THE 
GENOTHALMIC REFRACTOR The 
Genothalmic Refractor 
By 
DR. W. B. FISHER 
A descriptive manual of instruction in the use 
of the Genothalmic Refractor, with 
a short description of the 
Genothalmic Unit 
PRICE ONE DOLLAR 
GENERAL OPTICAL COMPANY, Inc. 
Chicago 
Mount Vernon, N. Y. 
San Francisco 
1922 Copyright 
1922 
GENERAL OPTICAL COMPANY, Inc. PREFACE 
It is not the purpose of the author to attempt in this 
volume a complete treatise on the principles and use of 
the Refractor. It is his desire to present a concise state- 
ment of the chief points of value of this most useful 
instrument and he hopes a clear and understandable 
exposition of the most important details of its use as an 
instrument of precision in the refraction of the human 
eye. It is the author's belief that as the instrument is 
better understood it will prove one of the most valuable 
aids to the refractionist. Little claim is made for 
original matter in the pages which follow and would 
give full credit to the work of Kletsky, Sheard, Ryer, 
Maddox and Savage, et al., whose writings and research 
are largely responsible for many of the ideas which 
follow. CONTENTS 
CHAPTER PAGE 
I The Phoro-optometer as an Essential Factor in 
Refraction 11 
II The Refractor 13 
Stevens Phorometer 13 
Maddox Rods 15 
Rotary Prisms 15 
Spherical Lens Batteries 16 
Cylinder Lens Batteries 17 
III Dynamic Retinoscopy with the Refractor 23 
IV Static Retinoscopy with the Refractor 27 
V Distance Visual Acuity Tests with the Re- 
fractor 30 
VI Near Visual Acuity Tests with the Refractor.. .32 
VII Distance Muscle Tests with the Refractor 36 
Phoria Test 36 
Duction Test 38 
Muscle Exercise 39 
VIII Near Muscle Tests with the Refractor 40 
Phoria Tests 40 
IX The Genothalmic Unit 45 1 ■-Suspending arm 
2 -Leveling screw 
3 -Reading rod 
4 -Reading rod lock nut 
5 -Spirit level 
6 -P. D. Lever arm ad- 
justment 
7 -P. D. scale 
8-8 -Risley Prisms rotating 
knobs 
9-9 -30A Risley Prisms 
10-10-Axis changing levers 
11-11-Maddox rods 
12-12-Maddox rods turning 
pins 
13-13-Cylinder lens chang- 
ing knobs 
14-14-Cylinder lens housing 
15-15-Supplementary spheri- 
cal lens changing 
knobs 
16-16-Spherical lens chang- 
ing Knobs 
17-17-Spherical lens hous- 
ings 
18-18-Stevens Phorometer 
19 -Phorometer rotating 
knob 
3 
24 
-5 
~6 
"7 
"8 
-9 
-10 
-II 
-12 
-13 
-14 
-15 
-16 
THE GENOTHALMIC REFRACTOR 
17 18 19 18 17 
I 
2 
8 
9 
10 
II 
12 
13 
14 
15 
16 The Genotlialmic Refractor 
CHAPTER I 
THE PHORO-OPTOMETER AS AN ESSENTIAL 
FACTOR IN REFRACTION 
That the coming generation will see an immense 
development of the practice of refraction in volume, 
scope and refinement of detail is the firm belief of all 
who are interested in eyes and the conservation of vision. 
That this growth will depend largely upon instrumenta- 
tion can hardly be denied. Phoro-optometry fills an im- 
portant place in the development of instrumentation, a 
place believed to be as important as that filled by the 
ophthalmometer and its use as distinct and necessary as 
part of the practice of refraction as ophthalmometry is 
now acknowledged to be. 
The past decade has added much to the practice of 
refraction and the coming years, without doubt, will add 
much more. The busy refractionist finds himself forced 
to seek methods of greater speed and greater accuracy 
to serve his increasing clientele. 
Phoro-optometry presents many advantages over more 
ancient trial case methods, not only in speed and ease of 
operation, but most important, in accuracy; allowances 
which must be made in any arrangement of lenses before 
the eye become a constant factor as the units go into 
position always in the same order, a condition which is 
hardly possible with the trial lenses. 
As to the measurements of muscular functions, the 
trial case methods are so cumbersome and inaccurate as 
to be a real hindrance to the development of this im- 
portant phase of refraction. As Phoro-optometry de- 
11 12 
THE GENOTHALMIC REFRACTOR 
velops and becomes more widely adopted, it is believed 
that muscular functions will receive more attention than 
they do at present and we will advance far along the path 
toward a true understanding of the relationship of the 
ocidar muscles to comfortable vision. 
The need of the Phoro-optometer in muscle testing can 
hardly be denied, as only by the use of this instrument 
can we control prisms and lenses with that degree of 
accuracy that is necessary. 
