Photodynamics of cataract: an update on endogenous chromophores and antioxidants

Cataract of the eye lens is characterized by (1) progressive opacification or loss of transparency; (2) accumulation of molecules that absorb in the UV-visible range of the spectrum; and (3) formation of fluid-filled vacuoles, particularly in diabetics when sugar levels in the lens are high. Of the various causative factors for cataract, light is an important one. Because the level of light below 320 nm reaching the lens is quite low, photodynamic effects of endogenous compounds absorbing in the UV-A-visible region become important in this connection. In this update we summarize a list of accumulant chromophores that have been identified in aging and cataract human lenses and their roles as potential sensitizers, antioxidants or as benign filters. Because such photodynamic cataractogenesis is oxidative in nature, we also cite examples where administration of antioxidants could help delay cataract progression.