**## MMWMIiWMM ft 1 m>-fs*T*i<!-;Vi*
V697s
m
fek^

3 ?|*^{^r%4^ia2^r^syt^
<^3K^%UySMM%EA3(d^r,i!
^.v^y-;; £■/•/. fc?--:iC 
   DUNCAN  BKOS.,
 lomeopathic Pharmacy,
  ITS Madison St., and
|131 and 133 S. CUrk St.,
   CHICAGO, ILL.
  Surgeon  General's  Office





Cree&on,             .^..........  ........
 
 
 
 
 
SPECTACLES;
AND
HOW TO  CHOOSE  THEM.
AN ELEMENTARY MONOGRAPH.
          By C. H. VILAS. M. A., M. D.,

Professor of Diseases of the Eye and Ear in the Hahnemann Med-
      ical College and Hospital, Chicago, Illinois;
    President of the Western Academy of Homoeopathy ;

Author of "A System of Eye and Ear Notes;" of "The Ophthal-
         moscope, its Theory and Practical
                Uses," etc.. etc.
     CHICAGO :
DFXCAX BROTIIEKS.
       1SS1.
 
WW
 Entered according- to Act of Congress, in the year 1880, by
                  C. H. Vilas. M. D..
in the office of the  Librarian of Congress, at Washing-ton. 
PREFACE.
  The aim of this little  work is so plain as scarcely to
need an explanation.

  It is  the intention to mtike  clear,  by an agreeable
compound ot medical and common terms, the uses  and
modes of  fitting Spectacles.   Such intercurrent facts
only as may serve to elucidate these  subjects will be
incorporated.  The medical treatment, often so essenti-
ally accompanying the correction  of diseases due to the
anomalies of refraction and accommodation,  forms no
part of the scope of the work.
  The attempt to render the whole as entertaining as
possible, must be an apology for a certain lack of con-
nection  apparent throughout the book.  A  too close
adherence to any one topic would  render the subject
somewhat  tedious, and while  undoubtedly  scientific,
might induce the less ardent student to throw away in
the beginning that which, when led on by easy stages,
he would gladly read to the  end. 
12                   PREFACE.
  The illustrations are  carefully selected to elucidate
the letter-press,  and although some of the cuts are
seemingly large, it is deemed  best  to give, as far as
possible, the actual  size  of  the  glasses worn.  It is
believed that this will materially aid in their selection.
Whenever  desired,  Messrs.  Meyrowitz  Bros.,  297
Fourth  Avenue, New  York, will supply by  mail or
otherwise, all varieties of Spectacles  mentioned herein.

  My assistant, C. F. Barker, M. D., has my grateful
thanks for relieving  me  of much labor  necessarily at-
tendant  on the passage  of  the volume through the
press.
  Chicago, February, 1881. 
CONTENTS.
                                                   PAGE,
Introduction,.........17

                      CHAPTER I.

The Uses of Spectacles;  Their Value;  Popular Notions ;
    Colored Glasses;  Difference between Focal and  Non-
    Focal Glasses; Importance of an Intelligent Discrimin-
    ation between Them,       ......     21

                      CHAPTER II.

Lenses; Their Shape, and the Material from whicli They are
    made; The  Prevalence of the Travelling Impostor; The
    Method of Distinguishing between the Different Mater-
    ials used in  the Manufacture of Glasses,    ...    30

                     CHAPTER III.

Selection of a Proper  Frame;  Material for its Construc-
    tion; Dangers  of  Eye-Glasses;  The General Adjust-
    ment of Glasses;  Colored Glassas and  Goggles;  The
    Destruction  of all Benefit, from a Faulty position of the
    Glasses,       .........41 
14                     CONTENTS.
                     CHAPTER IV.

                *                                 PAGE,
The Old and New Ways of Numbering Lenses ; The Deter-
   mination of Their Refractive Power ;  Tables Showing
   the Equivalents  of Dioptries  in  English and  French
   Inches, and in Millimetres, according to the Index of
   Refraction,     .........    51

                     CHAPTER V.

How to Test the Eyes ; Test-Cases ;  Different Styles ex-
   plained ; The Adjustment of Lenses of Different Pow-
   ers to Companion Eyes ;  The  Right  Eye generally the
   One used for Fixation ; Power  of the Two Eyes in Fus-
   ing Objects; Disadvantages of  the  Loss of an Eye,   .    59

                     CHAPTER VI.

How the Sight is Measured;  Old and New Methods; The
   Adjustment of Spectacles in General  for Myopia, Hy-
   permetropia and Asthenopia ;  General  Hints as to the
   Care and Convenient Use of Spectacles ; We do not See
   with the Eyes,      ...       ....    73

                    CHAPTER VII.

The Adjustment of Glasses for Hypermetropia ; Directions
   for Beginning the Examination in Cases of Suspected
   Need of Glasses from any Cause,     ....      86 
CONTENTS.
15
                    CHAPTER VIII.
                                                   PAGE.
The Adjustment of Spectacles for Hypermetropia con-
    cluded ;  Their Use often not Easy at first:  Hyperme-
    tropia often a Cause of " Stupidity " in Children ; The
    Use of Spectacles by Children,.....92

                     CHAPTER IX.

The Adjustment of Lenses for Myopia; The Weakest that
    are  Required  are the Best; The Principle upon which
    the  Treatment of Myopia Depends;   Slight degrees
    Overcome by  Old-Sight;  Spasm of the Ciliary Muscle;
    Rapidly Advancing Myopia should Excite Suspicion of
    this Trouble,      ........     99

                      CHAPTER X.

The Adjustment of Lenses for Myopia concluded ; Insuffic-
    iency of the Internal Recti Muscles ; Action of Prisms ;
    Reasons  why  Glasses do not Always  Benefit in'This
    Trouble;  Causes and Prevalence of This Trouble  in
    This and Other Countries,......107

                     CHAPTER  XL

The Adjustment of Glasses for Presbyopia; Changes in the
    Eye  due to Age; Recession of the Near Point; The Cal-
    culations Required;  Presbyopes should have Abundant
    Aid ; General Principles for the Treatment;  Dangers
    of Error..........118 
CONTENTS.
16
                     CHAPTER XII.

                                                    PAGE.
Spectacles for Irregular Sight; Stenopeic  Spectacles ; Or-
    thoscope Spectacles ;  Submarine Spectacles ;  Forms of
    Oculists' Prescriptions,       ......12G

                    CHAPTER XIII.

Other Devices for Aiding the Accommodative Effoit; The
    Type Writer;  Thursfield's Writing Slate;  Standing
    Desks;  Means of Illumination ; Oil or Gas,    .   .     145, 
         SPECTACLES;
AND   HOW  TO  CHOOSE  THEM.
                INTRODUCTION.

  The first knowledge of the use of Spectacles is gen-
erally attributed to, Roger Bacon.   It was probably to
compensate for the deficiencies of old-sight (presbyopia)
that they  were first used, for it is  said that  he pointed
out the benefit to old men and " to  those that have weak
eyes," of viewing letters through a plano-convex lens.
But whether  he did or not,  it  seems certain that they
were known  and  used  about  the time  of his death
(V2\)2).
  To a monk  of Pisa, however, who died in 1313, Ales-
sandro cli  Spina, is sometimes accredited the giving to
the public of  the use of Spectacles.  It is said  he saw a
pair of lenses in use which wrere made by some person
who was unwilling  to disclose the secret of their manu-
facture.  He  obtained a pair for  himself, and finding;
                            17 
18                 INTRODUCTION.

them very useful, cheerfully made the invention public.
  For many years  after this  discovery, no special ad-
vancement was made, and the use of Spectacles remained
confined  to supplying the deficiencies of the eye conse-
quent on age.  During the past half century, however,
and especially during the last quarter, the subject has
been carefully studied by men eminent in the known
sciences.   That use which was bused on a simple acci-
dental discovery, has been supplanted by one controlled
by unvarying laws solved by the higher  mathematics.
Opinions based on  the knowledge of past years should
be discarded.  No age  is now necessarily implied  by
their use.  They may be worn by anyone at some period
of life, for one or more of the many affections to which
they give relief.
  These  researches have also shown that a large class
of trouble-;, hitherto  numbered among the incurable,
are readily amenable to treatment by Spectacles alone;
and diseases formerly allowed to go on for the want of
a remedy, are now by  their use promptly arrested.
Many who are totally unconscious that their sight is
defective, are  made to see in a manner  never deemed
possible.  Man\r who  have  been obliged to  abandon
occupations on account of  supposed failing sight, can
now return to them.  Indeed,  most of those troubles
popularly known  as cross-eye,  scrofulous affections of 
INTRODUCTION.
19
the lids, paralysis of the eyes, and similar diseases, can
be cured by the proper adaptation of Spectacles.
  It was but recently that the inheritance of an optical
defect was one of the most  unfortunate of hereditary
calamities.  This thorough study of the laws governing
the  use of Spectacles, however, has  wrought  one of
the pleasantest, as well as one of the most remarkable,
of changes.   By it, members  of the same family may be
placed upon  widely differing planes  of life;  for occu-
pations closed to the older members by reason of such
inheritance, are open to  the younger.  Inability to use
the eyes for  near work  from inherited defects, has, in
nearly all cases, become a thing of the past.
  Furthermore, it is clearly  demonstrated that it is as
useless  to expect to do away with  Spectacles for eyes
impaired by the natural changes of age, as it is foolish
to attempt it.  Not all eyes  require Spectacles  for ad-
vancing age.   Isolated cases  seen by those not familiar
with known optical laAvs, and cited  as proofs of the
error of these  assertions, avail nothing.   Simple ex-
planations often overthrow seeming miracles.
  The changes wrought  by age rendering  Spectacles a
necessity to most, are  entirely physiological.  No per-
son with  normal eyes in youth can  escape them; for
the  eyes of those who do not  require their aid  from
these changes,  were not normal in  youth, and their 
20
INTRODUCTION.
possessors lost a portion of those things seen by others.
The  correct use of Spectacles as their values are now
known, would  have revealed much that was lost  to
them.  There  is no absolute standard of vision;  it is
but relative.
  The value of Spectacles  to every one at some period
of life, and their  absolute necessity to many at all
times, should do away with all prejudices against their
use, and  lead to its study.   Such study will  not only
remove erroneous  notions, but by awakening  interest
in newly-discovered optical laws, stop the impositions
of prowling pretenders.   The optician's  trade  is no
part of the oculist's profession, but  the optician bears
the same relation to the ophthalmic surgeon as does
the manufacturer and seller of deformity apparatus  to
the general surgeon, or tiie druggist to the physician.
  Physicians of skill do not give prescriptions unsought.
A like self-respect, and the  customs of society, debar
oculists of reputation and professional eminence from
proffering advice,  though it  frequently happens that
they see improperly adapted Spectacles.  Neither does
professional etiquette admit of their soliciting patron-
age, much less of haranguing strangers  with the impu-
dence of  a triple-tongued  marauder. 
CHAPTER  I.
THE USES OF SPECTACLES ;  TIIEIU VALUE ; POPULAR NOTIONS *,
  COLORED GLASSES ; DIFFERENCE BETWEEN FOCAL AND NON-
  FOCAL GLASSES ; IMPORTANCE OF AN INTELLIGENT DISCRIM-
  INATION BETWEEN THEM.
  From early  childhood nearly  all have been familiar
with the fact that Spectacles, or lenses as the oculists
oall them, have been worn as aids to  sight; but nearly
all grow up with somewhat confused notions regarding
their  functions.   Indeed, it will not  be far out of  the
way to say that a large proportion know almost nothing
of their uses beyond that they  help the aged and  the
short-sighted.   So strong  have  these notions  become
implanted, that  it is  not infrequent to  find employers
declining to engage  an  applicant wearing glasses;  or
those  needing them going without them, because of a
silly (and generally incorrect)  idea that they  impart a
tinge  of age or foolishness.
  In the hands of a skillful ophthalmologist there is no
one remedy at  this day, which will, in  their various com-
binations, correct so many troubles and restore good
sight, as suitable lenses.
  Four great causes  for the use of lenses are  found in
                        21 
22
SPECTACLES;
the defects of refraction and accommodation.  They are
known as follows:
  1.  Popularly as short-sight, or technically as myopia,
hypometropia,  or brachymetropia ; being that condition
where the focus of parallel rays of light is  situated an-
terior to the retina.
  2.  Oversight, or hypermetropia, that condition where
the focus of parallel rays of  light is situated posterior
to the retina.
  3.  Old-sight, long-sight, or presbyopia, thatcondition
where there is a deficiency in the powers of accommoda-
tion, and possibly also in the refraction.
  4.  Irregular sight, or astigmatism, a condition duo
to a lack of symmetry between the  different meridians
of the refracting surfaces.
  Other causes are found in:
  5.  The common weak-sight, or asthenopia.
  6.  Double sight,  (diplopia), or  where the  visual
lines of the eyes are not  directed  to the same point of
an object;  and
  7.  A vast class where various non-focal colored glasses
are required.
  To  overcome myopia,  concave  spherical  lenses are
used,  because they render parallel rays of lio-ht suffi-
ciently divergent to impinge  sharply on the retina; to
overcome  hypermetropia, convex  spherical lenses are 
Fir.  I.
   Very light steel frames, with no nose-rests, the rim of steel  holding
the lens on either side pressing directly against the nose.  Preferred by
those objecting to much weight of frame.
9999��99999� 
24                  SPECTACLES;

used because they produce the opposite effect optically;
presbyopia is corrected by convex spherical lenses be-
cause they supply the deficiencies of accommodation and
refraction; astigmatism is corrected by concave or convex
cylindrical glasses, with or without a combination with
the other kinds  as may be indicated, by  restoring the
symmetry of the different meridians of the refracting
surfaces; asthenopia,  or  weak-sight, by a suitable ad-
justment of the required kind  or kinds  hitherto men-
tioned;  and double-sight by another  kind known  as
prismatic lenses.
   Were a  pause made here and  these troubles alone
considered as in the majority cured, the great value  of
lenses would be seen.  But when it is  understood that
many diseases, unsightly and dangerous to vision, as well
as vast numbers of lesser ones, caused by these errors in
refraction  and accommodation, are cured by  the  relief
afforded by lenses to these  errors, there opens  a  far
larger field for their usefulness.  Myopia alone is a study
for  months; combined  with hypermetropia, in their
far-reaching effects  and  anomalous  conditions, it can
be made the special study of any oculist, and with dif-
ficulty comprehended in the short time usually allotted, by
many, to the supposed mastery of the whole specialty.
Astigmatism, though seemingly the most  difficult, is  by 

fc                                         Fio II.
              Light steel frames, with supports rendering them suitable for per-
             sons wide between the eyes.  Much worn and justly entitled to their
             popularity. 
26
SPECTACLES;
far the  easiest of these three anomalies  to understand,
so far as they at present are known.
  Hand-in-hand with  the old notions regarding Spec-
tacles, as part of the common ignorance concerning then-
uses, has gone the idea that all persons can choose their
own glasses.  Many persons who evince a decided repug-
nance to wearing  ill-fitting ready-made clothing, with-
out  thought or in confirmation  of profound  conceit,
select their own glasses without an apparent idea of the
incongruity or danger  of  thus treating an  organ whose
mechanism is of the most delicate nature, and whose use
to most is  as valuable as  life itself.  It  must not be
inferred  that I think nearly all seriously suffer by such
a course, but that a large  number do, there is no doubt.
To  avoid risk it  is far better in all  cases to consult
an oculist; in cases where trouble in their use is experi-
enced, it should never be omitted. While preparing these
pages for the press, a lady has consulted me whose selec-
tion of  glasses for a  rapidly  advancing old-sight, has
in her own language "quickly hastened, but in ignor-
ance," a disease (glaucoma  absolutum), which has  ren-
dered her hopelessly blind.
  In that large class where colored glasses are required,
great care should  be exercised in selecting those which
certainly have no foous.    Blue coquilles  are  much
worn, but in all troubles  of the delicate internal parts 
  A plain style of hard-rubber frames, much worn on account of their
easy adaptation to those persons who  are wide  between the eyes, with
thin, sharp noses.  They are light, but somewhat clumsy. 
28                   SPECTACLES;

