Abstract

Accommodation, the mechanism by which the eye focuses on near objects, and the age-related loss of this function leading to presbyopia are inextricably linked to the development and aging of the anterior segment. Steady lens growth primarily in the sagittal direction throughout life and the concomitant shallowing of the anterior chamber are both highly correlated to reduced accommodative range (p≪0.001; Koretz et al., 1989), and other changes in the lens with age (e.g., increased scatter of light at high angles; Cook et al., 1994) are also observed. In addition to age-related changes in lens thickness, mass, and placement relative to the cornea and retina, the non-accommodated shape of the lens is itself age-dependent, becoming more sharply curved on both the anterior and posterior surfaces with increased age. This phenomenon was first characterized by Brown (1974), who noted that the human eye should lose far, not near, vision with aging based on these observations; this "lens paradox" can, of course, be resolved by assuming an overall reduction in lens refractive power with age (Koretz and Handelman, 1986; Cook and Koretz, 1995) without or with (Smith et al., 1992) a fundamental change in the shape of the refractive index gradient.

© 1996 Optical Society of America