The Centre reporter. [volume] (Centre Hall, Pa.) 1871-1940, 1878-05-09
Nnar.SirhlndueSS.


edness, " is from the pen Of an authority,
a Chicago optician: This defect Is COM
paratively easy TO detect, especially in
the higher grades; yet there are some
phases of il that require extreme eau
ton and delicate manipulation 10 arrive
at complete understanding Of their
condition.
Myopia, or near-sightedness is, more
popularity speaking, a disease rather
than a structural defect in the eve. This
disease, however. has the effect OF caus-
ing change in the construction, thus
producing the same result; il is gener-
ally conceded to be hereditary, accumu-
lating in posterity, and when once de-
veloped, even in very slight degree,
its tendency is 10 increase and assume a
more decided form and higher degree.
IL consists in diminution Of the far
point of vision, and the consequent ina
bility to perceive and recognize objects
lying beyond this distance, which varies
more or less with the grade or degree oi
the imperfection.
In the low or medium grades, which
are the Smost numerous, objects lying
within this visual distance are seen Just
MS distinctly and with less straining or
exercise Of the muscle of accommodation
than is experienced by person having
normal or perfect vision.
But the myopic eve is largely defci-
ent in penetration, and requires much
stronger illumination. especially at
night, 10 render objects distinctly yisi-
hle within the same proportionate dis.
tance, as compared with the results OBJ
tanned from experiments with normal
or perfect vision under the same circum-
stances.
To illustrate Assume normal vision
in daylight 10 be represented by 100,
that of myope in the same light and
upon the same basis 20 be seventy five,
then try the experiment with weaker
illuminations, say az night, and Sgain let
the acuteneSs or penetration OF perfect
vision be represented 10y 100, the experi-
ment will show the aouteneSs Of the
myope 10 be diminished to range Of
from forty-five 70 tifty-fve. This want
Of acuteneSs will only prove true, for
distance, while for near vision the op-
pOSite is the rule, the myopic eve being
able to see under weak illumination with
less pro porbonate weArineSs than is eN-
perienced in perfect vision.
In the myopio eve, when ocular esti-
nation Of distance Is 81 be made, the
tendency Is to orcr rather than
underestimate it This has appeared
very prominently in estimating the dis
tanee Of lights at night As applied TO
railway or vessel management this, when
combined with the want Of penetration,
VIII prove 70 be the most serious defect
noticed under this phase OF imperfect
vision. The different forms and degrees
Of the defects elaSSed under this head
the most numerous of all structural or
optical imperfections of the eve, and
they have an existence in low or
medium grade in a very large proportion
Of the population without there ever be-
ing a suspicion Of their presence.
The comparative frequency OF near
sightelness has been the subject of dis
cussion 8 great many times, and Il Is
found to prevail % a much larger ex'
tent IN the cities than IN the country.
This difference has been ascribed 20 s
variety of causes, among which is the
fact that persons living in cities have
but little occasion to relax the muscle
Of accommodation for infinite distance,
they being habituated 70 using then
ewes for comparatively short distances
hence the muscles become accustomed
to these shorter distances, thus losing
much OF their natural power of relaxa
bOn beyond certain points through want
OF exercise. This Is also increased ant
fosterei by the studious habits # th,
American people generally, and the de
feet Is undoubtedly acquired in s. grea
number Of instances through the pro
longed tension Of muscular accommoda
ton in studying, by children at school
Il will be an interesting as well as i'm
pOrtaut fact TO notice IN this connection
some Of the results Of the examination
Of large number OF school children
Drs. Avres and Williams examined the
ewes Of ], ,264 pupils in different depart
ments of the Cincinnati public schools
which showed the proportion OF near
sightedness in the district schools TO b,
1913 per cent; intermediate schools
1873 per cent. and in the high schools
DIS per cent. These results CORE
spond with those obtained from examin
ations made in Brooklyn and in tn,
College Of the City Of New York.
Il may not be uninteresting to notice
the fact that of the large number o.
cases Of color-biindness which l hay,
had the privilege Of examining during
the past seven years, a large proportion
were found to have low grade of near
sightedness combined with some one o
the forms OF color blindness The dan
gerous character Of the error depending
upon this defect for development het
mainly in the general progressive nature
Of the disease, which at first may be o.
q low grade, but soon increases anC
forms higher grade every step in tht
prOgres sion becoming more and more
marked as an element susceptible o.
causing false perceptions and thereby
incorrect Judgment Growing out o.
this is the diminished penetration anC
over-estimation Of distance which
attend the defect in both the high ant
low grades.
1t might not be out of place in thii
connection to say that this defect can bt
almost entirely neutralized by spectaclei
properly selected and adjusted bu
the diseased condition nearly always at
tending it generally demands some med
ical treatment, especially in the highei
grades. before glasses can be properl,
adapted to the eye. Insuperable objec.
tions, however, attend the use OF specta
cles in railway service in many Of il