal length towards the ora serrata: 
about six lines posterior to this point they form a series of bifurca- 
tions, until lost within its substance. These strife are formed by a 
deposit of pigment cells and granules, which are of a more intense 
color than the surrounding parts, as seen through the transparent 
retina. They have not been inaptly called the choroidean arborisa- 
tions, and they vary in intensity in the same ratio as the choroid, 
which, as above mentioned, varies with the hue of the skin. In 
Albinos there is a complete absence of them: in the negro they are 
most beautifully developed. And so it varies in blonde and bru- 
nette, the one having blue eyes, fair hair and complexion, has less 
pigmentum; the other with a flashing eye, sparkling like the meteor 
of an August night, with hair as the raven’s wing, and face as the 
olive’s hue, possesses a choroid strongly charged with pigmentum. 
Between these arborisations there are seen patches of a beautiful 
rose tint, furrowed with the vessels of the retina. Having thus 
cursorily glanced at the normal condition of the eye, as seen by 
means of the ophthalmoscope, we are prepared to enter into a 
discussion of its utility as revealing diseased conditions, such as 
without its use would remain unknown, or at least without a diag- 
nosis during life; and, whether the ophthalmoscope be of any 
benefit as to the therapeutics of impaired vision. 
Prior to Helmholtz’s discovery, there is but one case on record 
where the agency of external light was used in the investigation of 
diseases seated in the deep-seated structures,1 and oculists were able 
1 In Mackenzie's Practical Treatise, p. 508, 1840, the following may be found: 
“ I had under my care, at the Glasgow Eye Infirmary, a young man with incom- 
plete amaurosis in each eye. His vision had failed suddenly about two years 
before. At that time it was subject to frequent alterations, becoming suddenly 
diminished, and as suddenly regaining its usual acuteness. He complained of 
headache, with painful sensations over the body. He was troubled with red 
spectra before the left eye, but not before the right. The left eye was presbyopic, 
but with the right eye he perceived near objects more distinctly than distant ones. 
Deep in the right vitreous humor, a spotted opaque appearance was observed. On 
dilating the pupil by belladonna, it was evident that there were two sets of opaci- 
ties behind the lens. One, consisting of a central spot, with numerous opaque 
threads radiating from it, especially downwards and outwards, was situated exactly 
in the axis of the eye, and a little way behind the lens. The other opaque spot 
was much deeper in the eye, but without radii, and evidently moved up and down 
when the patient moved his eye. Each pupil possessed considerable power of 
motion, and there was no tremulousness of either iris. I considered the appear- 
ances in the right eye as indicative of inflammation of the hyaloid. In two sub- 
sequent cases, I have seen similar appearances. In one of these I discovered what I THE OPHTHALMOSCOPE. 
51 
to recognize only such diseases as were manifest to inspection, such 
as were seated upon the external parts of the eye, or anterior to 
the vitreous body, unless there existed some preternatural arrange- 
ment, as in Beer’s case of congenital absence of the iris above men- 
tioned. In rare instances some very expert diagnosticians observed 
a commencing cataract, but only after it had reached a compara- 
tively considerable size, for the simple thin strice recognized by 
the ophthalmoscope necessarily must have escaped the most rigid 
examination. 
As to recognizing the pathological conditions of the deep-seated 
parts, all diagnoses had to be made per exclusionem; and in all 
treatises upon the eye, with regard to the subjects of amaurosis 
and amblyopia, page after page is filled with the subjective symp- 
toms of diseased retina, optic nerve, and brain, as to the production 
of these diseases. Now, with regard to the discovery of the oph- 
thalmoscope, it is for ophthalmology what auscultation and percus- 
sion are for the physical exploration of general diseases, which were 
at first feeble in their results, producing but meagre benefits, but 
are at present mighty as a giant oak, towering far above the other 
trees in the forest of medicine. 
It is a principle of fundamental philosophy which holds good 
throughout the whole fabric of creation, that in order to remove 
an evil we must know its cause. It is upon this principle that 
therapeutics and diagnosis are based, and the former resting upon 
experience, begins where the latter ends, and when diagnosis fails 
there is no rational therapeutics: even empirical therapeutics loses 
all consideration if not based on sufficient differential diagnosis. A 
cure supervening upon any peculiar treatment, a question naturally 
arises, what has been cured ? Hence, every assistance in the ex- 
ploration of disease is a most welcome light in the search for truth, 
particularly when it renders us able to observe the changes in 
morbid structures, and associate them with functional derange- 
ments. Thus, it is with the ophthalmoscope 1 By it we are able 
to refer the evil to its cause, and boldly strike at its very root. 
Many, very many diseases of the eye, embraced under the head of 
considered the effects of hyaloiditis on diverting the light op a gas .iet through thk 
PUPIL WITH A LENS.” 
T. Wharton Jones, F. It. S., says: “Furthermore, Dr. Mackenzie tells me that 
by concentrating the daylight by means of a convex lens, he has seen red angular 
patches on the retina. The retina, when bulged forward and flapping in the dis- 
solved vitreous humor, can he well seen.” 52 
prize essay: 
nervous or amaurotic affections, whose nature was misunderstood) 
and whose treatment has led to many injudicious if not fatal conse- 
quences, have been proven by this instrument to be totally local, 
and not in the least referable to the brain. Take, for instance, 
an affection which has lately been discovered to have been fre- 
quently referred to a wrong cause, and consequently treated empiri- 
cally and irrationally. We refer to myodesopia or muscce volitantes, 
symptoms frequently met with in all kinds of medical practice. 
Yet, Mackenzie1 devotes twenty pages to the consideration of this 
subject, dividing it into sensitiva and insensitiva, and again subdi- 
viding it into other heads, learnedly descanting upon the various 
forms as depending upon a variety of causes, proposing prognoses 
and treatments, fixing their causes in the brain, the optic nerve, 
retina, vitreous body, lens, cornea, and aqueous humor; and, still 
Mackenzie is about the highest authority we have upon the subject 
of eye diseases. Many hundreds, yea thousands of practitioners 
strictly follow him to the letter as regards treatment, etc., blindly 
following his directions, and urging onward the unhappy victim of 
misplaced confidence. Visions of cupping, bleeding, leeching, and 
purging, rise in ghastly array! Setons and blisters, fell caustics 
and rank poisons follow on, swelling the list in horrible numbers! 
Turn we away from the unhappy picture, and behold the brighter 
side! These formidable muscce, which for years past have arisen 
from a mind diseased, are, by the ophthalmoscope, brought to their 
proper sphere, for Desmarres, Graefe, Donders, Arlt, and Van Trigt, 
have found that the greatest number of these cases were nothing 
more than a commencing cataract, or probably some floating parti- 
cles in the vitreous body, or punctiform blood-spots, or an entozoon 
upon the retina, or a hopeless disease of the choroid, or an altera- 
tion in the papilla of the optic nerve. And all of these diseases 
deserve at least a different treatment, which is rather negative than 
otherwise; and, if the ophthalmoscope has not induced a curative 
treatment or beneficial therapeutics, it has at least saved many an 
unfortunate individual from an useless course of medicine. For 
who would treat any of these affections (save, perhaps, punctiform 
blood-spots upon the retina) in a constitutional manner? Certainly 
no one! Yet, reason and the severest inductive analysis would tell 
us to so do, as the seat of reason, “the dome of thought and palace 
of the soul,” affect such symptoms when deranged ; but, fortunately 
1 A Practical Treatise on the Diseases of the Eye, by William Mackenzie, M. D., 
loc. cit. THE OPHTHALMOSCOPE. 
