CHAPTER XXII THE CARE OF THE EYES AND EARS
The visual apparatus (eye, optic nerve, nerve endings, etc.) furnishes one of the most important paths from the world without to the brain within, and it is of the utmost importance to the exercise of the highest functions of the human mechanism that this path be kept as smooth as possible. Unfortunately, however, the path is seldom either straight or smooth, and it frequently presents serious ob- stacles. The curvature of the cornea or of the lens may be irregular ; the muscle of accommodation may be weak ; the retina may be too near or too far from the lens, or its sensitive cells may too readily become fatigued by the stimulation of light; finally, the path into the brain may be made of poorly constructed nervous tissue, or in the brain itself the codrdinations upon which depend our visual judgments (p. 256) may be imperfect. The simplest act of vision is the end result of a most complicated series of events, difficulty with any one of which may make quick and accurate seeing impossible. Many a child has been considered stupid simply because an unrecognized condi- tion of myopia or astigmatism renders it impossible to read clearly the printed page or the distant blackboard; and many people, adults as well as children, suffer from head- aches and other troubles because of the strain thrown on the nervous system in the effort to work with defective vision.
When one is leading an outdoor life, occupied in the work of the farm or the lumber camp, and doing but little reading, the eyes usually give little trouble, because it is
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only when looking ‘at near objects (three feet or less away) that the mechanism of accommodation is called into vigor- ous action. Eye strain is usually produced by prolonged near work with eyes incapable of enduring without un- due fatigue what is demanded of them. Hence it is that defects of vision are more common to-day than they were a hundred years ago. Both the vocations and the avoca- tions of modern life, with their large amount of reading, writing, and other forms of near work, impose upon the eye the most trying and difficult task it can be called upon to perform. The use of glasses is more common than for- merly, and the care of the eyes is forced upon us as an important factor in the hygienic conduct of life.
- The Necessity of Expert Advice. — In the care of the eyes expert advice is indispensable. The detection of defects of vision frequently demands the best skill of those who are thoroughly acquainted with the physiology of the entire visual apparatus, including its relation to other bodily functions, and who are also provided with every means for gaining an insight into the conditions which are giving trouble. The selection of the proper glass, for example, when lenses are needed is more than a mere matter of test- ing vision with test cards; and eyes may be seriously injured by using glasses prescribed on the basis of informa- tion gained by imperfect methods.
First of all, then, let us insist upon the necessity of competent medical advice whenever there is reason to sus- pect something wrong with the eyes. If vision is not dis- tinct, if the eyes tire quickly when used for near work, and even when one suffers from headaches, “ nervousness,” and other forms of malaise without apparent cause, it is wise to find out whether some remediable defect of vision is not at the root of the trouble.
On first thought it may seem unreasonable to consult an oculist with regard to headaches or other troubles with
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organs having no obvious connection with the eye; but when we remember the fact that all parts of the central nervous system are connected with one another, it is easy to see how undue strain of one part in the effort to see with astigmatic or otherwise defective eyes may, by injuriously affecting other parts of the brain or spinal cord, unfavor- ably influence organs which themselves have nothing to do with vision. Over and over again it happens that head- aches and other troubles are relieved, as by magic, when vision is made perfect by the use of proper glasses.
With these remarks as to the importance of skilled advice in the care of the eyes, we may pass to those prac- tical measures which should be under the intelligent indi- vidual control of every man and woman. Suppose vision is perfect, or as nearly perfect as the best of medical skill can make it; what precautions in the use of the eyes favor the maintenance of their best working condition ?
Resting the Eyes. — First of all we would suggest the importance of resting the eyes now and then while engaged in near work. This is accomplished by the sim- ple expedient of looking for a few moments at some dis- tant object (p. 250). The brief relaxation of the effort of accommodation does for the neuromuscular mechanism involved exactly what a brief relaxation of the body in sleep accomplishes for the body as a whole.
