The Refraction of the Eyes of 
One Thousand School Chil- 
dren, with Particular Refer- 
ence to Astigmatism, as shown 
by the Javal Ophthalmometer. 
BY 
W. M. CARHART, M. D., 
Assistant Surgeon, Manhattan Eye ancfEar Hospital; 
Instructor in Diseases of the Eye and Ear 
in the New York Post-Graduate Medical School; 
Ophthalmic and Aural Surgeon, Helping Hand Hospital, 
Peekskill, N. Y. 
REPRINTED FROM THE 
Neto yortt fjaeMcal journal 
for April 17, 1S97. Reprinted from the New York Medical Journal 
for April 17, 1897. 
THE REFRACTION OF THE EYES 
OF ONE THOUSAND SCHOOL CHILDREN, WITH 
PARTICULAR REFERENCE TO 
ASTIGMATISM, 
AS SHOWN BY THE JAVAL OPHTHALMOMETER* 
By WILLIAM MERLE D'AUBIGNE CARHART, M. D., 
ASSISTANT SURGEON, MANHATTAN EYE AND EAR HOSPITAL J 
INSTRUCTOR IN DISEASES OF THE EYE AND EAR 
IN THE NEW YORK POST-GRADUATE MEDICAL SCHOOL ; 
OPHTHALMIC AND AURAL SURGEON, HELPING HAND HOSPITAL, 
PEEKSKILL, N. Y. 
About a year ago Dr. St. John Roosa suggested 
to me the importance of statistics of corneal astigmatism 
as throwing great light upon the study of asthenopia. 
None of the many school statistics which have been pub- 
lished have treated of the prevalence of corneal astig- 
matism, for the obvious reason that the ophthalmometer 
was not in general use in any country until 1890, when 
it began to be widely employed in our own through the 
example and efforts of Dr. Roosa. These tables repre- 
sent the results of the examination which the courtesy 
of the school trustees enabled me to make last winter and 
* Read before the Ophthalmological Section of the New York 
Academy of Medicine, January 18, 1897. 
Coptright, 1897, bt D. Appleton and Cost?any. 2 
REFRACTION OF THE EYES OF CHILDREN. 
spring of the eyes of one thousand children in the 
schools of Peekskill, a town of somewhat over twelve 
thousand inhabitants. The statistics will be found fairly 
representative of the conditions existing in the eyes of 
the American school child, although large cities like 
New York might show somewhat different results in cer- 
tain details. For instance, the myopic element of re- 
fraction is considerably less than I have reason to be- 
lieve is the case where the children have longer hours 
of study, less hygienic surroundings, and weaker vital- 
ity. Also I might find a higher percentage of pathologi- 
cal changes in the eyes of children from the heterogeneous 
population of New York tenement houses than I ob- 
served in Peekskill, where the foreign element is insig- 
nificant, and where village life insures a more healthy 
environment. 
The method of obtaining my statistics was as follows: 
A room was kindly furnished me by the principal of 
each school, into which the children were sent two by 
two as needed. A very good dark room was made by 
pulling down the shades, and my first step was a careful 
ophthalmoscopic examination, re-enforced in doubtful 
cases by retinoscopy. As mydriasis was out of the ques- 
tion, it was impossible to eliminate all chance of the pres- 
ence of spasm of the accommodation on the part of the 
patient examined, and of course I do not pretend to any 
absolute accuracy in estimating the degree or nature of 
the refraction. Nevertheless, I think the results are as 
accurate as circumstances permitted. In making a diag- 
nosis of emmetropia I considered all children emmetropic 
where the retinal picture began to blur at -f- 0.50 D., 
while perfectly clear at the aperture of the ophthalmo- 
scope. I did not think that my own personal equation REFRACTION OF THE EYES OF CHILDREN. 
3 
admitted of any closer approximation, although many 
authorities will probably take exception to this definition 
of emmetropia. 
