Comparison of endogenous and exogenous photosensitization in the lens using in vitro and photophysical studies.

Age related, photochemically induced damage to the lens can eventually lead to light-scattering areas which would be evidenced as an opacification of the lens. These modifications may occur at ambient radiation over an extended period, resulting from the initial absorption of radiation by relatively inefficient endogenous sensitizers (eg. tryptophan and/or 3 hydroxy kynurenine glucoside). However, the introduction of an efficient exogenous photosensitizer into the lens can markedly increase the rate by which these changes occur. Photophysical studies of various excited states of these endogenous and exogenous photosensitizers of the lens help explain these differing rates of photolytically induced damage in the lens.