Cellular composition of post-haemorrhagic opacities in the human vitreous.

The morphology of vitreous membranes from enucleated human eyes containing vitreous haemorrhage was studied by electron microscopy. Three types of membrane are described, based on their cellular composition: haematogenous, fibroblastic and neovascular. Simple vitreous haemorrhages usually failed to stimulate a fibroblastic cellular response, whereas vitreous blood clots in eyes with penetrating injuries were frequently invaded by choroidal and/or scleral fibroblasts. Fibroblast-like cells were also found in neovascular membranes, but not as a major cellular component. They had the appearances of astrocytes, suggesting an origin from the retina or optic disc in association with the intravitreal new vessel growth. These data suggest that two factors are necessary for intravitreal fibrosis: an adequate port of entry for cellular invasion and a suitable substratum on which migrating cells can crawl.