Retinal vascular patterns. VII. Acellular change.

The trypsin digestion technique has revealed a preferential loss of endothelial cells (in conditions other than diabetes) and eventually a total acellularity of many retinal capillaries. The surprise is that this may occur toithout recognized functional abnormality or without appreciable histologic change in the rest of the retina. Perhaps the retina has a large reserve capacity normally or perhaps the choroidal circulation compensates for loss of the retinal circulation. In any case the retina shows little reparative response to these capillary changes. Unlike what one expects in most other tissues, there is no formation of fibrous scar tissue, no infiltration with histiocytes, and no neovasculo genesis. Instead .Midler's cells fill up the tissue defect and their processes insinuate into what had been the capillary lumina.