of the  globe,  are injurious  unless  positively with-
out focus.   Plain glass, or that without focus, does not
distort or dim the objects seen  through it.  Non-focal
glass may be recognized by  holding it up to the light
and noting if any perpendicular line move with the glass
when it is slowly moved from 1 ight to left, or the reverse.
If it  does, or move in an opposite  direction, or  if ima-
ges are distorted,the glass is not a safe one to wear. The
common cheap coquilles, and by these arc meant the com-
mon curved blue glasses  so generally worn in the coun-
try (but not what are known as goggles, whicli never
Bhould be habitually  worn in eye disease, and  not at all
unless by direct order of some oculist,) are made ofpressed
or molded glass, and it is quite rare to find such without
focus, nearly all presenting a negative meniscus.  This
defect can be obviated, however, by purchasing a pair of
glasses of this shape which have been correctly ground,
not molded. The effect of  such  glasses when  imper-
fectly made, is to render the  eye hypermetropic, (over-
sighted) and still farther endanger an increase of  the
disease  by  adding another cause  of irritation.   The
reasons for  this are given in Chapter XII.
  The colors proper  for these glasses, and their correct
adaption to the various diseases, Avill be considered in
another chapter: but the caution here given  cannot be
too  often placed before the eye of  the reader; for it is 
AND  HOW  TO CHOOSE  THEM.
29
extremely rare to find anyone who has any suspicion that
such glasses are m any manner injurious to the eye or
sight.   It  is not  at all  uncommon, however, to find
cases where the deeper portions of the eye are kept in a
state of chronic irritation from their use, by which other
parts of the eye, from what is known as  reflex action,
are often sympathetically injured. 
                   CHAPTER II.
LENSES ; THEIR SHAPE, AND  THE MATERIAL FROM WHICH
  THEY ARE MADE ; THE PREVALENCE OF THE TRAVELING
  IMPOSTOR ;  THE  METHOD  OF DISTINGUISHING BETWEEN
  THE DIFFERENT MATERIALS USED IN  THE MANUFACTURE
  OF GLASSES.
  When a person  enters a store for the purpose of
selecting a pair of glasses, as many  are obliged to do,
there being no  oculist or other  competent person in
the place to assist in the selection, he will m many
cases  be asked whether he Avill have the periscopic or
double lenses ?  This will be the first time many  have
ever heard the question, and  unless  it has been previ-
ously considered, no intelligent answer can be given.
  The ordinary double-convex or double-concave lenses
are alike on both sides, the convex lenses being convex
on both sides, the concave lenses concave on both sides.
Periscopic lenses are concave on one side  and convex on
the other, the concavo-convex having a  shorter radius
of the convex surface ;  the convexo-concave a longer.
Could it be done, all lenses would  be put into the eye,
so that they would really become an integral  part of
the eye-globe.    Such  not being possible, they  are
placed directly in  front  of the  eye.  Unfortunately
                          on                       * 
AND HOW TO CHOOSE  THEM.
31
                          Fio. IV.
  Heavy gold-framed lenses. Much worn by elderly ladies, but
not usually with great comfort, on account of their weight tend-
ing to make them fall off or tip down.  Touching  the  nose but
lightly, as they do, also adds to this defect. 
32
SPECTACLES;
 they cannot  move  with the eye, and  hence when the
 axis of  vision, owing to the turning of the eyes, is no
 longer directly in front through the centres, as is often
 the case, they prevent free vision in a greater or  less
 degree, according as they are stronger or weaker in
 power.   To  overcome this  trouble, one must turn his
 head rather than his eye.   With periscopic lenses, less
 of this trouble is noticed, for there is a freer range of
 the eye behind the glass, thus permitting a clearer view
 of objects lyina' in  an oblique field of vision.
  Our great authority on these subjects, Donders, of
 Utrecht, who has done for the sight what Edison has
 for the voice, says " We can also see satisfactorily in an
 oblique  direction  through bi-convex and bi-concave
 glasses, provided they are not too strong;  and if high
 powers are required, the periscopic have again the dis-
 advantage  of greater weight.   Were  it only for  this
 reason,  the latter  do not  unconditionally deserve the
 preference.   When Ave add that, under some circum-
 stances, the periscopic glasses are more liable to pro-
 dace disturbance by reflection on the  concave surface
 turned towards  the eye, and that they are, moreover,
 somewhat  more expensive," it  can  be seen that they
 have disadvantages rendering it  quite an open question
among oculists as to Avhich kind has the greater num-
ber of points of  merit.  Without  going into reasons 
AND HOW TO  CHOOSE THEM.
33
at length, I favor the bi-convex and bi-concave for  the
most  general  use.   I  order each,  however, at times,
according to special cases.
  The question of material tor the composition of  the
lenses must be decided by the use to which the glasses
are to  be put.   Whole country districts,  as  Avell as
cities, are now and then agitated by the arrival of some
"distinguished Russian" (from New York?) or "cele-
brated  Pole" (from  Chicago?) Avho has  brought,  un-
friended and alone, at the sacrifice of health and happi-
ness,  but actuated solely by the love of his fellowmeu,
a peculiar and hitherto unknown kind of "pebble,"
from  which in consideration of the aforesaid  love,  and
some  ten  to twenty times the usual commercial price
for the same article,  he  is willing to sacrifice a  few
pairs, positively  the last  he has,  to as  many  dear
friends  as he can find before leaving for the next town,
(there to  repeat the  swindle, etc.)   Probably this state
of affairs Avill long continue, and cannot be  arrested
by  the  ordinary dissemination of knowledge.   But it
might save much vexation  of spirit and  some money,
were it generally known that all lenses are made from
two materials, glass and rock crystal, the latter being
the material  generally known  as " pebble,"  the  dis-
tinctive  adjective usually  being  taken from  some re-
mote  district of high-sounding name. 

Fio, V.
  A style of hard-rubber frames provided with springing rests that admit
of a more delicate adjustment than those usually made of this material. 
AND  HOW  TO CHOOSE THEM.
30
  In this country Brazilian pebbles, Russian  pebbles,
etc., are common.  It is interesting' to know that as a
nearer  approach to these foreign  countries is made,
North   American pebbles,  Colorado pebbles,  etc., are
esteemed the most  valuable.
  The great object  is to select  that  material which dis-
perses   light  the least in proportion to its refractive
power.   Crown glass  does this the least  of  all, and
hence should be used for all  glasses of great power.
Opticians often claim the preference for pebbles on the
ground that the polish on their surfaces is  higher, and
hence they do not scratch as easily; and that the mate-
rial is perfectly Avhite and transmits a pure light, Avhile
even the best glass has a greenish tint.  Formerly this
remark about  the non-transparency of glass Avas true,
but a   perfectly  transparent glass  is hoav  readily and
cheaply available to all opticians, and transmits a pure,
clear light.  In this preference  the greater object should
overcome the  lesser one;  hence for glasses  of high
poAver,  and especially concave ones, crown glass should
be selected;  for  weak ones, and especially Aveak  con-
vex ones, one may Avith safety  indulge in any prejudice
for pebbles.   By the  use of the " pebble-tester," how-
ever, one often will find his supposed pebbles to consist
of glass, and thus his  ideas of  the relative value of the
different kinds encounter a rude shock.   All  oculists 
36
SPECTACLES;
and opticians should have this apparatus for the testing
of lenses, and allow anyone  to use it, or what is still
better, be honest enough not to misrepresent the qual-
ity of their goods.  This test consists of two plates of
tourmaline, between which the lens is placed, and then
held up to the window.  If the lens be pebble, the light
is polarized, and colored rings appear; if it be glass, no
effect is produced.  Pebble is also a better conductor of
heat than glass, hence a lens made from it will seem
colder to the tip of the tongue than one made from glass.
  Furthermore, in order  that a pebble lens may be of
its greatest value, it is  essential that its axis be at an
exact right angle to the axis of double refraction, this
latter being  a peculiarity of pebble  in  one direction.
But if  care be taken in  this respect, not  so many lenses
can be  cut out of one piece of crystal, hence it is some-
times disregarded, and in consequence the image seen
through them is more  or less blurred and " fuzzy" on
its edge.    Resource being again had to the " pebble-
tester," the defect can be easily  detected;  for if the
lens be rightly cut, the rings of colored light Avill  be
circular; if not, they Avill be more  or less irregular or
eliptical in shape, or, as opticians usually say, prismatic
colors will be abundant.
  When  glasses are once chosen  they are  not to  be 
AND HOW TO CHOOSE  THEM.
37
                          Fig. VI.
  A  style of frames  much worn when the material used for
their composition is gold.  The peculiar shape of the nose-restc
is designed to prevent their slipping, as is the tendency where
a material as heavy as gold is used. 
38
SPECTACLES;
 used interchangeably Avith those of anyone else  Avho
 happens along.
   Furthermore, it should be quite  unnecessary to add
 that whatever kind of material for the lens be selected,
 the best of its kind should be used.
   Different opticians* often obtain great reputation by
 pretending to have superior glasses  under the names of
 "clearers," "restorers," and such nonsense.   A favorite
 trick also, with  the unprincipled, is to give too strong
 glasses;  these for a short time seem to make the sight
 better, but quickly fail to do so and cause  the eyes to
 ache.  It is best not to deal with those whose reputa-
 tion is not knoAvn.
   There are some opticians abroad, Avho, by a long course
 of honorable dealing, have justly Avon  their  favorable
 reputation, but they  have  no glasses  Avhich are  not
• known in this country.  Some of these glasses, hoAV-
 ever, have often obtained great reputation from travel-
 ers' tales of their  great  superiority. A person Avho is
 not  skilled in a certain  business is not competent to
judge of the merits or Avonders of that business.  What
 are to some seemingly new and  wonderful things, are
 often to others articles known  for years.   Perchance
 the products of our own toAvn may  be seen abroad for
 the  first time,  as every old European traveler  can
 testify. 
AND HOW TO CHOOSE  THEM.
39
  It is a very common occurrence after giving a short-
sighted person a pair of concave lenses, or in trying to
improve the vision Avith tliem, to have such person say,
" Oh! yes, of course I see better; I see just as 3^011 see
at the  opera Avith  a glass."  An endeavor to explain
that a person Avith normal sight always sees exactly as
he iioav sees, provokes a hasty interruption to the effect
that " You need not tell me that I am short-sighted, I
see just as Avell as anybody, and never wore Spectacles
in my life!"  A lengthy explanation is required to con-
vince, even in part, that vision is in any Avay deficient,
so unconscious is the person  that  the full amount of
sight is not present.
  Anyone  Avith normal sight desiring to know  how
poorly a short-sighted person sees Avithout glasses, has
only to place in front of his oavii eyes the convex
glasses  corresponding  in  number  Avith the concave
glasses  worn by such short-sighted  person.   His eyes
thus become the same in refraction as those of the short-
sighted person  Avithout glasses, (that  is  myopic),  and
he has  just the same amount of accurate sight—a fact
difficult to believe, and always exciting compassion for
the unfortunate myope.
  Hoav  much more deficient the eyes  of  an astigmatic
person  are, can be  readily determined by a  perusal of 
40
SPECTACLES;
the causes of that trouble;  it  is almost impossible to
accurately depict it.
  There is quite a general belief, too, that  dark-colored
eyes, (eyes Avith dark-colored irides) are much stronger
and less inclined to groAV  old than those of  lighter
color.  There seems  to  be  no  foundation for  such a
belief.   Perhaps as  favorable statistics  could be accu-
mulated to associate a similar belief with  red  hair, or
any other personal peculiarity.  The eyes of all  infants
of Avhatever nationality or race are blue at birth, and
remain so one to three Aveeks.   This blue appearance is
due to a lack of coloring matter in the  iris, and is Avhat
is known as an  interference phenomenon. The sky is
blue for the same reason. At about the age mentioned,
however, a pigment  begins  to be deposited in  the iris
which makes the color of the eye. There are occasional
exceptions to this rule, as there are freaks  of Nature  of
all kinds, but only enough to prove it.   It Avould save
a vast amount of maternal  anxiety, and infantile eye
disease, if all mothers knew this,  and  Avould not feel
compelled  to frequently pull the baby's lids open for
the first Aveek or tAvo after birth, to find out  the color
of its eyes. 
CHAPTER III.
.- ELECTION OF A PROPER FRAME ; THE MATERIAL FOR ITS CON-
  STRUCTION ; DANGERS OF EYE-GLASSES ; THE GENERAL AD-
  JUSTMENT  OF GLASSES ; COLORED GLASSES AND GOGGLES ;
  THE DESTRUCTION OF ALL BENEFIT,FROM A FAULTY POSI-
  TION OF THE GLASSES.
  The proper  kind of glass having been  determined
upon, it is important that the correct frame be selected.
It is not enough that the lens is correct, its erroneous
adaptation  to the eye  may defeat  much  gained  by its
use.  The distance betAveen the eyes should be consid-
ered, in connection Avith the shape and style of the  nose,
and an adaptation be made  of some one of the  kinds
shown  herein.  Thus in a  presbyope,  Avith the eyes
Avidely apart, and a thin, sharp  nose, avIio desired eye-
glasses, such a frame as Fig.  I portrays Avould be unsuit-
able, because the centres of  the  lenses Avould be Avithin
the line of vision, in which case  such a frame as Fig. II
or Fig. HI,  Avould be required, as it Avould throAv them
out into the line of vision.   Such styles as Fig. IV or
Fig. V  are  sometimes  useful.  I do not like such as
Fig. VI, but it is  Avorn  considerably.   Figs.  XVI,
XIX, and XX  are also much  Avorn and convenient;
                         41 
42                  SPECTACLES;
Fig. XXI not so much so.  For astigmatic glasses it is
essential that they should be set in " spectacle frames"
and  those  which are known as hooks or riding-bows
(Figs.  VII, XVIII, and XXIII)  are  generally pre-
ferred.  Some prefer the old " specs," similar to  Figs.
VIII or IX.  Fig.  XVII  is  another kind knoAvn  as
" Turn-pin Temples," greatly preferred by some,  espe-
cially the aged.
  Many other styles of frames Avith the material  suita-
ble for their construction, and the proper-shaped lenses,
are also given in the plates.  An examination of all—
sufficient to be thoroughly  familiar Avith them—should
be made before any be chosen.
  As to the material for the construction of the frames,
it is often a matter of taste.  Gold, especially,  is too
heavy  for some kinds of eye-glasses, and inclines one
to look older;  rubber has  the advantages of  little
Aveight, Avith no troublesome  reflection of light from its
surfaces, but is clumsy; the same remarks apply to
horn or bone.  Balancing all the defects and excellen-
cies, I  incline to nickle-plated steel.  The plating in-
sures no rusting, and can be easily replaced if Avorn off;
the steel admits of delicate Avorkmanship, the nickle-
plating tends to make one look younger, and the total
effect is pleasing.  1 order  all kinds, hoAvever,  and de-
tect a  groAving tendency  to the use of the rubber for 
AND  HOW  TO CHOOSE  THEM.
43
those Avho " bang their glasses around,"  as many say
they do.
  I am  often asked if in the use of eye glasses there  is
danger  from  the  pressure on the bridge of the  nose.
In  one case I have known of a cancer located  there,
and its  immediate cause attributed by a very intelligent
gentleman to  the pressure of  tightly-pressing eye-
glasses.  The position of the loAver  lid is sometimes
changed, and the lower pimctum (the little hole for the
drainage of  the tears) displaced by the  clraAving, by
which diseases of the lachrymal sac (the reservoir  of the
Avaste tears and other  secretions,) may  be induced or
perpetuated, so that I am constrained to  say that as
often used  I think they are dangerous.  All this  might
be  avoided,  however,  by proper care and a  suitable
mode of use.
  When glasses are to be avoiti for seeing at a distance,
the connecting bridge should be longer than Avhen they
are to be avoiti for near vision, because the visual lines
are practically  parallel; if for both near and  far,  a
medium should be sought after.   In addition, the lenses
of the first  should be set high, in order that they may
correspond to the planes of the pupils, and for this pur-
pose Avhat is knoAvn as an  X nose piece  (Fig. VII,) is
required.   To  see  near objects,  hoAvcver,  the  lenses
should be set Ioav, and the loAArer edge of the lenses in- 
                                  Fin. VII.
  A very light steel frame, with riding bows, and an X nose-piece.  Suitable
for a person requiring a medium position of the lenses as regards height. 
AM) HOAV TO  CHOOSE THEM.
45
clined backwards.  For  this purpose a nose-piece as is
shoAvn  in Fig. XVIII or  XXII,  known as  a  K nose-
piece, may be necessary.
  Sometimes Avhen a person has presbyopia (old sight)
supervening on hypermetropia (over sight), or has ab-
solute hypermetropia (complete oversight) it is conven-
ient to  have two pairs of lenses in  one frame, the lower
half of the lens stronger than the upper; or if myopic
(short-sighted), with diminished range of accommoda-
tion, the upper half concave and the loAver half coirvex.
Such glasses are knoAvn  as Franklin glasses, or glasses
a-double-foyer  (French;  of double  focus), and may be
ground directly,  or made of the half of tAvo lenses cut
and mounted in the same frame, as represented in Fig.
X.    If suitably  adjusted, they are very convenient,
and  greatly  liked by the Avearer, but  in the hands of
many require such careful adjustment, constantly main-
tained,  to keep each kind in place, that  they Aveary and
annoy.
  These glasses derive their name from the philosopher,
Franklin, avIio  being slightly myopic Avith diminished
poAvers  of accommodation, required  concave glasses for
distance and convex for the near point.
  The natural stimulant to the special nervous elements
of the retina is sunlight, Avhich is reflected by objects
in their different colors.   If blue-tinted glasses be or- 
C2
o
<o
Fig. VIII.
  A light-framed glass that meets with general favor from those who prefer
spectacles to eye-glasses.  Permits of easy vision over the lenses, as in speaking
to audiences. 
              AND HOW TO CHOOSE THEM.           47