53 
we call in the aid of a little yet mighty instrument, the ophthal- 
moscope, and see if the patient need the fearful array of implements 
necessary to beat down inflammation of the brain and its mem- 
branes, or whether the troubled mind of a fellow being can be 
alleviated by the sweet assurance that he is not vitally hurt, and 
that useless medication need not be persisted in, as it is a sure 
precursor to after-constitutional diseases. The same remarks are 
pertinent to various other affections of the eye, as brain diseases 
present all the symptoms which are also met with in extra-cerebral 
diseases of the inner portions of the eye. Such, for instance, as the 
appearance of a black cloud hiding a portion, if not the whole of 
objects from the vision of the patient, or a crossing myopia, w'hich 
is the apparent crossing of objects seen at a little distance. The 
ophthalmoscope has discovered the latter symptom to be due to a 
posterior sclero-choroiditis, and the former to a variety of pathological 
conditions, more particularly, however, to a detachment of the retina. 
Yet, how many treat these diseases empirically, not knowing what 
they do, and still at the same time are high-minded, honorable, and 
conscientious physicians. These lamentable facts are but stronger 
reasons why we should hasten to avail ourselves of every means of 
physical exploration, as applicable to the cure of disease, and of 
alleviating suffering humanity, advancing our science to a rapidly 
approaching perfection, and thereby promoting the moral tone, the 
honor, and the ability of the profession, so that each individual 
may become an ornament to society, a healthful member of the 
body politic, and by his integrity let it be said of him, dux hominum 
medicus est. 
As above mentioned, one of the greatest advantages which the 
ophthalmoscope offers, is the ready recognition of cerebral and extra- 
cerebral amaurosis (so called), for a physical exploration of the eye 
immediately reveals whether or not it be the seat of disease or of 
derangement. 
With one who is skilled in the ophthalmoscopic art, how easy 
it is to save the willing patient from “a course of mercury,” holding 
out as hopeful a hopeless termination. One of the first principles 
of the morale of the science of medicine is to alleviate, not to harm. 
We shudder to think of the baneful errors committed in the name of 
medicine, and yet would be the last to say that they were know- 
ingly so done, hence we grasp with avidity all diagnostic helps, and 
cry out with thanks to their inventors. Humanity thanks Helm- 
holtz, medicine honors him, and charity lauds him as a benefactor! 54 
prize essay: 
Who would, possessing ophthalmoscopic knowledge, treat spark- 
ling synchisis of the vitreous body, formative cataract stride of the 
lens, mnscce volitantes arising from entohyaloid bodies, and a thou- 
sand and one other amblyopias with mercury ? No one of con- 
science, yet we do it, promising a cure to the patient, at the same 
time defibrinating him, entailing untold miseries upon him and his 
offspring unborn. Ay, frequently does the physician, from an in- 
correct diagnosis, become the instrument of the revelation of the 
prophecy, that the sins of the father shall descend to his children, 
even unto the third generation. Witness the various statistical 
reports of surgical operations throughout the whole of the civilized 
world, and there count how many are attributed to mercury! Do 
not think that we decry mercury, far from it, we look upon it as 
one of the most useful remedies in the whole pharmacopoeia, yet 
when unskilfully and wrongly used, it becomes as fire in a powkler 
magazine. Thus, much of the unskilful application of mercury 
may be avoided by a judicious use of the little yet mighty ophthal- 
moscope ! 
Henceforth the words “amaurosis” and “amblyopia” maybe ex- 
pelled from the dignified positions which they formerly held in the 
category of diseases, and always known as symptoms only, of the 
numerous affections recognized by the potent instrument in ques- 
tion. Amaurosis and amblyopia may be considered symptomatic 
of cerebral disease; of hyperaemia, anaemia, atrophy and hypertro- 
phy of the papilla of the optic nerve; of detachment, oedema, in- 
flammation, congestion and apoplexy of the retina; in fact of the 
various pathological conditions which will be sketched further on. 
Included among the primary results above mentioned, to the pa- 
thologist, accruing from the use of the instrument, there are also 
many secondary beneficial results which assist the surgeon, as to 
the propriety of operating for the various diseases requiring such 
interference. 
We are now prepared to enter upon the consideration of some of 
the anomalies of vision as revealed by the ophthalmoscope, or 
rather to sketch the pathological conditions of the various parts of 
the eye as seen by means of this instrument which constitute the 
OPIITHALMOSCOPICAL APPEARANCES OF THE ABNORMAL OR 
UNHEALTHY EYE. 
Omitting the diseases of the cornea and the aqueous humor, to- 
gether with the entozoa found there, we proceed to glance at the 
affections of the THE OPHTHALMOSCOPE. 
55 
Crystalline Lens.—The most frequent diseases of this body are 
what are known as lenticular and capsular cataracts, and at certain 
stages of development are readily recognized -without any aid to 
the naked eye. Frequently, however, the surgeon is consulted at 
a very early stage in the progress of the disease, and a judicious 
examination may save the patient a considerable degree of useless 
medication for muscce volitantes. At this stage the surgeon will see 
(after having well dilated the pupil with atropine, and using a light, 
less intense than such as is used to explore the deeper structures) 
delicate cataract striae, either in the centre or upon the circumference. 
The method of detecting the seat of these striae is the result of a 
per exclusioneum reasoning. The patient is directed to turn his eye 
upwards, and the streak upon the posterior portion either of the 
capsule or lens, instead of being dragged upwards as if it were on 
the anterior surface, is on the contrary depressed from its pre-ob- 
served situation, so much so that it becomes hidden behind the 
inferior segment of the iris. If the patient looks downwards, the 
reverse of this takes place. The catoptrical test of Purkinje answers 
very well for all cataracts after a certain period of development, 
but it cannot demonstrate as does the ophthalmoscope, the forma- 
tive stages, such as the striae above mentioned, the presence of a 
very slight false membrane, or of pigmentary cataract, which con- 
sists in the deposition of pigment granules within the substance of 
the lens, which, according to Desmarres, constitutes more than 30 
per cent, of so called muscce volitantes. Anaemia of the choroid is 
most generally associated with opacity of the lens, for vision does 
not solely depend upon the amount of light, but frequently upon 
the quantity of blood in the various tunics; and, the greater the 
amount of blood, less than congestion, the better the sight, owing 
to the relation between all parts of the eye. To observe the affec- 
tions of the vitreous body, the use of the bi-convex lens may be dis- 
pensed with. The most frequently observed affections of this 
medium are sanguineous effusions, floating bodies, glistening or spark- 
ling synchisis, and urinoid turbidity. 
A. Sanguineous effusions are most frequently the result of a rup- 
ture of the vessels of the retina, or a sub-retinal apoplexy produc- 
ing a rupture of that tunic, thereby permitting the blood to be 
effused within the substance of the vitreous body. Farther on we 
propose to give the differential diagnosis between an effusion of 
blood within this medium and a sub-retinal effusion. 
B. Floating bodies are free and mobile, of variable forms and prize essay: 
dimensions, most generally seen as minute corpuscles. These cor- 
puscles are either the debris of a sanguineous effusion, or are fibrino- 
albuminous exudations the results of a previous inflammation, and 
appear black in consequence of the absorption of the refracted 
light. Perhaps these corpuscles are the combined results of all of 
the above mentioned causes. However, whatever be their nature, 
they are seen flying about, as it were, within the vitreous body 
when the eye is in motion, appearing and disappearing at each 
moment. These floating bodies are generally connected with a 
preternatural fluidity of the vitreous. What is the normal fluidity 
of the vitreous has not as yet been determined; and, in a healthy 
eye, no mobility or fluidity can be perceived. In the majority of 
cases where these floating bodies have been observed with fluidity 
of the vitreous, it was referable to some antecedent syphilitic taint. 
These corpuscles may sometimes be confounded with cataract-striae 
of the lens, but a little attention may prevent such an error. Thus, 
if the patient be told to look alternately upon two fixed points the 
cataract-striae will be seen to be moving always in the same direc- 
tion, but if the abnormal products be corpuscular floating bodies, 
they will be seen swimming about in various directions, never the 
same. 
Sometimes the papilla of the optic nerve, in short-sighted indi- 
viduals, is mistaken for a free foreign body within the vitreous. 
