[Studies on the ultrastructure of the inner limiting membrane of the retina--distribution of anionic sites in the inner limiting membrane of the retina].

For demonstrating ultrastructurally the distribution of anionic sites (AS) in the inner limiting membrane (ILM) of the rabbit's retina, the immersion method with cationic tracer, polyethyleneimine (PEI) was applied. This method was found to be simple and useful for the observation of AS in the ILM. In the posterior pole of the eyeball (visual streak and medullary ray), PEI particles were arranged evenly in the lamina rara (LR) of the ILM. The mean diameter of PEI particles was 20 nm, and intervals between them (40-50 nm) were the same as those of fine strands in the LR. However, the peripheral retina, the distribution of PEI particles were sparse and random, while in the lamina densa (LD) of each ILM, PEI particles were absent. AS stained with PEI were present in the residual vitreous fibers. These results may provide the morphological basis for the theory that AS of the ILM act as a charge barrier between the retina and the vitreous cavity.