dercd, certain colors arc  changed or shut out.  This is
often desirable for  traveling in torrid climates, or on
lakes, when the refljction from the water is  strong, or
in some morbid states of the retina, as in snow-blincl-
ness.  To  prevent the former troubles, these  common
glasses are all-sufficient; but what are known as steno-
peic glasses are essential for the latter in arctic regions.
Dr.  Kane and other polar explorers, Avere compelled to
use them.  Formerl y green protective glasses were given
by oculists and almost universally used, but have been
generally displaced by blue ; for while the reflected green
light is agreeable, transmitted is not, but rather irritat-
ing.  It is often suggested by patients that green is pre-
ferable  because the grass is green; but,  reasoning in
this same manner, the sky is blue, and the preference, I
think, should be given to looking upAvard rather than
downward in this Avorld, all things considered.  But if
it is not desirable to so shut out or change certain col-
ors,  it is necessary to order a  neutral tint  known as
gray, or London smoke,  for these glasses  exclude each
color of the solar spectrum in equal proportions,  and so
simply soften the light.  As already indicated, I do not
approve  of  goggles (Fig.  XXV.)  Such  protectors
are  unnecessary  except of plain Avhite glass to shut
out  the dirt and  dust in high  Avinds, and  they confine
the eye too closely and cause it to be half smothered in 
4y
SPECTACLES;
its own vapors.  They thus often perpetuate the trou-
ble sought to be relieved, as in granulated lids, etc.
  Lenses of any power, hoAvever,  may  be of a blue,
green, or neutral (London  smoke)  tint, as may be nec-
essary or desirable in different forms of trouble.  It is
often better not to order them ground in tinted  glass,
for the glass being of varied thickness, the shade is mi-
equally distributed over the field  of  vision, especially in
the stronger glasses, but preferable to  attach to one of
the surfaces a colored  plain glass by means of Canada
balsam.
  Oftentimes  even Avhen great  care has been taken to
select and adjust suitable lenses, the Avhole n jeopard-
ized  or overturned by the  light, or its manner of use.
As an example, blue glasses may be carefully selected
to be worn at night; the person takes them home and
sits doAvn  to read by a light having  a translucent green
shade, thus changing the color of the transmitted lfght.
By this means the light reaches the  eye composed  of the
color engendered by the  combined blue and  green,
which is not that originally intended.
  Again glasses will  be selected  for  a person Avho is
old-sighted to be used by a good light at a distance of
say tAvelve inches.   The glasses,  on the  contrary,  are
used in a dim light at a distance  of  thirty inches, Avhen,
as a  matter of course, the Avhole adjustment of the eye 
OS
o
■O
  An old style of steel frames still much worn by those who  prefer  a plain,
useful kind of frame, and whose shape of face admits of their suitable adjust-
ment. 
50
SPECTACLES;
is strained, and vision becomes painful or blurred after
a short time.
  The correct position for the light in the use of glasses
for reading,  is behind and to the left of the head, and
strong enough to illuminate the paper Avell.  The book
or paper should be held about twelve to fourteen inches
from the eye, and an  erect and comfortable posture
maintained.
  For those Avho have to select their work for evening
and such times, it will  be found that Avriting is gener-
ally read easier than printing at such a time; that com-
posing is easier  than  copying;  and  that  a frequent
change  from one occupation to  another will assist in
keeping the strain on the accommodation to a minimum.
   A further consideration of this subject wrill be found
in Chapter XIII. 
CHAPTER  IV.
THE  OLD AND NEAV WAYS  OF NUMBERING LENSES; THE
  DETERMINATION OF  THEIR REFRACTIVE  POAVER ; TABLES
  SHOWING THE EQUIVALENTS  OF  DIOPTRIES IN  ENGLISH
  AND FUENCII INCHES, AND  IN MILLIMETRES, ACCORDING TO
  THE INDEX OF REFRACTION.
  Lenses being so  often demanded in the treatment of
the eye, a clear understanding of the manner of their
construction and measurement is  as  necessary  as of
their adjustment.  Unfortunately, just  now is a tran-
sition  period in their nomenclature, rendering it a
matter  of more than ordinary difficulty;  for like the
change in the nomenclature  of chemistry,  it  requires a
knowledge of both kinds to understand current litera-
ture.  An endeavor  will be  made,- hoAvcver, to  make
both systems plain, Avith the reasons for the  change.
  Up to about the year 18(50, Avhen the present system
of measurement of lenses in inches Avas  practically in-
troduced, there Avas no way of numbering lenses.  A
manufacturer might make twenty grades of lenses and
number them from 1 to 20; another might make only
twelve grades of lenses (embracing the same range),
and number  them from 1 to 12; and so on, so that the
                        51 
52
SPECTACLES;
number 10 of one manufacturer might be the number
7 of another, and  the number  13 of another, etc.  To
overcome this, it gradually came to be  understood
that the  number of the glasses indicated their focal
length in inches.   But the refractin'g poAver of  a lens
also depends on the index of refraction of the glass, vary-
ing Avith the kind of which it is composed.  Noav the
Parisian inch is the equivalent of 27.07 millimetres; the
English of 25.30; the Austrian of 26.34; and the Prus-
sian of 26.15; Avhile the index of refraction  of the
glass of which lenses are constructed varies all the Avay
from 1.526 to 1.534.  Hence there are sources of error
in all  calculations, for  even  though the  country  is
known Avhere the  lenses are made (presumably  on the
standard of that country), the refracting power can
never be  told unless the  index of refraction of the glass
is  known as well.  In order to simplify the latter, a
common  index of refraction of 1.5 Avas accepted, but
even Avith that Avrong basis, only part of the trouble
was removed, so that as a compromise it became gen-
erally accepted that the  number  of a  lens  indicated
both the  focal distance  and  the  refracting  poAver.
Thus, a lens numbered 9 had a focal distance of nine
inches, and  a refracting  poAver of  1-9.  But it Avas
really knoAvn all the time that  it had not, and it in no
wise made an intelligent person feel that he had  solved 
AND HOAV TO CHOOSE  THEM.
53
a  practical  matter by trying to deceive himself with
what he knew to be Avrong.   In other words a sensible
system of notation Avould indicate cither the power of
refraction or the focal  distance of a lens.  This old
system did neither, and  by making the unit too strong
necessitated the constant use of tractions in all calcula-
tions.  Practically avc have much more  to  do Avith the
refracting power of a lens than Avith its focal distance.
The refracting power is  always the inverse of the focal
distance.   The  numbers of  the old system give the
focal distance of the lens in  inches, the unit  being a
lens of one  inch Avith a refracting power of 1-1.  There
is seldom need of this  lens in practice, and it  is not
put in trial cases.
   To  obviate these difficulties,  many oculists  offered
plans  and  introduced them at different conventions.
As a result, at the International Congress of Ophthal-
mology in  1867, a new system of numbering all  lenses
according to the refracting poAver Avas proposed.  After
a short delay, that Avhich is knoAvn as the  new or the
metrical system, Avas adopted.  A lens of one  metre
(instead of one inch as in the  old system) focal distance
Avas selected as the  unit, called a dioptry, and num-
bered  1.  This  dioptry (a metre) is the equivalent of
100 centimetres, 1,000  millimetres, or  39.33  English
inches.  Thus by following the cardinal numbers, we 

                                 Fig. X.

  Spectacle frames holding lenses Avhich are known  as  Franklin glasses.  So
called after that great Philosopher, who wore them.  Their peculiarities are
fully explained in the text. 
AND HOW TO CHOOSE  THEM.
55
have a series of lenses Avith an  interval of one dioptry,
as No. 2  is twice as strong as No. 1; No. 20 twenty
times as strong as No.  1.  Unfortunately there is need
of lenses  Aveaker  than  one dioptry,  and a*t intervals
between dioptries, so that this system does  not after all
remove the need of fractions,  and there are lenses  of
.25 and .50 dioptry,  1.75 and 2.50 dioptries, etc.
  For convenient  reference and a ready determination,
the following tables  are given: 
56                  SPECTACLES;
  The equivalents, in English and French inches and in
Millimetres, of each dioptry  or  fraction of a  dioptry
where the index of refraction is  1.5:
Dioptries.	French Inches.	English Inches.	Millimeters.
.50	73.8816	78.7416	2.000
.75	49.2544	52.4944	1.S40
1.	36.9408	39.3708	1.000
1.25	29.5526	31.4966 '	800
1.50	24.6272	26.2472	667
1.75	21.L090	22.4976	571
2.	18.4704	19.6854	500
2.25	16.4181	17.4981	444
2.50	14.7763	15.7483	400
2.75	13.4330	14.3166	363
3.	12.3136	13.1236	333
3.25	11.3664	12.1141	307
3.50	10.5545	11.2488	285
3.75	9.H509	10.49;8	266
4.	9.2352	9.8427	250
4.25	8.6919	9.2637	235
4.50	8.2090	8.7500	222
4.75	7.7978	8.2886	210
5.	7.3881	7.8741	200
5.50	6.7165	7.1583	181
6.	6.1568	6.5618	166
7.	5.2772	5.6243	143
8.	4.6176	4.9213	125
9.	4.1045	4.3745	111
10.	3.6940	3.9370	100
11.	3.3582	3.5791	90
12.	3.0784	3.2809	83
13.	2.8416	3.0285	77
14.	2.6386	2.8122	71
15.	2.4627	2.6250	66
16.	2.3088	2.4606	62
18.	2.0522	2.1872	55
20.	1.8470	1.9685	50
 
AND  HOAV TO CHOOSE THEM.
57
  The equivalents in Millimetres and Paris inches Avhere
the index  of refraction is not 1.5 but 1.53, which is
generally more correct, and should have the preference.
                    NEW  SYSTEM.
	Focal Distance in	Focal Distance in	Number in Old
Dioptries.	Millimeters.	Pakis Inches.	System.
.25	4.000	148.	156.
.50	2.000	74.	78.
.75	1.333	49.	52.
1.	1.000	37.	39.2
1.25	800	29.6	31.2
1.50	666	24.6	26.1
1.75	571	21.	22.3
2.	500	18.5	19.5
2.25	444	16.4	17.4
2.50	400	14.8	15.6
3.	333	12.3	13.
3.50	286	10.5	11.1
4.	250	9.23	9.78
4.50	222	8.22	8.7
5.	200	7.4	7.8
5.50	182	6.71	7.1
6.	166	6.15	6.5
7.	143	5.29	5.59
S.	125	4.6	4.89
9.	111	4.1	4.35
10.	100	3.7	3.91
11.	91	3.37	3.56
12.	83	3.07	3.26
13.	77	2.84	3.01
14.	71	2.63	2.8
15.	67	2.47	2.60
16.	62	2.3	244
17.	59	2.18	2.30
18.	55	2.03	2.17
20.	50	1.85	1.95
 
58                 SPECTACLES;
  The same when the index of refraction is not 1.5 but

1.53, etc.
                    OLD SYSTEM.
	Focal Distance in	Focal Distance in	Equivalent in
Number.	Paris inches.	Millimeters.	Dioptries.
72	67.9	1837	054
60	56.6	1523	0.65
48	45.3	1225	0.81
42	39.6	1072	0.93
36	34.	920	1.08
30	28.3	766	1.30
24	22.6	612	1.63
20	18.8	509	1.96
18	17.	460	2.17
16	15.	406	2.46
15	14.1	383	2.61
14	13.2	357	2.8
13	12.3	332	3.
12	11.3	306	3.26
11	10.3	280	3.56
10	9.4	254	3.9
9	8.6	230	4.35
8	7.5	203	4.9
7	6.6	178	5.6
Gi	6.13	166	6.02
6	5.6	152	6.52
5i	5.2	140	7.12
5	4.7	127	7.83
4i	4.2	115	8.70
4	3.8	102	9.72
3i	3.3	89	11.2
3i	3.1	83	12.
3	2.8	76	13.
21	26	' 70	14.4
24	2.36	64	15.7
2i	2.1	57	17.4
2	1.88	51	196
 
CHAPTER V.
HOW TO TEST THE EYE6 ; TEST-CASES ; DIFFERENT STYLES
  EXPLAINED ; THE ADJUSTMENT OF LENSES OF DIFFERENT
  POWERS  TO COMPANION EYES ;  THE  RIGHT EYE GENER-
  ALLY THE ONE USED FOR FIXATION; POAVER OF THE TAVO
  EYES IN FUSING OBJECTS ;  DISADVANTAGES OF  THE LOSS
  OF AN EYE.
  To make use of these tests and to adjust lenses, " trial
cases," or " test-cases " are  necessary for one Avho is not
skilled  in the  branch of ophthalmoscopic optometry
that treats of measuring the refraction of the eye Avith
the ophthalmoscope.*  This power is  usually acquired
by oculists only, and even Avith  them, advantage is de-
rived from  being able to confirm their estimate of the
refraction Avhen taken by the latter method.
  These trial cases, Avhen  complete, are  composed of
sample glasses  of the various kinds known, Avith Avhich
the applicant for glasses tries or tests  his eyes himself,
the examination being subjective.  When the correct
lenses are thus  found by trial, the oculist  orders dupli-
cates of such lenses for the patient to Avear, they being
ground and  set  in any suitable frame as before indi-
 * This subject is fully explained in the author's work entitled "The Oph-
thalmoscope ; its Theory and Practical Uses."
                          59 
60
SPECTACLES;
                          FIG. XL

             NACHET'S SET OF TRIAL GLASSES.

Comprises when complete, 33  pairs each of spherical, convex
and concave lenses  from 2 to 144 inches focus ; 22 pairs each of
cylindrical,  convex and concave lenses from 5 to 144  inches
focus; 10 prisms of  angles from 2 to 20 degrees ; 4 plane colored
glasses; one white glass disc ;  1  half-ground surface ; 2 metal
discs with stenopaic slit, 1 metal  disc with  hole, and 1 solid ;  1
adjustable spectacle frame, with revolving graduated fittings for
holding the A-arious  lenses, and 1 single non-graduated.
  This case has only one cylindrical concave and convex lens of
each number, and one trial frame. 
             AND HOW TO CHOOSE  THEM.          61

cated.   With the  ophthalmoscope, hoAvever,  the  ex-
amination is entirely objective, or the oculist names  the
right glass unaided by the applicant.  Such trial cases
Avhen complete are, as a matter of necessity, more or  less
expensive.  One of the  best, though not complete,
known as Nachet's, is represented in Fig. XI.  Such a
case is iioav quoted  at $90.00 net.
  One of the principal reasons Avhy students and phys-
icians in general practice do not give more attention to
optical defects, has been due to the cost and supposed
intricacy of the glasses necessary.   By the aid of the
metric system, simple  combinations can be made Avith-
out any knoAvledge of mathematics Avhatever.
  To render  trial-cases as inexpensive as possible, in
order that more might have them, has been the study
of  a number  of oculists for some time  past.  As  a
sequence, different  cases  have appeared as time  has
elapsed.
  One  of these, second  only  to Nachet's in  point of
utility, is the case arranged by Loring, and illustrated
in Fig. XII.   Like  the ophthalmoscope devised by him,
it is valuable, nearly equaling in  efficiency  those of
larger size and more complete equipment.  For those
practitioners avIio have considerable fitting of Spectacles,
and are not  pressed for  time, it will  prove especially
serviceable. 
.  62
SPECTACLES;
                         Fig. XII.

             LORING'S SET  OF TRIAL-GLASSES.

Contains one pair each of the following dioptry numbers:

     Spherical, concave and convex: .25, .5, 1., 2., 3., 4., 8.
     Cylindrical, concave and convex :  .25, .5,1., 2., 3.
  Also a set of Test-Types, and a triple-grooved graduated trial-
frame, into which one, two, or three lenses may be slipped to
obtain by combination the desired number. 
AND  HOAV TO CHOOSE THEM.
63
   There is,  moreover,  considerable advantage to the
comparatively inexperienced in having a pair of similarly
numbered glasses.   With them both eyes can be simul-
taneously examined with glasses of equal strength.
   The following numbers can be made by singly using,
or combining the numbers contained in the case:
   Spherical:  .2'), .5,  1., 1.25,  1.5, 1.75,  2., 2.25, 2.5,
2.75, 3., 3.25, 3.5, 3.75, 4., 4.25, 4.5, 4.75, 5., 5.25, 5.5,
6., 6.25, 6.5,  7., 7.25, 7.5, 8., 8.25,  8.5, 8.75, 9.,  9.25,
9.5, 10., 10.25, 10.5,  11., 11.25, 11.5, 12., 12.25,  12.5,
13., 14., 15.
   Cylindrical; .25,  .5, .75, 1.,  1.25, 1.5, 1.75, 2.,  2.25,
2.5, 2.75, 3., 3.25, 3.5, 3.75,  4.,  4.25, 4.5, 5.,  5.25,
5.5, (>.
   Its price is $14.00.
   But in  the endeaAror  to cheapen cases  by removing
more and more glasses, their efficiency rapidly declines,
and one often finds  that a case is expensive  enough to
require quite  a  sum of money  Avithout being of  suffi-
cient usefulness to compensate  for the outlay.
   Fig. XIII is a representation of a set Avhich  barely
escapes falling into this category; for I think Avhen one
has to pay for it $12.00 (its price), the sum has already
become so large that it Avould be better to pay more
and get a completer one. 
SPECTACLES;
                         Fig. XIII.

            CONDENSED SET OF TRIAL LENSES.

Comprises eighteen pairs each of spherical convex and concave
lenses from Nos. 5 to 60, directions and test-types for the testing of
vision and the diagnosis of some common optical defects.  De-
signed for the general practitioner by D. 13. St. John Koosa, M. D
  Contains no cylindrical, or lenses other than spherical. 
AND  HOW TO CHOOSE THEM.            65
  Fig. XIV  is a representation of a case arranged Avith
a view to assist  those Avho Avish to pay the least pos-
sible  for one that will enable them to  test the refrac-
tion and diagnosticate diseases incident thereto.
  Its total cost  is $4.00,* a sum  so  small as to Avar-
rant its purchase by all, even though each  has very
few cases  to treat. With it, there can  be diagnosti-
cated and  fitted any case of refractive error that comes
 in  the  range of the set described before it, or that can
be  corrected by any case containing only the ordinary
spherical  lenses;and Avhile it cannot  be justly claimed
that it is as convenient or useful as the expensive ones,
it combines all that is  essential for those Avho, having
feAv cases,  Avish  to economize money at the expense of
time.
  This loAvering of the number of glasses Avithout sac-
rificing the  utility of the lenses is brought  about  by
combining them, Avhen necessary, in  a  clip.   Using
them  singly, or placing one or more behind  another  ac-
cording to the folloAving table, there can be formed all
ordinary, viz., the following
 ♦Messrs. Duncan Bros., 133 Clark St., Chicago, will supply the case  and
this  book, free by express or mail, for $5.00. 
66                   spectacles;
COMBINATIONS.
New System. Dioptries.	Convex.	Concave.	Approximate Equivalents in Old System.
.5	+ -5	— .5	1-72
1.	+ 1.	— 1.	1-36
1. 5	+ 1. +.5	— 1. — .5	1-24
2.	+ 5.-3.	— 5. + 3.	1-18
2. 5	+ 3.-5.	— 3. + .5	1-15
3.	+ 3.	— 3.	1-12
3. 5	+ 3. + .5	— 3. — .5	1-11
4.	+ 5.-1.	-5. + 1.	1-9
4. 5	+ 5. — .5	— 5. + .5	1-8
5.	+ 5.	— 5.	1-7
5. 5	+ 5. + .5	— 5. — .5	L-61
6.	+ 5. + 1.	— 5. — 1.	1-6
6. 5	+ 5. + 1. + .5	— 5. — 1. — .5	
7.	+ 5. + 3.-1.	— 5. — 3.+ 1.	1-5
7. 5	+ 5. + 3. — .5	— 5.-3. + .5	
8.	+ 5. + 3.	— 5.-3.	1-44
8. 5	+ 5. + 3. + .5	— 5.-3. — .5	
9.	+ 5. + 3. + 1.	— 5. — 3. — 1.	1-4
 
AND HOAV TO CHOOSE THEM.              67
Fjg. XIV.
               FMALL SET OF TRIAL LENSES.