In subjective testing, as well as in retinoscopy, both 
static and dynamic, the shifting of lenses is accomplished 
with so much greater facility that it means a real saving 
of nerve energy on the part of both patient and operator. 
This conservation of energy may frequently have an im- 
portant bearing on the success of the refraction. The 
tests of the reserve functions, ciliary, accommodative 
convergence, and fusional reserve, which are so impor- 
tant a part of careful refraction, are a "bugbear" when 
undertaken with the trial case, but are easy of accom- 
plishment with the Phoro-optometer. These tests are so 
important that the Phoro-optometer would warrant its 
existence if for no other reason than its use in making 
them. THE GENOTHALMIC REFRACTOR 
13 
CHAPTER II 
THE REFRACTOR 
The Refractor is a very valuable addition to the 
armamentarium of the refractionist and consists of a 
Stevens phorometer, proper Maddox rods, rotary Risley 
prisms, spherical and cylindrical lens batteries, a spirit 
level, reading rod and auxiliary near tests, all mounted 
on a base of exceptional rigidity. The parts are so ar- 
ranged and controlled as to be susceptible of adjustment 
with great facility and precision. 
STEVENS PHOROMETER 
Pupillary Distance Adjustment and Stevens Phorometer  THE GENOTHALMIC REFRACTOR 
14 
The Stevens phorometer consists of a 5A prism 
mounted in each right and left cell. The cells are geared 
in such a manner that the bases may be both in, both 
out or base up in the right cell and down in the left 
cell or vice versa. This relationship never varies. Its 
use with the Maddox rods and other devices will be 
explained later. This phorometer is especially sturdy 
in construction, being controlled by a knob and bronze 
gears, eliminating handles whose frailty would have a 
tendency to loss of accuracy through accident or natural 
wear. Another advantage of this method of control lies 
in the fact that the knob is always in the same position 
in all phorometric tests and its manipulation does not 
at any time detract the attention of the patient, as it 
lies entirely below the line of vision. The markings and 
calibrations are made very legible and are white or red 
against a black background. The phorometer is sus- 
pended in such a manner that when not in use it is 
thrown up out of the way of emanations from the mouth 
The Red and White Maddox Rods THE GENOTHALMIC REFRACTOR 
15 
or nostrils of the patient, a point of value both in sani- 
tation and convenience. 
MADDOX RODS 
The Maddox rods are both of white glass, or red and 
white according to choice, one for each eye. These rods 
are multiple in form and accurately ground to insure 
a sharply defined light streak of maximum width. These 
are far superior to the molded rods in general use. The 
rods are mounted in discs, which can be rotated by a 
lever to any desired axis. They snap into position at the 
vertical and horizontal positions. The discs are cali- 
brated in degrees to assist in the diagnosis and the 
exercise of the muscles involved in cyclophoria. 
ROTARY PRISMS 
The rotary prisms, one for each eye, have a range of 
powers from 0° to 30A. The graduation of power is 
controlled by a knurled handle and accurately cut gears, 
which insure precision and smoothness of operation. The 
Risley Rotary Prisms of thirty prism diopters each THE GENOTHALMIC REFRACTOR 
16 
discs are calibrated in degrees of power 0° to 30^ at 
the edge of the prism disc and in degrees of arc in the 
plate in which the prism disc is mounted and have a 
spring device which causes the bases of the prism to 
snap in place in the vertical and horizontal positions. 
SPHERICAL LENS BATTERIES 
The spherical lens batteries (a unit for each eye) 
consist of four discs in which are mounted + and - 
lenses ranging in power from + 0-25 to + 17.75 and 
- 0.25 to -18.00 both + and - in quarter diopter 
graduations. These lens discs are remarkably compact 
and are enclosed in a dustproof housing. All of the 
powers are obtained by rotating a knob located in a 
Spherical Lens Batteries and Housings THE GENOTHALMIC REFRACTOR 
17 
convenient position in the lower part of the battery 
housing. The lens power is shown in plain figures 
directly under the control knob; the complete power, 
not the various lens values separately. 
CYLINDER LENS BATTERIES 
The cylindrical lens batteries of which there are two 
(a unit for each eye), are enclosed in a dustproof 
housing similar to the housing that contains the spheres. 
In accordance with established modern practice, minus 
2 Dec. 22 
Cylinder Lens Batteries and Housings 18 
THE GENOTHALMIC REFRACTOR 
cylindrical quantities are usually employed, ranging in 
power from -0.25 to -3.75. The lenses are controlled 
by a knob placed in a convenient position in the upper 
part of the housing. The power of lens in use shows in 
plain figures just above the control knob. The axis 
control is far superior to anything yet attempted. A 
lever with an automatic latch sliding along a scale cali- 
brated 0° to 180° responds to the slightest touch yet locks 
with absolute accuracy at any desired axis, all lenses com- 
ing into position at the axis selected, until the axis is 
changed. The gears which control this action are 
Removable Eye Cups THE GENOTHALMIC REFRACTOR 
19 
accurately cut to the fraction of a degree so that the 
axis of the cylinder is never off by reason of play in 
the gears. An auxiliary calibrated lens cell is provided 
for additional lenses should upon some rare occasion 
more than 3.75 of cylindrical quantities be required. 