Illumination of the Object. The Importance of Con- trast. — The ease with which the details of an object are seen depends chiefly on the contrasts of shade and color which these details present to the eye, and nothing so influences this contrast as the amount of illumination. Thus as the light fades in the evening, the white paper of _a printed page becomes darker and darker, until finally it reflects to the eye little more light than the black ink of the printed letters, which consequently no longer stand out clear and distinct. In order to admit all the light
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possible, the pupil enlarges, and in so doing lessens the.
distinctness of the retinal image (spherical aberration); more important than this, we hold the page closer to the eye, thereby enlarging the retinal image and increasing the intensity of stimulation, but throwing far more work upon the ciliary muscle to focus for the near object. All of these unfavorable conditions taken together placé undue strain upon the mechanism of accommodation.
Hardly less objectionable is excessive illumination of an object. After a certain intensity of light is reached, the retina no longer responds to increase of stimulation with increase of visual reaction. If there were in addition to our sun a second sun which sent into the eye twice as much light, the second sun would seem no brighter than
- the first because the effect of the first upon the eye has already passed the point which calls forth the greatest possible reaction in the retina. To apply this principle to the case in point, we have only to remember that a printed letter is not absolutely “dead black,” but reflects some light. When the illumination is moderate this reflected light hardly affects the retina at all, and the contrast between the black letter and the white paper is marked. As the intensity of illumination increases, however, the effect upon the retina of the light coming from the letters increases more rapidly than the effect of that coming from the paper. Contrast. is lessened and sharper accommoda- tion as well as closer attention is needed to see distinctly. Added to this, no doubt, is the fatigue and lack of sensi- tiveness in the retina, resulting from overstimulation.
- The Size of Type. — The use of fine type should be reduced to a minimum, because it necessitates greater effort of accommodation and intensifies all the evils of improper illumination. Any printed matter which must be held less than eighteen inches from the eye in order to be seen clearly is undesirable for long-continued reading.
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Especially is this true in youth, since then the eye is more plastic, and excessive strain of the muscle of acecommoda- tion, pulling as it does on the sclerotic and the choroid coats, may lead to permanent deformation of the curved surfaces. The marked increase of myopia within the past forty or fifty years is explained in this way.
Highly Calendered Paper Objectionable. — Closely con- nected with the size of the type is the character of the paper on which it is printed. This should be as dull as possible in order to avoid the confusing effect of a glossy surface. The use of highly calendered paper in many books and serial publications, because such paper lends itself more readily to the reproduction of pictures in half tone, is a sacrifice of hygienic considerations to cheapness.
Importance of a Steady Light. Reading on Railroad Trains. — The source of illumination for near work should be as free as possible from unsteadiness or flicker, since a flickering light necessitates the most accurate accommo- dation. A “student's lamp,” “ Rochester burner,” or incan- descent electric lamp is preferable in this respect to candles, gas jets, and arc lights for near work.
For the same reason caution is demanded in the matter of reading on railroad trains. American railway trains have recently become so heavy, and the roadbed, rails, etc., have been so much improved in various ways, that the danger of reading or writing while traveling by rail is much less than formerly. At the same time the danger still exists, and reading on many railway and trolley cars is still to be done with caution, or, better still, avoided altogether.
7%. Microscopes, Telescopes, and other optical instruments require close and sometimes continuous use of one or both eyes, and are popularly supposed to be “hard on the eyes.” But this is not necessarily the case, except for beginners and investigators; for beginners, because they
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try to see clearly by focusing with the eye rather than —
with the use of the focusing apparatus of the instrument; for investigators, because the eyes are used for too long periods at a time. Optical instruments are easily focused, and, if care be taken to provide good lighting, routine work with them need not be specially trying to the eyes.