  Contains eight lenses; spherical, concave  and convex:  .5,1.
3., 5., Dioptries.
  The lenses are also marked in inches.  It contains, in addition,
a triple-grooved clip for holding the lenses while testing the vis-
ion.  When desired, a similarly  grooved spectacle frame,  by
which the efficiency will be  greatly increased,  may be ordered
with it at a slight additional expense. 
68
SPECTACLES;
  It is essential in all cases to test the eyes separately,
for it  is not at all uncommon to find them differing in
their refractive poAver.
  The lenses being marked in the metric system, as well
as in the  old inches, in ordering Spectacles, if the new
system is used, the numbers should be designated by a
"D"  (Dioptry)  following each  number thus: .5D.,
I.D.,  etc.
  At first glance, it seems to all that there could be no
objection to giving  a glass  suitable for the  correct
measurement of  the refractive poAver of each eye;  in-
deed,  it  seems the sole and sensible Avay to meet the
anomaly.  But as will be explained  in Chapter VI., Ave
do not see Avith the eyes, they acting simply as an op-
tical box, but  Avith the  brain.  Convex lenses enlarge
the image  of an  object, and concave ones diminish it.
If there  be placed before one eye an enlarged image, as
would be brought about  by the use of a convex  glass
essential  in the case  of a hypermetropic (over-sighted)
eye, and  a  diminished image before the other  eye, as
Avould be produced by a concave lens  essential in the
case of a companion myopic (short-sighted) eye,the effect
would be the same as in endeavoring to see tAvo similar
objects at once Avith one  eye.  Neither Avould be seen
we'll,  but both would appear " fuzzy" and indistinct.
There are  exceptions to this rule, as to all others, but 
AND HOW TO CHOOSE THEM.
m
the general principle holds good.   The practical differ-
ence found to exist,  if it does not  exceed l-48th or
1-G0th of an inch,  may be neutralized in both eyes by
the correctly fitting  glasses; Avhen it exceeds  this, it
Avill be  found  the better  rule to fit the  better eye,
that is the one  Avith the better sight, and  give a cor-
responding glass for the other eye.  It by no means is
always true that the eye with the better refraction is
the better one for vision, for it may be amblyopic, and
hence not see as well as the other which has the poorer
refractive poAver.
  If, hoAvever, the  eyes are to be used for any purpose
requiring accuracy of fixation, as in rifle-shooting, or the
determination of lines,  as m  surveying, etc.,  it will
generally be found that the right eye must  be the one
to be  fitted; for on  trial  it Avill be found  that Ave  all
usually give the preference  to  the right eye in  such
matters.   This  may  quickly  be made manifest on  at-
tempting to place the finger  in  the line of vision Avhen
both eyes  are directed to the same object.   It Avill  be
found  that the finger is in the Avay of  the visual line of
the right eye, and  this Avhere both eyes are about the
same  in visual power.  Another good Avay of proving
this is, Avhen both  eyes arc in a casual manner looking
at an  object in front of a prominent background, to
place  a card in  front of one and  then the other.  It 
"4
©
    Heavy, coin silver Spectacles, with octagonal shaped lenses and frames.  Not very much
worn, the material used in the construction of the frame being  too heavy to admit of popu-

larity. 
AND HOAV  TO CHOOSE  THEM.
71
will be found that when the card is in front of the left
eye, the disappearance of that portion  of the back-
ground  directly in front of that eye Avill scarcely be
noticed, but when it  is  in front of the  right eye, the
disappearance of the  portion  alone visible  to that eye
will at once be missed.
  Those who shoot much, as at a target,  may  find as-
sistance  from  Avhat  are known  as shootino-.o-lasses.
These  Spectacles are  made  of ground  opaque glass,
Avith a yelloAV colored disk in  the center, the effect of
which is to define distant objects more clearly.
  The stereoscope also affords a good test of this kind;
for a person Avith marked difference between the eyes,
cannot fuse the images Avell, and complains of their in-
distinctness.   Persons troubled Avith asthenopia (Aveak-
ness of  vision) Avhether  dependent on Aveakness of the
accommodative apparatus, the globe muscles, or of the
retina, usually quickly tire and complain of the fatigue
of  looking through  this same  popular instrument of
diversion.
  The ascertainment of just Avhere the trouble lies in
these cases is a matter of particular and careful study,
and requires  an extended knoAvleclge of the physiolog-
ical, pathological and optical questions involved.
  One eye is not nearly as good as two, notwithstand-
ing such is commonly thought to be the case.   Persons 
72
SPECTACLES;
with one eye do not perceive as  readily as  those Avith
two, and where form and position are concerned, often
err in judgment. They also perform delicate operations
slowly,  and often  Avithout accuracy. 
CHAPTER VI.
HOW THE SIGHT IS MEASURED; OLD  AND NEW METHODS;
  THE ADJUSTMENT OF SPECTACLES IN GENERAL FOR  MY-
  OPIA, HYPERMETROPIA AND ASTHENOPIA ; GENERAL HINTS
  AS TO THE  CARE  AND CONVENIENT  USE  OF SPECTACLES ;
  WE DO NOT SEE AVITH THE EYES.
  Iii order to make a practical application of Spectacles,
it is essential to have in addition to a trial-case, as de-
scribed heretofore, a selection from what are known as
Test Types.  For this purpose there have been  chosen
a carefully assorted  number from those known as
Jaeger's and Snellen's, which Avill be found in the back
part of this book.  With these appliances any physi-
cian or surgeon may diagnose and fit any  ordinary  case
of refractive error.   By them, also, the laity avIio are
remote from points where competent aid may be had,
Avill be greatly aided in  the  proper selection  of their
glasses.  Indeed,  with a careful study of Avhat is given
herein, they aviII as guides be far superior to that class
to Avhom  in those districts, is entrusted this delicate
matter.  It must not be  expected that  the more dif-
ficult cases Avill be quickly mastered;  such should be
referred to one avIio has made of these subjects a study 
74
SPECTACLES;
                         Fig. XVI.

  A style of lenses where no  frame is used; the bow and other
jarts being attached  directly to the glasses.  Greatly preferred
by some on account of their light appearance.
1199999999999999999999� 
AND HOW TO  CHOOSE THEM.
75
sufficient  to  understand Avhat is known, and to take a
comprehensive vie\v of  the Avhole matter.
  In explanation  of these test-types and their names,
it  should be  understood that for a number of  years
much confusion resulted from there beino- amono- ocu-
lists no uniform Avay of testing vision.  To overcome
this, it Avas agreed, by common consent, to make use of
a set of letters draAvn upon a given scale.  Snellen and
Jaeger both devised  such  sets, and as  each has merits
peculiar to itself, both are  used; the  former being
considered better  for the determination of the  acuity
of vision, and the latter for the ease of reading.   Snel-
len's letters  are square and their size  increases in a
definite ratio, so that each kind  is  seen  at an angle of
five minutes, No.  3  being seen at a distance of three
feet, Xo. 2 at a distance of two  feet, and so on.  As a
rule, these  letters cannot be seen distinctly  beyond
these distances.
  Quite recently the standard of measurement has, by
vote of an International Congress, been  changed from
inches  into dioptrics, so as to have a uniform standard—
the foot and inch, Avhich have been taken as the stand-
ard, varying in different countries.  This has been ex-
plained in a preceding chapter.   The  same unit  of
measurement, the  dioptry,  which Avas taken for the
measurement of Spectacles, as has also been explained, 
OS
                                Fig. XVII.

   A style of frame known as "Turn-pin Temples." Not much worn, but suitable
for those who desire one which feels firmer, and is more strongly fastened than the
usual kinds. 
             AND HOW TO CHOOSE THEM.           77

is again used here. It is the equivalent of 39.3 English
inches; by  calling  it forty inches, which  is correct
enough for all ordinary calculations, the change from
one system to the other can b:> easily made.
  A person Avho has normal sight reads the  test types
at the distances corresponding to the numbers marked
thereon.  Thus, if in feet, No. 200 is read at 200 feet,
No. 20 at 20 feet,  and  so on.  The dioptry card is
divided into GO, 20, and 6 dioptries respectively, which
will be seen to be the nearest approach to the old foot
measure that could be selected and easy calculations be
retained.   So that if the new system be used, No.  60
is read  at 60 dioptries, (nearly 200 feet), and No. 6 at
6 dioptries, (nearly 20 feet), and so on.
  Now, if an eye be suffering from diminished acuity
of vision, in order to gain large retinal images, it will
demand a larger retinal angle than five minutes to see
the letters,  and  hence No.  1 cannot  be seen at one
foot, but for example, only at a distance of six inches,
and so on.
  If, then, the card  be placed at a distance  of twenty
feet, or, according to the new nomenclature, at a dis-
tance  of six  dioptries, and the observer  see  No. 20 of
the first, or 6 of  the  second, plainly, his vision is per-
fect, 20-20ths, or 6-6ths.  If,  however, he can only see
that which should be seen at  70 feet,  his  vision  is 
   A light steel frame similar to Fig. VII, but with a K nose-piece.
agreeable frame which is much worn. 
             AND HOAV TO CHOOSE  THEM.           79

 20-70ths, or about 2-7ths  Avhat it would be were it
 normal.  In practice the fractions  should  never be re-
 duced, but thedenominator alloAved to remain the dis-
 tance at which the test types  should  be seen, and the
 numerator the distance at which they are placed.  The
 eye in a state of rest depends on the refraction alone,
 but when viewing any object nearer than about eighteen
 feet,  the accommodation is used,  so  that practically
 2-7 ths  is not 20-70ths.  In the former  case  the  ex-
 pression would mean  that the types used should be
 seen  at 7  feet,  and  Avere only seen  at 2  feet,  the
 accommodation  being  used, or in a condition Avhere
 it might be used  if not diseased, (an element always
 to  be borne  in  mind).   In the latter  case  the ex-
 pression would mean that the types should  be seen
 at 70 feet, but were only seen at 20 feet, the refraction
 alone being used, (as  the distance  at which the types
 were placed was such as to  preclude the  use of the  ac-
 commodation, for it must be at rest at a distance of 20
 feet).  Moreover, there is some advantage in using the
 scale  of tens Avhen fractions are involved, as  will be
 seen when the adjustment of lenses is attempted.
  Jaeger's types are not square, but similar to those in
 ordinary use.  We have already become  familiar Avith
 them  in ordinary reading, hence they  are the more
readily seen and recognized. 
80                    SPECTACLES J
                         Fig. XIX.
  A light steel frame, which, when nickel-plated, is very much
worn.  Preferred on account of its delicacy  and genteel ap-
pearance. 
AND HOAV TO CHOOSE THEM.
81
     Other styles have been devised, but, as those described
%  are  in general use throughout the civilized world, a
   description of them seems superfluous.
     Under the various heads of Hypermetropia, Myopia,
   etc., Avhere the subject  is further considered, hints are
   given as to the correct Avay to adjust glasses.  The adjust-
   ment of glasses for asthenopia (Aveak-sight) is not con-
   sidered, because they ought not to be avoiti for such
   an affection unless medical means fail.  Much can now
   be done by remedies exclusive  of lenses,  and the too
   common  habit of putting  on lenses  tor  this trouble
   ought to  be  abandoned, unless  done  by order of  an
   oculist.   But there are several little points that assist
   in making their use pleasant that  belong to no  one
   heading; hence they will be considered here.
     To one avIio is familiar Avith the great value of Spec-
   tacles, it is annoying to see Avhat little care is taken
   of them.   Some persons Avill go a Avhole lifetime obey-
   ing the most trifling superstitions regarding the Avetting
   of their eyes Avith saliva before opening them in  the
   morning, or ahvays putting their head in  the  Avash-
   basin and turning it over sideAvays to prevent injury to
   the  delicacy of the lid movements,  etc.   Then,  when
   age comes on and Spectacles are a necessity, they Avill
   struggle  with a  scratched, greasy pair, trying  to see
   some dim embroidery  or mechanical Avork, until weak 
00
                             Fio. XX.
  Hard-rubber frames, Avitli steel spring covered with  serrated edges of
hard-rubber. A popular style with those who do not object to the  bulky
frames. 
AND HOW TO  CHOOSE THEM.
83
 vision becomes  fixed,  accompanied  Avith red and  un-
 sightly lids.  Such persons are also, as a rule, the last
 ones to change  for a neAv pair,  and multiplied  defects
 increase the dimness of the already troublesome  vision.
   Eye-glasses are nearly always Avorn pinching the nose
 too tightly; this is not only Avholly unnecessary, but
 unpleasant and  not entirely free from danger.  The
 pressure on the nose may cause  trouble with the ducts,
 and, as has been said  before, this may be the cause of
 more serious difficulties.  If the spring be  too strong,
 heat it a little in a flame, and carefully bend it until it
 is of the requisite strength.
   Neither should the glass be Avorn  so near  the eye as
 to gather the moisture or  rub against the lashes.  a±
 the best, lenses  grow " steamy" on  going from a cold
 to a Avarm  atmosphere, or the reverse.   This becomes
 a serious annoyance when it is complicated Avith any
 other apparently trifling error.
  Do  not  buy a fine  pair of glasses, and  then spoil
 them  by scrubbing them, Avhen soiled, Avith anything
 that comes handy for  the purpose.   Good lenses are
quite easily scratched.   Use a piece of chamois skin, or
 what is.known as wash-leather, to clean them, and then
put them in a case.
  Always have  eye glasses  attached by a  cord  to
the person  Avho uses them, for this will save breaking 
84                    SPECTACLES;
^
Fig. XXI.
  A style of gold-framed lenses similar to those worn in  hard-
rubber frames.  Preferable to those of heavier manufacture. 
             AND HOW TO  CHOOSE THEM.           85
them by accidental  falls, not to mention the frequent
searches for them, which is  so vexatious to  those re ■
quiring their aid.  A hook to be pinned to the clothing,
illustrated in Fig. XXNIII, on  Avhich  they may  be
hung, will also be found very useful.
  Short-sighted glasses should be Avorn near the eyes;
over-sighted ones not necessarily so.   Astigmatic glas-
ses, should be  carefully  kept in the exact position
ordered by the  oculist,  otherwise they impede,  rather
than benefit vision.
  Finally, it  should be understood  that Ave do not  see
with the eye, but Avith the brain; hence it is  that  the
eye may  be  perfectly fitted as  to its refraction,  the
image perfectly formed, and  yet no vision be present,
the sensorium taking no cognizance of the image pres-
ent.   A remembrance of this fact, Avhich can only be
diagnosticated  by a competent  medical  person, Avill
afford  a  solution to many  otherwise unsolved, and
seemingly incomprehensible, optical problems. 
                   CHAPTER  VII.
THE ADJUSTMENT OF GLASSES FOR HYPERMETROPIA ; DIREC-
  TIONS FOR BEGINNING THE EXAMINATION IN CASES OF SUS-
  PECTED NEED OF GLASSES  FROM ANY CAUSE.
  A person desiring  glasses  for  hypermetropia,  or
Avhose vision is  suspected to  be imperfect, should be
seated at  twenty feet  from  No.  20.   If every letter
seems  black and the outlines of the letters  clearly de-
fined,  he  apparently has  normal vision  for distance,
but  may  still be over-sighted (hypermetropic).    In
order  to determine  this,  place in  front  of his eye  a
plus 72 inches  lens, and  let  him look at No. 20.*  If
the letters are slightly dimmed, or less distinctly  seen,
the eyes are normal for distant sight.  If, however, Avith
such a lens  the  sight  continues as good as before,
try a plus  36 inches lens;  if he  still sees as avcII, try a
stronger, and so on until he says  the letters are getting
dimmed.   The manifest hypermetropia is now overcome,
but  most  likely there  is  some latent.  The strongest
lens Avith  Avhich  sight  is  as good as it  is  Avithout
  * The difficulty of adjusting lenses by the  different systems  of nomen-
clature will be apparent at the outset of practical work. Therefore to com-
pel a practical familiarity with them, the  author has made u>c of both
systems  at times. A reference to the tables alrealy given will soon render
this easy, though the number of the glass is usually marked in both inches
and dioptries. It will be well to use the new system wherever possible.
                           86 
AND HOAV TO CHOOSE THEM.          87
 it, represents the manifest hypermetropia.  With this
 trouble, however, as Avith myopia, there is danger  of
 confounding  spasm  of the  ciliary muscle.  A more
 complete description of  the latter  affection  will  be
 given further on; it requires skill to detect ft.
   The total hypermetropia is determined by paralyzing
 the accommodation with atropine and then selecting a
 lens  of  sufficient strength  to render distant  objects
 clearly visible.  This lens represents the total  hyper-
 metropia.
   When atropine is  used, it is best for the patient's
 convenience and comfort to test only one eye at a time,
 allowing the  influence  of the drug  to  pass off  before
 subjecting the other eye to its poAver.
   It is well to completely paralyze the accommodation
 in cases  Avhich seem to require special examination.
 This is effectually done  by instilling three times  a day,
 for one or  two days, a drop of the folloAving solution;
              5  Atropine  sul. gr. iv,
                Aquae dest.    rj,  M.
   As a rule, it will  be  found, in  practice, that the
strength of the lenses to  be prescribed for individual oases
 should not be sufficient  to correct the total hypermetro-
 pia.   Correction  of the manifest hypermetropia  Avith a
small amount of the latent,  is often sufficient at first,
and relieves any asthenopia (loss of strength of the eye) 
88
SPECTACLES;
due to the affection.  Lenses sufficient to do this may
be worn until an additional amount of the latent hyper-
metropia  becomes manifest, and then  be replaced by
stronger ones.
  The correction, at first, of the total hypermetropia,
is  found practically to be attended Avith more or less
discomfort to  the  patient; for it  is  seldom  that  a
patient can  at  once Avholly dispose  of his habit of ac-
commodating.  His involuntary accommodation added
to  glasses of full  strength, renders his refraction  in
effect myopic.  He  must, therefore, by easy stages, be
educated to  the use of stronger and stronger glasses,
until  he has become accustomed  to the use of those
Avhich are equal to Irh total  hypermetropia.
  For children affected  only in a  slight degree, and
in Avhom the  accommodative  apparatus is in full vigor,
glasses Avhich overcome the hypermetropia for distance
are all that  may  be  required for many years.  For old
people, in whom the power of accommodation is nearly
lost, glasses  equal to the total hypermetropia may gen-
erally be prescribed at once.
  In  regard  to the use of Spectacles, it is best  that it
should be constant.  If the glasses are laid aside at
intervals, a return of the old symptoms is  apt to fol-
low, and no  progress will have  been jnade in overcom-
ing the disorder  of the  accommodation. HoAvever, in 
STs
X)
O                                           Fig. XXII.
H
£       " Pantoscopic  Spectacles," so called  from the ease with which vision of all objects is
o    obtained.  The sliape  of the  bridge, permitting it to rest low on the nose, enables one to
     see over the lenses, while the joints being set at a sharp angle to the plane of the lenses, the
55    Spectacles are always tilted.  Hence the wearer may sit erect.  Especially adapted to desk-
"^    work and similar occupations. 
90
spectacles;
young persons Avho experience no inconvenience, except
Avhile engaged in near and  fine  Avork, the Spectacles
may meet all requirements if worn only Avhile engaged
in such Avork.
  In advanced life, after presbyopia has set in, hyper-
metropes often require two pairs of glasses, the stronger
for near, and the Aveaker for distant vision.
  When Spectacles of a high poAver are required, as in
near vision  in hypermetropia of high degree, the  cen-
tering and adjusting  the  lenses properly, is a very im-
portant matter.  By centering is  meant that the lenses
should be so adjusted  as to  allow the  visual lines
to pass very near, or directly through, their axes.
  The necessity of this precaution will be very evident
if the reader reflects that  Avhen  light passes  too  near
the edge of  either a convex or a concave lens, the  lens
acts as a prism.
  So close is the association  between the functions of
accommodation and convergence,  that a slight disturb-
ance in their equilibrium (as by the action of improp-
erly centered lenses) maybe attended Avith very pain-
ful nervous symptoms.   It  should also be remembered
that  notwithstanding the lenses  may be properly cen-
tered, they cannot change Avith the movements  of the
eye.
  If the visual lines always remained in the same rela- 
AND HOAV TO  CHOOSE THEM.
91
tion  to  the centers of the lenses, or, in other Avords, if
the eyes always maintained  the same degree of con-
vergence and only  moved in exact conjunction Avith the
movements of the head, Spectacles could be so centered
and adjusted as to  be always a fixed and reliable  factor
in the visual  apparatus.  But not only does  the angle
which  the visual  lines make Avith each other change,
according as  we observe  near or  distant objects,  but
also  when the eyes  are  turned outwards, upwards or
downwards, the visual lines pass near and even beyond
the edges ot the glasses, thus causing confusion and in-
distinctness of vision.
  Hence, it will be seen that it is only when the  move-
ments of the head and the movements of the eyes are
equal, and in the same direction, that the most perfect
and satisfactory aid is obtained from  Spectacles. 
CHAPTER VIII.
THH ADJUSTMENT OF SPECTACLES FOR HYPERMETROPIA CON-
  CLUDED ; THEIR USE OFTEN NOT EASY AT FIRST ; HYPER-
  METROPIA OFTEN A CAUSE OF "STUPIDITY" IN CHILDREN;
  THE USE OF SPECTACLES BY CHILDREN.
  Eyes that are unused to the wearing of convex glasses
must often become accustomed to them in more respects
than one, before the effects of the new conditions, con-
sequent upon their use, Avill seem real and agreeable.
  At first, objects will often appear magnified and  be-
yond their usual  distances.
  We  learn to judge of the distance and size of objects
by the amount  of effort required in the accommodation
and the convergence of the eyes Avhile viewing such  ob-
jects.  The association  between the functions of  ac-
commodation and convergence is constant.   CoiiArex
glasses placed in front of hypermetropic  eyes cause  the
accommodation to relax; a certain degree of converg-
ence has always been associated with some given degree
of accommodation, hence the patient  at once associates
with the relaxed state of accommodation, a certain in-
crease  in the size and distance of objects.   Objects often
seem to recede, and in Aval king,  the floor or pavement
                          92 
AND HOW TO CHOOSE THEM.
93
                          FIG. XXIII.