The back of each lens battery housing is provided with 
a hard rubber eye cup which is made removable so 
that it can be easily cleaned. This sanitary feature has 
another point of value in that it enables the refraetionist 
to have a duplicate pair for sterilization, one pair in use 
while the other is being sterilized. Notable features of 
the Refractor which are an advance in phorometric con- 
struction are the spirit level, P. D. adjustment, reading 
rod, and auxiliary tests. The spirit level is placed at 
the top of the instrument where it is in plain sight and 
easy reach of the operator at all times. A level position 
is obtained by a simple screw adjustment. 
Pupillary distance adjustment is made by means of 
a lever with a rack and pinion action which gives a 
remarkably quick and accurate pupillary adjustment 
with a range from 48 m/m to 72 m/m. The compact 
construction of the Refractor gives a more narrow and 
a wider P. D. than has as yet been attained in any other 
phoroptometer. The ease and accessibility of this device 
will be much appreciated by those wTho have experienced 
the inconvenience of fumbling around for the knurled 
screw as contained in previous designs of phorop- 
tometers. 
The rod for holding the reading and other auxiliary 
near tests is 24 inches long and calibrated in centimeters, 
diopters, and inches. Its attachment to the instrument 
is such that while it admits of perfect adjustability, 
it is absolutely rigid in use. When not in use it need 20 
THE GENOTHALMIC REFRACTOR 
Accessories thrown up out of way of patient's mouth and nose 
not be removed but may be swung up into a vertical 
position where it is entirely out of the patient's and 
the operator's way. 
Before concluding the description of the Refractor 
three of its most important points of superiority should 
be emphasized. FIRST-It is suspended from its holder 
and all accessories are suspended from the top of the 
Refractor head. When not in use they are thrown up 
entirely out of the operator's way and when in use 
can in no manner be contaminated by emanations from THE GENOTHALMIC REFRACTOR 
21 
the mouth or nostrils of the patient. This sanitary ad- 
vantage must surely make a strong appeal to both the 
fastidious patient and refractionist in this day of close 
attention to sanitization in refraction room equipment. 
SECOND-A grevious fault of all previous phoropto- 
meters has been a lack of rigidity and weakness of 
construction which sadly interfered with their accuracy 
and efficiency. This fault the manufacturers of the 
Refractor have labored strenuously to overcome and 
Reading Rod thrown up out of way 22 
THE GENOTHALMIC REFRACTOR 
have successfully produced an instrument which will be 
a revelation to the refractionist who appreciates fine 
instrument construction. Hard tempered brass and 
steel are used throughout, and all parts subjected to ex- 
ceptional wear are of phosphor bronze. The finish of the 
lens battery housings and Maddox rod discs, etc., is 
dull black wherever possible. There are no brightly 
polished nickel parts in the instrument head to be a 
constant source of annoyance to the retinoscopist. 
THIRD-Previous instruments have provided a sort of 
friction sleeve arrangement for three coarse adjustments. 
This is awkward and unsatisfactory in use as the sleeve 
sometimes catches when it is wanted free and slips when 
it is wanted to hold. To be safe with this device one has 
to make all coarse adjustments at some distance from the 
patient's face at a considerable loss of time and efficiency. 
The Refractor when used with the unit, chair attachment 
or wall bracket is instantly placed in approximate posi- 
tion and locked by a set screw. All subsequent adjust- 
ments, coarse and fine, are by means of racks and pinions 
or quick acting worm gears. The instrument is under 
perfect control at all times and all adjustments are 
made with ease, precision and absolute rigidity. THE GENOTHALMIC REFRACTOR 
23 
CHAPTER III 
DYNAMIC RETINOSCOPY WITH THE 
REFRACTOR 
It is not intended to enter here into any discussion 
as to the various theories of dynamic retinoscopy. Too 
extravagant claims may have been made for it; there 
may be a question as to just what the quantities found 
by this method really represent, but there is no question 
as to the value of the information to be gained from it, 
as to the refraction and working conditions of the eye 
under test at the point at which the test is made. 
Dynamic retinoscopy at 13 inches gives us information 
of great value as to the refractive condition of the eye 
while working at 13 inches. The for distance is based 
upon tests made at a distance. Is it not logical to esti- 
mate the needs of the eye at a given near point by means 
of tests made at this point ? Those who fail to appreciate 
the value of dynamic retinoscopy do so because they 
attempt to prescribe the exact amount which this test 
discloses and do not take into consideration other factors 
which should have an important bearing on the final . 
The exact amount shown is not as important as the 
discrepancies disclosed between it and other tests. It is 
an important diagnostic clue if it shows higher or lower 
plus quantities, higher or lower cylindrical quantities, 
axis at a different meridian than either the ophthal- 
mometer or static retinoscopy or the subjective tests. 