The Removal of Cinders. — Particles of dust, cinders, etc., are often washed away from the surface of the eyeball by the copious secretion of tears which they call forth. Sometimes, however, they must be removed directly from the eyeball or the inner surface of the eyelid. In the case of the lower lid this operation presents little difficulty, for the eyelashes of this lid are easily seized, the lid drawn forward away from the eyeball, and the surfaces of the eyelid and eyeball readily inspected. If any foreign body is there located, it may be removed by the corner of a handkerchief. Successful manipulation of the upper lid is more difficult, because a piece of cartilage immediately above the eyelashes interferes with turning back the lid. The gaze of the patient should be directed downward, a small pencil or other cylindrical object pressed against the upper portion of the lid, above the cartilage, the eyelashes seized, and the lid turned upwards and backwards over the pencil.
Recapitulation. The Care of the Eyes. 8 summa- rize, we may remind the student that the eyes, no less than other organs, should be kept sound and strong by attention to the general health and welfare of the body. Work, play, rest and sleep, muscular exercise, wise feeding, and regular removal of the wastes, — these and all other general hygienic habits help to keep the eyes sound and strong; but besides these, posture in work, lighting, paper (not forgetting wall paper), printing, dust, cinders, smoke, acid fumes, traveling, sight-seeing, and many other con- ditions have their effect. Finally, it must not be forgotten
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that the eyes are too precious to be trifled with, and that if one has sore or weak eyes, or pain in the eyes, or cannot see clearly to read or to write, or cannot plainly distinguish things near or at a distance, then it is always best to con- sult an oculist or the family physician for advice. Remedies or doctors puffed in high-sounding advertisements should be carefully avoided.
- The Care of the Ears. — Besides good care of the general health, which common sense dictates and which we have repeatedly urged as the fundamental requirement in the hygiene of all organs, there is but little which the individual can do for the ears. Deafness, especially total deafness, is a defect or injury perhaps no less serious than blindness. Acute hearing is probably as valuable as acute vision, and a partial loss of hearing is a handicap often harder to overcome than are some defects of vision.
Keeping in mind the auditory apparatus and its connec- tions (Chapter XIV), it is easy to see that the drum may . be pierced or otherwise injured by slender objects thrust in from without; that catarrh of the throat may easily extend into the Eustachian tube, inflaming it or choking its lumen or outlet; and that any thickening of the drum must tend to make its vibrations slower and more diffi- cult. In these possibilities we have some of the actual causes of deafness, and none of them is of a kind to be treated by the patient. Any recognition of incipient deat- ness in oneself should be regarded as cause for consulting a good physician. No attention should be paid to adver- tisements promising to relieve deafness, for these are usu- ally traps calculated to catch the ignorant, unwary, or credulous. It is dangerous to explore the outer ears with hairpins or other pointed objects, as the drum may thus be broken or other harm done.
- Noise, though delighted in by savages, who beat tom-toms, blow conch shells, or otherwise tickle the sense
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of hearing, and though in moderation often found stimu- lating and enjoyable by persons who have been living in solitude or isolation, is by adults among the most highly civilized peoples more and more regarded as a necessary evil, or even as a nuisance. Children, on the other hand, often delight in noise, and horn blowing, firecrackers, and pistol firing on holidays like the Fourth of July appear to give to them as much pleasure as to their elders pain. Adults also on occasions of rejoicing still ring bells, beat drums, blow horns, and fire cannon in order to express — their emotions. Loud noise, like strong light, is unques- tionably stimulating and exciting, and for these reasons, though justifiable at times of rejoicing, is something to be ordinarily avoided as far as possible in city life, itself already much too stimulating and exciting. One can, in- deed, often learn to sleep even in the presence of dis- _ tracting noises such as those of a busy city street; but such sleep cannot possibly be as wholesome as that enjoyed - in quiet places. The constant whistling of locomotives, which was formerly a great nuisance in many American cities and towns, has been largely done away with, and the tendency of the times is to cultivate quiet, not only as a private luxury but also as a public necessity.
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