[Experimental studies of proliferative vitreoretinopathy]

A new experimental rabbit model was developed to investigate vitreoretinal proliferation (PVR). PVR was initiated by injection of zymosan A from Saccharomyces cerevisiae into the vitreous. The experiments were performed in two groups. In group A zymosan was injected into the normal vitreous; in group B zymosan was injected after the vitreous body had been degraded by the previous injection of hyaluronidase. In group A only moderate phagozytotic activity was found up to the 5 h day. However, in group B excessive invasion of macrophages was observed within 20 h and phagozytotic activity increased markedly. This was confirmed by an increase of enzymatic activity of beta-n-acetyl-glucoseaminidase in the anterior chamber and in the vitreous space. Transmission electron microscopy revealed characteristic morphology in zymosan A, which can apparently only be digested very slowly in the phagocytes. Therefore, macrophages could be traced during their transformation into fibroblastlike cells forming the vitreoretinal membranes.