This may be detected by using a bi-convex lens, and causing the 
patient to execute slow lateral movements of the eye, when the 
assumed foreign body will be seen to be moving always in the 
same direction, possessing the uniform silvery white color, charac- 
teristic of the entrance of the optic nerve. Sometimes these floating 
substances assume an arachnoid appearance, having either free or 
attached borders, sometimes both. Again, they may be one or two, 
or several distinct masses of shreddy gray exudation-plasma, and 
may even hang pendant like a curtain. This complication affects 
vision less than do many small bodies moving about in all direc- 
tions. Another complication is, 
C. Glistening synchisis (Svyyiws, from I mingle), which 
consists of the presence of a number of small scales or crystals of 
cholesterin. Desmarres was the first to describe this affection, and 
he observed it to be frequently complicated with other floating 
bodies. When the complication exists, an ophthalmoscopical exa- 
mination reveals a most beautiful sight, for the glittering cholesterin 
scales, by their reflection, act upon the other bodies, giving them THE OPHTHALMOSCOPE. 
57 
the most brilliant hues of the rainbow, and the scales themselves 
present a more beautiful exhibition of natural pyrotechnics than 
artifice can possibly devise. 
T). The last form of floating bodies consists in an urinoid turbidity1 
of the vitreous humor. Desmarres reports the only cases on record 
of this affection, which consists of a more or less notable quantity 
of microscopical corpuscles, giving the vitreous the appearance of 
the urine of herbivorous animals. These corpuscles are composed 
of an albumino-fibrinous exudation, the result of a previous inflam- 
mation. 
As to the treatment of these various affections of the vitreous 
body, it consists in the prevention of medication: it would be just 
as probable to see a man’s head absorbed as many of these floating 
bodies. 
The diseases recognized by an ophthalmoscopical examination 
of the retina are either simple or complicated, that is to say, they are 
seated in the retina only, or extend to other structures. We pro- 
pose noticing the simple ones only: the complicated ones will be 
described when the affections of the other structures are entertained. 
The simple diseases are oedema, anaemia, hypercemia, separation or de- 
tachment, and apoplexy. 
(Edema is the result of a sub-retinal serous infiltration, referable 
to some obstruction of the circulation, either mechanical or other- 
wise. The ophthalmoscope reveals a swelling, circular in form, 
surrounding the papilla of the optic nerve, somewhat raised above 
the other parts of the membrane, and whitish in color, with very 
minute punctiform blood-spots scattered through it. This oedema 
is sometimes associated with sub-retinal apoplexy, and is frequently 
seen when there is either papillary or retinal hypersemia, or both. 
Desmarres frequently diagnosticates morbus Brightii, or at least 
suspects it, when there is considerable amblyopia and other con- 
comitant constitutional symptoms, and when oedema retinae is revealed 
by the ophthalmoscope. We have frequently seen the French ocu- 
list detect albumen in the urine of such patiChts. Donders, of 
Utrecht, has likewise observed the same pathological changes in 
the retina, and upon several post-mortem examinations he has de- 
1 Desmarres calls this condition, etat jumenteux du corps vitrt: as there is no 
word in English corresponding to jumenteux, an adjective from the substantive 
jument, a mare, we metonomyze, as it were, a translation, and render it “urinoid 
turbidity,” as the urine of the mare, as well as of all herbivorous animals, is more 
or less turbid. 58 
prize essay: 
tected fat globules deposited therein: hence, he called oedema of 
the retina, attendant upon morbus Brightii, fatty degeneration of the 
retina. The treatment, as a consequence, is necessarily ad expectan- 
dum, and must be followed upon general principles. In albumi- 
nuria—the writer has seen several cases (one in Paris and three 
in the United States), wherein an ophthalmoscopical examination 
revealed a deposition of pigmentum between the forks or divisions 
of the vessels upon the retina. (Vide Appendix, Fig. X.) 
Ancemia retince is a consequence (most generally) of a constitutional 
anaemia, or it may be partial and dependent upon some local cause. 
The ophthalmoscope reveals a general paleness, either of the whole 
retina or of a part, as either one or the other is affected, and in 
proportion as is the anaemia so is the pallor: the vessels are smaller 
than normal, so small sometimes as to appear perfectly empty, and 
the arterial pulsations cannot be detected. The affection is charac- 
terized by more or less amblyopia, and sometimes by a complete 
amaurosis. The treatment is by tonics, more especially the chaly- 
beates, fresh air, generous diet, etc. The patient should be particu- 
larly guarded against using his eyes in such a manner as to overtask 
them: the writer has frequently seen incurable anasmic congestions 
of the retina result from such imprudences. 
Hypercernia retince (Fig. XI., Appendix.) is the most common of all 
intra-ocular lesions, and at the cliniques of Desmarres and Sichel, in 
Paris, and the Augenklinik of Grraefe, of Berlin, hundreds of patients 
thus affected present themselves during the year. One half of the 
ophthalmoscopical observations noted in Desmarres’s case-book in- 
dicate this lesion: during a three months’ course there, the writer 
has notes of over forty sucli cases, the majority of whom were 
women who sewed for a livelihood, and the others were made up of 
artisans whose labor required a considerable degree of fixedness of 
sight upon small objects, such as engravers, printers, instrument 
and watchmakers, jewellers, etc. etc. There also were glass- 
blowers, cooks, bakers, etc., who are particularly prone to all intra- 
ocular diseases from the varying intensity of heat and light to 
which they are subjected. The second category embraces those, 
whose amblyopia is readily explained by a mechanico physiological 
over-use of the eye; whereas the first class and by far the greatest 
number of amblyopics are sewing-girls, tailors, etc., who, to the 
causes pertinent to the second class, have added a sedentary life, 
close and heated rooms, everything in fact tending to a cachectic 
disposition or habit, inducing local hypercemias, congestions, and in- THE OPHTHALMOSCOPE. 
59 
flammations; and the retina is by election, as it were, the most fre- 
quent seat of such changes in the eye, in the quantity and quality 
of the blood. 
The ophthalmoscope reveals a turgidity of all the vessels, a 
marked injection of the veins in particular, of which there is a 
fresh crop developed by the increase and dilatation of the capilla- 
ries. The retina proper loses, in a measure, its brilliant transpa- 
rency, and becomes of a deeper red, and looks drier than normally. 
The most frequent complication is a hyperaemia of the papilla of the 
optic nerve, of which more anon. 
Were it not for the ophthalmoscope this affection would not be 
recognized (at least by any external evidence), for at first the symp- 
tomatic amblyopia is but slight, and it is here that therapeutics 
come to the rescue, and save perhaps an ulterior destruction of 
the functions of vision. A proper and judicious course of mer- 
cury, joined to other antiphlogistic remedies, at this stage is of the 
first importance; but, if the hypersemia should have gone beyond, 
to a condition of apoplexy or of detachment of the retina, then, as 
before mentioned, mercury is but an useless and baneful remedy. 
Other frequent complications are, the oedema above noticed, hyperce- 
mia of the choroid, sub-retinal apoplexy, atrophy of the papilla, and 
posterior sclero-choroiditis. 
Detachment of the retina from superjacent parts is an affection of 
more frequent occurrence than is generally supposed; yet some of 
the latest writers on the subject of the diseases of the eye hardly 
more than refer to it. Mackenzie indicates such an affection, Nela- 
ton1 describes it only when it has reached such a degree of severity, 
that the whole retina is floating in the vitreous humor, so as to be 
readily recognized behind the lens: he advises the method of Mr. 
