WEAKNESS OF THE EYE MUSCLES.—There are six muscles attached to the outside of the eyeball which pull it in various directions, and so enable each eye to be directed upon a common point, otherwise objects will appear double. Weakness of these muscles or insufficiency, especially of those required to direct the eyes inward for near work, may lead to symptoms of eye-strain. When reading, for example, the muscles which pull the eye inward soon grow tired and relax, allowing the opposing muscles to pull the eye outward so that the eyes are no longer directed toward a common point, and two images may be perceived or, more frequently, they become fused together producing a general blurring on the page. Then by a new effort of will the internal muscles pull 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 from following the optician's prescription than that of the apothecary, because nature would soon offset the effects of an inappropriate drug; but the damage to the eyes from wearing improper glasses would be lasting.
Properly to determine the optical error in astigmatic and farsighted eyes it is essential to place drops in the eye, which dilate the pupil and paralyze the muscles that control the convexity of the crystalline lens, and to use instruments and methods of examination, which can only be properly undertaken and interpreted by one with the general and special medical training possessed by an oculist.
The statement has been emphasized that farsighted and astigmatic persons, up to the age of forty-five or fifty, can sometimes overcome the optical defects in their eyes by exercise of the ciliary muscle which alters the shape of the lens, and, therefore, it would be impossible for an examiner to discover the fault without putting drops in the eye, which temporarily paralyze the ciliary muscles for from thirty-six to forty-eight hours, but otherwise do no harm. After the age of fifty it may be unnecessary to use drops, as the muscular power to alter the convexity of the lens is greatly diminished. Opticians are incompetent to employ these drops, as they may do great damage in certain conditions of the eye which can only be detected by a medical man specially trained for such work. Opticians are thus sure to be caught on one of the horns of a dilemma; either they do not use drops to paralyze the ciliary muscle, or, if they do employ the drops, they may do irreparable damage to the eye. Any abnormality connected with the vision, especially in children, should be a warning to consult an oculist. Squint, "cross-eye" (Strabismus), as has been stated, may often result from near- or far-sightedness, and it may be possible in young children to cure the squint by the use of glasses or even drops in the eye, whereas in later life it may be necessary to cut some of the muscles of the eyeball to correct the condition. It is a wise rule to subject every child to an oculist's examination before entering upon school life.
DEAFNESS.—Sudden deafness without apparent reason is more apt to result from an accumulation of wax than from any other cause. It is a very common ear disorder. The opening into the ear is about an inch long, or a little more, and is separated from that part of the ear within, which is known as the middle ear, by the eardrum membrane. The drum membrane is a thin, skinlike membrane stretched tightly across the bottom of the external opening in the ear or auditory canal, and shuts it off completely from the middle ear within, and in this way protects the middle ear from the entrance of germs, dust, and water, but only secondarily aids hearing. The obstruction caused by wax usually exists in about the middle of the auditory canal or opening in the ear, and only causes deafness when it completely blocks this passage.
The deafness is sudden because, owing to the accidental entrance of water, the wax quickly swells and chokes the canal; or, in attempts to relieve irritation in the ear, the finger or some other object is thrust into the opening in the ear (auditory canal) and presses the wax down on the ear drum. The obstruction in the ear is usually a mixture of waxy secretion from the canal, and little scales of dead skin which become matted together in unwise efforts at cleansing the ear by introducing a twisted towel or some other object into the ear passage and there turning it about; or it may occur owing to disease of the ear altering the character of the natural secretion. In the normal state, the purpose of the wax is, apparently, to repel insects and to glue together the little flakes of cast-off skin in the auditory canal, and these, catching on the hairs lining the canal, are thrown out of the ears upon the shoulders by the motion of the jaws in eating.
Nothing should be introduced into the ear with the idea of cleansing it, as the skin growing more rapidly from within tends naturally to push the dead portions out as required, and so the canal is self-cleansing.
Symptoms.—Sudden deafness in one ear usually calls the attention of the patient to an accumulation of wax. There is apt to be more or less wax in the other ear as well. Noises in the deaf ear and a feeling of pressure are also common. Among rarer symptoms are nausea and dizziness. But the only way to be sure that deafness is due to choking of the ear passage with wax is to see it. This is usually accomplished by a physician in the following way: he throws a good light from a mirror into a small tube introduced into the ear passage. This is, of course, impossible for laymen to do, but if the ear is drawn upward, backward, and outward, so as to straighten the canal, it may be possible for anyone to see a mass of yellowish-brown or blackish material filling the passage. And in any event, if the wax cannot be seen, one is justified in treating the case as if it were present, if sudden deafness has occurred and competent medical aid is unobtainable, since no harm will be done if wax is absent, and, if it is present, the escape of wax will usually give immediate relief from the deafness and other symptoms.