Northern tribune. [volume] (Cheboygan, Mich.) 1875-1885, 1883-07-07
NEAR.SIGHTEDNESS.

NEAh.SlU0 lEDNESSs
Of the optical defects, or retroactive
errors, which to a greater or less extent
are capable of correction. l will first
mention my0piG or near-sightedness,
since it is not only of greater frequency
than any other eye defect, but from its
very nature tends to develop into Sc
rious organic diseases. When I said in
a previous article that the human eye
was practically round, | referred, of
course, to that organ in its normal con-
dition. The myopic eye, instead of
possessing this spherical shape is elon-
gated from before backward. The
round eye is so constructed that the
parallel rays Of light are brought to
focus on the retina. If this retina be
pushed further back-as it virtually is
I'm near-sighted eye-the rays of light
will be focused before reaching it, In
other words, there will be no screen
upon which to receive the image formed
by the condensing media, and hence no
impression can be conveyed to the
BRAIN This variation in tIr shape of
the organ is not to be measured by
inches hardly by lines. A single half
turn of the adjusting screw of the micro
scope, though produc 'ng no visible
lengthening of the instrument, yet
causes the object which was before so
sharply defined to become blurred and
Sndistinct. So it does not require much
pressing back of the rear wall of the
eye-ball to render cur vision decidedly
defective 1t is generally supposed,
and was even form arly taught, that the
<>f Gin
rly protruded, and that the cornea
in such cases was more convex than
usual. 1t is now known that it is the
posterior segment of the eye-ball which
is at fault-that portion pierced by the
optic nerve, and which, as l have al
ready told you, is the weakest part of
the entire globe.
Near-sightedness is most frequently
an acquired condition, though the
tendency to this defect may, and in the
majority of cases probably does, exist
at birth That it is one of the unhappy
results of our modern civilization and
our closer application to intellectual
pursuits can not be questioned. No
one ever heard of near-sighted Indian,
and before our civil war the full-blooded
Southern negro was equally exempt
from this defect. The difference be-
tween the eyes of children who attend
she public schools of our large cities
where their brains are developed at the
expense of their bodies-and of those
residing in the country, WHERE at most
only one-half of the year is devoted to
school duties, can not have failed to at
tract the attention of all observant per-
sons. From Germany, Russia, France
and England we have reliable statistics
to prove the relative frequency of these
eye defects. Germany, as we know, is
land of students, and so common is
myopia in that country that it has long
been impossible to fill the ranks of its
armies without admitting those who are
compelled to wear glasses.
The progressive character of this de-
feet is likewise clearly illustrated by
some statistics furnished by DR.. Cohn,
of Breslau He examined the eyes of
ten thousand school children and found
results as follows: In the elementary
school about six per cent. were myOpic,
in the intermediate school over ten per
cent, in the high school about twenty
per cent, and in the gymnasia over
twenty-six per cent. Other examina-
tons, both in Europe and this country,
furnish us with closely corresponding
data. A very interesting and still more
suggestive series of experiments was
reported from ST. Petersburg, few
years since, where, according to high
authority, thirteen per cent. of the
scholars begin life with inherited myo-
pia Several thousand children were
selected from the public schools of that
city, and had applied themselves more
or less closely to their books outside OF
school hours. Among those who had
habitually studied two hours each day
the thirteen per cent. had increased to
seventeen per cent, while those who
had devoted four hours to their
books twenty-nine per cent. had
become near-sighted; and among
the most Industrious ones and those
who, In their competition for elias;
prizes had averaged six hours of daily
outside work, more than forty per cent
had injured their eyes and required
concave glasses for distant vision. One
authority claims that some of the
graduating classes in the highest
schools of the continent of Europt