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”. 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.