These clues often point the way to the solution of many 
of the difficult cases. Thus, while many disagree as to 
theory, those who have used dynamic retinoscopy are 
practically unanimous in claiming that it is well worth 24 
THE GENOTHALMIC REFRACTOR 
a high place in the practice of refraction. The important 
place occupied by the object of fixation should be empha- 
sized before proceeding with the exposition of the tech- 
nique of the test. Not only should the object of fixation 
be sufficiently varied in character to sustain the interest 
of the patient, but the refractionist should at all times 
be on guard that the attention of the patient does not 
stray. 
The Refractor is peculiarly well adapted to dynamic 
work as the lens quantities turn into position with an 
ease that is little short of automatic. One of the dis- 
agreeable features of the trial case, in this test, has been 
the distraction of the patient caused by changing lenses 
from test case to frame. 
Making a Dynamic test with the Genothalmic Dynamic 
Retinoscope and Refractor 
The technique of dynamic retinoscopy is not at all 
difficult and varies from static retinoscopy in only two 
essentials: FIRST-In regard to the allowance for the THE GENOTHALMIC REFRACTOR 
25 
working distances; in dynamic the eye supplies its own 
neutralizing lens. SECOND-As to the point at which 
we cease applying plus power; in static this is at the 
point of reversal, in dynamic it should he at the point 
of neutralization as will be explained later. 
To proceed with an explanation of the dynamic test 
with the Refractor. The instrument is properly adjusted 
in front of the patient's eyes, careful attention being 
given to the P. D. and height of the lens openings. The 
patient's attention is now directed to the fixation object, 
which may be any small object, but preferably a group 
of letters or symbols of sufficient variety to hold the 
patient's interest and small enough to insure accommo- 
dative action. This may be at the plane of the retino- 
scopic mirror, but for the sake of accuracy should corre- 
spond to the nodal point of the examining eye, which 
would bring it about one-half inch back of the plane 
of the mirror. It is best that the fixation object be 
located an inch or two to the side of the mirror to 
mitigate the action of the light on the sphincter of the 
iris causing the pupil to contract and making our work 
unnecessarily difficult. Having obtained accommodative 
fixation, maintain it by frequent questions to the patient 
as to the letters or symbols, number of each on a line, 
number of duplicates, etc. Now by means of the knurled 
knob, which controls the spherical lens batteries, turn up 
sufficient lens quantities to neutralize the movement of 
the shadow. If there be an astigmic element present, 
apply plus quantities until you have reached neutraliza- 
tion in the meridian of greatest error and neutralize the 
meridian of least error by means of minus cylindrical 
quantities. The reason neutralization is stopped at is 26 
THE GENOTHALMIC REFRACTOR 
because this gives the information sought, viz.: the actual 
refractive condition of the eye under test at the point 
selected for fixation. This amount contains some accom- 
modative lag or ciliary muscle tone or negative accommo- 
dation, whatever we may choose to call it. This may 
amount to one-half to one diopter. If the shadow is 
brought to reversal, the total amount of ciliary tone is 
obtained. This may be important knowledge too, but 
should not be confused with the true dynamic finding. 
Dynamic retinoscopy may be practiced with either 
the luminous or non-luminous instruments. If the in- 
strument has no attachment, the cards can be attached 
to the plate of the instrument by paper clips if such a 
makeshift is of temporary necessity. However, the use 
of the luminous instrument with proper attachments for 
dynamic work is strongly advised. Convenience and 
accuracy will more than pay for the outlay. To repeat: 
The two most important points in dynamic retinoscopy 
are control of the patient's accommodative fixation and 
the operator's care in working up to neutralization of the 
shadow. If but little experience has been had with 
dynamic retinoscopy do not be discouraged if some of 
the findings it gives seem inconsistent. Look for the 
reason for this inconsistency and as proficiency is had 
it will always be found. This inconsistency may be the 
very clue needed to make a perfect refraction. THE GENOTHALMIC REFRACTOR 
27 
CHAPTER IV 
STATIC RETINOSCOPY WITH THE 
REFRACTOR 
Static retinoscopy with the Refractor presents no 
very difficult problem. The facility of adjustment and 
control of lens quantities leave the mind free to analyze 
the retinoscopic picture as it presents itself under differ- 
ent refractive conditions. Direct the patient's attention 
to some sort of fixation object, which should be as distant 
Static Retinoscopy with the Refractor 
as possible at about the level of the patient's eye from 
the floor and of sufficient size to stimulate accommodation 
to a minimum degree. The 200-foot letter of the sub- 
jective test chart will do very nicely. In static, as in 
dynamic retinoscopy, it is important that the patient 
give sustained attention to the fixation object, with this 
difference, that in dynamic the directions to the patient 
should convey the suggestion of maximum accommoda- 28 
THE GENOTHALMIC REFRACTOR 
tive effort, stressing the necessity of close attention to 
detail and the importance of maintaining clear vision. 