  A  style of steel-framed lenses Avell adapted to children, or
 young persons.  The riding bows ensure their easy adaptation
 and firm position.
  For persons narrow between the eyes, especially when Pulpit-
 Glasses (See Fig. VIII.) are desired, they are sometimes espec-
ially useful. 
94
SPECTACLES;
seems farther away than natural, and the patient feels
as though he were constantly stepping to a lower level.
These false impressions are soon overcome, hoAvever, and
the estimation of distances and sizes becomes so natural
and connected as to meet the neAV conditions.
  It has already been mentioned that late  in life hyper-
metropic eyes (and in fact all eyes) become presbyopic,
and cannot  exert  the  accommodation  necessary  for
reading and fine Avork; therefore stronger glasses  are
required for such purposes, Avhile those glasses to which
the patient has already become accustomed, remain
good for distance.   A patient Avith  hypermetropia of
two dioptries, and Avearing lenses of sufficient strength
to correct it, would, in the ordinary course of events, at
the age of forty-five,  have presbyopia amounting to
about one dioptry.   He Avould  therefore require,  for
near vision, the addition of one dioptry to the strength
of his lenses, making the lenses three  instead of  two
dioptries.
  Aphakial  eyes are those from which the  crystalline
lens has been removed, perhaps for the cure of cataract,
perhaps by absorption after an injury.   It is scarcely
necessary to observe that such eyes are, Avith extremely
rare exceptions, intensely hypermetropic,  and destitute
of all accommodative power.  For such eyes, lenses of
great strength  are required to render  vision distinct. 
AND HOW TO CHOUSE  THEA1.
95
Those from two to two and one-half inches focal length
Avill usually be required for near vision, and those from
three to four inches focal length  for  distance.   These
lenses can be set in almost any spectacle frame desired.
It is Avell  to select one of the stronger kinds.  Such
lenses are generally known as  " Cataract glasses."
   Of course, owing to their great convexity, the  lenses
are  A'ery  heavy,  unless made  small.  Such being  the
case, special contrivances  have been devised for  reduc-
ing their size and  weight.
   Owing to the great pre\ralence of hypermetropia at
the present day, and the consequent suffering entailed
upon so many persons by the Avant of knowledge of its
nature and consequences, it is of the utmost importance
that physicians, at least, should become familiar with its
more prominent subjective as Avell as objective  symp-
toms.  A moderate  degree of intelligence upon  this
subject  Avill prevent many and grave mistakes.
   When a child is taken from school complaining of
headache and fatigue of the eyes, and, in addition  per-
haps charged  Avith stupidity and punished for idleness,
it is neither aviso nor kind for the  physician  to  advise
in every case, "Change of occupation, abstinence from
study, etc."  Nor does the child need the additional in-
fliction  of powerful medicines for an imaginary nervous
trouble.   Such a course is not Avise, because  a pair of 
                                      Fig. XXIV.

   A stvle of straight temple, gold-framed, Pulpit Spectacles.  Preferred by some presbyopes
on atcouit 0f this peculiar shape of the lenses, the upper part being cut away to permit of vis-
ion oveithe!  These peculiar^ lenses can be set in frames made of any kind ot meUu. 
AND HOW TO  CHOOSE TIIE31.           97
properly fitting lenses Avill often  remove the  headache
and the fatigue, and will perhaps restore the child to the
ranks of the brightest  and the  most studious of his
companions.   Such  a  course is  not kind because, too
often, it  blights the  brightest prospects of developing
maturity.
  Were there no other  moral obligations to be consid-
ered, man's responsibility to his  felloAV-man should be
sufficient to teach us, as physicians, to fit  ourselves to
recognize what these cases may  require and to advise
accordingly.
  Teachers in public schools should never  be  ignorant
of the nature and effects of hypermetropia;  for, by
proper and timely advice to parents,  they may be the
means of relieving some of their pupils of  much suffer-
ing.
  One of the most common results of hypermetropia is
convergent squint, or cross-eye.   At about the age of
five or six years, children are usually  put to school and
there required to read and Avrite,  and to ctherAvise use
their eyes for fixing small objects more or less distinctly
and continuously.   This  is the time when convergent
squint roost often makes its appearance.  The  explana-
tion  of this fact need not be added here, but it is proper
to remark that the timely use of convex Spectacles may,
in very many cases, prevent this condition. 
98
SPECTACLES;
  Without doubt, it will be no easy matter to compel a
child Avho is under six years of age to Avear Spectacles;
and too many parents have neither the faculty nor the in-
clination to see that the prescription of such Spectacles is
faithfully carried into effect.  Again, some children are
exceedingly tractable and  submit to  the Avearing  of
glasses, even at a very early age, Avhile  other  children
cannot be  made  to  tolerate them, even for a few mo-
ments at a time, notwithstanding the most patient and
well-directed  efforts on the part of those in charge  of
them.   Reasoning and kindness go  a great ways  in
this process; Avhen these  fail, judicious shaming in the
wray  of strong appeals to personal pride, generally  suc-
ceeds. 
CHAPTER IX.
THE ADJUST3IENT OF LENSES FOR MYOPIA;  THE WEAKEST
  THAT ARE REQUIRED ARE THE BEST ; THE PRINCIPLE UPON
  AVHICH  THE TREATMENT OF MYOPIA  DEPENDS ;  SLIGHT
  DEGREES OVERCOME BY OLD-SIGHT ; SPASM OF THE CILIARY
  muscle;  RAPIDLY ADVANCING MYOPIA SHOULD  EXCITE
  SUSPICION OF THIS TROUBLE.
  The patient should be seated as directed in the chap-
ter on hypermetropia, that is, at twenty feet from No.
20.  If now he sees  neither the letters distinctly ac-
cording  to their numbers, nor do convex glasses of any
power improve his vision, myopia may be suspected to
be present.  Place in front of his eye a minus 36 inches
lens; if this improves his vision and brings to his vieAV a
smaller set of letters  than he could  before see, change
to a stronger concave lens, and so on  until he reads No.
20.  The Aveakest lens Avith Avhich he can read No. 20 eas-
ily, Avill be the measure of his myopia (no spasm of the
ciliary muscle  being  present).   But if no glass be
found Avhich permits him to  do this,  he may be ambly-
opic or astigmatic and  require medical  or  other aid.
But OAving to the complications  Avhich may exist and
render vision otherwise defective, cases of mvopia must
                          99 
o
o
Fig. XXV.
of the common styles of Goggles, alluded to on page 28. 
AND  HOW  TO CHOOSE THEM.
101
not ahvays  be expected  to  be brought to a  normal
standard of vision for all distances.
  In regard to the choice of Spectacles, it is hard to give
anything like arbitrary rules, since so many complica-
tions are met in individual  cases.   In high  degrees,
Aveaker glasses for near and stronger for far  vision are
usually given.   In moderate cases (those of three diop-
tries or less) one pair of Spectacles will  often subserve
both purposes, and should be constantly worn.
  For  far vision in any case, the  glasses chosen should
be the weakest which render distant objects most dis-
tinctly visible.  These same glasses  Avould answer for
near vision (reading etc..) Avere it not for the diminished
poAver of accommodation, so common in myopic eyes.
This is the result of disuse  of the accommodative ap-
paratus,  and consequent Aveakness.  Therefore  Avhen
either one  or two  pairs of  glasses are required,  those
which fully correct the myopia, and  no stronger ones,
should be given for distant vision.
  The strength of the glasses to be used for near vision
in any given case, must  depend  much  upon the state
of the patient's accommodation.  If the accommodation
is good and the myopia  docs not exceed five  or six
dioptries, a patient  can sometimes, without  incon-
venience,  wear  lenses which nearly but do not quite
correct  the  defect.  But  the stronger the lenses used 
©
                         Fig. XXV1.
Hard-rubber frames, with pateut self-adjusting rubber clips,
371 
AND  HOW  TO CHOOSE 'I HEM.
103
the smaller will be the retinal imasres and the greater
the strain  upon the accommodation.
  The treatment of myopia,  by the  use  of concave
lenses, depends upon  the principle that carrying ob-
jects  farther from  the eye does away Avith an exces-
sive amount of convergence Avhich overtasks the  eyes,
and increases and perpetuates the trouble.   This fact
should be  impressed upon the minds of patients, or
the most carefully adapted glasses Avill often fail to
accomplish their purpose; for habits  once  formed are
hard  to  overcome, and the habit of bringing the  Avork
very  near  the eyes, unless due  care is exercised by the
patient,  will  often be  persisted in after the  glasses
are given.   This  matter needs especial attention in
the cases of children; for in them the disease is especi-
ally apt to increase.
  As the chief object in using  glasses at all  for  near
vision, is to  remove the far point to a convenient dis-
tance for reading and fine Avork,  (thus preventing strain-
ing of the  eyes by unnecessary convergence), let us see
how this may be accomplished.
  Suppose a patient has a myopia of five dioptries; his
far point is at about b' inches.  We Avish to remove it to a
convenient distance for reading.   A  myopia  of  three
dioptries has the far point at about thirteen inches; a
myopia of two and one-halt dioptries has the far  point 
104                SPECTACLES;
at about sixteen inches, and either distance is convenient
for reading.  We therefore give  lenses  Avhich reduce
the myopia to either 3 or 2.5 dioptries.  A  lens of 2 di-
optries will accomplish the first, a lens of 2.5 dioptries
will accomplish the second.
  In slight cases of myopia, (1.5 dioptries  or less)  the
only inconvenience experienced is  in not  seeing dis-
tant objects distinctly; so if  the patient  does not  un-
conciously, or  through ignorance of the effect,  bring
his Avork too near his eyes, he will suffer very little in-
convenience,  and may prefer  to use no glasses at,  all.
Children need especial care in regard to this  matter of
holding the Avork too near, for the defect is not only ag-
gravated by it, but often  created in perfectly  normal
eyes.   Children in Avhom nryopia exists to quite a de-
gree are often unjustly punished, through the  ignorance
of paients or teachers, for  a habit for Avhich they are in
no Avise responsible.  Until his  vision has been properly
tested, a child should never be corrected for holdinp; his
work too near.
  Slight degrees of the affection may not only be over-
come  by advancing presbyopia, but the latter sometimes
removes the near point to  such a distance, that  convex
glasses may be required for  reading  and concave  for
distance.  In most cases it  will be found that, OAving to
the addition of presbyopia, the concave glasses  may bo 
O
                         Fig, XXVII.

   The common curved-glass, blue coquille, referred toon page 28.
It more commonly has straight frames and bows, 
106
SPECTACLES;
replaced by Aveaker ones, and sometimes laid aside alto-
gether.
  The remarks concerning the centering of the lenses
under hypermetropia, are quite as applicable to myopia.
The visual lines should pass  through  the  axes of the
lenses, and, for this reason, the Spectacles for near vis-
ion, OAvino- to the convergence of the visual lines, should
have their axes nearer together than those used  for far
vision.
  Spasm of the ciliary muscle occurs  in hypermetropia
or myopia.  When due to  hypermetropia  it occurs in
young people most frequently.  While their eyes appear
myopic and concave glasses improve  vision, the  use  of
the ophthalmoscope, or paralysis of the accommodation
with atropine, reveals hypermetropia.  The state of the
refraction in such  eyes  is  also variable,  causing one
power of lenses to fit at one time and another poAver at
another.   But the strength of the  lenses  Avhich render
vision normal at any time, is much less than the apparent
degree of the myopia  would seem  to indicate.   Such
cases require careful  medical treatment.
  Cases of myopia Avhich increase rapidly, should  ex-
cite suspicion of spasm of the  ciliary muscle, especially
if they are accompanied by marked symptoms of asthen-
opia on  using  the  eyes for reading,  or for near work. 
CHAPTER  X.
THE ADJUSTMENT OF LENSES FOR MYOPIA CONCLUDED ; IN-
  SUFFICIENCY OF THE INTERNAL RECTI MUSCLES ;  ACTION
  OF PRISMS ; REASOXS AVHY GLASSES DO NOT ALAVA YS BENE-
  FIT  IN THIS TROUBLE ; CAUSES  AND  PKEVALEXCE OF
  THIS TROUBLE IN THIS AND OTHER COUNTRIES.
  One of the various complications, Avhich often  accom-
panies and is dependent upon myopia, is insufficiency of
the internal recti muscles, Avhose function it is to draw
the eye inAvarcls.   This affection is most  common in
myopia of  high degree,  though it may  be  present in
almost any grade.   The cause is to be found in the over-
work of the internal recti muscles, Avhile producing the
excessive convergence of the visual lines necessarv for
near vision.   The muscles become fatigued after con-
tinued exercise  in  reading, and  one eye finally  rolls
outwards.
  The subjective symptoms of Avhich the patient com-
plains, are heat, pain, fullness and pressure in and about
the eyes, with dimness and confusion of vision.  These
disappear after resting  the  eyes aAvhile,  only to be
reneAved as work is resumed.
  On  examination the eyes may appear normal, but if
                         107 
                           Fig. XXVIIL
   A style of Spectacles made to be worn by Surgeons while operating.
The lenses are plane and white ; If inches in diameter. 
AND HOW TO CHOOSE  THEM.
109'
we hold a pencil, or some similar object vertically in
front of the patient's eyes, and, Avhile he continues to
look steadily at the  object, gradually carry it  towards
his eyes, Ave shall find that when the object is within
five or six inches of the patient, one eye becomes un-
steady and rolls outAvards.    This outward deviation
may be gradual or sudden.
   But perhaps the best method of detecting this affec-
tion is by means of  prisms.  Hold a  prism in  front of
one of the eyes under examination, Avith its base either
upwards or dowiiAv^irds, and double images will be pro-
duced, Avith lateral displacement of these images.   That
is, one image will appear above the  other and to one
side.   In  the normal, or  emmetropic  eye, the prism
Avould simply have the effect of causing the images to
appear double, one image being directly above but not
to one side of the other.
   A Avhite card, Avith a dot in the middle of a vertical
line, is a convenient object for  the patient to observe
Avhile  undergoing the test.   He  should  fix  his  eyes
upon the dot and then note the effect.
   The strength of the prism required to fuse the tAVO im-
ages, is the measure  of the insufficiency.
   In order to treat these cases  intelligently, the prac-
titioner must not only be able to exclude cases of insuf-
ficiency of the internal recti muscles clue to other causes 
110
SPECTACLES;
than  myop'a, but he must also provide himself with a
set of prisms and the appropriate frames for adjusting
them. Some cases are greatly benefitted, and others are
completely relieved, by the wearing of proper prismatic
glasses.  The prisms are placed in the spectacle frames,
bases iiiAvards, and  combined Avith the  proper  concave
lenses; or, what is better, the concave lenses maybe
ground into the prisms.
  The action of the prisms is to deflect rays of light in-
wards toAvards their bases; therefore, rays from near
points, on passing through them,  enter  the  eyes  as
though they came from greater distances.  This disposes
of the excessive convergence of  the optic axes.  The
relations between accommodation and  convergence of
the eyes has already been referred to under hyperme-
tropia.  The proper concave lenses  relieve the accom-
modation, the proper prisms (bases iiiAvards) relieve the
convergence:  to  so adjust and combine the tAvo, that
these  functions shall remain in harmony, requires care
and an experimental knowledge of the subject;  to fully
elucidate it, by words, is difficult.   Experience is the
best teacher.
  With the best possible adaptation of glasses, the vision
of many myopic eyes is but little improved, especially for
distant objects.  This fact is susceptible of explanation
in various  ways; but perhaps  the most constant and 
H                                          Fio. XXIX.
S              A gold frame, ornamented with faceted work, presenting a particularly
33         genteel and elegant appearance. 
112                 SPECTACLES;
potent cause is to be found in the fact that the percep-
tive elements of the retina are spread over a larger space
in the myopic than in the emmetropic eye. Furthermore,
concave glasses, Avhile they bring parallel rays to a focus
at their proper place upon the retina, and  thus  maKc
the image distinct, also diminish the size of the images
so much, that sometimes little advantage is gained.
  Many persons affected Avith myopia, refuse to Avear
glasses  in the hope  that, Avith  the  advance of age,
they may have no need for them.  Such a course is
not to be commended, for not only is the affection more
apt to increase thereby, but  these persons constantly
undergo much unnecessary discomfort.
  When two pairs of glasses are given to one person,
explicit directions should be given regarding their use,
and the patient should be especially  Avarned against
attempting to use the  stronger glasses for near vision.
It is a question whether considerable harm is not caused
by the thoughtless observation of near objects Avhile the
stronger glasses are in  use.   The  stronger glasses  are
simply intended to contribute to the comfort of persons
wearing them, permitting  them to see at a distance;
the Aveaker glasses are intended to  prevent the progress
of the affection.  The  latter should not  be laid aside
while engaged in reading or near Avork.
  In  conclusion of the subject of the adjustment of 
AND HOAV TO  CHOOSE  THEM.
113
                 Fig. XXX.



