The wearing of correcting lenses en ables the myope to reduce his efforts of convergence to nearer the normal. But there still remains the increased diffi culty of turning an elongated eye in its socket. To help still farther, the amount of near work required of such eyes must be limited, and surrounded with the most favorable conditions, including the use of the best illumination and a correct posture, with frequent interruptions dur ing which the eyes are permitted to rest on distant objects. These precautions are of the greatest importance during childhood and adolescence, when myopia begins and shows the most general tend ency to increase.
Series of tables from observations based upon the results obtained from an exami nation of 200,000 formula2 for spectacles and eye-glasses in Philadelphia. The whole number of eyes for which distant glasses has been furnished by the optician was 1S7,01S, of which 21.6 per cent. were for myopia. Of these, 39.5 per cent. were for simple myopia, while 60.5 per cent. were for myopic astigmatism. ..kmong the private cases, however, where the re fraction had been done under mydriasis, 22 per cent. were myopic; of these, 9.67 per cent. were instances of simple myopia, while 90.33 per cent. were astigmatic in varying degrees. In a very large number of patients there Wa S mixed astigmatism on one side, while on the other there was either simple or compound myopic astig matism, similar pathological symptoms being present in both eyes. The percent age of myopia was 3 per cent. higher among private eases than among those selected from the books of the optical companies. The progress of the increas ing refraction, both in percentage of eases and in the degree of the increase, was arrested by the treatment and glasses received. Risley (Archives of Ophtlial., July, '94).
The prophylactic treatment of myopia consists in the following: 1. Making the patient employ the full correction of his myopia all the time and both for dis tant and near use. This is of prime im portance in all varieties of myopia,— b»v, medium, and high,—and, if applied early, may cheek the progress of the myopia altogether. 2. Proper attention to illumination, the size and legibility of the print, the quality of paper used in the books read, the relative height and disposition of the seat and desk, and the many other factors that have been brought out by the zealous investigators into the subject of school - hygiene.
These are important, but subsidiary, matters. 3. In low and medimu myopia moderate restriction of near work or rather its better distribution, so that it is done mainly by daylight and not for too long at any one time. Furthermore, momentary rest of the eyes at frequent intervals during the work. These rules to be the more strictly enforced the higher the myopia and the younger the patient. 4. In high myopia with evi dences of progress much more stringent restriction of near work. Open-air work to be encouraged and the adoption of confining and eye-taxing occupations forbidden. 5. In merlitim and especially in high myopia plenty of sleep and out of-door exercise. 6. Re-examination of the patient at frequent intervals (which in the case of high myopia, should be very frequent) to determine how much the myopia has increased. Tf it has in creased, the glasses should be increased also vip to the full strength, and the hygienic regulations above detailed mod ified accordingly. Alexander Duane (New York Med. Jour., June 7, 1002t.
The surgical treatment of myopia by removal of the crystalline lens is appro priate for a few cases of very high de gree,-15 D. and upward,—in which cor recting lenses give unsatisfactory results, although the eyes are capable of good vision. In children the removal is to be effected by a small discission of the lens, repeated several times, if necessary, until the absorption of the lens-substance leaves a clear pupil. In adults the lens may be extracted after a preliminary small discission to render it opaque. The operation is quite as formidable and dangerous as that of the removal of the opaque lens,—cataraet. (See volume ii.) The removal of the crystalline will generally correct about 1S I). of myopia; and the higher the myopia, unless it be due to increased curvature of tbe cornea, the greater will be the effect of the op eration. The removal of the crystalline also gives a larger retinal image than can be obtained through concave correcting lenses, with a correspondingly superior acuteness of vision. In cases suitable for this operation such improvement should amount to 50 or GO per cent. After re moval of the crystalline, although the patient is much less dependent on his glasses, they will still be necessary to secure the best vision; and different lenses will be required for near and far seeing, on account of the loss of all power of accommodation.