[Studies on the ultrastructure of the inner limiting membrane of the retina. I. Surface replication study on the inner limiting membrane of the retina].

In order to clarify the ultrastructural details, electron microscopic observations of the inner limiting membrane (ILM), critical point drying and surface replication methods with collagenase digestion were performed on rabbit's ILM. The results were as follows,: 1) This method was simple, the electron microscopic image is highly reproducible and a bird's-eye view of the ILM is possible. 2) The ILM was composed of a fine three-dimensional meshwork structure with numerous pores (sieves). 3) The diameter of the pores varied from 10 to 25nm. Mean diameter of the pores is 13.43nm in the visual streak, 13.59nm in the medullary ray, 13.40nm in the peripheral retina, and there were no statistical differences among these three regions. 4) In the peripheral retina, it was difficult to observe the ILM because vitreous fibrils lay densely on it. The pore's shape in the peripheral retina was different from that in the posterior pole retina. These results may provide the morphological basis for the theory that the pores of the ILM act as the main filtration barrier between the retina and the vitreous cavity. It is supposed that the bulk of substances are transported from the retina mainly through the ILM of the posterior pole, because dense vitreous fibrils of the peripheral retina disturb that transport.