In static, however, the directions should convey the sug- 
gestion of relaxed accommodative effort, that the eyes 
should be merely kept fixed in the direction of the 
fixation object, that no particular effort to see is neces- 
sary, that the fixation object will probably appear very 
blurred as the test is proceeded with, and if it does it is 
not important. Now having the patient maintain a 
steady gaze in a definite fixed direction approach the 
working distance found most convenient. (The author 
uses 26 inches as this brings the Refractor within easy 
reach and permits changes of lens quantities, etc., with- 
out moving the body. Also the average reach is about 
26 inches and this serves as a check on the working 
distance.) 
Having selected the working distance slowly move 
the beam of light from the retinoscope across the pupil 
of the eye under examination and carefully note the 
reflex, applying lens quantities, as indicated, until the 
point of reversal is reached. If there is any cylindrical 
element present measure the meridian of greatest error 
in hypermetropia and least error in myopia first and 
then by means of - cylindrical lens quantities neutralize 
the remaining astigmia. It is presumed that the reader 
is familiar with the retinoscopic picture under different 
refractive conditions. Many practitioners give strict 
attention to the edge of the shadow. However, a superior 
technique in retinoscopy will be developed if all other 
areas of the pupil save the center are ignored and the 
movement and appearance of the reflex in this portion 
of the pupillary area are carefully observed. This will THE GENOTHALMIC REFRACTOR 
29 
increase accuracy in eyes having spherical aberrations 
because of a large pupillary aperture, in eyes having 
irregular astigmia, and in eyes having irregular refrac- 
tion in different areas of the pupil. 
The center of the pupil is the position used for keen 
vision and is, therefore, the area primarily of interest. 
Having neutralized all meridians add to the spherical 
finding a minus quantity equal to the dioptric power of 
our working distance (- 1.00 if at 40", - 1.50 if at 26", 
etc.). Then transpose the entire finding to gain the best 
optical effect for the patient. 30 
THE GENOTHALMIC REFRACTOR 
CHAPTER V 
DISTANCE VISUAL ACUITY TESTS WITH 
THE REFRACTOR 
Having made the static and dynamic retinoscopic 
tests with the Refractor the next stage of its use would 
be the obtaining of visual acuity at distance and the 
relationship of different lens quantities in regard to it. 
First be sure the aperture is cleared of all lens quanti- 
ties; then occluding one eye (preferably the left eye 
first as it is desirable routine to begin all tests with the 
right eye) find the smallest line of type the patient can 
read correctly and make a proper notation either in the 
older system of fractions, in which the numerator repre- 
sents the distance at which the eye is being tested and 
the denominator represents the distance at which the 
given line of type should be legible to a normal eye, 
2%o, 2%o, etc., or by the decimal system of notation now 
provided by most modern test charts, .5, .81, etc. The 
latter is preferred. Having obtained and recorded the 
visual acuity with no correction, turn into position the 
approximate correction found by static retinoscopy and 
increase or decrease spherical or cylindrical lens quanti- 
ties until the combination which gives normal or nearest 
normal visual acuity is found. Record this lens combina- 
tion and also the visual acuity obtained with it. Repeat 
this with the other eye and this gives the subjective visual 
acuity findings. After making the monocular visual acuity 
test it is good practice to make it binocularly by leaving 
the lens quantities in position and note the effect on 
acuity of the addition of plus and minus spherical 
powers. This is particularly important in cases which THE GENOTHALMIC REFRACTOR 
31 
show at distance an esophoria or exoplioria of any appre- 
ciable amount, or more. In hypennetropia it is 
always advisable to crowd on all possible plus with an 
existing esophoria. In exophoria be cautious in crowd- 
ing on plus power and perhaps give muscle exercise to 
strengthen the external recti. In myopia be cautious in 
applying minus quantities if an esophoria exists, giving 
perhaps muscle training for the external recti or exercise 
for the ciliary if indicated. If exophoria exists with 
myopia full minus quantities may be safely prescribed 
if no ciliary deficiency exists. If the exophoria be exces- 
sive (over 5^) muscle training is indicated. Too little 
attention is usually paid to those cases having deficient 
functions and the average refractionist depends too 
much upon the correction of the refraction alone and 
ignores the equally important need of developing de- 
ficient functions that a proper refractive examination 
discloses. 32 
THE GENOTHALMIC REFRACTOR 
CHAPTER VI 
NEAR VISUAL ACUITY TESTS WITH 
THE REFRACTOR 
In the Refractor closer attention has been given to 
the needs of the refractionist as to tests on the dynamic 
functions, i. e., accommodation and convergence, than 
have other previous phoroptometers. The phorop- 
tometer is so beautifully adapted to investigation of these 
functions that this is indeed fortunate. An improved 
reading card is provided, also a card especially adapted 
for investigating accommodative power without which 
no refraction is complete. 