Steel-framed eye-glasses, French modeled clips. 
114
SPECTACLES;
Spectacles for myopia, it will be interesting to note some
of the causes and the relative prevalence of this disease;
for myopia, without question, is often a disease.
  Cohn, of Germany, some years ago published a mono-
graph  upon this  subject, giving the results  of actual
examinations upon 10,060  school children.   He found
that the affection increased in proportion as the school-
rooms  Avere poorly lighted, or the  desks  badly con-
structed.  Of the 10,060 children examined 1,004 Avere
myopic.  The elementary scholars Avere less frequently
affected, and the number of cases increased as the grade
of the school was higher.
  That the disease  was an  acquired  one, is shoAvn by
the fact that out  of all  these  children,  only 28 had
myopic parents.
  According to the experience of Donders, who made
extensive observations in Europe, myopia  is much more
prevalent in Germany than elseAvhere.  Angell attrib-
utes this fact to the peculiar type in Avhich the German
text is printed; Avhile to confute this supposition, the
report made by Liebold in 1877  may be cited.   This
report shoAvs that among 600 girls in a grammar school
of New York, 53 were  myopic, 459 hypermetropic, 59
astigmatic and hypermetropic, and only 23 were emme-
tropic.  The ages  of these  scholars ranged  from eight
to eighteen years.   Such a report, if confirmed by others 
AND HOAV TO CHOOSE THEM.
115
of a similar nature, would seem to prove that the people
of  the  United States are far from being able to claim
any special exemption from the affection.
  The higher and better educated classes of society show
a much larger percentage of myopia than is found among
people in the loAver Avalks of life.   In the Eastern  and
Middle states it  is much more  common than in the
Western; and Fenner  says  "The great  number of
persons Avearing concave glasses in Boston, is a subject
of remark with many Southern and Western visitors to
that city, and is often attributed to a desire to appear
fashionable."
  Out  of the  10,060 children examined b}; Dr. Colin,
only 107 Avore Spectacles, and 99 of these had  selected
them themselves.   Only 11 Avore Spectacles  Avhich Avere
not injurious to the eyes.  Such  facts  need little com-
ment; for the injurious effects of a haphazard plan of
selecting Spectacles is too  plainly evident.
  In furtherance of the theory that myopia is acquired, and
not congenital as a rule, Mr. Macnamara, a distinguished
British surgeon resident in India,  says: " It is  remark-
able Iioav feAV cases of impaired vision, due to anomalies
in the refraction and accommodation ot the eye, are met
with among the loAver classes in India.  In  fact, Avhole
races of people appear to actually be strangers  to these
diseases.  For instance, some  years ago I Avas among 
                           Fig. XXXI.

   Lenses with  the attachments made directly to them, and known
as'Trameless Eye-glasses."  Being without frames, the lenses must
be made of a heavy  glnss, or pebble, to admit of a secure fastening.
Hence, the peculiar clips are advantageous in preventing their slip-
ping. 
AND HOAV TO CHOOSE THEM.
117
the Sonthals, the aborigines of Bengal, dwelling in the
Rajahmahal hills, and I took every opportunity of ex-
amining the eyes of the people I was brought in contact
Avith, for the purpose of discovering if myopia and such
like diseases existed among them; but I never yet saw a
young Sonthal Avhose eyes Avere  not emmetropic; the
same  remarks apply to nearly the whole of the lower
classes in Bengal, with the exception of those living in
Calcutta and other large toAvns, where overwork, sensual
indulgence, and a polluted atmosphere have done a vast
deal of harm to the physical, as Avell as the moral eyes
of the inhabitants." 
CHAPTER  XL
THE ADJUSTMENT OF GLASSES FOR PRESBYOPIA ; CHANGES IN
  THE EYE DUE TO AGE ; RECESSION OF THE NEAR POINT ; THE
  CALCULATIONS  REQUIRED ;  PRESBYOPES  SHOULD  HAVE
  ABUNDANT AID; GENERAL PRINCIPLES FOR THE TREAT-
  MENT; DANGERS OF ERROR.
  The nearest point of  distinct vision begins to  recede
at a very early  period  of life.  A child, at the age ot
ten years, can usually thread a small-eyed needle held
at a distance of two and three-quarters inches from the
eye; at the age of  fifteen years, the  near point has re-
ceded to about three and a quarter inches;  at tAventy,
it has gone to about three and three-quarters inches; at
thirty, to about  four and a  half inches;  at  forty,  to
about nine inches;  at forty-five, to about tAvelve inches;
at fifty to about eighteen  inches;  at fifty-five, to about
tAventy-tAVO inches; at  sixty, from thirty to thirty-six
inches; at eighty,  there  is no distinct vision Avithout
glasses.  As a rule, a young person avIio sees as well,
or better, Avith his mother's or grandmother's glasses,
is hypermetropic.
  Other changes also take place in the eye as age comes
on.   There is a loss of  the transparency of the media, 
eft
                                            Fig. XXXII.

§           Coin  silver frames Avith " Split lenses," or " Franklin glasses." It is a matter of
         taste, generally, as to whether the different powers shall be ground on a single piece
'*        of glass, or two half-ienses be placed together.   Sometimes they are ground on one
         piece in more fanciful shapes, as the upper half with a shorter radius than the lower
         half, etc., presenting a very genteel appearance. 
120
SPECTACLES;
which though gradual, is yet so steadily progressive that
oculists are able to closely estimate the age of a person
by this change alone.  The entire construction of the
eye also undergoes  changes not necessary to enumerate
in this connection.   The practical results of these are,
decrease in the refraction of the eye and shortening of
the range of the accommodation.
  I shall not  discuss these matters, since, for the pur-
poses of this subject, we may regard the recession of the
near point beyond 8 inches in emmetropic eyes, as the
beginning of  presbyopia.   By  means of convex Spec-
tacles,  the near point is restored to its normal distance
and the overtasked accommodation relieved.   In uncom-
plicated presbyopia, the patient can generally read No.
20 of the test types at 20 feet, but he cannot see small
objects well.  Ordinary fine print cannot be distinguished
at the  former distances of 8 inches and less, but it must
be carried farther from the eye.  The accommodation
is evidently at fault, and rays from near objects are not
focussed upon the retina.
  In the beginning of presbyopia, when  the near point
has not receded beyond 9 or  10  inches, very Aveak
glasses Avill supply the deficiency in the accommodation,
and Avill need to be Avorn  only in the evening and by
artificial light.  It is not Avell to begin Avith too strono-
glasses, for they hasten rather than retard the difficulty. 
AND  HOAV  TO CHOOSE THEM.
121
If the near point has receded to 9 inches, and  Ave Avish
to restore it to its original distance of 8 inches or less,
the lens necessary to do this may be found as follows:
1-8—1-9 = 1-72, Avhich sIioavs that  a  lens of 72 inches
focal  length (about  a plus  .5 dioptry) is required to
supply the deficiency in accommodation.   If the near
point is at 12 inches, then 1-8—1-12=1-24.  If the near
point is  at 16 inches, then 1-8—1-16=1-16, and so on:
or in other Avords,a 24 inches convex  lens (about a plus
1.5 dioptries) will supply the first case, and a 16 inches
convex lens (about a  plus 2.5 dioptries), Avill supply the
second.
  Inasmuch  as  presbyopia can be neutralized by con-
vex glasses, and that failing to  use them when indicated
Avill sooner  or  later cause  asthenopic  symptoms,  Ave
should insist that those suffering from this  defect Avear
glasses.   The weakest convex-lens Avhich  will  enable
them  Avithout fatigue to read  No. 1  of Snellen's test-
lypes at from eight to tAvelve  inches from  the eye,  are
the correct ones.   In  the greatest  number of cases,
plus 36 to plus 40 will be quite strong enough in  the
beginning; an increased power will be required as age
comes on.  In some cases it will be better to begin Avith
plus 72, or a number  but little  stronger.
  If, in addition to the presbyopia, the  patient is am-
blyopic, glasses Avill not improve the  vision much, if at 
122
SPECTACLES;
all.   It should  not be forgotton that  the perceptive
power of the  retina diminishes as age increases, thus
causing a defect in the visual apparatus  Avhich lenses
cannot remedy.
  Care should be observed to note that the patient has
abundant aid.   Many  Avill  endeavor to  conceal  their
" infirmity," as they often call it, through false motives
of pride, hoping thus to retain a baseless reputation for
juvenility.  Cataract and glaucoma, I believe, may often
find their cause in  the strain put upon aged eyes by im-
properly fitting  glasses.
  It should be remembered that the object of the con-
vex lenses, except  in extreme old age, is not to magnify
J   the  retinal images, but  to bring back the
          near point of distinct vision  to  a convenient
          distance,  thus making  the images  distinct
          and  of the same size as before;  furthermore,
          glasses adapted  for near vision are not suita-
          ble for far sight, their use  for such  being
          often injurious.
Fig. xxxin. The many  devices Avhereby the lens of the
eye is temporarily  made more elastic* are  in no Avise to
be recommended.   Their  after affects are often painful
and destructive  of good sight.
  The general principles  on which to treat presbyopia
are to recognize it early, and to supply abundant optical 
         AND HOAV TO CHOOSE THEM.       123

 It is quite impossible to determine an exact standard of vision
for what is called a normal eye.  As is wellltnown, no eye is
perfect. But by careful experimenting, I have found that print
of this size should be easily read in a good light, by what may
be called a perfect eye, at a distance of from four to four and



one-half feet,  while print of this size may be eas-
ily read, under similar conditions, at from five to
five  and one-half feet.  To secure a good illum-
ination,  the patient should sit with his back to

the light.



   Type of this size, however,  under

favorable  conditions,  should be read

at a distance  of about seven feet; and




when  this  size  is used,


good  vision should be


attained  at  a distance


of about  fifteen feet. 

iS
^
^J

                           Fig. XXXIV.

    Gold folding eye-glasses, suitable for ladies desiring a stylish and
convenient bow.
9999999999� 
AND HOAV TO  CHOOSE THEM.
125
aid.   If the glasses fail to relieAre, a more  careful con-
sideration of the convergent muscles must be made,and
such Spectacles as are described in the next chapter, the
orthoscopic, may be required.  I have  not  entered into
their discussion, because they require a someAvhat com-
prehensive knoAvledge of  the subject of the Avhole eye,
and information must be sought from larger works,  or
from some oculist.
  AVhile the dangers of carelessly choosing one's own
Spectacles are perhaps at  the minimum in presbyopia,
it must never be forgotten that a rapid increase of this
trouble is  one  of the premonitory  symptoms of that
little understood, but terrible trouble, glaucoma.  For
this  reason, and lest glasses be erroneonsly ordered for
anyone avIio applies for them by reason of suspected
advancing  " old-sight," all eyes  should be carefully ex-
amined for glaucomatous  symptoms, prominent among
Avhich are increase of tension, diminution of the  acute-
ness of vision, limitation of the  visual  field, etc.  Men-
tion has already been made of a case Avhere entire loss
of sight Avas due to this error.  In nearly every case of
this  kind, the remark is made that no  doctor had ever
before suggested any  danger, though several had been
consulted. 
CHAPTER XII.
SPECTACLES FOR  IRREGULAR SIGHT ;  STENOPEIC  SPECTA-
  CLES ; ORTHOSCOPIC SPECTACLES ; SUBMARINE SPECTACLES ;
  FORMS OF OCULISTS' P INSCRIPTIONS.
  A considerable number of cases of defective sight will
be found that cannot be fitted by any of the foregoing
rules, Avhich however, are not to be classed by the state-
ment  made  at  the end of Chapter  VI.  Among such
may be found eyes known as astigmatic.  The astig-
matism  may be  separate  from,  or  co-existent  with
myopia, hypermetropia, or emmetropia (normal refrac-
tion) in the same eye.  The companion eye may be em-
metropic or not.
  This subject of Astigmatism Avas briefly  alluded to
in Chapter I.  Before proceeding to consider the meth-
ods of correction of this anomaly by lenses, the nature
of the defect, and its varieties, need further description.
  That astigmatism is a defective state of the vision due
to a lack of symmetry between  the  different meridians
of the refracting surfaces, has been stated.  This asym-
metry or irregular curvature, may be found in the cornea
or in the crystalline lens.   The  principal meridians of
the cornea are those of the greatest and the least curva-
                        126 
5<1
g                                         Fig. XXXV.
p             Gold Spectacles, with colored-glass side-light protectors.  Preferred  by
'<,          some on account of their excluding the rays of reflected light.  The protec-
           tors may be of any colored glass desirable, 
128
SPECTACLES;
ture.  These two meridians are always at right angles
to each  other, and usually  one  is horizontal and the
other vertical.  Sometimes they lie obliquely.
  The two chief divisions are regular and irregular as-
tigmatism.  Different focal lengths of principal merid-
ians cause regular astigmatism ; differences of refraction
in the same meridian cause irregular astigmatism.   The
varieties of the regular form  are several, the degrees
are almost innumerable.  A patient Avith one meridian
emmetropic, and the meridian at a right angle to it my-
opic, has simple myopic astigmatism; or if the one me-
ridian be  emmetropic, and the one at a  right angle
hypermetropic, he has simple hypermetropic astigma-
tism.  Hypermetropia in both principal meridians, but
differing in degree, constitutes compound hypermetropic
astigmatism; myopia in both principal meridians, but
differing in degree, constitutes compound myopic astig-
matism.   Finally,  if a patient has myopia in one prin-
cipal meridian, and hypermetropia in the other, he has
mixed astigmatism.
  Regular astigmatism is usually a congenital heredit-
ary defect, while irregular astigmatism  is more apt to
be acquired.  The  former is  amenable to treatment by
lenses, the latter is seldom much benefited by any treat-
ment.
   The methods of testing and measuring astigmatism 
              AND HOW TO CHOOSE THEM.           129

are very numerous, and, as in the other forms of ame-
tropia, may be either subjective or objective.  The dif-
ference between  these  latter methods has  been  ex-
plained in a preceding chapter.
  All subjective tests depend upon the  fact that if the
astigmatic eve looks  at a number  of lines of uniform
width, drawn in  different directions, some will appear
clear,  and others more or  less indistinct.   The lines
used  for this  purpose should be clear, sharply defined,
and not too narrrJAV.  :;
   The normal eye is  said to be slightly astigmatic,
but if the  difference is less than l-40th of an inch,  it
causes no appreciable  disturbance of vision.
   The kind of lens necessary  to correct this  defect has
been already  mentioned.  All lenses for the correction
of ordinary errors of refraction are segments of spheres;
those  for  astigmatism often combine  tAvo kinds, the
spherical and  the cylindrical.   Sometimes  the latter is
sufficient.   A cylindrical lens is the longitudinal section
of a cylinder, and may be either convex or concave ac-
cording to the portion  of  the cylinder  it  is  taken
from.   It  may also be either plano-convex  or plano-
concave, bi-convex or bi-concave, a positi\e or negative
  * Diagrams for this  purpose may be obtained at any medical booksel-
ler's. The collection known as Green's Astigmatic Tests are among the
best. (Price,  $5.00). Pray's Astigmatic Letters are also useful. 
130
spectacles;
 meniscus.   When a cylindrical lens, is combined Avith a
 spherical lens, the resulting lens is termed sphero-cy-
 lindrical.  This lens is ni.de with one side ground spher-
 ical and the other cylindrical.
   Simple astigmatism is corrected by a cylindrical lens,
 while compound astigmatism requires a  combination of
 the tAvo kinds.  Success in treating astigmatism  lies
 in removing the difference betAveen the two meridians
 by a  cylindrical  lens appropriate  to such  difference;
 the spherical lens equalling the ametropia still remain-
 ing Avill then enable the  rays of  light  to  impinge
 sharply  on the retina, and  the  anomaly will be cor-
 rected.   A little  reflection  will shoAV that it is some-
 times a question of judgment as to  Avhetherit is better
 to  correct the anomaly as  apparent, or by a suitable
 cylindrical lens, create the  opposite one, and then re-
 lieve that by its suitable lens.
   Rays of light falling on  the plane of the  meridian
 passing through  the axis of a cylindrical  lens, do not
 change their direction, there being no refraction in this
 meridian.   In all  other meridians, hoAvever,  the light
 is refracted, but in  degrees,  increasing as the  meridian
 is more nearly perpendicular to the  axis of the  cvlinder.
 In the perpendicular meridian, the highest degree of re-
fraction is  obtained.
  Similar differences  of refractive power taking  place 
AND HOW TO CHOOSE THEM.
131
                       Fig. XXXVI,

