The Redwood gazette. [volume] (Redwood Falls, Minn.) 1873-1940, 1878-05-02
Near.SIghtedness.

Near.SIEhtedness.
THOMAS F. NELSON, a Chicago opti-
clan, furnishesthe Rail,cay Revseao with
the following interesting article on
Myopia, or Near-Sightedness:''
This defect is comparatively easy to
detect, especially in the higher grades;
yet there are some phases Of it that re-
quire extreme caution and delicate
manipulation to arrive at q complete
understanding of their condition.
Myopia, or near-sightedness, is, more
popularity speaking, q disease rather
than a structural defect in the eye.
This disease, however, has the effect of
causing change in the construction,
thus producing the same result; it is ;,
generally conceded 10 be hereditary,
accommodating in posterity. and when
once developed, even in very slight
degree, its tendency is to increase and
assume more decided form and high
er degree.
1t consists in diminution of the far
point of vision, and the consequent in
ability to perceive and recognize OBJ
jects lying beyond this distance, which
varies more or less with the grade or
degree of the imperfection.
In the low or medium grades, which
are the most numerous, objects lying
within this visual distance are seen just
as distinctly and with less straining or
exercise of the muscle of accommOda-
ton than is experienced by q person
having normal or perfect vision.
But the myopic eye is largely de-
ficient in penetration, and requires
much stronger illumination, especially
at night, to render objects distinctly
visible within the same prOportionate
distance, as compared with the results
obtained from experiments with nor
NAL or perfect vision under the same
circumstances.
To illustrate: Assume normal vision
in daylight to be represented by 100,
that of myope in the same light and
upon the same basis to be seventy-five,
then try the experiment with weaker
illumination, say at night, and again
let the acuteness or penetration of per-
feet vision be represented by 100, the
experiment will show the acuteness of
the myope to be diminished to a range
of from forty-tive to tifty-five. This
want of acuteness will only prove true
for distance, while for near vision the
opposite is the rule, the myopic eye be-
ing able to see under weak illumina-
ton with less proportionate WEAKNESS
than is experienced in perfect vision.
In the myopic eye, when ocular est.
nation of distance is to made, the tend
ency is to 0Uer rather than under-esti-
mate it. This has appeared very promi-
nently IN estimating the distance of
lights at night. As applied to railway
or vessel management this, when COM
bined with the want of penetration,
will prove to be the most serious de-
feet noticed under this phase of imper-
feet vision. The different forms and
degrees of the defects classed under this
head are the most numerous of all
structural or optical imperfections of
the eye, and they have an existence in
low or medium grade in very large
proportion of the population without
there ever being suspicion of their
presence.
The comparative frequency of near
sightedness has been the subject of dis
cussion a great many times, and it is
found to prevail to much larger ex-
tent in the cities than in the country.
This difference has been ascribed to a
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 to using their
eyes for comparatively short distances;
hence the muscles become accustomed
to these shorter distances, thus losing
much of their natural power of relax
alton beyond certain points through
want of exercise. Thisis also increased
and fostered by the studious habits of
the American people generally, and the
defect is undoubtedly acquired in
great number of instances through the
prolonged tension of muscular accom-
mediation in studying, by children at
school. 1t will be an interesting as
well as important fact to notice in this
connection some of the results of the
examination of large number of
school children. Drs. Ayres and Will
Jams examined the eyes of 1864 pupils
in different departments of the Cincin-
natl public schools, which showed the
proportion of near-sightedness in the
district schools to be 1873 per cent; in
termediate schools 1873 per cent; and
in the high schools, 22.8 per cent.
These results correspond with those OBJ
tanned from examinations made in
Brooklyn and in the College of the City
of New York.
1t may not be embarrassing to notice
the fact that of the large number of
cases of blindness which have
had the privilege of examining during
the past seven years, large proper
ton were found to have a low grade
of near-sightedness combined with
some one of the forms of colOr-blind-
ness. The dangerous character of the
error depending upon this defect for
development lies mainly in the general
progressive nature of the disease,
which at first may be of a low grade,
but soon increases and forms higher
grade; every step in the progression
becoming more and more marked as an
element susceptible of causing false
perceptions and thereby incorrect judy
ment. Growing out of this is the d.
minished penetration and over-estima-
ton of distance which attend the defect
in both the high and low grades.
It might not be out of place in this
connection to say that this defect can
be almost entirely neutralized by spec
tacles properly selected and adjusted;
but the diseased condition nearly al
ways attending it generally demands
some medical treatment, especially in
the higher grades, before glasses can
be properly adapted to the eye. Insu-
perable objections, however, attend the
use of spectacles in railway service in
many of it's branches. ar
Mr.. Caleb Cushing has received .
fee of more than 100000 for recover
ing the estate of a Cuban which was
seized by the Spanish Government, and
another claim for $4,000, 900 has been
made, which, if established, will make
Mr.. Cushing o very rich man.
THE lARKETS.