It is known that the nearest point at which an object can be seen distinctly gradually recedes with advance in age and that this recession in the near point of distinct vision varies so regularly as one grows older that it may be used in determining the age of a person. Figures such as the following are reported in the literature: At 10 years of age the near point of distinct vision is 7 cm. ; at 20 years, 10 cm. ; at 30 years, 14 cm.; at 40 years, 22 cm.; at 50 years, 40 cm.; at 60 years, 100 cm., and at 70 years of age all power of accommodation has been lost. At 40 or 50 years of age this lengthening of the near point of distinct vision obtrudes itself on one in the use of the eyes for near objects, reading, for example, and it becomes necessary
BURGE WE, WICKWIRE GC, SCHAMP HM. CAUSE OF CALCIFICATION OF THE CRYSTALLINE LENS: WITH ADVANCE IN AGE AND IN CATARACT. Arch Ophthalmol. 1937;17(2):234–240. doi:10.1001/archopht.1937.00850020040005
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