My second step was to use the Javal ophthalmom- 
eter, and this part of the routine I consider the unique 
feature of my paper. In order to get at the actual amount 
of corneal astigmatism which is of importance for re- 
fractive purposes I decided to follow the example of 
Javal, and estimate as 0.50 D. the normal corneal astigma- 
tism, which is neutralized by the corresponding lenticular 
astigmatism at right angles to it, due to the anatomical 
inclination of the crystalline lens obliquely to the vis- 
ual axis. That is to say, in astigmatism with the rule 
I disregarded an overlapping of the mires of 0.50 D., 
while I added 0.50 D. to astigmatism against the rule, 
since, in that case, the lenticular astigmatism increases 
the effect of the corneal astigmatism. In this way the 
total astigmatism better represents the refraction of the 
eye than if I had not allowed for the normal corneal 
astigmatism. In consequence all the children, for in- 
stance, under the percentages of emmetropia, are to be 
considered as showing an overlapping of 0.50 D. 
My third step was to use the test letters at a dis- 
tance of twenty feet, to determine the acuity of vision. 
This test I have not embodied in my statistics, because 
I consider tables of percentages of "defective sight " 
to be too indefinite and inexact to find a place in an 
article addressed to the profession. Normal vision in the 
first place is surely not exactly , even if by that is meant 
the vision of the emmetropic eye. I think under favor- 
able circumstances of good light, absence of all deviation 
from perfect health, and patience and skill on the part 
of the examiner, the emmetropic eye is often capable of 4 
REFRACTION OF THE EYES OF CHILDREN. 
seeing with ease, although at other times the vision 
may drop to f $, or even -|$, in the same eye if the cir- 
cumstances are adverse. The least suspicion of hyper- 
metropia is sufficient to put the vision beyond f$, but, of 
course, we expect that to occur in such cases. If by nor- 
mal vision is meant useful vision without asthenopia of 
we can not help finding such vision frequently in 
varying states of refraction-in emmetropia, in low de- 
grees of astigmatism, both hypermetropic and myopic, 
and also sometimes, I believe, in the incipient stages of 
myopia. I found the test of acuity of vision extremely 
useful as an aid and check to my ophthalmoscopic ex- 
amination, but for the reasons given I decided not to add 
another item to my tables. 
Finally, my routine was completed by observing any 
pathological changes or abnormities of the eyeball or its 
appendages. In this I was gratified to find exceptionally 
few pathological or abnormal eyes. In great degree 
I believe it to be due to village life and vigorous native 
stock. I found few cases of trachoma, in striking con- 
trast to its prevalence in our city clinics. Blepharitis mar- 
ginalis was the most common disease observed, and I am 
sorry to say I noticed many cases of asthenopia, due to 
the lack of proper correction of refractive error. Per- 
haps this fact can be explained by the presence and 
activity in our village of "refracting opticians" and 
other venders of optical goods. The most common and 
perfectly natural mistake made by these gentlemen seems 
to be placing a weak minus spherical glass over the eyes 
of children having hypermetropic astigmatism of mod- 
erate degree. The correct diagnosis of astigmatism is 
naturally entirely beyond their power, as they possess 
neither the appliances nor the skill for accomplishing REFRACTION OF THE EYES OF CHILDREN. 
5 
such a difficult task. The law is plain on this subject. 
No one not licensed by the regents can legally practise 
medicine in this State, and to prescribe a pair of lenses 
after an examination of the eye is to practise medicine. 
But the people need to be aroused to the necessity of 
enforcing this law. Perhaps the day may come in the 
future when the examination of the most delicate and 
sensitive, and in many ways the most important organ 
in the human body will be recognized by the intelligence 
of the people to be a part of medical practice, and the 
prescription of a pair of lenses by a layman as much an 
offense against the rights of the community as the 
prescription of a powerful medicine by a druggist is now 
admitted to be. I have thought my observation of the 
prevalence of marked asthenopia so important that I have 
made a place in my statistics for its percentages. Chorioid- 
itis was occasionally noticed, but in general the fundus 
of the eye presented a perfectly healthy appearance. 
Of course a few cases of strabismus were encountered, 
and also an occasional scar due to old traumatism. I 
am very sure an equal number of city children would 
have presented many more abnormal and diseased eyes, 
but our village seems to me fairly typical in this respect 
of suburban and rural populations. 
Before passing to comment on the tables herein given, 
perhaps my usage of one or two terms may need a word. 
I have classified as anisometropia all similar differences 
of refraction of one dioptre or over, and I have also given 
separate items for cases where the difference existed 
in the astigmatism and where it was due to hypermetropia 
or myopia. Antimetropia I have limited to dissimilar 
or opposite states of refraction, but I have included in 
that definition cases where one eye was apparently emme- 6 
REFRACTION OF THE EYES OF CHILDREN. 
tropic and the other pronouncedly myopic or hyper- 
metropic. 