The improved visual acuity and accommodation amplitude cards 
There are three subjective methods of obtaining in- 
formation as to accommodative amplitude, each of which 
has value. First, using a distant fixation object and 
noting the ability of the ciliary to overcome minus lens THE GENOTHALMIC REFRACTOR 
33 
The improved accommodative convergence cards 
quantities and still maintain clear vision. Second, by 
finding the punctum proximum, i. e., the point nearest 
the eyes at which fine print is still legible. Third, by 
taking a fixation object at a definite near point and 
finding the greatest minus lens power which the ciliary 
can overcome and still maintain clear vision. While all 
of these methods yield information of value the third is 
believed to be the most accurate and worthy of an 
explanation of its technique. This should be a monocular 
test for if it is made binocularly the accommodative con- 
vergence is brought into action and thereby detracts 
from the accuracy of the findings. 
Leaving the lens quantities called for by the distant 
correction in the lens cells, occlude each eye in turn and 
swing into position the rod provided for tests at near and 
insert in the holder the card provided for this test which, 
note, consists of an arrangement of short words printed 
in small type. (Be careful that the rod is in such a 
position that there is neither convergence or divergence 34 
THE GENOTHALMIC REFRACTOR 
Making the near visual acuity tests 
of the visual axis of the eye under test.) Now rotate 
minus lens quantities into position before the eye, in- 
creasing by one-half diopters until the print is no longer 
legible. It will assist in maintaining accommodative 
effort if the patient is made to skip about the card and 
read words in different positions. The minus lens 
quantity thus obtained plus the dioptral equivalent of 
the distance at which the test is made is the measure of 
ciliary power or positive accommodative amplitude. 
Example-the test object is distant 13" or 1/3 meter 
from the eye. In order to obtain clear vision the eye 
must use 3 D. of accommodation at this distance. If then THE GENOTHALMIC REFRACTOR 
35 
it can overcome up to a - 2.00 lens and still maintain 
clear vision there must be available a total amount of 
accommodative amplitude of 5 D. 
The reading rod provides an excellent means of 
checking the presbyopic correction. The reading card, 
being fixed at any definite distance selected, makes it 
a simple matter to note the effect on visual acuity at 
this distance of greater or less plus quantities and is not 
misleading as is the case when the patient moves the 
card if the reading card is held in the hand. 36 
THE GENOTHALMIC REFRACTOR 
CHAPTER VII 
DISTANT MUSCLE TESTS WITH THE 
REFRACTOR 
A phoroptometer is an essential in the proper tests 
upon ocular muscles and the Refractor provides the 
means of investigating these functions with accuracy 
and facility. 
PHORIA TESTS 
The first test will be to disclose any phorias that may 
exist. Leaving the distant correction in the lens cells 
swing into position the phorometer and set the tell-tale 
line at zero on the left disc which is calibrated for 
csophoria and exophoria. Swing the Maddox rod into 
position in front of the right eye and direct the patient's 
The Refractor properly set for distance muscle tests THE GENOTHALMIC REFRACTOR 
37 
attention to any bright source of light at 20 feet or 
greater distance either directly or by use of a mirror. 
It is essential the illumination of the room be dim and 
that there be no other bright light sources in the patient's 
visual line. If the patient states that the streak is at the 
right it is known that the diplopia produced is 
homonymous, i. e., on the same side as the rod and that 
it signifies esophoria. Therefore, turn the knurled knob 
which controls the prism, moving the tell-tale mark up 
on the segment of the left disc marked esphoria until 
the streak bisects the light and the amount designated 
is the measure of the esophoria. Should the patient 
state that the streak is at the left (the Maddox rod 
being over the right eye) it is known that a heterony- 
mous diplopia is produced, i. e., crossed or on the 
opposite side of the rod. Proceed as before moving the 
tell-tale mark along the segment marked exophoria. To 
test for vertical phorias reverse the Maddox rod so that 
a horizontal streak is produced and shift, by means of 
the knob, the prisms around in the disc until the tell- 
tale mark on the right disc is at zero. If the patient 
states that the streak is below the light (the Maddox rod 
being over the right eye) a right hyperphoria is recog- 
nized and the prisms are turned until the streak is at 
the same height as the light and the amount designated 
by the tell-tale mark is the measure of the hyperphoria. 
If the patient should indicate that the streak is above the 
light a left hyperphoria exists. Proceed in the same 
manner to measure it, moving the tell-tale mark along 
the segment marked left hyperphoria. It is advisable 
to duplicate these measurements, applying the Maddox 
rod over each eye in turn. 38 
THE GENOTHALMIC REFRACTOR 
To measure cyclophoria turn a Maddox rod in posi- 
tion in front of each eye, the corrugation of the rods 
being vertical, thereby producing a horizontal streak. 
Next lift the phorometer into position and turn the 
prisms so that one is base up and the other base down. 