Ware, of making an exploratory puncture, to see if this foreign 
floating body really be a cataract or not. Desmarres,3 in his first 
edition, gave a more detailed description of the affection, but like 
Ndlaton he spoke only of such cases as were easily appreciated by 
the surgeon’s eye alone. At present, all of the European oculists 
use the ophthalmoscope, as being absolutely necessary to recognize 
with precision such a pathological condition of the retina as a de- 
tachment would present. Eor, as above mentioned, when speaking 
of the utility of the instrument, we noticed the benefits accruing 
from an early recognition of any intra-ocular lesion whatsoever, and 
1 Nelaton, Elements de. Patholog. Chirurg., t. iii. p. 212. 
2 Desmarres, Traite Tlieor. et Prat, des Maladies des Yeux, p. 710. 60 
prize essay: 
at present, in considering a disease, the ulterior termination of 
which is a certain destruction of sight, it is of the greatest import- 
ance to diagnosticate it at the very beginning. For, according to 
Desmarres and others, an early diagnosis of the disease sometimes 
brings about a cure, and judicious treatment may induce an ab- 
sorption of either the serum or blood effused which produces the 
disease, and this being done, the retina recovers its healthy tone. 
The rational symptoms generally come on in a regular order: 
the patient at first perceives luminous images as a result of the 
compression made upon the retina by the effusion. These images 
frequently affect the various colors of the prism; sometimes they 
are seen as through a colored veil, of a relative and proportional 
size corresponding to the effusion. Later the patient is struck 
with sudden blindness, all before him appears as black as night, or, 
if not so complete as total blindness, a dark cloud screens a portion 
of objects within his field of vision. In some instances he can trace 
the shape of the screen, which corresponds to the effusion upon the 
retina (in shape), as seen by the ophthalmoscope. The phosphines 
before mentioned are recognizable if there be not complete anaes- 
thesia of the retina, and as is the seat of these luminous rings, so 
is the chance of a recovery of complete vision, provided the ab- 
sorption of the effusion can be induced. 
There are two kinds of retinal detachments, referable to the effu- 
sion of either serum or blood. Physical or ophthalmoscopical symp- 
toms. In order to recognize these detachments, it is not always 
absolutely necessary to use the bi-convex lens, and when the de- 
tached portion is seen, it is well to cause the patient to execute 
rapidly certain lateral and vertical movements of the eye, when the 
tumor will be recognized. 
A. Detachment as a result of a serous effusion. The base of the 
eye presents a tumor of a whitish, or bluish, or grayish, or even 
reddish color, of a variable form and dimension: the tumor pre- 
sents some red lines, which are the vessels of the retina furrowing 
it even in its abnormal projection beyond its natural plane. Some- 
times the retina is of a dull white color, presenting the appearance 
of a false membrane, but the presence of the vessels and the sud- 
denness of the attack would preclude such a supposition. Upon a 
careful examination the detached portion may be seen floating in 
the vitreous humor, and with a bi-convex lens the line of separa- 
tion, between the detached tumor and the retina in its place, may 
readily be traced by fixing one of the vessels, and following its THE OPHTHALMOSCOPE. 
61 
course until it suddenly bends, as it were, upon itself. Having 
thus done, the tumor presents itself frequently as an opaque body, 
not glistening and shining as does the normal and healthy retina 
lying in its proper position. This condition may be complicated 
with any or all of the other intra-ocular diseases. 
B. Detachment as the result of a sanguineous effusion, or sub- 
retinal apoplexy. The rational symptoms are pretty much the 
same as in detachments, the results of serous infiltration, with this 
difference, that they are more sudden. The cause is a rupture of 
one or more of the swollen, turgid, or diseased vessels of the cho- 
roid, happening most frequently in that pathological condition 
denominated by Graefe, of Berlin, as posterior sclero-choroiditis. A 
sudden rupture of a vessel behind the retina, rolls this tunic (by 
the accumulation of blood between it and the choroid), forward 
into the vitreous humor. An ophthalmoscopical examination re- 
veals, in such an instance, a tumor of a deep red color, formed by 
the prominent retina; the blood itself may be seen through its 
walls, the retinal vessels are seen furrowing it, and trembling, as 
does the mass, when the movements of the eye are communicated 
to it. The conditions of the parts do not always thus remain; fre- 
quently the effusion is much increased, so much as to interfere with 
the nutrition of the retina, in such a manner as to produce its 
entire absorption in one, or several spots, or its bursting or rup- 
turing, causing an effusion of blood into the vitreous humor, where, 
later, it forms one species of foreign bodies above mentioned. Some- 
times these effusions do not produce a tumor, but are extravasated 
under the retina, and pass forward to be evacuated, as it were, from 
the ora serrata1 to be adapted to the fossa hyaloidea, presenting a 
concavity, as if the whole vitreous humor were completely filled 
with blood. The fixedness, however, of this concavity precludes 
its being within the vitreous, as all foreign bodies partake more or 
less of the mobility of that body. Desmarres, after many ophthal- 
moscopical examinations, has discovered a new rational symptom, 
which is still a physical sign of sub-retinal sanguineous effusions, 
viz., a preservation of all the characteristics of the iris, save its 
color, which becomes of a dirty green color, owing to an overdue 
compression exercised by the effused blood. These effusions fre- 
quently undergo variations of color, being at first of a deep red, 
then of a light pink, afterwards of a muddy yellow, and finally 
gray; these transformations in color being nothing more than the 
usual changes undergone by subserous effusions of blood. When 62 
prize essay: 
these effusions are not, or are only partially absorbed, an inflamma- 
tion is set up around, exudative most generally in its character, and 
false membranes are formed; a choroiditis ensues, followed by a 
maceration of the pigmentum, inducing most serious and incurable 
derangements in the functions of vision. As in serous effusions, 
relapses from a partial cure of sanguineous effusions are not per- 
ceived by the patient, who, nolens volens, becomes totally amaurotic, 
applies to an oculist not using the ophthalmoscope, is put upon a 
“ course of mercury,” undergoes that treatment for six months or 
more, and finishes disgusted, defibrinated, shattered in constitution, 
low in spirits, and not so well in health as when he commenced! 
Apoplexy of the retina is an effusion of blood into the substance 
proper of the retina. It is extremely rare, and but few cases of it 
are on record. The rational symptoms are those of sub-retinal 
apoplexy, or detachment of that structure from sanguineous effu- 
sions, with the exception of being sudden and more complete. The 
physical or ophthalmoscopical signs are, a normal and healthy ap- 
pearance of the transparent media (the cornea, aqueous and vitreous 
humors, and crystalline lens); the retina is completely discolored, 
the optic nerve and macula lutea invisible; the position of the for- 
mer is only recognizable by the ruptured vessels being there traced. 
Numerous clots are seen hanging upon the coats of the vessels, and 
projecting into the vitreous body. Liebrich1 has detailed a very 
interesting case of apoplexy of the retina, but space will not per- 
mit of its being quoted. 
The papilla of the optic nerve is subject to various alterations, 
discovered by the ophthalmoscope; viz., hypercemia, anaemia, hyper- 
trophy, atrophy, and prominence. 
With regard to the exploration of the diseases of the papilla, a 
bi-convex lens is absolutely indispensable. The rational symptoms 
are altogether negative, indicating nothing more than possibly can 
be attributed to other intra-ocular lesions. The physical signs are 
such that, by an ophthalmoscopical examination, an early diag- 
nosis may be made, a judicious treatment given, and a cure effected. 
Ilypercemia papilla. ( Vide Fig. XI., Appendix.) The ophthalmo- 
scope reveals in this pathological condition, a loss of the bright 
shining whiteness of the normal papilla, which, from an over-de- 
velopment of the vessels, becomes red, varying from a rose-pink 
tint, to the deepest scarlet. In the less serious congestions, the 
color is of a light pink, and the papilla is seen as through a gauze 
1 Arcliiv. Ophtli. Graefe, Donders und Arlt, B. I. s. ii. p. 346. THE OPHTHALMOSCOPE. 
63 
veil; but, in the more serious ones, it is completely hidden by the 
numerous distended vessels, and its position is only known by the 
fact, that the vessels spring from, and enter about its centre. In 
some few cases, however, a small portion of the papilla may be 
seen through the network of vessels covering it; in others, the 
vessels surround it in such a manner as to make it appear as if it 
were scooped out, not unlike the cornea in chemosis conjunctivas. 