Ages 5-18. 
Emmetropia 
13'90 
Hyperm etropia 
36-20 
H. Ast. Co 
44-00 
Myopia 
1-40 
My. Ast. Co 
3-50 
Mixed astigmatism 
1-00 
100-00 
Table I.-Percentages of 1,000 School Children. 
Table II.-Percentages of 1,000 School Children. 
H. + H. Ast. Co 
Ages 5-18. 
.... 80-20 
H. Ast. Co. + My. Ast. Co. + Mix. Ast 
.... 48-50 
My. + Mv. Ast. (Jo 
.... 4-90 
My. + My. Ast. Co. + Mix. Ast 
. ... 5-90 
Astigmatism, a. t. r 
.... 2-90 
Ast. | - If D 
.... 34-40 
Ast. 1| - 2f D 
.... 10-30 
Ast. 3 D. + 
.... 3-80 
Anisometropia 
.... 11-20 
Anisometropia H. or My 
.... 4-40 
Anisometropia Astig 
.... 6-80 
Antimetropia 
. ... i-io 
Marked asthenopia 
.... 0-70 
Pathological cases .. 
.... 2-60 
Tables I and II, giving the percentages of all ages, 
will receive only a few words of comment. Except in 
the appearance of the items relating to the classification 
of astigmatism, they are not markedly different from 
similar tables of Loring, Noyes, Risley, Southard, and 
others. Table II is largely formed by combining and 
subdividing the items of Table I, to bring out more clear- 
ly the astigmatic element in the refraction. I would 
call attention to the fact that 48.5 per cent, of all the REFRACTION OF THE EYES OF CHILDREN. 
7 
children examined were astigmatic, of which hyperme- 
tropic astigmatism compound claims forty-four per cent. 
It is also interesting that hypermetropic astigmatism 
compound outnumbered hypermetropia, forty-four per 
cent, as compared to 36.2 per cent., and still more im- 
portant to notice that the percentage of myopic astigma- 
tism compound is nearly three times as great as that of 
myopia. In subdividing the astigmatism the low degrees 
are overwhelmingly prevalent, 34.4 per cent., while mod- 
erate and high degrees are 10.3 per cent, and 3.8 per cent, 
respectively. Many of these children having low degrees 
of astigmatism undoubtedly had little or no asthenopia, 
and most of them were not wearing glasses. But, as I 
hope to show further on in my paper, such eyes are de- 
fective and weak, and will surely give the owner trou- 
ble later in life. The presence of astigmatism against 
the rule in a considerable number of cases is of interest. 
In anisometropia it is seen that the difference in astig- 
matism occurs more often than the difference in hyper- 
metropia or myopia, 6.8 per cent, and 4.4 per cent. I 
should like to comment further on the remaining items 
in these two tables, but must hurry on to the more 
important tables III and IV, where comparative per- 
centages by ages are given. 
Table III. - Percentages by Ages o/ 1,000 School Children. 
Ages : 
5-8. 
9-12. 
13-18. 
Emmetropia 
10-00 
16-43 
14-33 
Hypermetropia 
53-48 
37-27 
22-81 
H. Ast. Co 
33-48 
40-05 
55-55 
Mvopia 
0-87 
1-85 
1-17 
Mv. Ast. Co 
1-74 
3-01 
5-26 
Mixed Ast 
0-43 
1-39 
0-88 
100-00 
100-00 
100-00 8 
REFRACTION OF THE EYES OF CHILDREN. 
Tables III and IV corroborate in a remarkable man- 
ner the conclusions and views expressed by Dr. William 
F. Norris, in a paper published in the Transactions of 
the American 0phthalmological Society at its twenty- 
Table IV.-Percentages by Ages of IfJ00 School Children. 
Ages : 
5-8. 
9-13. 
13-18. 