   Monocle, or quizzing glass.  Not much used in this coun-
try.  Not recommended on account of the disuse of the com-
panion eye tending to weaken it. 
132
SPECTACLES;
in the astigmatic eye betAveen the least and the greatest
deviating (principal) meridians, it follows mechanically
that if a glass of the cylindrical  form compensating for
the deviation in any meridian, be placed in front of such
meridian, the eye Avill  be in a  correct state of refrac-
tion.
  The solving of the optical  problems presented  by
these various  forms of  astigmatism,  especially Avhen
they are combined  Avith  failing poAvers of accommoda-
tion, etc., Avhile not difficult, is of such seeming intri-
cacy that it is seldom ventured upon by one Avho is not
familiar  Avith the Avhole  subject of the anomalies of re-
fraction and accommodation.
  It is no uncommon thing, for one  avIio  has  not seen
Avell,  to find, on consulting an  oculist, that the Avhole
cause of his deficient sight is a trouble like one of those
Avhich have just been mentioned, and one which might
have  been corrected,  and  the  Avhole defect  removed,.
years  before.  Eyes not infrequently become astigmatic
after cataract operations; sometimes after any affection
requiring a  cutting of the cornea to any considerable
extent.
  Stenopeic Spectacles and Stenopeic Apparatus, are
terms applied to contriATinces designed to  improve the
vision in some special forms of  eye  trouble.   By an-
other'application of the same principle, they  shut out 
AND HOW TO  CHOOSE THEM.
133
intense transmitted and reflected light, as in the snoAV-
bound arctic  regions,  and thus avert  injury  to  the
sight by preventing damage to the retina.
  Corneal opacities are s3ldom so dense as to shut  off,
by reflection or absorption, all of the rays Avhich meet
them on the Avay to  the retina.  A clear portion of the
cornea, in the line of vision, allows all the rays Avhich
reach it  to  pass uninteruptedly  to  the retina, there to
form a distinct image of any external  object; but  the
part of the  cornea rendered translucent by an opacity,
transmits a  sort of diffuse light.    The latter acts as a
veil,  or  hazy obscuration, to  the images on the retina.
One office of Stenopeic Spectacles is to limit the field of
vision to a  clear portion  of the refracting media, and
to prevent  light from reaching the  corneal opacities.
The  light is  made  to pass through  a  comparatively
small opening in some opaque substance,  such opening
being made to conform someAvhat  to  the shape of the
clearest space in the  line of the pupil.  This  opening is
often in the form of a narroAV  slit; it mav be oval, or
round, according as the best result is  produced.   Ocu-
lists are pnrvidecl with different forms of this apparatus,
.and  are  enabled, by  their application,  to  determine
whether particular  forms of defective  vision  can be
improved.   Numerous ingenious appliances have been
devised for this purpose,  and have been found useful 
134
SPECTACLES;
in some forms of astigmatism, and  in high  degrees  of
myopia, etc.  In all cases the opening Avhich admits the
light should be as near the eye as possible.
  A simple  Avay of making Stenopeic Spectacles is to
blacken the  glass worn in an ordinary spectacle frame,
leaving only a small  clear space to correspond to the
clear portion of the cornea in front of the pupil.   The
glass worn in the spectacle frame may be plane or lens-
shaped, according to the  requirements of individual
cases.  It is sometimes necessary to make an iridectomy,.
to permit them to be worn to advantage.  On the other
hand, an iridectomy well-made often renders the steno-
peic apparatus  no longer necessary.
  Orthoscopic Spectacles is a term  applied to a  kind
consisting of lenses with a spherical surface on  one side
and  a  prismatic surface on the other.  The spherical
surfaces remove all  need for the exercise  of the  ac-
commodation, and the prismatic surfaces do aAvay with
the necessity for convergence. When properly adjlisted,.
they enable  one, up to a certain point,  to exercise the
eyes Avithout any strain upon them.  Practically, they
are limited in their use, but great advantage may some-
times be obtained from them.
  The uses of Prismatic Spectacles have been alluded  to
frequently in the course of descriptions of other kinds.
A special study may  be made of them Avith advantage. 
CO
                         Fig. XXXVII.
    A tortoise-shell frame, with peculiar self-adjusting whalebone
clips. These clips admit of an adjustment not obtainable by those
of a firmer nature. 
13(i
SPECTACLES;
Such study, as  well as a much more extended one of
the various kinds used for astigmatism Avill  be  a neces-
sity  for  those  avIio  desire  to  master  the  highest
branches of the adjustment of Spectacles.
  My venerable friend, Dr. R. E. Dudgeon, of London,
England, in his Avork entitled " The Human Eye;  its
Optical Construction," explains a device of his  oavh for
seeing under Avater.   As is Avell knoAvn, the eye alone
does not enable a person to see Avell under water; to
overcome this, Dr. Dudgeon has devised  and constructed
a pair of Spectacles that  restore the refraction to the
same  extent that  exists before the eye is immersed in
this fluid.
  When in London last, I was not only fortunate enough
to be  honored with the presentation by the inventor of
one of the  original air-lenses described  in the text, but
of Avitnessing a practical demonstration of his theory of
the accommodation which  has given him such a high
rank among scientists.  It must at least, be entitled to
rank Avith any theory concerning this subject,  (though
that of Helmholtz is perhaps the  most  generally  re-
ceived).  For my  OAvn part, I have  never been able to
reconcile Avith either, the fact that  some eyes  will  ac-
commodate  Avhen  the lens  is removed, for the lens is
essential  to  the  successful  demonstration of either
theory. 
AND HOW TO CHOOSE THEM.
137
  Dr. Dudgeon  remarks  that " The  sight  which  in
reality  remains to  us  Avhen immersed in the  clearest
water is the  perception of light and of color, but only
the vaguest  perception of form.  And even this poor
amount of vision  only remains for objects at  a  small
distance from us;  a feAV yards off, e\ren objects of con-
siderable size are unseen.
  " In order to restore perfect vision under water, we
must use a lens capable of concentrating the rays of
light transmitted to it  through Avater into a focus at 1
1-2 inch behind it; this being  the focus of the  aqueous
lens lost by immersion in the Avater.
  " If Ave use a glass lens for this purpose  it is obvious
that it must be a much more powerful lens than Avhat
would have a focus of that length in air.  For Avhile the
refractive index of air compared with that of glass is as
1 to 1.5, the  refractive index of Avater  compared Avith
that of glass is only as 1.33 to 1.5.  Hence glass Avill
refract the rays of light to a very much smaller extent
in Avater than in air, in fact about one-fourth.  I have
found experimentally that a glass lens Avhich has a focus
of three-eights of an inch in  air Avill have a focus of 1
1-2 inch in AA^ater.   Therefore a glass lens of this power
Avill be required in order to enable an eye immersed  in
water to see distinctly, and I have practically proved that
this is so. 
138
SPECTACLES;
  " But it is obvious that Avater being itself a medium of
high refractive power, it Avould be better to avail our-
selves of a medium either of much greater refractive
power than  itself, or of much less.  Now it is difficult
to procure a transparent medium of much  greater re-
fractive poAver than glass for use in the Avater.  Diamond,.
Avhich would do, its refractive power being as high as
2.4, is for obvious reasons not to be thought of.  But
there is nothing to prevent us using a medium of very
inferior refractive power to water in the construction of
subaqueous  lenses.   The medium of least refractive
poAver is air.  The relation of lens medium to surround-
ing medium being reversed, the  shape  of the air lens
must be also reversed, as before shown.   We must here
use a double  concave air lens in place  of the double
convex glass lens.
  "By taking twTo of the  old-fashioned highly-curved
watch glasses, and fixing them in a ring Avith their con-
cavities outwards, we  enclose a  portion of air of the
shape of a double concave lens.   Immersed in Avater,
this air lens will  refract the rays of light from objects
reaching it through the Avater, convergently.  It will
resemble in  its optical properties a double convex glass
lens in air, as I have explained.
  " I found that a double concave air lens, made Avith tAVO-
sections of a glass globe of 2 inches diameter, consti- 
AND HOW  TO CHOOSE THEM.           139
Fig. XXXVIII.
    A  very  handsome faceted  frame of gold.   For
those who desire a gold eye-glass, no haDdsomer frame
can be selected. 
140
SPECTACLES;
 tute a lens of 1 1-2 inch focus when immersed in Avater
 This lens accordingly supplies the refractive poAver lost
 by the eye Avhen immersed in water.
   "I thought it might be advantageous, or at all events
 agreeable to be able to see distinctly when diving; so I
 constructed a pair of Spectacles fitted Avith air lenses ot the
 kind just described.   It is obvious that Spectacles fitted
 Avith air lenses Avould be much more convenient for diving
than glass lenses.  For Avhereas the glass lenses required
 for subaqueous purposes are of such very short focus in
 air (only three-eights of an inch), that they Avould pre-
 vent  all vision Avhen the  diver  came to  the  surface,
 these air lenses Avould offer  no impediment to  perfect
 vision in the air, and so might continue to be avoiti Avith
 equal advantage both  in air and Vater.   I found, how-
 ever, that  the  tAvo  sections  of  a  glass  globe  Avhich
 form  the concave air lens, have in the air the effect of a
 verv  Aveak  concave glass lens, * such a lens  as  is used
 to  correct  the  slightest degree  of short-sight.   The
 cause of this is that the inner concave surface of the
 glass globe is a curve of smaller  radius than the outer
 convex surface.   Thus it is a  concavo-convex  lens,
 though of very small power.  But Avhen tAvo such glasses
 are placed together the refraction they produce is appre-
  *Such an effect as is produced by the common cheap blue-glasse3 (< o-
<quilles), as mentioned on page 28. 
AND  HOAV TO CHOOSE THEM.
141
ciable,  and someAvhat impairs  perfect vision  to a  non-
myopic eye.
   "In order to counteract  this slight refraction in the
lens Avhen used in the air, in place of having the glasses
made of sections of a glass globe, I had them ground
with surfaces of precise^ the same curvature. *
   " By this means  I obtained glasses for my  air lenses.
Avhich,  having their surfaces of precisely the same curve,
cause no  deflection of the rays of light.  These lenses
therefore restore perfect vision beneath  the water, and
offer no impediment to  perfect sight in the air."
   When  the  oculist has made his examination  of  a.
patient, if he decides to order  Spectacles, he writes  a
prescription as the case  may demand.  In this, as  in  a
prescription to an apothecary, certain symbols are used,
intelligible only to  the initiated.   Ordinarily  a printed
form is used, Avhich the oculist fills and sends to the
optician.   One of these  forms is given on the  folloAving
page.   AVith  the exception  of the  radiating lines, Avith
their corresponding numbers, as shown in the cut, the
items explain themselves.   The lines and numbers are
intended to indicate the various degrees of inclination
at which the axes of cylindrical lenses are set in spec-
 »Exactly as may be done when coquilles are necessary. They are  much
more expensive than the pressed or molded ones, however. 
142                   SPECTACLES;
18-
Spherical
Cylind.      Axis:
   it            u
Prism.      Base:
Spherical
Cylind.      Axis

Prism.      Base
Distance between centres of pupils,
   "      "    temples,    .....
   "    from inner Canthus to Crest of nasal bone,
       For distance ?          or near point ?
       Crown glass ?          or Pebble ?
inch.
.. M. D.
To 
AND HOAV  TO CHOOSE THEM.
143
 tacle frames.   This cut, while very useful, is not essen-
 tial if the directions are plainly Avritten.
   Some of the symbols in common use, Avith their signi-
 fications,  are  the  following:  O.  D.  (opticus  dexter),
 the right eye;  O. S.  (opticus sinister), the left eye;
 -f- positive; — negative; s., spherical; c., cylindrical;
 3 or |   combined  with;  = equality; -4-stands for a
 convex glass, —  for a concave.
   A  few  examples  of the practical uses of symbols are
 as folloAvs:  -f~ 60 s, represents a convex spherical lens
 of 60 inches.    When  no symbols are used before  or
 after the nnmber of the lenses, the symbols -f- and s.
 are understood.   — 42 c represents a concave cylindri-
 cal glass of 42 inches.
   O. D. —  36 and O. S. — 36, signify that a  concave
 spherical  lens of 36 inches is  to be used for each eye.
 A prescription Avritten as follows:
   O. D.                      O. S.
 -8C-^C Axis H.      — 8 C — 30 c Axis H.
 signifies that for the right eye, a concave spherical glass
 of 8 inches is to be used in combination Avith a  concave
 cylindrical glass of 24 inches, the latter having its axis
 horizontal;  for the left eye a similar spherical glass is
 to be used, but combined with a concave cylindrical
one of 30 inches, axis horizontal.   Some further exam-
ples from practice are: 
144
SPECTACLES;
    O. D.                       O. S.
— 24 o  Axis V.             — 30 c Axis V.
    O. D.                       O. S.
+ 13C + 30C Axis 60°    + 13 C + 48caxis 120°.
    O. D.                       O. S.
— 13 C 10 prism, base       — 13 C 1° prism, base
    iiiAvard.                     inward.
    O. D.                       O. S.
— 9                       —6J 3 y° prism, base
                                outAvard.
    O. D.                       O. S.
— 12 C — 30 c axis 60°.    — 14 C — 36° axis 120°.
  The items in the printed forms are also to  be filled
us essential aids to the symbols. 
CHAPTER XIII.
OTHER DEVICES FOR AIDING THE ACCOMMODATIVE  EFFORT;
  THE  TYPE WHITER; THURSFIELD'S WRITING SLATE; STAND-
  ING DESKS ; MEANS OF ILLUMINATION ; OIL OR GAS.
  Ill the preceding chapters, stress has frequently been
laid upon the value Spectacles have in assisting the ac-
commodation, etc.   While not strictly embraced under
the title of this volume, it Avill not only be  fitting  but
most valuable to refer to  some accompaniments especi-
ally adapted to those who are,  even Avith  the  best ot
glasses, obliged to economize in the use ot their eyes.
All devices Avhich tend to save the  strength necessary
to be  applied in this direction, are  a great boon  to
mankind, in that they permit many to engage,  or con-
tinue, in occupations Avhich  they othenvise Avould be
obliged to abandon altogether.
  Prominent among these stands a  contrivance knoAvn
as  The  Type-writer.  Fig.  XXXIX  sIioavs this ap-
paratus in one of its best  styles.   It consists essentially
of a square iron frame Avith a key-board, containing the
keys Avhich control the letters.  The latter are arranged
in the  order of their respective frequency in Avords
                         145 
146
SPECTACLES;
   Fig. XXXIX.




The Type-Writer. 
AND  HOW  TO CHOOSE  THEM.
147
and not in alphabetical order.  The Avhole apparatus is
placed on a table.   By striking the proper key, an arm
containing the  desired  letter is immediately  thrown
upAvard, and the letter is imprinted on the paper in its
correct position.  Mr.  Carter has so well described the
invention that I quote him as far as applicable, slightly
changing the wording in some minor details to make it
correspond  to the improved machines. *  Quite  large
portions of intercurrent irrelevant matter  have also
been omitted.   "Even in learning the use of the instru-
ment, Avhen the letters have to be looked for one by
one  until the fingers  become sufficiently familiar with
their several positions to touch them instinctively, the
characters are so  large  that there is no appreciable
strain on the vision; and, Avhen once  dexterity is  at-
tained, the eyes can scarcely  be said to be used at all.
My own eyes have never occasioned me any discomfort;
and  my own use  of the  type-writer  rests  upon quite
different grounds;  but yet my experience of it enables
me  to  recommend it,  very strongly, to all  persons
Avho, having to Avrite  much, are made conscious that
they have eyes.   For the short-sighted it  is  especially
valuable;  because there can never be any inducement
to stoop over it, so that a great snare to them in Avrit-
ing  is  set aside altogether.  Next only in advantage
  * For sale by Messrs. E. Remington & Sons, 38 Madison street, Chicago. 
148
SPECTACLES;
to  the  facilities it affords  for writing are  those  it.
affords for reading what  has  been Avritten; for this is-
printcd iu perfectly spaced  lines at regular and  if de-
sired, at rather Avide intervals, in capital or small letters
of perfect clearness.    The author Avho Avishes to glance
back over his  manuscript is almost as much helped as
he  who only wishes  to produce it; and the  labor of
seeing, in every stage ot the process, is either abolished
or reduced to a minimum.
  " I most strongly  recommend the type-writer to all
persons who Avrite for considerable  periods  of  time,
more especially the short-sighted, or to those Avho have
any trouble about their eyes.
  " In using it, it is quite possible to keep the shoulders
square and to sit erect;  but nearly  all persons who
Avrite Avith a pen at a  Ioav desk contract a habit of stoop-
ing, which is in  many ways  prejudicial  to them.  It not
only contracts the chest, so  as to interfere Avith the
freedom of respiration and thus Avith the due  aeration
of the blood; but it also tends to produce congestion of
the head generally and of the eyes in particular."
  My experience with the type-Avriter, though someAvhat
different, has been quite  as favorable as Mr. Carter's.
It did not take  me  so long  to learn, and I naturally
Avrite so fast that I did not increase  the speed as rapidly
as he did.  I  also was very loth to take it  up, being 
J5
Fig. XL.
    Colored coquille eye-glasses.   Subject to the same criticism as the
straight-temple bows, but useful under the same conditions, 
150
SPECTACLES;
naturally very conservative.  But  after much use of it,
I must say I regret very much to have so long lost the
very great aid I Iciioav it to be, for it Avould have saved
me many weary hours of drudgery in Avriting, and much
strain upon the eyes.
  The extract just quoted has so fully covered the usu-
ally claimed advantages that any farther commendations
may seem unnecessary, but I shall  add that the greatest
advantage I have  derived from it has been in the rest to
the eyes it has afforded  in composing articles for the
printer, and  in my correspondence.   I  can use it as
one composes on  the piano, in Avhich occupation, as an
expert knoAvs, the composer  is seldom compelled to
look at  the keys,  they being absorbed  in the mental
act of  composition.   The manuscript  for  this book
was  entirely prepared on the  type-writer, and that
too,  Avith an ease and accuracy  not to  be attained in
any other Avay.
  From the great distress it formerly gave me to Avrite
Avhen fatigued, or after eating,  I had to come to  the
conclusion that I must give up this labor at such  times
and had in fact  made arrangements tending towards an
early release from such Avork, for all  oculists  knoAv
that the process of digestion often  diminishes the poAver
required to sustain the eye-sight.   The  relief  in pos- 
Fig. XLI.
    Gold mounted "Frameless Hook Spectacles,"  with wide nose-
rest.
    All kinds of riding bow, or hook, Spectacles, can be made with
what are known as short hooks. Such hooks do not curl around  the
ears, but are firmly made, and simply hook on to them.  The catch-
ing in the hair, and  the difficulty sometimes  experienced  in  not
readily taking them off, are thus in a great measure obviated. 
152                 SPECTACLES;
ture afforded by this instrument, has saved  me from
an unwelcome change.
  I was also fearful that the cramped position ot  the
hand required in writing Avould impair my manual dex-
terity, to  attain which I  had sacrificed  so  much;  for
the muscles of my fingers and thumbs have often felt so
stiff, hours after writing, that I was unable to  use them
naturally for other work.   With the type-writer,hoAv-
ever, I have written  for hours at a time and then risen
fresh and  comfortable, a thing I cannot say ever oc-
curred after a similar use of the pen.  Therefore I com-
mend it highly as an agreeable  relief in literary labors,
and as an aid in saving and preserving the eyesight.
  Another device deserving mention is what is known
as ThursfielaVs  Writing Slate.   The object of this device
is to enable one to write in the dark, or Avithout the  use
of the  eyes; it accomplishes its purpose admirably.   It
is essentially a flat surface, Avhich may beheld in the lap
or placed upon the table, with a horizontal bar to guide
and support the hand.   When  the  end  of  the line is
reached, the bar drops, by an automatic movement, so
as to bring the next line into proper  position.
  After a  little  practice,  its  use becomes  easy, and a
greater or less degree of speed is attained.   This may
be kept up without the aid of sight.  Thus the machine
is equally  useful in  the  railway carriage for those avIio 
AND 1IOAV TO CHOOSE THEM.          153
are compelled to economize their time while on a jour-
ney : to  those avIio  are  unable to sleep at  night  and
desire  to  pass the time  in  an agreeable manner,
Avithout  injuring their  eyes,  as they are  extremely
liable  to  do  reading in bed, or  by  a continuous use
night after night even though they occupy a better po-
sition ; to the blind  avIio desire to continue an occupa-
tion formed in happier  hours;   as Avell  as  to many
others, to Avhom it is not necessary to allude; for each
may recognize its adaptation to some Avant.
   If the writing is to be  preserved, a metallic paper can
be used Avhich renders the  Avriting indelible, or an or-
dinary style and carbon  paper may be used.
   For those  avIio Avrite much, hoAvever,  a frequent
change of  posture as has been  indicated,  Avill afford a
most agreeable relief.  To gain this, I have been in the
habit of changing from a sitting to a standing position.
The only objection to the latter is that,  too long con-
tinued, it tends  to the formation of varicose veins in the
lower limbs.
   Any form  of desk that admits of a standing position
will do; but  for those  avIio desire to economize room,
or avIio  have but little use for such  a desk,  one  that
folds is a convenience.
   But among all the most important things to be  con-
sidered in this connection, that  Avhich perhaps stands 

                            Fig. XLII.