Sometimes the veins are so turgid, that they present a varicose 
condition, constituting what is known as varix papillce, and varix 
retince, by no means rare affections, and readily recognized by pres- 
sure upon the ocular globe, which produces a prominence of the 
vessels, whereby their pulsations may be made visible. 
If the disease be attacked before exudations have formed, it 
generally yields to general and local antiphlogistic measures ; but, 
if the plasma should have done its work, the masonry of nature is 
not often removed from the spot upon which it has been deposited 
by the vis medicatrix. The exudations consecutive upon a hyperse- 
mia are the real causes which induce a blindness, and in such cases 
a course of mercury is warrantable, but fails more frequently than 
otherwise, not from the non-absorbability but from the various 
relapses, for after one hypermmia of any portion of the intra-ocular 
structure there is a tendency to another: the eye, in fact, is in the 
condition of an exudative crasis, viz: that condition which Eoki- 
tansky describes, when the system has a tendency to any peculiar 
lesion, such as the pneumonic crasis, the febrile crasis, etc. etc. 
Always, when there is hyperaemia of the papilla, there is a like 
condition of the retina; but the latter’s being thus affected does 
not necessarily imply such a one of the former. All of the other 
intra-ocular lesions before described may be, and sometimes are 
associated with hyperaemia of the papilla. 
Anaemia papillce is a condition quite the reverse of the preceding, 
and is characterized by a diminution in the calibre of the vessels, 
or even their complete absence. The normal color is absent, and 
there is a marked paleness in the whole of the surrounding struc- 
tures. Anaemia of the retina is attendant upon anaemia of the 
papilla, and vice versa. 
Hypertrophia papillce has been observed but once, at least there 
is only one case on record,1 and in this case the conditions of the 
apparatus of vision were healthy, save an increase in the size of 
1 Medico Chirurgical Review, April, 1855, p. 386. 64 
prize essay: 
the papilla, its diameter being about seven lines. “ The patient, 
who was a vigorous man, without any known cause had lost all 
sensibility to light.” 
A trophia papillae is totally the reverse of the last-named affection, 
and is a disease known only since the discovery of the ophthalmo- 
scope. It is an infallible symptom of cerebral affection, and the 
amaurosis which it entails is altogether organic, dependent upon 
some interference with the nutrition of the optic nerve. In such a 
condition the ophthalmoscope reveals a most marked diminution 
in the size of the papilla, which seems shrunk and shrivelled. The 
retina also partakes slightly of this shrivelled appearance. This 
atrophy is nothing more or less than a paralysis of the nerve, which 
may be complete or incomplete. The treatment of this lesion de- 
pends upon the cause, and all therapeutics must be directed towards 
it. It may be congestion, inflammation, tuberculosis, ramollisse- 
ment, the presence of a tumor, in fact any disease of the brain; 
and to the treatment of the cause the result of the amaurosis must 
tend. 
Prominence of the papilla is one of the gravest of affections, and 
as it is beyond the resources of therapeutics or surgery, it is well 
to be able to diagnosticate it from the beginning, for many reasons 
above mentioned. The ophthalmoscope shows a shaded ring all 
around the papillary circumference, owing to its overhanging the 
choroid. The bloodvessels, which in the normal condition proceed 
in rather direct lines from the centre of the papilla, in this condi- 
tion, after reaching its circumference, are bent down, and completely 
hidden under the margin ; they are so abruptly bent as to give the 
appearance of having been cut away: a line or so from the margin 
they make their reappearance. Prominence of the papilla is most 
generally associated with posterior sclero-choroiditis, although the 
latter is not always met with in conjunction with the former: hy- 
persemia and anaemia are not unfrequently associated with it. In 
fact all of the intra-ocular lesions are so apt to be blended together, 
that it is rather a rarity than otherwise to find a purely uncom- 
plicated case of a lesion of any one of the internal structures of 
the eye. 
The pathological conditions of the choroid, as revealed by the 
ophthalmoscope, constitute some of the most interesting discoveries 
in ophthalmology, and the researches instituted by modern inves- 
tigators upon the subject are worthy the attention not only of the 
oculist, but of the general pathologist. The affections of the cho- 65 
THE OPHTHALMOSCOPE. 
roid, as classified by the latest authorities, are choroiditis, and pos- 
terior sclero-choroiditis. 
Choroiditis is acute and chronic. The symptoms by which acute 
choroiditis was recognized prior to the discovery of the ophthal- 
moscope, or the indications furnished by an inspection of the ex- 
ternal portions of the globe were (and are now) as follows: The 
patient complains of a severe shooting and pulsating pain within 
the eye and the surrounding parts on that side of the head *. this 
pain intermits, and is very much exaggerated during the night. 
Photophobia is one of the earliest and most constant symptoms, 
as well as excessive lachrymation. Photopsia or spontaneous 
flashes of light are frequent, for the patient complains of such 
flashes of brilliant yellowish and reddish light, even when in ob- 
scurity. All motions, either of the eyeball or of the body, are 
attended with acute pain. The ocular globe, felt through the lids, 
is as hard as rock, and the slightest touch thereon produces violent 
pain. If it be possible to obtain a view of the eye in such a con- 
dition, the sub-conjunctival and sclerotical vessels are found to be 
slightly injected, the larger exterior vessels anastomosing around 
the cornea, and (according to Mackenzie) are in a state of passive 
congestion. The whole white of the eye presents a dirty yellowish 
aspect. The cornea is frequently cloudy and hazy, and sometimes 
rough, and the edge presents a milky bluish aspect, owing to the 
overlapping of the sclerotica. The iris is at first in a state of con- 
traction, presenting a dirty green color, but soon assumes a slate 
color, and is permanently dilated, often misshapen and ragged. In 
acute choroiditis the ophthalmoscope reveals a great deal, but to 
make a thorough examination it is absolutely necessary to chloro- 
form the patient, as the involuntary contraction of the palpebral 
muscles, and the intense photophobia, render it impossible without 
the aid of anaesthetics. The retina rarely, if ever, escapes being 
complicated with the inflamed choroid; hence, in an ophthalmo- 
scopical examination the appearances are pretty much the same as 
in retinitis or hyperaemia of the retina, with the exception of a very 
peculiar rolling, as it were, of the pigmentum into irregular bun- 
dles, which completely destroys the before-mentioned radiated 
arrangement of that substance. The treatment in these instances 
requires the most active antiphlogistic measures and regimen, 
conjoined with opiates, and an excito-secretory expectant use of 
remedies. 66 
PRIZE ESSAY: 
The non-ophthalmoscopical symptoms of chronic choroiditis, such as 
are furnished by the feelings of the patient, and an examination of 
the external tunics of the eye, are as follows: The lesion makes its 
appearance slowly and step by step: a dull heavy pain is felt 
in the eye and circumorbital regions, photopsia, slight photopho- 
bia, and iridescent vision daily become of a more alarming cha- 
racter. The sub-conjunctival vessels are injected, and become very 
tortuous and varicose, the iris loses its normal appearance and as- 
sumes a dirty lead color. Later the sclerotic becomes thinner by 
interstitial absorption, and presents a blue or even dark color: in 
certain spots it is much thinner than the surrounding tissue, and 
the choroid bulges forward, forming incomplete hernias of that 
membrane, true (so called) posterior staphyloma of the choroid. 
The eyeball becomes harder as the disease advances, which is just 
the reverse of what takes place in acute chronic retinitis. To sum 
up in a few words, the symptoms offered by chronic choroiditis, are 
the same as in acute choroiditis, being, however, of a milder type. 
