Nomarski evaluation of rod outer segment renewal in a hereditary retinal degeneration. Comparison with...

Differential interference contrast (Nomarski) optics and autoradiography were used to estimate independently the rate of outer segment renewal in the early stages of progressive rod-cone degeneration (PRCD) in dogs. We have found that significant reductions in renewal rate are demonstrable using the two methods of analysis: autoradiography = 34% reduction; Nomarski method = 18% reduction. Nomarski analysis of affected rod outer segments (ROS) demonstrated optical periodicities (light/dark bands) extending from the base to the tip of the outer segment. Nineteen percent of the cells, however, showed areas where the light/dark bands were not apparent. These homogeneous, "optically silent" regions were interpreted to possibly represent areas where the disc orientation was not perpendicular to the long axis of the ROS.