Cataract or the progressive opacification of the eye lens is far more prevalent in the tropics than in the temperate zones of the world. Epidemiology implicates several factors in cataractogenesis, including climatic factors such as sunlight. Two features of the aging and cataractous lenses are: (a) the accumulation of colored compounds with time, often dark brown in color, in the tropical lens, and (b) high molecular weight protein aggregates that increase light scattering and lens opacification.We intend investigating normal aging lenses obtained from eye banks as well as intracapsularly extracted intact cataract lenses. The strategy involves first recording the in situ fluorescence spectra, in both the normal excitation/emission mode and the synchronous scan mode, of these lenses so as to record the presence and amounts of pigments in them. The synchronous scan mode has been earlier found by us to be of particular value in multi-fluorophore situations as obtained in aging and cataract lenses. The same lenses will then be used to record their photoacoustic spectra (PAS) so as to detect the presence of non- fluorescent pigments. PAS allows the study of chromophores in an intact biological specimen without the need of any sample pre- treatment or preparation. The various pigments accumulated in the lens will then be isolated (by solubilizing them using enzymatic and other treatment of the lens and HPLC separation) and their chemical structures and amounts will be determined using IR, NMR and mass spectroscopies. In formulating this approach, we exploit the ready availability of intracapsular cataract lenses in India and our unique expertise in applying sophisticated spectral methods in studying lens proteins and intact lenses. Our preliminary results with a modest set of lenses have shown a steady rise in pigment levels with age (steeper in Indian lenses than in US lenses), and also the presence of a hitherto unreported compound in the Indian cataract lens. The specific questions that the proposed study addresses include: What are the pigments that accumulate with age? How are they generated? Do they also accumulate in the senile cataracts? Are they benign or photodynamically active? Can anti-oxidants alter their generation and/or action?
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