Conditions of the Parts in Chronic Choroiditis as seen by the Ophthal- 
moscope.—After having examined the transparent media, as should 
always be done prior to the deep research, the entrance of the optic 
nerve is sought for, as well as the yellow spot of Soemmering, which 
being found, the rest of the examination is made with a greater de- 
gree of certainty. And as the congestion or inflammation is of an 
active or passive character, so are the appearances presented by the 
parts, more particularly as regards the bloodvessels than the other 
structures. In an active or sthenic congestion the choroid is of a 
very bright red color, approaching to a vermilion or scarlet tint—- 
the arteries and veins upon the retina numerous, following the 
normal disposition and maintaining their normal size. The trans- 
parent media assume a very brilliant appearance, owing to the mo- 
mentum of the red rays of light: frequently the lens is affected with 
undulating and transverse strise, which are not cataract-strim, as 
they disappear if the choroiditis be ameliorated. There is always 
a slight maceration of the pigmentum in this form of choroiditis. 
In the passive or asthenic condition, the choroid is of a dirty dark 
red, approaching to a leaden hue, and is covered by numerous 
spots of brownish red pigmentum. Upon the retina numerous 
swollen, turgid and tortuous veins are seen, whereas there are very 
few small and thin arteries. The crystalline lens and vitreous body 
are muddy, often glaucomatous, and in the latter, shreds of detached 
retina and pigment cells are seen floating. These pigment cells THE OPHTHALMOSCOPE. 
67 
floating in the vitreous body constitute one of the characters of 
maceration of the pigmentum. 
This condition is readily understood by its name: it consists of 
a detachment of a greater or less quantity of pigmentum, and a 
derangement of the normal radiated appearance of that substance : 
there is a certain quantity rolled as it were upon itself, which pre- 
sents a brownish black appearance with ragged edges. Wherever 
there is a detachment of this pigment, the white sclerotic is seen 
through the somewhat hazy retina, presenting white patches which 
reflect the light. This maceration of the pigmentum at once ex- 
plains the photopsia and other peculiar symptoms with regard to 
deranged sensation, as referred by the patient. Thus a confusion 
of images is explained by there being a reflection of light from the 
retina, which has no pigmentum behind it to absorb a superabund- 
ance of the luminous rays, which are reflected in various ways 
upon different parts of the retina, thereby producing a confusion 
of images. Again where the pigmentum is detached as in the last 
instance, the retina is extremely sensitive, and is affected by a very 
moderate light, hence the photopsia and iridescent vision. This 
exquisite sensitiveness of the retina, finishes by a complete anes- 
thesia of such parts as are deprived of pigmentum. One of the 
most dreaded results of a lesion of the choroid is an exudative in- 
flammation, which explains the anesthesia in question; for, wher- 
ever there is a maceration of the pigmentum, the exudation takes 
place, as it were, by election, and pressing upon the retina from 
behind, causes it to bulge forward into the vitreous body. This 
pressure being constant, generally ends by a complete change in 
the structure of the retina, causing it to become opaque or hazy 
from an effusion of lymph, or the contrary takes place and the re- 
tina bursts, allowing the pigment granules and cells to enter the 
substance of the vitreous body. This latter complication is more 
frequently met with in passive or asthenic inflammation than in 
the other conditions of active or sthenic choroiditis. The explana- 
tion of the entrance of these pigment particles into the vitreous 
body, at once accounts for the mv.scce volitantes so frequently met 
with, as symptomatic of diseased brain> and which, combined with 
the other symptoms of choroiditis would lead us to anticipate a 
lesion rather more fatal to life than eye disease. It is very, nay 
absolutely necessary, in choroiditis to use the ophthalmoscope in 
the formation of a diagnosis and prognosis; and, it would be use- 
less for us to reiterate what we have frequently before advanced,. 68 
prize essay: 
viz., the baneful results of a mistaken diagnosis, and of the misap- 
prehension of brain disease for eye disease, and vice versa. There 
yet remains to be described an affection, which, in point of fre- 
quency of occurrence, and interest to the special and general pa- 
thologist, is worthy of the greatest attention, viz :— 
Posterior Sclero-choroiditis.—Graefe,1 of Berlin, was the first to call 
attention to this disease, and as such deserves the thanks of the 
profession, not only for his Herculean labors in this field, but 
also for his manifold works in the ophthalmological science. His 
statistics, with regard to the disease in question, have been confirmed 
by Arlt, of Prague, Donders, of Utrecht, and Desmarres, of Paris. 
Graefe found that out of one thousand cases of so-called amblyopia, 
four hundred and twenty (42 per cent.) were connected with a pos- 
terior sclero-choroiditis. Another remarkable point in connection 
with the disease, is that short-sighted persons more particularly 
labor under this disease than any other class. Graefe states that 
myopics who use concave glasses ranging from two to six (German 
enumeration), nine out of every ten (90 per cent.) possess this lesion. 
The writer would state that he saw many such cases at the cliniques 
of Desmarres, and all, with but one exception, were myopic. Since 
the discovery of the disease by the ophthalmoscope, we are enabled, 
without this instrument, to at least suspect the presence of the 
disease through subjective phenomena. Thus, a patient presents 
himself, complaining of either amblyopia or amaurosis, which is 
symptomatic of what ? A farther interrogation reveals that myopia 
has been constant from the beginning, or at least the short-sight- 
edness was the first symptom through which the disease was first 
noticed, and that it increases; that the examination of near and 
small objects becomes painful, and finally, as the disease becomes 
more developed, the use of concave glasses is altogether hurtful, 
and becomes so much so that they have to be thrown aside. Pho- 
topsia, photophobia, iridescent vision, circumorbital, and orbital 
pains, develop themselves as described above, when speaking of 
acute and chronic choroiditis. What, then, is the nature of this 
disease? According to Graefe, who had, up to July, 1857, exa- 
mined over one thousand cases upon the living and dead, it consists 
of a co-existing inflammation, involving at the same time the scle- 
rotic and the choroid at the posterior portion of the orbit, hence 
his naming it posterior sclero-choroiditis. It might be objected that 
1 Archiv. Oplithal., Graefe, Donders, und Arlt, b. i. s. 390. THE OPHTHALMOSCOPE. 
69 
the word inflammation is a misnomer, but the hypersemia of the 
choroid, the alterations in the pigmentary secretion, the obliteration 
of the ciliary vessels discovered upon a post-mortem examination, 
the atrophy of the posterior portions of the choroid, the nutritive 
derangements of the vitreous body, frequently in a state of fluidity, 
the frequently observed complications of hemorrhages, and finally, 
the happy results obtained from an antiphlogistic plan of treatment, 
would, per exclusionem, induce us to believe that the disease was of 
an inflammatory nature. 
The complications of the disease are many, the most noted of 
which is a rupture of the choroidean vessels, producing a sangui- 
neous effusion under the retina. And the writer believes that the 
extension of inflammation from the sclerotic and choroid has less 
to do with the consecutive alterations than the effused blood. For, 
to this effusion, as we have above seen, are referable detachment, 
hypersemia, and anaesthesia of the retina, foreign and floating sub- 
stances in the vitreous body, cataract and other striae of the lens, 
and, in a word, all the diseases before mentioned as attacking the 
various structures of the eye. At the same time he would not pre- 
tend to say that all of these complications could not, and are not 
produced by an extension of inflammation from the affected tissues, 
as he well knows that such is frequently the case, but he believes 
the effused or extravasated blood to be the principal or chief casus. 
The ophthalmoscope reveals the pathological conditions upon 
which the so-called amblyopias and amauroses (to which the disease 
in question is referable) are dependent, and which are as follows: 
The bottom of the eye is more or less white, according as the 
disease is more or less extensive; this white patch is owing to a 
maceration of the pigmentum : it is irregular in shape, with fringed 
or ragged borders, if it be of a size greater than the papilla of the 
optic nerve. This brilliant white patch is the sclerotic made visible 
by the maceration of the pigmentum of the choroid, and were it 
not for the vessels seen furrowing the transparent retina, the pre- 
sence of that membrane would be altogether ignored. These ves- 
sels are so marked, so well defined upon the white ground of the 
sclerotic, that they seem to be enlarged and turgid from a hyperse- 
mic condition; but this is not the case, as they are really so small 
that they almost become lost upon that portion of the retina, where 
the choroid remains intact. A very peculiar deception exists in 
this disease, viz: the appearance as if the white patch were project- 
ing or prominent, whereas in reality it is just the reverse, presenting 70 
prize essay: 
a concavity forwards.1 This condition of affairs is very deceptive, 
and tends to an incorrect diagnosis: for one readily might mistake 
a maceration of the pigmentum for a plastic exudation, and vice 
versd. When the disease first makes its appearance it is with dif- 
ficulty recognized, as it most frequently appears at the juncture of 
the choroid and the papilla of the optic nerve, and may be readily 
confounded with the latter. As the disease advances, the size of 
the white patch increases, and it is particularly at this stage that it 
may be confounded with an hypertrophied papilla presenting rag- 
ged outlines; but a careful examination displays the normal papilla 
not being altered in size or appearance, and what was presumed to 
be a disorganized papilla proves to be the maceration of the pig- 
mentum. 
