Popular Education / For the use of Parents and Teachers, and for Young Persons of Both Sexes

by Ira Mayhew

It would be interesting to notice the protecting organs of the eye, consisting of the orbit, which is a deep bony socket, in which the eye securely rests; of the eye-brows, which are two projecting arches, covered with hair, and so arranged as to prevent the moisture that accumulates upon the forehead, in free perspiration, from flowing into the eye; of the eye-lids, which are two movable curtains for the protection of the eye, and which secrete a fluid that moistens and lubricates it; of the lachrymal gland, with its ducts, which keeps the eye constantly moist, and whose secretions go on while we wake and when we sleep, etc., etc.; but the preceding must suffice.

With this brief description of the apparatus of vision, we proceed to the consideration of the means of preserving and improving this sense, and of rendering it tributary to intellectual and moral culture.

The rule requiring that action should alternate with rest, which has been so often stated, and which applies to all the organs of both body and mind, should be especially observed in relation to the eye. This organ requires exercise, and light is its appropriate stimulus; but injury is the inevitable consequence of keeping it too constantly employed, or too intently fixed for a long time on any object. Whenever the eye is fixed for any length of time upon an object which it distinguishes with difficulty, it experiences a painful sensation, which is a sure indication that it has been overtaxed. The sight is also impaired when the eye is too little used, or when its natural stimulus is shut out, as is strikingly illustrated in the case of persons confined in dungeons. A distinguished oculist has said that many men daily impair or destroy their eyes by immoderate use, and that not a few have done the same by too little use of them.

The exposure of the eyes to sudden transitions from weak to strong light is very injurious. This may be regarded as one of the must prolific causes of weakness of sight. The injury is generally gradual, it is true, but it is none the less fatal on that account. The immediate sensation of pain, when a strong light is brought into a dark room, should be a sufficient warning to avoid such sudden extremes. The iris dilates and contracts, and thus enlarges or diminishes the size of the pupil as the light that fails upon the eye is faint or strong; but this dilation and contraction are not instantaneous. There are numerous instances on record in which total blindness has resulted from a sudden transition from darkness to the brilliancy of day. The habit of looking at a bright light of any kind, and especially of watching flashes of lightning, which is practiced by many, is exceedingly dangerous. The practice which many students and others indulge in, of resting their eyes as the twilight of evening advances, and allowing the pupil to dilate until it is quite dark, and then suddenly introducing a bright light, is a palpable violation of this rule, and one that is sure, sooner or later, sensibly to injure the eyes. The exposure of the eyes suddenly to a strong light upon waking from sleep, and all sudden changes of whatever kind from darkness to intense light, should be carefully avoided by persons who would preserve their sight unimpaired.

The strength of light used should be regulated according to the powers of the eye. This is a general, though a very important rule. Both the amount and the distribution of light should be such as to produce no unpleasant sensations. The eye possesses a certain degree of adaptation to light, according as it is intense or feeble. Some eyes require a stronger light than others, but all eyes are injured by being used in light that is too intense or too feeble. Reading by a strong sunlight, and by moon or star light, may be adduced as illustrations which are alike painful and injurious.

Too little light is well-nigh as injurious as too much, as he can not fail to have noticed who has had occasion to travel a difficult road in a dark night. The injury, in such cases, is two-fold; for while, on the one hand, the radiated muscle of the iris is unduly contracted for a length of time, in order sufficiently to enlarge the pupil to render objects visible, the sensitive retina, on the other hand, is overtaxed to gain a knowledge of them in too feeble light. The pain which the strained eye thus experiences is only an indication and a warning to the individual of the permanent injury he is inflicting upon this delicate organ.

Rooms should be well and evenly lighted. The irregular and flickering light of common lamps and candles is very injurious, and should be avoided in the study, and in all mechanical pursuits where the eye is much taxed. The best oculists concur in the opinion that reflected and concentrated light are highly injurious. Several cases of actual blindness are recorded as having occurred within a few years from exposure to concentrated light, and weakness of sight that has unfitted the individual for usefulness through life has often been thus produced. The rays of the sun are considered as peculiarly injurious when reflected from an opposite building or wall, or even when they pass through a window, and, descending to the floor, are thence reflected to the eyes. What, then, shall we say of the habit of constructing school-rooms in such a manner that perhaps a majority of the scholars are obliged to write and study at desks upon which the direct rays of the sun shine for a considerable portion of the day unbroken unless it be by a passing cloud! And yet thousands of school-houses are situated in such a manner as to create this very necessity all over our country. At a moderate estimate, the eyes of one hundred thousand children are taxed in this manner in the schools of the United States every passing year. A vast amount of discomfort and unhappiness is produced in this way that might easily be avoided, would parents and teachers take the trouble. Any exposure of this kind should be immediately obviated, either by blinds, or by curtains of some soft color. A few newspapers are much better than nothing. The desks and furniture should be of such a color that the eye may repose upon them with agreeable sensations. Nature is clothed with drapery whose color is refreshing to the eye; and it is false taste, as well as false philosophy, which attempts to dazzle in order to please it.

The use of side lights is injurious. The eye will accommodate itself to light of different degrees of intensity within a limited range, but both eyes should be exposed to an equal degree of light. The sympathy between the eyes is so great, that if the pupil of one eye is dilated by being kept in the shade, as must, of course, be the case where the light is on one side, the eye which is exposed can not contract itself sufficiently for protection, and is almost inevitably injured.

When viewing objects, we should avoid, as far as possible, all oblique positions of the eye. By neglecting this rule, an unnatural and permanent contraction of the muscle is liable to be produced, as is illustrated in the numerous instances of strabismus, or cross-eye, which are every where too common.

We should accustom the eye to viewing objects at different distances. The muscles upon which the form of the eye and the size of the pupil depend are subject to the general laws of muscular action. Their strength and flexibility, which are increased by healthful exercise, are impaired by disuse. Hence students who have neglected this rule, and have accustomed themselves for a long time to view objects near by, lose the power of adjusting the eye so as to view things at a distance. As a consequence, they become near-sighted, and put on glasses, when, by a proper use of the eye, their vision might have been preserved unimpaired many long years. I know some students upon whom this habit became so firmly fixed before they were twenty years of age, that they felt compelled to put on glasses, but who, unwilling to contract so pernicious a habit in early life, commenced a course of discipline in accordance with the suggestions here given. By perseverance, their eyes not only recovered their former healthful action, but became so improved that they now possess the sense of vision unimpaired not only, but in a very high state of cultivation.