COMBINED ELASTIC AND RAMAN LIGHT-SCATTERING OF HUMAN EYE LENSES

The distribution of the scattering coefficient (as defined in the appe ndix) at a wavelength of 647.1 nm along the visual axis of human eye l enses was investigated using a specially designed set-up for spatially resolved measurements of the intensity of the scattered light. For th e same lenses, the distribution of the protein content was measured us ing confocal Raman microspectroscopy. Data collected by both methods w ere processed in terms of a recently developed theory of short-range, liquid-like order of crystallin proteins that accounts for eye lens tr ansparency. Seven fresh intact human lenses of varying age have been i nvestigated. In addition, elastic and Raman scattering measurements ha ve been performed on fixed lenses. The main results and conclusions ar e: (1) Fixation significantly affects the light scattering properties of the eye lens. The average level of scattering increases and a chang e in the distribution of scattered light intensity along the visual ax is occurs. Protein content and average distribution were not altered b y fixation. (2) There are significant differences between the distribu tion of the scattering coefficient for lenses of different ages. For y oung lenses (18 and 20 years) regions with a low protein content (ante rior and posterior cortex) show a higher level of elastic light scatte ring, while for older lenses (42-78 years old) there is no obvious cor relation between the scattering level and protein content. (3) Changes in the level of light scattering along the visual axis of the lens ca nnot be explained by protein concentration effects. Therefore, these c hanges must be caused by changes in the supramolecular organization of lens proteins in the fibre cytoplasm. (4) The observed changes in lig ht scattering may be related to the zones of discontinuity as observed in slitlamp and Scheimpflug photography of human lenses.