NMR & fluorescence studies on human and animal lenses.

Abstract

Our laboratory has demonstrated the potential of non-invasive biophysical methods in studying cataractogenesis. Initially these studies involved in vitro spectroscopic assays (UV, fluorescence and phosphorescence) on excised lenses or lens matter. In addition, we performed NMR pulse relaxation studies on extracted lenses which demonstrated an age-related increase in the T1 and T2 values of the normal lens. The in vitro fluorescence and NMR data suggested potential parameters for monitoring human and animal lenses in vivo. We then developed in vivo lens fluorescence densitography utilizing the Scheimpflug camera and have recently employed our Magnetic Resonance Imaging (MRI) method (using specially constructed small coils) to measure the moderately bound lens water compartment (T2) in vivo. Both of these in vivo methods correlate with our in vitro data and they demonstrate age-related changes in the normal lens; - i.e. - a progressive increase in fluorescence intensity and longer T2 values. Indices have been developed which permit us to detect abnormal lens fluorescence and changes in the moderately bound lens water (T2) compared with normal values for each specific age group by decade. These 2 non-invasive biophysical techniques can detect pre-cataractous changes in the living clear lens, months to years before any type of opacity becomes manifest with the conventional slit lamp method. The MRI technique can be performed in less than 20 minutes and the lens fluorescence method requires 4-6 minutes; thus they provide a rapid and objective in vivo measure of the status of the living lens as well as a method for evaluating anti-cataract drug efficacy.