As the disease advances the patch enlarges, the outlines become 
more fringed and ragged, the anaesthesia of the retina increases, and 
the general visional functions more deranged. Having sketched 
posterior sclero-choroiditis as regards its pathology, it would be 
well to examine it as regards its connection with myopia. The 
frequency of the disease conjoined with myopia led Graefe to the 
conclusion, that the latter defect consisted in an enlargement of the 
antero-posterior axis of the ocular globe; post-mortem examinations 
having always revealed such a condition, and always when myopia 
and the disease in question were co-existent. Graefe’s conclusions 
were fallacious, and he reasoned by a vicious circle: thus, in cer- 
tain conditions of a diseased eye myopia exists, the eye in these 
conditions is lengthened antero posteriorly, therefore myopia de- 
pends upon the lengthened axis. Graefe, however, forgot that 
myopia exists without posterior sclero-choroiditis, and vice versa; 
and, if they can exist separately, they are in no wise absolutely de- 
pendent one upon the other. Besides, if posterior sclero-choroiditis 
be successfully treated, even in the earlier stages, if myopia had 
previously existed, the cure of the disease does not remedy the 
defect. From these facts the writer is led to believe that myopia 
and posterior sclero-choroiditis are frequently complicated and con- 
nected, but, that in the present condition of ophthalmoscopical 
science, it would be extremely difficult to say that one depended 
1 It should he borne in mind that in an ophthalmoscopical examination of the 
bottom of the eye, all white surfaces or spots appear as if in relief, and all dark or 
black ones seem to be scooped out or excavated. This condition of affairs is the 
rule, the reverse is the exception. THE OPHTHALMOSCOPE. 
71 
upon the other; and, that the remarks made in another part of 
this paper concerning myopia explains the defect in the only ra- 
tional manner, as far as observation has been able to determine. 
The Entozoa as yet met with in the eye are few, and of these 
only one species has been seen posterior to the lens, or has been 
discovered by the ophthalmoscope, viz., the Cysticercus telce cellulosce. 
The other entozoa which were seen by the naked eye of the ob- 
server, were the Filaria Medinensis (dranunculus, Guinea worm), a 
species of entozoa found in the tropical regions of Africa, two cases 
of which are reported by Dr. Loney, and one by Mongin.1 In Dr. 
Loney’s cases, the worms were extracted alive from the inner cir- 
cumference of the cornea, and each measured two inches in length. 
Filaria oculi humani.—Dr. Nordman, of Odessa, detected in a lens 
extracted by Graefe, Sr., two very delicate and small rings, which 
upon a microscopical examination proved to be filarige.2 
Monostoma oculi humani.—Dr. Nordman reports the discovery of 
eight specimens of this species in an extracted lens.3 
Distoma oculi humani.—Gescheidt and Ammon found four of 
these entozoa in an extracted lens.4 
Echino coccus homini.—This entozoon has been frequently met 
with in the areolar tissue surrounding the orbit; but Mr. Bowman5 
relates two cases of its being found within the orbit. Mr. Lawrence, 
in his excellent treatise on eye diseases, reports one case of its oc- 
curring within the ocular globe. 
The Cysticercus telce cellulosce is the entozoon most frequently met 
with as occurring intra-ocularly. Mackenzie6 reviews the subject, 
or rather reiterates the cases of its having been found, A, in the 
areolar tissue of the eyelids; b, under the conjunctiva; c, in the 
anterior chamber; and, d, in the cornea. 
Graefe,7 however, was the first to describe the presence of the 
entozoon within the deep structures, such as in the vitreous body 
and upon the retina. As to the knowledge of the presence of 
1 Mongin, Journal de Medecine de Paris, 1770; tome xxxii. p. 338. 
2 Mikrographiscbe Beitrage zur Naturgeschichte der wirbellosen. Thiere. Ber- 
lin, 1832, H. i. p. 7. 
3 Ibid. H. ii. p. 9. 
4 Zeitschrift fur die Ophthalmologie, vol. iii. p. 75. Dresden, 1833. 
5 Medico-Chirurgical Transactions, vol. xvii. p. 48. London, 1831. 
6 Mackenzie, loc. cit. 
7 Archiv. Ophthal., loc. cit., t. i. 2te part, p. 343—t. ii. lte part, p. 263—t. i. lte 
part, pp. 452-463. 72 
prize essay: 
these entozoa, it does not in the least contribute to the therapeutics 
of ophthalmology, save in a negative manner, viz., by preventing the 
use of medicine, and by assuring the patient that all artificial means 
for the removal of the offending body are perfectly useless. In a 
purely scientific point of view, the discovery of the presence within 
the eye of a living animal is in the highest degree interesting, as it 
involves the various questions of generation. 
The rational symptoms presented by the appearance of a cysti- 
cercus are not at all conclusive, and are nothing more than what is 
common to any so called amblyopia. 
Ophthalmoscopical examinations indicate the presence of the en- 
tozoon in the vitreous body and upon the retina. 
A cysticercus of the vitreous body is readily recognized when it 
is in a state of quiescence, and also when the eye is in a similar 
condition: it presents the following characteristics: A bluish or 
greenish-white tumor of a spherical form, obstructing the view of, 
or at least interfering with the regular position of the retinal ves- 
sels. The tumor is formed of a membrane of envelop which con- 
stantly surrounds the entozoon, and through which the character- 
istic form and movements of the cysticercus are readily recognizable. 
Within the sac enveloping it, the various portions of the entozoon 
may be distinguished, at least the outlines: thus, in a case seen by 
the writer at the klinik of Graefe, the head seemed adherent to an 
exuded false membrane within the vitreous, behind which there 
was a very perceptible narrowing, corresponding to the neck, which 
was about a line in length. From the base of the neck, the body 
began to increase, presenting rather a pear-shaped appearance of 
about three and a half lines in length, of a pearl-gray color, and 
was folded upon itself rather like the plaits of a shirt bosom. 
The complications are always numerous, and may be any one 
or all of the diseases before described. The most frequent lesion, 
however, met with as a complication, is a maceration of the pig- 
mentum. Cysticercus of the retina presents the same extra-ocular 
phenomena as does that of the vitreous body, always being in more 
exaggerate conditions. 
We have thus finished a sketch of the various lesions presented 
by means of the ophthalmoscope, and although by it this paper is 
brought to a close, it is by no means so complete as might be de- 
sired ; for many points of interest have been but glanced at, and 
others entirely omitted: the general therapeutics indicated in some, 
and the particular treatment of each left out. Why such has been THE OPHTHALMOSCOPE. 
73 
the case is readily understood, when we say, that had we given to 
each particular lesion its proper therapeutical consideration, this 
essay might have assumed such formidable dimensions, as to be 
totally devoid of any merit save verbosity. As we merely pro- 
posed to consider some of the anomalies as revealed by the oph- 
thalmoscope, it would be inappropriate to say aught more, and 
having accomplished our task, we make our bow, hoping it has not 
been a fruitless one. APPENDIX. 
Fig. I. Normal eye, as presented by Desmarres’s ophthalmoscope. The 
subject from whom the figure was drawn is a brunette of a marked type. 
