Repair of retinal pigment epithelium and choriocapillaries after laser photocoagulation: correlations between scanning electron, transmission electron and light microscopy.

Cell-to-cell interactions between retinal pigment epithelial (RPE) cells and vascular endothelium were examined by scanning electron microscopy, which demonstrates many facets of surface topography. The repair process after laser photocoagulation was characterized by a morphologically heterogeneous population of regenerated RPE cells, including normal-looking cells, macrophage-like cells and large elongated RPE cells. The macrophage-like and normal-looking RPE cells were predominantly seen adjacent to growing new choroidal vessels. Large cells appeared mainly in the vicinity of the extracellular matrix, where no viable new vessels were seen. The observed association between a specific phenotype of regenerated RPE cells and neovascularization may further support the hypothesis that regenerated RPE cells have a dual function, exerting both stimulatory and inhibitory effects on endothelial cells.