ll the eyes into line again, only to have the performance
repeated, all of which entails a great strain upon the nervous system,
and may lead to permanent squint, as has been pointed out. In addition
to these symptoms caused by weakness of the eye muscles--seeing
double, blurred vision, and want of endurance for close work--there
are others which are common to eye-strain in general, as headache,
nausea, etc., described in the following paragraph.

=Symptoms of Eye-strain.=--Headache is the most frequent symptom. It
may be about the eyes, but there is no special characteristic which
will positively enable one to know an eye headache from that arising
from other sources, although eye-strain is probably the most common
cause of headache. The headache resulting from eye-strain may then be
in the forehead, temples, top or the back of the head, or limited
to one side. It frequently takes the form of "sick headache" (p. 113).
It is perhaps more apt to appear after any unusual use of the eyes in
reading, writing, sewing, riding, shopping, or sight-seeing, and going
to theaters and picture galleries, but this is not by any means
invariably the case, as eye headache may appear without apparent
cause.

Nausea and vomiting, with or without headache, nervousness,
sleeplessness, and dizziness often accompany eye-strain. Sometimes
there is weakness of the eyes, i. e., lack of endurance for eye work,
twitching of the eyelids, weeping, styes, and inflammation of the
lids. In view of the extreme frequency of eye-disorders which lead to
eye-strain, it behooves people, in the words of an eminent medical
writer, to recognize that "the subtle influence of eye-strain upon
character is of enormous importance" inasmuch as "the disposition may
be warped, injured, and wrecked," especially in the young. Some of the
more serious nervous diseases, as nervous exhaustion, convulsions,
hysteria, and St. Vitus's dance may be caused by the reflex irritation
of the central nervous system following eye-strain.

=Treatment of Eye-strain.=--The essential treatment of eye-strain
consists in the wearing of proper glasses. It should be a rule,
without any exception, to consult only a regular and competent
oculist, and never an optician, for the selection of glasses. It is as
egregious a piece of folly to employ an optician to choose the
glasses as it would be to seek an apothecary's advice in a general
illness. Considerably more damage would probably accrue