The Hawaiian star. [volume] (Honolulu [Oahu]) 1893-1912, 1896-03-13
LIGHT, COLOR AND THE EYE.
Extraordinary Differences In the Power
NInion-SOme Interesting ExperIme u =,

Extraordinary Differences In the Power of
Niaion-some Interesting Experiment.
While the eyesight of many persons is
defective, a still greater number have eyes
which are unlike each other In seeing power.
In fact, many practically make use Of one
eye only; the other, having been originally
q little defective, was by degrees called on
for duty less and less and accordingly de.
generated.
One gentleman could see with his right
eye the figures on the face of n clock five
,ighths of an inch high at IL feet, while he
i'l see them as clearly with the left eye
/, at eight inches distance, and curiously
iough this extraordinary difference in the
powers Of vision of both eyes was not de
tected by him until he had reached middle
age. Many people are unable to keep one
eye shut and the other open at the same
time
This is especially common with children,
but less frequent with adults, and 1t will
be readily understood that In such cases
considerable differences In the powers Of
the eyes may exist without being suspect
ed. Sir John Herschel mentions the case
Of an elderly person who by chance made
the unpleasant discovery that he was alto
gether blind In one eye.
Some simple and easily performed ex-
periments give interesting glimpses into
the constitution Of theeye. Go into dark
room with candle, Looking at the wall,
which should be of uniform dark tint, on
moving the candle up and down close to
the outer side Of one eye. so that the light
falls very obliquely onto 1t, one Of what
are called "Purkinje's figures" will be
seen. This is an appearance OF u crlles OF
diverging and branched red lines on dark
field, In the interspace OF two or three of
which Is sort Of cup shaped disk
These lines are the blood vessels Of the
retina, and the disk is the yellow SPOT or
most sensitive part Of the eye In the same
| situation, looking still at the dark wall ard
keeping the eye fixed on one point, hold
| the candle at arms length and move 1t To
and fro for distance Of about two inches
on level with the point toward which the
eye Is directed and II little to the right OF
left Of 1t, when faint light may be seen
moving In the opposite direction to the can
die and on the lower side Of the point looked
i at.
| This light, il more nearly Inspected, il
seen TO he an inverted image of the candle
fame, equal in size to it, but very faint,
and il, in fact, the light OF the candle re
hected from the lens Of the eye. Other in
ternal parts of the eye also reflect some Of
the light that falls into IL, but the images
formed by them are not SO easily seen.
1t Is well known that the pupil contracts
mechanically in bright light and expands
In faint light, but it has been found that
to some extent this change is under the con
troll Of the will. A scientific observer writ
ing on this subject says that when fronting
| q window or other light he can make tn,
pupil expand or contract at the desire o.
any one looking into his eyes.
The pupil is contracted while he steadil,
looks at the light, and when he wishes {,
expand 1t all that is necessary Is TO take hi
attention away from the eye and fix it OF
some other part Of the body without NOV
ing his eyes. This he does, say, by bit
ing his tongue, pinching his arm or il
some such way. The sensitiveness of tn
retina is diminished by this means, and tn
pupil dilates. 1t contracts again when tn
mind Is once more recalled TO the eye an,
the bright light.-Tit-Bits.