This produces diplopia and the patient states that he 
sees two horizontal streaks, one above the other. If the 
streaks are parallel there is no cyclophoria. If the 
patient states that either streak is tilted up or down at 
either end a cyclophoria is indicated. Now rotate the 
Maddox rod which is before the eye seeing the streak in 
a tilted position until this streak is parallel to the other 
and the amount and kind is designated by the tell-tale 
mark at the upper segment of the disc. A plus cyclo- 
phoria is a deviation of the vertical plane in which the 
upper extremity of the plane deviates toward the nasal 
quadrant. A minus cyclophoria is a deviation of the 
vertical plane in which the upper extremity of the plane 
deviates toward the temporal quadrant. 
DUCTION TESTS 
Duction tests are in reality tests upon the fusion 
sense and are essential in any case in which prisms are 
indicated. To make these tests swing into position the 
rotary prism before the right eye and direct the atten- 
tion of the patient to the bright light which is used for 
the phoria tests. To measure adduction turn the disc 
until the prism base line is out and rotate the prism, 
starting at zero, until the patient states that he sees 
two lights. Insist that the patient make every effort 
to keep the light single as long as possible. The amount 
designated on the prism scale is the amount of adduction. THE GENOTHALMIC REFRACTOR 
39 
To measure adduction reverse the disc so that the prism 
base line is in and proceed as before. To measure 
superduction the prism base line should be down, and 
to measure infraduction the prism base line should be 
up. A simple rule of thumb which may simplify muscle 
work a bit for the student is, that, in prescribing prisms 
the base of the prism is over the weak muscle. In 
measuring muscles the apex of the prism is over the 
muscle to be measured or, to paraphrase it, measure 
with the apex and prescribe the base. 
MUSCLE EXERCISE WITH THE 
REFRACTOR 
In exercising muscles with the Refractor the small 
light used with the phoria and duction tests may be 
used. A better fixation object, however, is a single letter 
at a suitable distance, 20 feet or still further if possible. 
The large letter of the test chart will do very nicely 
providing there are no other confusing letters in its 
immediate vicinity. Direct the patient's attention to the 
fixation object, swing into position the rotary prism 
and adjust it so that the apex of the prism power is 
over the muscle to be exercised (or the prism base line 
opposite the muscle to be exercised). Starting at zero 
turn in prism quantities until the patient can no longer 
see the fixation object single then turn back to zero and 
proceed as before. Continue this from five to fifteen 
minutes at each visit, being careful not to fatigue the 
patient too much. In turning in prism power a better 
result will be had if the power is jumped up to 2 to 4 to 6, 
etc., rather than steadily increased. 40 
THE GENOTHALMIC REFRACTOR 
CHAPTER VIII 
NEAR MUSCLE TESTS WITH THE 
REFRACTOR 
PHORIA TEST 
It is advisable to check the distant phoria tests with 
tests made at the approximate reading distance of the 
patient. This can be done by using the Maddox Rod 
and a bright light, or a small highly polished disc of 
metal and reflected light, as the fixation object at the dis- 
tance selected and proceeding as with the distance phoria 
tests. There is also the von Graef test which is suitable 
for testing phorias of the lateral muscles. This consists 
of a white card having in its center a dot, small cross 
or other distinct small character. Insert this card in 
the holder on the reading rod and set at the patient's 
reading distance. Now swing into position the pho- 
rometer with the base lines of its prisms vertical, i. e., 
one base up and the other base down. This produces a 
vertical diplopia and the patient sees two images, one 
above the other. If the vertical alignment of the images 
is perfect, orthophoria is indicated. If one of the 
images is at the right or left of the other, swing into 
position one of the Maddox rods on the position of the 
prism base line and the amount of prism power neces- 
sary to align the images vertically indicates the kind 
and amount of phoria present, exophoria if the prism 
base line is in and esophoria if the prism base line is out. 
