WATER EXCHANGE IN HUMAN EYE LENS MONITORE D BY THE CONFOCAL RAMAN MICROSPECTROSCOPY

We have employed the technique of the confocal Raman microspectroscopy to monitor water exchange in human eye lens in vitro. Heavy water (D2 O) was used as a marker of the exchange. Raman spectra in the high fre quency range (2200-3500 cm(-1)) were successively recorded at several locations inside the lens in order to register dynamics of the replace ment of H2O by D2O. The intensities of the Raman peaks at 2450 cm(-1) (OD stretch) and 3390 cm(-1) (OH stretch) were used as indicators of H 2O/D2O exchange, whereas the Raman peak at 2935 cm(-1) (CH stretch of protein) served as an internal standard. The ratios of the Raman inten sities I-2450/I-2935 and I-3390/I-2935 determined the relative concent rations of D2O and H2O, respectively. For the quantitative description of the exchange, we proposed a diffusion model assuming a constant di ffusion coefficient over the volume of the lens. We report the results of experiments performed on four fresh and one fixed lenses. The diff usion coefficient of D2O in the human eye lens was estimated using the least-squares fit of the experimental data.