Front surface fluorescence measurements of the age-related change in the human lens

Tryptophan (trp) and non-tryptophan (non-trp) fluorescence measurements of the sectioned lenses were made using front surface technique. Measurements on concentrated protein solutions showed that inner filter effect (attenuation of both excited and emitted light) rendered the conventional right angle detection less accurate. For fluorescence measurement of the intact lens, because of the presence of a high protein concentration and abundant aggregated and insoluble proteins in the aged lens, a better result can be obtained by front surface detection. In this study, dissected human lenses were measured with front surface detection to observe age related changes. A decrease in trp fluorescence and an increase in non-trp fluorescence were observed with age. The emission maximum of trp fluorescence was shifted to a longer wavelength in old lenses. These results indicate that front surface fluorometry is more useful in studying proteins in concentrated solutions and intact tissues than the conventional right angle fluorescence detection.