The process of wound healing of the avascular outer layers of the retina. Light- and electron microscopic studies on laser lesions of monkey eyes.

The process of wound healing of the avascular outer layers of the retina is studied on a series of Laser lesions of the monkey, Cercopithecus aethiops. The extent of the retinal lesions is limited to the pigment epithelium and photoreceptor cells, whereas Bruch's membrane and the vascular inner layers of the retina intact. The retinal lesions are not seen to be invaded by cells from the choroid, nor from the retinal vessels. During the first three days after irradiation the pigment epithelial cells in a zone, about 75 micrometer wide, around the lesions appear to be changed into bi- or multinucleate cells with the additional nuclei situated in apical cytoplasmic protrusions which extend towards and into the lesions. During the second and third days after irradiation the lesions are invaded by two kinds of cells which both appear to arise through the off-budding of the nucleus-containing apical protrusions of the pigment epithelial cells around the lesions: (a) phagocytic cells which disintegrate the damaged tissue and, as this process is completed 4--9 days after irradiation show evidence of melanogenesis; and (b) regenerated pigment epithelium which form a single layer of cells along Bruch's membrane, but show no evidence of phagocytosis or intracellular disintegration of the damaged tissue. Within the lesions both these kinds of cells show mitotic figures the third day after irradiation.