    Gold Spectacles, of the kind known as "Slide Temples," with me-
dium sized frames, 
AND HOAV TO CHOOSE THEM.
155
most prominent is the method of illumination.   It
Avould seem almost unnecessary to some,  I  presume,
to say that the  light supplied by nature,—pure, clear,
non-dazzling sunlight—is  the best of all  lights;  but
the assertions of ignorant  or designing persons avIio
have given out that some modes of artificial  illumina-
tion are  better  than this gift of nature, Avill account
for the necessity of the remark.   While it cannot be
denied that some forms of artificial  illumination are far
superior to others, Ave  must still return to the original
fountain source  for the  best.
  From time to time, articles  are  scattered broadcast
by the public press, extolling this or  that special  kind
of oil as superior to some rival oil or even to street gas,
and I am often asked Avhich kind should be  used; or if
all oils should be given  up,  and the gas used.   After
considerable examination into the subject, and numer-
ous inquiries among those who also  have had experience
Avith such matters,  I am of the opinion that we cannot
in every case lay doAvn  the same laAv, for some persons
see better by gas and others by oil light.  With proper
care,  one can soon learn  which kind  of illumination
suits best, and then folloAv  out his desires; but I am
satisfied that the common attempt  to compel each  one
of a  family to use  oil for  near lights, and especially
at night, is a  mistake.   Kerosene  oil  has at times a 
156
SPECTACLES;
very marked effect on my own eyes; I have verified this
statement too often not to be sure of it.  Even though
entirely uhaAvare that kerosene is being consumed in  a
room, a feAv moments Avork  by it, at near objects, will
reveal  the  fact of its presence by rendering  my eyes
troublesome.  This is due to an  irritating and  smart-
ing sensation which, hoAvever, passes off after a feAv
hours rest.   A long continuance of close application by
gas light has never developed such distress.
  Those  Avho find oil more agreeable to the eyes, but
unpleasant on account of the greasiness Avhich pervades
the lamp, even though the latter does not leak, can
make use of the colza oil, it being free from this objec-
tion.
  But whatever  the material, care is again required to
secure  the most  perfect combustion.   This is best at-
tained  by  the burner now generally  introduced and
knoAvn as the Silber argand burner.  We are all famil-
iar Avith the fact that where gas  is being rapidly con-
sumed, or  in large quantity, the air  quickly becomes
foul; hence a free ventilation should always  be main-
tained, not only to secure the necessary air for properly
aerating the blood but to secure  the best illumination.
The  same  holds  true Avhen  oil  is being consumed,
though Ave may be less  conscious of it, and Ave should
see that ventilation is not neglected. 

  An elegant style of frame, known as the Lorg-
nette.  The bow folds on itself, and shuts in the
case, which is used as the hand piece.
  Such a frame is usually made of fine gold,
though shell, or hard rubber, is sometimes u.sed. 
158
SPECTACLES;
  The proper  kind of lamp may  also  be important.
Without going far into the subject, it may suffice to say
that a lamp Avith a steady flame is essential, and is all
the  better if it have  a good shade.   That  which is
known as  the  student's lamp, complies  Avith most of
the essential conditions.
  As usually hung over the head, the gas chandelier
is not a fit light by Avhich to read or study.   Neither
is any ordinary light placed  at that  distance.    There
is, perhaps, less harm done by  too strong light than
by too weak; Avith a little care there is  usually no ne-
cessity for either. 
AND   HOAV  lO  CHOOSE  Til KM.
159
                                   TEST  TYPES;
FOR  TESTING THE  VISION,  IN THE  SELECTION OF  SPEC-
                                       TACLES. *
                                     (No.   1  Jaeger.)

  The Beauchamp Tower, a portion of the Tower of London, and a monumeut of ancient times and custom", is built on
the bank of the river Thames, and stands on the brow of the eminence called Tower liill, the spot where so many persona
of distinguished character suffered death at the hands of the executioner. Judging from the position of the Tower, it seems
probable that it was intended to defend the approach, by water, to the famous Metropolis of the British Empire.  It has
been conSdently asserted that tho Tower owes its origin to the Romans, yet, though there are many circumstances which
appear to uphold ths truth of this supposition, we must not tike it for granted without examining the probabilities.
Mr. Burton, in his history of  the Tower, mentions that it is affirmed that the Tower  was built about  the time of
■Coastantine the Great; it is also stated, that  it was the treasury . n I mint of the Romans.  The grounds given by Dr.
Milles for this assertion are that In laying foundations for a new ordnance office, in 1777, the workmen discovered an
ingot of silver bearing the impression of Roman characters, and also several gold coins, etc. Judsing from these circum-
stances, and also from the naturally favorable position of the eminence on which it now stands, it seems probable that
the Romans had  some  kind of fortress on the site of the present building, though  there is no satisfactory ground for
supposing that any builling of importance existed herd before the  time of William the Conqueror, by whose command
the White Tower  was  built, under  the superintendence of  Gundulph, Bishop of  Rochester; and several important
fortifications were  added durin; the  time of William's two sons,  William Rufus and Henry I.  Since its erection, the
Tower has been used both as a Royal  residence and State Prison,  and if we consider  it in either of these characters, it is
full of interesting recollections to a contemplative mind.  Stephen  is the first monarch  mentioned as residing in the
Tower, he having kept bis Court here duriag his troublesome wars with the Empress Matilda.
                                     (No,  2 Jaeger )
                                     (No.   1  Snellen.)

   About the year 1180, the Tower was surrounded by a moat, by Longchamp, Bishop of Ely, who was left
 in charge by Richard I, during his expedition to the Holy Land.   King John frequently kept his Court
 at the Tower, and made many additions to the different fortifications; in 1215, the Barons besieged the
 Tower, and John was forced to make many concessions, amongst others the signing of Magna Charta.
 For some  time after  the death of John, his son was constantly employed  in repairing the injuries
 sustained by the Tower during the turbulent reign of his  father.  It was probably during his reign that
 the tower was built which contains the antiquities enumerated in this book ; he also began an additional
 line of fortifications, but was unable to complete his designs at this time, in consequence of the foundations
 giving way and the whole of the work being  destroyed. This accident took place a second time, in 1241.
 Henry appears to have made the Tower his chief residence; it was there that he was compelled to  sub-
 scribe to the conditions imposed by the Earl of Leicester and his traitorous  associates.  On the accession
 of Edward I, he considerably  improved the  fortifications of  the Tower, by completing what his fathi r
 began, and erecting several strong outworks as a defence to the principal entrance.  The Tower does not

   * Books of Tost-Typ  s,  in  several languages, with large cards to hang on
the  wall, may be  obtained of any medical  book-seller.   Snellen's  collec-
tion is one of the best. 
1G0
spectacles;
                             (No. 4  Jaeger.}

appear to have been much used as a Royal residence during his reign, but to have derived
its chief importance from its character of a State prison, to which purpose it was chiefly
appropriated throughout the active career of this monarch.  Of the Jews who were ap-
prehended in 1278, on suspicion of clipping and adulterating the coin of the realm, no less
than 000 were, at one  time, confined in the Tower.  In 1330, the infamous Mortimer was
conveyed a prisoner to the Tower, and from thence to the gallows, by the command of
Edward III. Though it is impossible, in this small book, to enumerate all the eventful
scenes enacted in this fortress, yet, before we close this notice,  we may mention that in
1509, Henry VIII brought his wife, Catherine  of Arragon, to  the  Tower, after her
coronation; and, in 1530, being tired of Catherine, he brought to the same place a younger
                           (No. 5  Jaeger.)
                          (No.  3 Snellen.)

and  fairer bride, who  was also destined,  very shortly, to give way to a^
rival, and to suffer death amidst the  scenes which  had witnessed her
former splendor.  During the reign  of  Mary, the Tower was the scene of
the imprisonment and death of her innocent  rival, Lady Jane Grey, who
was executed on the Tower Green in 1554.  After the death of Mary, the
Tower was very seldom used as a Royal residence;  the usual procession
from  thence to Westminster was abandoned on  the  accession of James
II, on account of the attendant expenses; nor have any of our Sovereigns.
since that period made the Tower their place  of abode. 
                     No. 10.
ECHDLUTOFS
No. 12.
FOLUEDSTCH
No. 15.
LSEOFDTHUC 
 
20 Feet.
UFDTCLSE
30 Feet.
C          H        O         F           D 
 
o
*j
(0
*j 
 
*i
n 
 
h}
 
 
200 Feet. 
 
BY  THE AUTHOR OF  J HIS WORK!
A  SYSTEM
OF
EYE   AND   EAR
               NOTES.
            ByC. H.Vilas, M. A., M. D.,

Professor of Diseases of the Eye and Ear in the Hahnemann Med-
     ical College, and Ophthalmic  and  Aural  Surgeon to
          the  Hahnemann  Hospital, Chicago, etc.
  These Notes were prepared to assist in the study and form
the basis of the  didactic lectures on the embraced subjects as
given by the author at the Hahnemann Medical College and
Hospital, Chicago.
  They are essentially elementary in their character, and  are
especially designed to give as much practical  information as is
consistent with little theoretical study.  They are not designed
to take the place of voluminous treatises, but aid the busy prac-
titioner or student, by picking out of the mass of writings  the
essential diagnostic points, and giving the treatment.
  They have been highly commended by Prof. T. P. Wilson, of
Ann Arbor, Mich., Pres't of the American Institute of Homoeo-
pathy; Dr. W. L. Breyfogle, of Louisville, Ky.; Dr. W. II. Win-
slow, of Philadelphia. Pa., and other physicians eminent in  the
department of ophthalmology and otology.       ,
  Price, $2.50.
  The edition published last January (2,500) is nearly exhausted.
    For Sale by
                               DUNCAN  BROS.,
131 & 133 S. Clark St.                   CHICAGO, ILL. 
HOW   to   be    PLUMP.
                         OR

TALKS  ON  PHYSIOLOGICAL FEEDING,
                              BY

               T.  C.  DUNCAN,  M.D.,

Author of a Professional  Treatise on Diseases of Infants

      and Children and their Homoeopathic  Treat-

          ment; Editor " United Stales Medical

                   Investigator,  etc.  etc."
Finely bound in Cloth      ...     -     Price, SO Cents.
   It is an admirable work on  hygiene, as faras i't relates to eating— Ohio.
Farmer.

   These " Talks " have their own charm, for most of us like to be plump.
— Women's Journal, Boston.

   Certainly all thin people should ponder well its suggestions and put them
into practice.— Voice of Masonry.

   A brochure which many persons of lean inclinations will be glad to read
and may be able to profit by.—Banner of  Light.

   The  little  volume  contains n uch sensible professional  advice upon
healthy and morbid digestion, and the occasions of it.—Zion's  Herald.

   The book is intended to indicate how anyone may become fat, fair and
jolly, and a careful perusal affords proof  that the authorisfully conversant
with his subject, and that he has done it full justice.—The Cmcago Grocer.

   It  is a common  sense volume, that  believes  in  rational  and practicl,
methods of preserving health,  beautv and happiness.  It  is not a receipt
book <>f  impos ibilities; it is a bright, genial book, that understands itself
from first to last.—The Chicago Cosmopolitan.

   We do most warmly applaud its purpose, and especially commend its
philosophy to theunnaturahy lean, and still mor ■ to mothers in the training
of delica e children  whose physical stamina hardly equals that of a iull-
grown rye-stalk. Theirs is a leanness to be  built up into steady strength
and pictutesque plumpness of limb and face.— The Standard.

                                         Chicago, Sept 18. 18T8.
   The  case referred toon page 45 of  " How to he Plump" is  our little boy,
who was certainly rescued from death'-; door.  This summer he began to riin
down again.  After Dr. Dun- an hart tried several medicines without benefit
he igain ndvised " inunction." and again with the same happy effect. The
little fellow is now plump and  well.                Chaklks Wales.
  l^~May  e  ordered through  your physician, or newsdealer, or will be sent
direct on receipt of price.

                         DUNCAN BROS.,  Publishers,
                    113 Madison and 131 &  133 Clark St., Chicago. 
THE
FEEDING AND  MANAGEMENT
OF
Infants   and    Children.
                         AND THE
   HOME  TREATMENT OF THEIR DISEASES.
                  By T. C. DUNCAN, M. D.,
President of the American P.edological Society. Consulting Phys-
   ician to the Chicago Foundlings' Home.  Clinical Lecturer
     on Diseases of Children.  Author of "a Professional
        Treatise on the Diseases of Children" (2 large
           volumes).  Editor of the United States
               Medical Investigator, etc, etc
                    What is said of it:
 Mrs. T. Wilce, Presidtent of the Mother's Society of Chicago, says : "It
is the most instructive book for mothers and especially young mothers,
that has come to my notice and I earnestly advise all prospective mothers
to read it. Would to God that I had had such a book years ago."
 Mrs. H. E.Redeker of Kenosha, Wis., writes: "I think it is the best work
of the kind I have seen.  1 am glad that I shall have Dr. Duncan at hand
ready to consult at any moment for I have the greatest confidence in all
that he says. It is a book that it seems to me every mother would like to
have."
 Dr. Edward Cranch, Secy, of the American Pasdological Society (com-
posed of the leading physicians interested in Children's Diseases), says :
" I have carefully examined the work and unhesitatingly  pronounce it a
most necessary book for all families.  It ought to go into every intelligent
household where the health of the little ones is valued."
 The Organon of London, Eng., says: ''Paedology is Dr. Duncan's Special-
ite and we may be sure that what he writes on this subject contains many
things worth reading.  His Encyclopedia on Diseases of Infants and Child-
ren is a work for the profession ; this one is for the public, and a  better
work on the subject we do not remember to have seen. * *  Every day
rules for diet and regimen generally, are what the public should know, and
without these the skill of the physician is daily thwarted ; in this respect
Dr. Duncan has.performed his work  admirably.   The book  is elegantly
gotten up."
               SOLD ONLY BY  SUBSCRIPTION.
             Prioe, Cloth, $2.00;  Half Morocco, $2.75.
 Agents wanted in every town. Ladies sell it rapidly. Address for terms
and territory,
                               DUNCAN BROTHERS,

 131  <& 133  Clark St.,                  CHICAGO. 
" DOCTOR,  WHA T SHALL 1  FAIT
                              A


                    HAND  BOOK

                              OF



DIET    IN    DISEASE.


              By CHAS. GATCHELL, M.  D.,

        Formerly Professor of Practice, University  of Michigan.

      It is  highly endorsed by the Profession and  Medical Press.

  How often do we hear that same question. Doctor; what shall I eat? and
though there are text-books enough on the Pathology and Trea tment of
Diseases, there is hardly ever a word found in them about the Hy giene in
Disease.  Gatchell as a teacher, found out this want, and thus piobably
originated this little treatise, for which we  rnpst  heartily  thank fhe
author.  We consider the recipes in it a little Materia Medica for itself, but
follow instructions closely ;  not quantity, but quality  of food deserves our
consideration. — North American Journal of Homcepathy.
                                             Milwaukee, Wis.
  "I consider your work on "Diet in Disease" to be the most practical, and
therefore the most useful, work on the subject with which I am acquainted.
No physician should be without it;  every mother should have it.  It is in
use in many of the households in which I practice." C. C. Olmstead, M. D.
                President of the Wisconsin Homozpathic Medical Society.

  "This work is plain, practical and valuable.  It  is really a clinical guide
on diet, and one the profession will find reliable and correct." — United
States Medical Investigator.

  "By far the best work on the subject in our literature.  I find it of use
every day.  I want one in every household in which I practice."
  Oak Park, III.                              F. G. Folsom, M.D.

  "Evidently much investigation, thought and carefulness  have entered
into the production of this work, and we believe it to be worthy a place in
every household." — The Magnet.

  *  * * "We have carefully examined the work  and shall cheerfully
recommend it for family use. The directions as to what food  and drinks,
and modes of preparation are very  judicious." * *  * Kesp. Yours,
  Janesville, Wis.                      Dr. G. W. Chittenden & Son.

  Professor Charles GatchelFs Manual of'Diet in Disease' is the best book
on the subject for the people. It contains in 160 pages an  astonishing
amount of condensed information  on a subject of great importance, and
one but little understood. Its style is admirable,  pithy and to the point.
The book has no padding about it and deserves an immense sale."
                          Samuel Potter. M. D.,
                        President, Milwaukee A eademy of Medicine,
                  Aathor of Index of Comparative Therapeutics, etc. etc.
  &&~ Sent free on receipt of price, $1.00.

                                DUNCAN BROS.,

131 & 133 S. Clark St.                           CHICAGO. 
          HOW TO  SEE  WITH
THE  MICROSCOPE:
Useful Hints Connected with the Selection and Use of the
   Instrument; also Some Discussion of the Claims and
      Capacity of the Modern  High-Angled Objec-
         tives, as Compared with those of Medium
            Aperture; with Instructions as to
              the Selection and Use of Amer-
                 ican  Object - Glasses of
                    Wide Apertures.

                           BY

        J.  EDWARDS SMITH,  M.  D.,

PROFESS'.R OFHTSTOLOGY AND  MTCROSCOPY IN THE CLEVELAND (O.), HOS-
    PITAL COLLEGE; CORRESPONDING MEMBER OF THE SAN FRAN-
        CISCO ; THE DUNKIRK, AND ILLINOIS STATE MICRO-
               SCOPICAL  SOCIETIES, ETC., ETC.
ILLUSTRATED.
  The book abounds in practical hints that will be most highly
appreciated by those of us who have had to work out  for our-
selves a great amount of experience at a great expense of pre-
vious time (and often more precious eye-sight), and who know
how serviceable a stray hint, or a word or two of suggestion has
often proved.       (Signed)        Albert H. Tuttle.
  Ohio State University, February, 1880.
  Prof. Smith is well known as the most expert manipulator in
this country, as regards  objectives of wide  aperture, and in
this volume he gives, in a clear and practical manner, all the
directions necessary to attain  the surprising  results which  he
has achieved.  No microscopist who uses anything better than
French triplets can afford to be without it.—From John Pfiin,
Esq., Editor Monthly Journal of Microscopy.
  There  is  at present no work in the English language which
gives instruction  in the best methods of handling the  most
modern microscopes and objectives.  Prof. Smith's work will,
therefore, till a long felt  hiatus in our microscopical literature.
—Journal of Microscopy.
  SgrMay be ordered of any prominent bookseller, or will be
mailed direct to any one on receipt of price, $2.00.
                            DUNCAN BROS.
                     131 and 133 S. Clark St., CHICAGO. 
 
V
I