CHAPTER XX PRESBYOPIA: ITS CAUSE AND CURE
A MONG people living under civilized conditions the accommodative power of the eye gradually de-b clines, in most cases, until at the age of sixty or seventy it appears to have been entirely lost, the subject being absolutely dependent upon his glasses for vision at the near-point. As to whether the same thing happens among primitive people or people living under primitive conditions, very little information is available. Donders1 says that the power of accommodation diminishes little, if at all, more rapidly among people who use their eyes much at the near-point than among agriculturists, sailors and others who use them mainly for distant vision; and Roosa and others2 say the contrary. This is a fact how ever, that people who cannot read, no matter what their age, will manifest a failure of near vision if asked to look at printed characters, although their sight for familiar objects at the near-point may be perfect. The fact that such persons, at the age of forty-five or fifty, cannot dif ferentiate between printed characters is no warrant, there fore, for the conclusion that their accommodative powers are declining. A young illiterate would do no better, and a young student who can read Roman characters at the near-point without difficulty always develops symptoms of imperfect sight when he attempts to read, for the first time, old English, Greek, or Chinese characters.
1 On the Anomalies of Accommodation and Refraction of the Eye, p. 223.
2 Roosa: A Clinical Manual of Diseases of the Eye, 1894, p. 537; Oliver: System of Diseases of the Eye, vol. iv, p. 431.