Chemical and Physical Properties of the Normal and Aging Lens

In vitro[UV absorption, fluorescence, phosphorescence, and nuclear magnetic resonance (NMR)] spectroscopic studies on the normal human lens demonstrate age-related changes which can be correlated with biochemical and photobiologic mechanisms occurring during our lifetime. Chronic cumulative UV exposure results in an age-related increase of photochemically induced chromophores and in color of the lens nucleus. This enables the lens to filter the incident UV radiation, thereby protecting the underlying aging retina from UV photodamage. We have measured the age-related increase in lens fluorescence in vivoon more than 300 normal subjects (1st to 9th decade) by UV slitlamp densitography. These data show a good correlation with thein vitrolens fluorescence studies reported previously and demonstrate that molecular photodamage can be monitored in the lens.In vitroNMR (human and animal lenses) andin vivoexperiments currently in progress are rapidly elucidating the physiocochemical basis for transparency and the development of light scattering areas. Surface scanning NMR can monitor organophosphate metabolism in the ocular lens in vivoas well as in vitro.These studies demonstrate the feasibility of using biophysical methods (optical spectroscopy and NMR analyses) to delineate age-related parameters in the lens, in vivoas well as in vitro.