DEGENERATION OF RETINAL CELLS AFTER PRESSURE-INDUCED ISCHEMIA IN THE RAT - AN ELECTRON-MICROSCOPIC STUDY

An ischaemia-reperfusion insult to the retina was produced in one eye of 29 rats by transitory elevation of the intraocular pressure. The ultrastructural morphology of the degenerating retinal cells was studied at several time points after the insult. Three morphologically distinct types of cell death could be individualized. Type I exhibited progressive karyolysis and cytolysis and was consistent with necrosis. Type II was characterized by progressive shrinkage and condensation of the nucleus and cytoplasm followed by heterophagic elimination, thus resembling apoptosis. The main features of type III cell death were homogenization of the nucleoplasm and cytoplasm and dilatation of the perinuclear cisternae; thus, they were evocative of "non-lysosomal vesiculate" cell death. Transitional stages were observed as well,