A clinical study of the human lens with a dynamic light scattering device

A study was conducted to determine the potential usefulness and repeatability of a new dynamic light scattering (DLS) device for clinical studies of the human lens and early cataract. Studies using the cold cataract model showed this new device to be more sensitive than the Scheimpflug cataract imaging system in detecting the earliest cataractous changes. A miniaturized clinical DLS device developed by NASA using fiber optic probes was mounted on a Keratoscope (Optikon 2000), which has a 3-dimensional aiming system for accurate repeated sampling of the same area of the lens. A test/retest study was then conducted on the nuclear region of the lenses of 12 normal eyes. After a full, dilated eye examination, DLS data were obtained using the new device on the same eyes twice, 30-60 min apart. Particle size distributions and mean log particle size data were obtained. The mean percent differences between the larger and smaller of the test--retest pairs was 6.4% (range 0.05--10.8%); the between-test S.D. was 0.116. Actual numerical margin of error was +/- 0.023. In addition, the mean coefficient of variation was 4.2% (range 0.3--7.3%). A useful clinical end point obtained from data produced by the device was the mean log particle size. These results suggest that the DLS will be useful in the detection and study of the beginning and earliest stages of cataract formation in humans.