Eyes

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.

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.

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.

This is a condition caused by inequality of the outer surface of the front of the eyeball, and rarely by a similar defect in the surfaces of the lens. The curvature of the eyeball in the astigmatic eye is greater in one meridian than in the opposite. In other words, the front of the eyeball is not regularly spherical, but bulges out along a certain line or meridian, while the curvature is flattened or normal in the other meridian. For instance, if two imaginary lines were drawn, one vertically, and the other horizontally across the front of the eyeball intersecting in the center of the pupil, they would represent the principal meridians, the vertical and the horizontal. As a rule the meridian of greatest curvature is approximately vertical, and that of least curvature is at right angles to it, or horizontal.

In the nearsighted eye the eyeball is too long for parallel rays entering the eye to be focused upon the retina; they are bent, instead, to a point in front of the retina, and then diverge making the vision blurred. The act of accommodation in making the lens more convex will not aid this condition, but only make it worse, so that it is not attempted.

Eye strain is commonly due to either astigmatism, nearsightedness, farsightedness, or weakness of the eye muscles. The farsighted eye is one in which parallel rays entering the eye, as from a distance, come to a focus behind the retina. The retina is the sensitive area for receiving light impressions in the back of the eyeball. Sight is really a brain function; one sees with the brain, since the optic nerve endings in the back of the eye merely carry light impressions to the brain where they are properly interpreted.

In order that vision be clear and perfect, it is essential that the rays of light entering the eye be bent so that they strike the retina as a single point. In the farsighted or hyperopic eye, the eyeball is usually too short for the rays to be properly focused on the sensitive nerve area in the back of the eye.

This is a severe epidemic form of catarrh of the eye, which is caused by a special germ known as the “Koch Weeks bacillus.” The treatment of this is the same as that outlined below. The germ of pneumonia and that of grippe also often cause conjunctivitis, and “catching cold,” chronic nasal catarrh, exposure to foul vapors and gases, or tobacco smoke, and the other causes enumerated, as leading to congestion of the lids, are also responsible for catarrhal inflammation of the eye.

In this disorder there is discharge which sticks the lids together during the night. The inner surface of the lids is much reddened, the blood vessels in the lining membrane are much enlarged, and the lids are slightly swollen. The redness may extend to the eyeball and give it a bloodshot appearance. There is no interference with sight other than momentary blurring caused by the discharge, and occasionally there is very severe pain, as if a cinder had suddenly fallen in the eye. This symptom may occur at night and awaken the patient, and may be the reason for his first consulting a physician.

This may be caused by smoke or dust in the atmosphere, by other foreign bodies in the eye; frequently by eye strain, due to far or near sightedness, astigmatism, or muscular weakness, which may be corrected by an oculist’s (never an optician’s) prescription for glasses. Exposure to an excessive glare of light, as in the case of firemen, or, on the other hand, reading constantly and often in a poor light, will induce irritation of the lids. The germs which cause “cold in the head” often find their way into the eyes through the tear ducts, which connect the inner corner of the eyes with the nose, and thus may set up similar trouble in the eyes.

The mucous membrane lining the inner surface of the eyelids also covers the front of the eyeball, although so transparent here that it is not apparent to the observer. Inflammation of this membrane is more commonly limited to that portion covering the inner surfaces of the lids, but may extend to the eyeball when the eye becomes “bloodshot” and the condition more serious. For the sake of convenience we may speak of a mild form of sore eye, as congestion of the eyelids , and the more severe type, as true conjunctivitis