H. + H. Ast. Co 
86-96 
77'32 
78'36 
H. Ast. Co. + My. Ast. Co. 4- Mix. Ast. 
35-65 
44-45 
61-69 
My. + My. Ast. Co 
2-61 
4-86 
6-43 
My. + My. Ast. Co. + Mix. Ast 
3'04 
6-25 
7-31 
Astigmatism, a. t. r 
1-30 
2-78 
4'09 
Astig. J - 1| D 
23-48 
32-18 
44'15 
Astig. D 
9'56 
7-87 
13-74 
Astig. 3 D. + 
2-61 
4-40 
3-80 
Anisometropia 
5-65 
10-88 
15-14 
Anisometropia H. or My 
2-17 
4-17 
6'14 
Anisometropia Ast 
3-48 
6-71 
9-00 
Antimetropia 
0-87 
1-62 
0'59 
Marked asthenopia 
0-23 
1-75 
Pathological cases 
2-17 
3-01 
2-34 
second annual meeting, on The Changes in Refraction 
in Adolescent and Adult Eyes. Dr. Norris there shows 
that congestion of the retina and sclerotic, if repeated at 
frequent intervals, will cause the undeveloped hyper- 
metropic eye of childhood and adolescence to undergo 
a slow distention even under normal intraocular tension. 
Any morbid condition coexisting makes this process 
more sure and rapid. The eyeball yields most promptly 
and effectively, as Dr. Norris states, at the posterior pole, 
where its anatomical structure allows a maximum of 
serum infiltration and a minimum of resistance, due 
to the passage through the sclerotic of the numerous 
posterior ciliary vessels and nerves. It follows from these 
facts that we must regard an increase of myopia to be but 
a more advanced stage of a process to which a decrease REFRACTION OF THE EYES OF CHILDREN. 
9 
of hypermetropia belongs, and that for many children 
emmetropia is but a mere halting place on the road to the 
goal of myopia. It may be objected that this theory 
proves too much. All myopia is not " school myopia " 
brought on by asthenopia. There is, indeed, an essential 
myopia seen in illiterates, criminals, and others. But the 
process is the same, although the existing cause is en- 
tirely different. Instead of excessive strain causing dis- 
tention in an otherwise healthy eye, the illiterates, crimi- 
nals, and others suffer from tissues made weak and easily 
distensible by inherited or acquired disease. Besides 
local diseases, such as chorioiditis, any constitution! di- 
athesis or dyscrasia may so weaken the eye that the physio- 
logical activity of daily life will be sufficient to cause 
distention. Indeed, I understand that statistics of pris- 
oners show nearly if not quite as high a percentage of my- 
opia as the schools. But I believe all such eyes will be 
found either themselves diseased or in diseased bodies. 
My tables show that the distention of the eyeball 
is nearly as disastrous to the cornea as to the fundus itself. 
We have long considered hypermetropic astigmatism to 
be congenital and fixed, and when we had reason to think 
otherwise we were apt to doubt our observation or put 
it down as a rare exception. I think my statistics prove 
that it is often neither congenital nor fixed. To be sure, 
it does not change as rapidly or as surely as myopic 
astigmatism, but then the latter is a later stage of the same 
process. The reason we have not observed more changes 
in degree of hypermetropic astigmatism is that the pro- 
cess is quite amenable to treatment in its early stage, 
proper correction of the refractive error arresting usually 
any increase of the astigmatism. Myopic astigmatism 
with considerable myopia represents the later stage of 10 
REFRACTION OF THE EYES OF CHILDREN. 
the process, where exact correction is not so much insisted 
upon by the patient, due to the absence of asthenopia, 
and where also often correction is of less avail to arrest 
the increasing distention. It has been well shown by 
Ely and others that babies are born hypermetropic, and, 
as numbers of them probably have imperfectly curved 
corneas, a considerable amount of hypermetropic astig- 
matism is undoubtedly congenital. I believe that a still 
larger amount of hypermetropic astigmatism is acquired 
during the years of childhood and early adolescence, and 
I think my statistics sustain that belief. 
In making the subdivisions of Tables III and IV I 
endeavored to divide the ages so as to give approximately 
the same number of pupils in each subdivision. The 
Peekskill schools not being graded, I did not follow the 
class divisions. The first item of Table III shows that 
the lowest percentage of emmetropia belongs to the 
younger children and the highest to the middle subdivi- 
sion. This is apparently in harmony with the view of em- 
metropia being an arbitrary distinction in many eyes, for 
a gradual lengthening of the optic axis would give the 
largest percentage of emmetropia in the ages of nine to 
twelve. Hypermetropia is shown to decrease in per- 
centage rapidly, and according to my opinion much of 
the decrease is due to the appearance of astigmatism in 
eyes formerly with perfect cornese. 
