Evening star. [volume] (Washington, D.C.) 1854-1972, 1889-10-05
WONDERS OF THE HUMAN EYE.
Lots OF Curious Things About Natures
Photographic Camera.

MIC SCIENCE WHAT IT Is-DAN9ERs OF GOING
TO AN oPTIcIAS FOB A SPECTACLE PREsoRrp-
TIoS-"oLD SIGHT" NEAR" AND FAR sIaHr. I"
Il would like to examine the interior of the
eye" said the oculist But. when he per-
ceiyed a slight shrinking on the part Of TIE
STAR reporter, who assumed for the time the
role OF patient. he smilingly added: You need
NOT be alarmed; it will not hurt you particle"
Then picking up little disk-shaped mirror
with hole through the center be led the pa
hent into dark closet. and after lighting
bright gas jet told him to sit down on the chair
Immediately beneath it. Next he himself Sat
down opposite, SO that the knees Of the two
touched. and held the small round looking
glass in front Of his own eye. like an eyeglass,
with the mirror side outward. in such man
ner that it reflected a ray from the gas jet
straight into the patients eye through the
pupil He could direct the ray easily enough,
inasmuch as he was looking along 1t through
the small hole that pierced the center Of the
disk II you will hold big, fiat button-mold
mp to your eve and look through IT at the eye
OF person seated in front of you you will get
a notion of the way In which the oculist oper-
ated. Suppose the button-mold has quick
silvered glass on the surface turned toward the
object, and you will perceive how easy 1t would
be to throw a ray reflected from a light above
the other persons head directly into that
other persons eye, and to watch, through the
hole in the button-mold,
WHATEVER THAr RAY REVEALED.
This was what the oculist was doing with the
mirror disk. The ray it reflected entered the
patients eve, through the pupil. and lighted
up the interior very much as a dark room is
lighted up by a bull's-eye lantern shining
through a doorway from outside. Just as the
lantern might be turned about this way and
that, to illuminate various parts OF the dark
ened chamber beyond the doorway, so the lit
forehnger and thumb of the physician,
he held it before his own eye,
in such manner as to reveal to
his view every portion OF the inside OF
the ocular camera obscura-for such the eye is;
very much like the camera of the photogra-
pher i'll its construction and mode of working;
and. by gravy it has been found out quite re-
Gently that the so-called ocular purple" in the
eye actually produces the pictures of objects
seen, on the nerye-screen that lines the organ,
by chemical process very much like that en-
ployed by the photographer to bring out the
lines of his negatives. Possibly, some day, by
studying natures method, the sun-print artist
may learn how to photograph colors as the eye
does. Who knows?
The patient was very much relieved at length
to hear the oculist say that there was nothing
serious the matter.
Il observe a slight Inflammation Of the inner
coat of the left eye," remarked the physician.
''as well as a mildly hyperemic condition of the
lids, both of which little troubles have un-
doubtedly been occasioned by the glasses you
wear. Now, may l ask where you got those
glasses?'
AT So-and-so's. the optician," replied the
applicant for treatment
''HE ADyERTIsEs To FIT THEM WITHOUT CHARGE"
What do you consider to be the business of
an optician?"
Grinding glasses and fitting them to frames
mostly, / suppose"
Precisely. In other words. he is a me-
ehanic. OF the eye. its structure and pathol-
ogy he has scarcely more knowledge than you
have. And yet he advertises-though there
are some opticians who are too honest to do SO
to perform what is nearly the most difficult
work the eye doctor has to peform; namely, to fit
people with glasses. 1t takes years of hard study
for an ophthalmic surgeon to learn how to fit
glasses. No two persons eyes are quite alike,
and few patients have both eyes the same; In
each case dozen different possible defects have
to be looked ont for and remedied by glasses
ground in special WAYS if they exist 1t is apt to
take an hour or more for q skilled ocuist to
find out just what glasses you require, but the
confident optlcian Will call your attention to q
few rows of Authenticated letters at the other
end of the shop, ask you what rows you can
read and sell you pair of spectacles accord
fngly. of-hand. OF course it is always a more
or less wild guess on the opticians part. in
fnitely more apt to be wrong than right, and.
II you will consider that every bit of error as
to ut in the glasses means just so much con-
tinual strain upon the eyes of the wearer. you
will see what an immense amount of harm must
be done in this way. Why, l have known OPP
ticians to prescribe near-sighted glasses for
over-sighted eyes. and vice versa"
SHOULD ONE, THEN. FoRswEAR oPrIc1ANs?"
Hardly. The thing to do, If you need
glasses. is to go to the ophthalmic surgeon for
the prescription, as you would go to any other 1
physician If you had pain, and then take the !
prescription to the optician, who is the eye
doctors apothecary. as it were, to be filed
The glasses are prepared for you--if need be-
specially ground-and you have the satisfac-
ton of knowing that they are precisely what
you require. The whole business will cost you
sis, perhaps"
What is the little round mirror called with
which you examined nv eyes insi6e?" asked
the patient while the oculist was engaged in
fitting glasses of various strengths into huge
nose frame for trial.
To that little instrument" responded the
surgeon, lis due nearly all of the progress
made in ophthalmic science since the days Of
the ancient Egyptians. 5000 years ago. And
yet, as you see, 1t is nothing but small. round
mirror with a hole through it. 1t is called the
.ophthalmoscope, and was invented by Helm
holtz in 1852. So few years ago as
that very little was known about the
eye beyond what the old Egyptian
physicians were acquainted with. They
were familiar with the structure of the organ,
through dissection, and they even performed
operations for cataract. That disease Won
know, is merely clouding of the crystalline
lens which lies Just behind the little hole in
the iris called the pupil and serves to bring the
rays OF hight that enter the eve through the
pupil to a focus on the nerve screen behind.
IL Is at this focus that the picture Of the object
seen Is formed. like photograph. But il the
lens. which Is like a wee bit of convex glass;
Is rendered opaque by any cause it is
termed cataract, and the lens itself
must be gotten out Of the way, so as not to in
terrupt the hight rays. So, nowadays, il is cut
out Of the eye and removed. while in ancient
into the lower part of the eye, frequently to
occasion subsequent Inflammation and loss of
sight. However, to the opthalmoscope, 1
was going to say that it afforded the first means
ever discovered for studying the interior of the
living eye. From that point modern ophthalmic
science really took its rise, and there is not
much about the eye today that is not UNDER
stood"
SEAR-s1oHrEDSEss AMONG THE ANc1ESrs
"Were people afflicted with near-sightedness
In ancient times?'
"Oh, yes; though probably not to the same
extent We read, write and study more than
the ancients did, ana for this reason near sight
Is more common with Us, for il is the excessive
use of the eyes at the point that propa-
gates the trouble. In old times troubles with
the eyes were regarded as Affections sent by
heaven, for which there was no cure Nero.
VIZ fs Led ~ D..