A modification of the von Graef test is the modern test 
on accommodative convergence without which no refrac- 
tion is complete. This consists of a horizontal line of 
printed matter (words, letters or figures) in the exact THE GENOTHALMIC REFRACTOR 
41 
The Refractor properly set for near muscle tests 
center of which is printed a larger symbol of distinct 
character (a dot, diamond or arrow. Stevenson uses 
a line of letters extending above which is an arrow 
pointing up. Leaving the near correction in the cells 
place this card in the holder and swing into position the 
phorometer with the right prism base down and the left 
prism base up. Now calling attention of the patient to 
this line he will say that he sees two lines, one below the 
other; if the center symbol is in perfect alignment 
vertically it is known that he is maintaining convergence 
in spite of the vertical diplopia. This is really an indica- 
tion of excessive convergence effort, as research has shown 
that normal eyes should show a physiological exophoria 
at near of the order of 4^ to 8^. If the lower line is dis- 
placed to the right it is known exophoria exists. Swing 
both rotary prisms into position and turn up prism power, 42 
THE GENOTHALMIC REFRACTOR 
base in, to an equal degree in both to bring the center 
symbols into perfect vertical alignment. The amount 
of prism power necessary to do this is the measure of our 
exophoria or convergence deficiency, less the physiologi- 
cal amount, say 5^, at near. If the patient says that the 
lower line is displaced to the left we have esophoria or 
convergence excess and the amount of prism power, 
base out, necessary to bring the center symbols into 
perfect vertical alignment is the amount of the con- 
vergence excess. As to whether the convergence de- 
ficiency or excess needs prismatic or lenticular assist- 
ance depends upon the amount of fusion convergence 
reserve at command. To obtain the fusion reserve now 
insert a card in the holder on the reading rod on which 
is printed a vertical line of letters. Swing the rotary 
prisms into position in front of both eyes. To obtain 
the positive fusion reserve set the prism base line out 
and turn in prism power until the patient can no longer 
maintain fusion and says that he sees two lines. The 
amount immediately below that at which diplopia is 
produced is the measure of positive fusion reserve. To 
obtain negative fusion reserve reverse the prism discs 
so that the prism base lines are in. 
While much research must be done before a positive 
statement as to accommodative convergent relationships 
can be made, the average pair of eyes can use with com- 
fort at least two-thirds of its fusion reserve. For in- 
stance, a given pair of eyes show 12^ of exophoria at 
near, 5A would be allowed as physiological, thus leaving 
a real deficiency of accommodative convergence of ?△. 
If this pair of eyes had 12A of positive fusion reserve 
it would undoubtedly be comfortable with a prescription 
taking care of its refractive errors alone. Its con- THE GENOTHALMIC REFRACTOR 
43 
vergent deficiency is ?△ and it has 8^ of reserve which 
it can use with comfort. If, however, the patient had 
had the same amount of exophoria at near and had only 
6A of positive fusion of exophoria at near and had only 
4^ of reserve to use with comfort. His accommodative 
deficiency being ?△ and he having 4A of positive fusion 
reserve to use with comfort would require prismatic 
assistance of 3A or 0. IT. !%△ base in added to his refrac- 
tive correction for use at near. In the Genothalmic Unit is combined the Genothalmic Refractor 
and Universal Opthalmometer with table, Current Controller 
and tray for holding small diagnostic instruments, 
and the Genothalmic Chair THE GENOTHALMIC REFRACTOR 
45 
CHAPTER IX 
THE GENOTHALMIC UNIT 
It has long been the purpose of the General Optical 
Company to supply the profession with a unit which 
would fill the same important place in refraction that 
the various dental units do in dentistry. The result is 
the Genothalmic Unit. Its purpose is to group in one 
unit the essential instruments used in refractive work. 
This is an ideal arrangement for the busy refractionist, 
adding to his efficiency and the comfort of the patient. 
The unit is built on a very substantial base designed to 
give great rigidity without bulk. Arising out of this 
base is the column which provides for the support of 
the various instruments and the hollow center of which 
conceals the counterweight which is the secret of the 
great flexibility of adjustment of the phoroptometer. 
A specially designed arm immediately above the base 
is attached to a table of improved design for the 
ophthalmometer. This is adjustable as to height, and 
revolving as it does about the supporting column, is 
swung in or out of position as needed. 
Just above the ophthalmometer table is a circular 
tray built completely around the supporting column. 
This tray is of ample size to hold the retinoscope, hand 
ophthalmoscope, cross cylinder, and any small instru- 
ments the refractionist may need. The tray is bowl 
shape with the concave surface uppermost to avoid the 
possibility of instruments rolling off. This device will 
prove a wonderful convenience. 
Above the instrument tray is the bracket which 
holds the Refractor. Attached to this bracket at a short 46 
THE GENOTHALMIC REFRACTOR 
distance from the column is the Genothalmic current 
controller or rheostat for the luminous hand ophthalmo- 
scope and retinoscope. This phoroptometer bracket is 
counterweighed and slides up and down on its support- 
ing column at the slightest touch and may be instantly 
firmly locked in any desired position. The current con- 
troller being a part of this bracket brings it at all times 
just where the refractionist will want it. The Refractor 
is remarkable for the extreme range and facility of its 
adjustments, yet when locked in any position is abso- 
lutely firm and devoid of the vibration which is objec- 
tionable in other instruments. 
This group of instruments, with their wonderfully 
convenient arrangement, make it possible for the entire 
refractive examination to be made without the patient 
leaving the chair, yet all instruments may be swung 
entirely out of the way if desired. This unit idea will 
save the operator many steps and the convenience of 
having all his instruments at his finger tips will prove a 
delight. From the patient's point of view this will be an 
improvement indeed, as seated comfortably in the re- 
fracting chair the examination speeds along so smoothly 
that it is completed before the patient has time to be- 
come tired or nervous. 
In the Genothalmic Unit the General Optical Com- 
pany has produced a group of instruments of which the 
refractionist may well be proud.