Generally Accepted as Normal 211
When the accommodative power has declined to the point at which reading and writing become difficult, the patient is said to have "presbyopia," or, more popularly, "old sight"; and the condition is generally accepted, both by the popular and the scientific mind, as one of the un avoidable inconveniences of old age. "Presbyopia," says Donders, "is the normal quality of the normal, emmetropic eye in advanced age,"1 and similar statements might be multiplied endlessly. De Schweinitz calls the condition "a normal result of growing old" ;2 according to Fuchs it is "a physiological process which every eye undergoes";3 while Roosa speaks of the change as one which "ulti mately affects every eye."4
The decline of accommodative power with advancing years is commonly attributed to the hardening of the lens, an influence which is believed to be augmented, in later years, by a flattening of this body and a lowering of its refractive index, together with weakness or atrophy of the ciliary muscle; and so regular is the decline, in most cases, that tables have been compiled showing the near-point to be expected at various ages. From these it is said one might almost fit glasses without testing the vi sion of the subject; or, conversely, one might, from a man's glasses, judge his age within a year or two. The following table is quoted from Jackson's chapter on "The Dioptrics of the Eye," in Norris and Oliver's "System of Diseases of the Eye,"5 and does not differ materially from the tables given by Fuchs, Donders and Duane. The first
1 On the Anomalies of Accommodation and Refraction of the Eye, p. 210.
2 Diseases of the Eye, p. 148.
3 Text-book of Ophthalmology, authorized translation from the twelfth German edition by Duane, 1919, p. 862. Ernst Fuchs (1851- ). Professor of Ophthalmology at Vienna from 1885 to 1915. His Text-book of Ophthal mology has been translated into many languages.
* A Clinical Manual of Diseases of the Eye, p. 535. «VoL i, p. 504.