Compound hypermetropic astigmatism increases al- 
most as rapidly as hypermetropia decreases, for the reason 
given above. Myopia is seen to be of largest percentage in 
the middle subdivision, and this fact, I believe, is due in 
part to myopia becoming compound myopic astigmatism 
in many of the older children. Some statistics of San 
Francisco schools, collected by Dr. W. F. Southard, show REFRACTION OF THE EYES OF CHILDREN. 
11 
the attendance in primary grades to be 69.63 per cent.; in 
grammar schools, 26.06 per cent.; and in high schools, 
4.31 per cent. This astonishing disproportion of the 
grammar and high schools, as compared with the pri- 
mary grade, leads me to believe that many children drop 
out as they grow older because large refractive error pre- 
vents them from keeping up in their studies. The next 
item gives an increase of three times as much compound 
myopic astigmatism in the ages thirteen to eighteen as 
occurs in the ages of five to eight, thus showing that 
compound myopic astigmatism increases much faster 
than myopia. Mixed astigmatism, by giving the highest 
percentage for the middle subdivision, shows itself to be 
similar in that respect to emmetropia. The second item 
of Table IV proves, in my estimation, the steady altera- 
tion of the curve of the cornea as the child grows older 
and uses the eyes for longer and closer study. The sub- 
division of astigmatism according to degree shows the 
low degrees to increase steadily, while the moderate and 
high degrees are more numerous in the middle subdi- 
vision of age. This fact I believe to be due, as in myopia,, 
to high refractive error causing children to drop out. 
The same is true of antimetropia, and for the same rea- 
son probably. Astigmatism against the rule and aniso- 
metropia seem to increase as steadily as the more com- 
mon refractive conditions, if not even faster. 
I suggest the following conclusions: 
I. Changes in refraction of childhood and adolescence 
are due to slow distention of the eyeball, caused either 
by strain of accommodation in an otherwise healthy eye 
or by physiological use of an eye weakened by local or 
constitutional disease or dyscrasia. 
Poor light in crowded schoolrooms is particularly 12 
REFRACTION OF THE EYES OF CHILDREN. 
productive of strain of accommodation, as was shown 
by Arlt, of Vienna, in an able monograph. 
II. Such distention of the eyeball results not only 
in progressive lengthening of the optic axis, but in altera- 
tion of the curve of the cornea. 
III. A considerable proportion of hypermetropic 
astigmatism is probably congenital, but much the larger 
proportion, and all of the myopic and mixed astigmatism, 
are caused by the same process which lengthens the optic 
axis from the congenital high degree of hypermetropia 
of infancy to the high degree of myopia seen typically 
in German universities and occasionally in our schools. 
IV. This process of distention is more easily arrest- 
ed in its earlier stages, and therefore prompt and exact 
correction of the refractive error, and particularly of 
low grades of astigmatism, is indicated in all cases to 
prevent an extension of the process. In compound my- 
opic astigmatism correction of the astigmatic element 
is of equal if not of greater importance than correction 
of the myopic element of the refraction. 
I hope to keep track of as many as possible of the 
one thousand children examined, and some time in the 
future I may be able to demonstrate the changes of re- 
fraction by comparing records of the same individuals 
taken at different times. 
The conclusions I have formulated apply with par- 
ticular force to the plastic period of growth, when the 
■eyeball is soft and yielding-that is to say, to the years of 
childhood and early adolescence. In adult life the eye- 
ball has become mature, and therefore is firm and re- 
sistant. In consequence the refraction of adults does not 
change in anything like the frequency observed in child- 
hood. We often notice marked increase of myopia, or of REFRACTION OF THE EYES OF CHILDREN. 
13 
myopic astigmatism, in adult eyes, but emmetropia and 
hypermetropia, as well as hypermetropic astigmatism, 
are usually fairly constant in healthy adults of normal 
vitality. The fate of the refraction of the eye is usually 
settled before puberty. Childhood is the critical period 
of growth. If that period is passed without undue dis- 
tention, myopia and astigmatism are not likely to develop 
at all in after life. 
147 West Forty-fourth Street, New York; 433 South Street, 
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