Photon correlation spectroscopy of light scattered by eye lenses in in vivo conditions

Abstract

The application of photon correlation spectroscopy on mammalian eye lenses in vivo is revisited. It is shown that the use of a short wavelength laser type and a logarithmic correlator improves the signal-to-noise ratio to such an extent that shorter measurement times are possible without impairing the information content of the correlation function. Experimental correlation functions obtained in vivo on a rabbit eye lens, are analyzed with several techniques. The histogram approach is most successful for the determination of the distribution function of relaxation processes in the correlation function and proposes four different populations of components in the lens. This result is comparable to that from in vitro measurements on highly concentrated solutions of alpha-crystallins and of fiber cell cytoplasm, the former proteins being the main scattering components both in vivo and in vitro in the eye lens system. Our results indicate that the application of photon correlation spectroscopy on eye lenses in vivo offers new perspectives to use this technique as a fast, noninvasive tool to study relaxation phenomena in normal and cataractous lenses. The sensitivity of the method allows it to be used as an important analytical technique in the study of prevention and treatment of cataract.

A Clinical Study of the Human Lens with a Dynamic Light Scattering Device

“…The scattered light was collected from a focused volume of 2 Â 10 À5 mm 3 in the region of the lens and then analysed and stored. A correlation function reduces the scattered intensity data obtained which can then be used to characterize the particle size in the lens (Benedek et al, 1987;Bursell et al, 1989;Van Laethem et al, 1991;Ansari et al, 1996;Thurston et al, 1997;Ansari et al, 1998).…”

“…Benedek and co-workers at MIT (Benedek, 1971;Tanaka and Benedek, 1976;Benedek et al, 1987) were the ®rst to use the DLS to study cataractogenesis. The DLS monitors the Brownian movement of the crystallins and shows the distribution of diffusion coef®cients (Benedek et al, 1987;Datiles, Podgor and Edwards, 1988;Bursell et al, 1989;Laethem et al, 1991;Thurston et al, 1997). However, because only a small portion of the lens is sampled during each measurement in order to maintain coherence conditions at the detector and hence good signal to noise, it was dif®cult to return to the same spot repeatedly (Datiles et al, 1988).…”