The figure is magnified one and a half diameters. A. Papilla of the optic 
nerve. B. Arteria centralis retinae. G is the accompanying vein (vena 
centralis retinae). D, D, D. Spreading out or concavity of the retina, 
through which the bright shining choroid is visible, as the radiated (folds 
or deposits) structure of the pigmentum nigrum of the choroid. 
Fig. II. Jiiger denominates this figure as amblyopia haemorrhoidalis 
simply. A. Optic nerve slightly tinged yellowish. B. The spot whence 
spring the artery and vein, covered by an exudation of plasma. G. Extra- 
vasations of blood. 
In the case seen by the writer, and whose eye presented an almost ana- 
logous condition, was a hypersemia papillae conjoined to chronic choroiditis. 
In this case, however, there was no exudation covering the origin of the 
vein and nerve. 
Fig. III. Amblyopia of a mild form, in a boy fourteen years of age. 
Although Jiiger denominates the pathological conditions presented by the 
figure in question as amblyopia, it is most undoubtedly the consequence of 
hypersemia of the retina and of the papilla, conjoined to a slight choroiditis. 
The spots upon the papilla being exudations, and the slight deposition of 
pigmentum above it indicating the derangement of the choroid. A. Papilla 
of the optic nerve, upon which are numerous bluish-gray exudation spots. 
B. The origin of the artery and vein. G, G. Darker parts of the retina, 
owing to the deeper color of the choroid: it must be borne in mind that 
the circumference of all of the figures is as far forward as the ora serrata, 
and that they should present a concavity. D. Radiated appearance of 
the pigmentum, very indistinctly represented, owing to the condition of 
the parts. 
Fig. IY. Amaurosis (congestiva) complela of Jiiger, chronic, of two 
years’ standing. This figure is given because of the apparent contradiction 76 
APPENDIX TO 
in the appearance of pathological conditions, for in the analogous case seen 
by the writer, the disease was amaurosis from anaemia of the retina. In 
all probability there had been some congestion previous to the writer’s 
having made any examination, and the presence of the pigment deposits 
would justify such a supposition. In the writer’s case, the vessels were not 
so large as is represented in the figure. (Vide anaemia retinae in the essay.) 
A. Papilla of the optic nerve. B. Spot where the vessels pass in and out. 
G. Deposit of pigmentum: a smaller deposit is seen on the inner side. 
I), D. Radiated arrangement of the pigmentum. 
Fig. V. Amaurosis completa of Jager, chronic, of nine months’ stand- 
ing. This is undoubtedly a case of hypermmia of the retina, in fact a very 
similar one to that of Fig. IV., as reported by Jager. The letters point to 
similar structures, and are the same as in Fig. IV. In the analogous case, 
as seen by the writer, the structures, as seen by means of the ophthalmo- 
scope, presented evidences of an existing retinitis, chronic in nature, and 
the remains of what was once a choroiditis of a mild type, the pigment 
deposits undoubtedly showing such a condition. 
Fig. VI. After Jager, who describes it as “amaurosis completa of three 
months’ standing, in a female aged twenty-six years. The retina moderately 
yellowish-red, the optic nerve uniformly yellowish-white. Upon the central 
artery, and scattered throughout the substance of the retina, are small, 
rounded, and oval whitish exudations.” This account is but meagre, and 
did we not know the results of hyperaemia of the papilla and the retina, we 
would be completely at a loss to know the cause of the amaurosis, which 
undoubtedly was occasioned by the lesions in question. A. Papilla. B. 
Origin of bloodvessels. G. Pigment folds. D. Exudation spots, the 
result of a prior inflammation. 
Fig. VII. Jager describes this as a "mild amblyopia, resulting from 
intoxication in a man forty-five years of age. It was of four weeks’ stand- 
ing, and there was a marked development of vessels, and more or less num- 
ber of extravasations of a light and dark color, partially enveloping the 
optic nerve. Yellowish exudations are seen upon the retina at (7.” 
Jiiger’s case was but a mild acute amblyopia ; the writer has seen several 
presenting similar appearances, which were completely amaurotic, being 
true cases of hvper,'em ia of the papilla and retina. Instead of there being 
straw-colored exudations upon the retina there were light-red exudations, 
apparently formed by arterial extravasations, as at G in the figure. This 
figure was drawn from Jager, but colored to represent the writer’s case. 
A. Papilla of the optic nerve partially surrounded by hypervascular retina. 
B. Venous extravasation. G. Arterial extravasation. D. Pigment folds. PKIZE ESSAY ON THE OPHTHALMOSCOPE. 
77 
Fig. VIII. Jager describes this to be a case of “amaurosis completa 
(of twenty years’ standing amblyopia, but five of complete amaurosis). 
Optic nerve and retina of a uniform orange color. G, C, G, are straw- 
colored arteries of the choroid. B. Black pigment spots about to undergo 
maceration.” The writer has somewhat altered the figure by coloring it 
to illustrate, almost faithfully, a purely uncomplicated case of choroiditis, 
which was completely cured by antiphlogistic measures. The case in ques- 
tion presented the symptoms described under the head of choroiditis in the 
context. Two veins are seen traversing the papilla, which were the only 
indications of the retina partaking of the affection. The arteries mentioned 
by Jager as being straw-colored, were in this instance of the bright-red hue 
represented in the figure. Xumerous streaks of pigment are seen to radiate 
from the optic nerve, and are very characteristic of the choroid’s having 
been once affected, or is subjected to some alteration at the moment of 
examination. 
Fig. IX. Jager describes this case as amaurosis arthritica (glaucoma- 
tosa). The writer gives the figure, and colors it to represent as nearly as 
possible the appearance of the fundus of the membrane of envelop surround- 
ing a cysticercus of the papilla. Jager’s description sheds no light upon 
the case, and the writer would not hazard an opinion as to the true patho- 
logical conditions of the eye, as glaucomatosa might mean sundry various 
ones. 
It should be borne in mind that none of the figures are colored by Jager, 
and that the writer reproduces them almost as an entire new series. Also, 
it should be remembered that the coloring has not been altogether in accord- 
ance with Jager’s descriptions. 
Fig. X. Appearances presented by the ophthalmoscope in albuminuria. 
A. Papilla of the optic nerve slightly tinged with yellow, owing to a 
deposit of fat globules. 
B. Central artery and vein. 
b, b, b, b. Pigment spots characteristic of the disease. 
Fig. XI. Hyperaemia papillae et retinae. This case is the one referred 
to in the context as being one of spurious color-blindness. In an uncom- 
plicated case of hyperaemia retinae, there is no network of vessels seen 
upon the papilla, as in this instance. The two diseases are represented 
together for two reasons : firstly, because in the case of color-blindness in 
question they co-existed, and secondly, hyperaemia papillae never exists 
without hyperaemia retinae. The individual who presented himself, from 
wrhose eye the figure was drawn, complained of being unable to distinguish 
colors by that affected eye (the right); that full greens and red were of a 78 
gray, and all others, with the exception of lemon-yellow, were black ; and 
that such a condition existed but about fifteen minutes after any excitement, 
such as a full meal, etc. These phenomena are readily explained upon the 
general principles of vision, and are referable to the turgid condition of the 
vessels during a state of excitement. The patient had for many years 
complained of amblyopia of that eye. 
A. Papilla covered by a network of vessels. 
b, b. New crop of veins developed by the inflammation in question. 
c, c. Arteries developed from the same cause. 
APPENDIX Fib. I. 
Fiy. II. 
Fm 111 Fuf IV 
Fig. V. 
Tig. VI 
( /gr //, 111, IV, V, Vi, vri, VIIl Sc /X art arier 
Jriyer, Itii colored and oerijle/i Sy Ike Wnle rJ. Fin. Vff 
fti/.vnr 
Fiit. IX. Fit,. X 
(Pi(f- I X Sr XI aFler ru&ire hy the Writer', 
Fid. XI 
Litk Sr Traded, ms Colors hy T. S. DuixxJ So Son,,PAii