[Electron microscopic observations on the effect of laser beams on the retina of the rabbit (author's transl)].

After laser irradations, retinas of 13 rabbits were examined by electron microscope. The laser focus was set between 30 min and 140 h or 6 weeks in advance. The anatomical separation between the retina and the connective tissue of the choriocapillary in all the lesions is preserved by an intact Bruch's membrane. Destruction of the pigment epithelium, rod layer, and outer granular layer occurs in the early stages after coagulation. Later the nuclei of the rods show various stages of degeneration with simultaneous increases in the volume of the Müller's cells. The cytoplasma of the Müller's cells penetrates the nuclei of the sensory cells undergoing degeneration. Proliferation of the pigment epithelium begins after about 20 h. The first appearance of macrophages in the retina is visible after 30 h. Between 92 and 140 h in the area of the pigment epithelium, variously differentiated cells, which partly contain pigment granules and lamellary inclusion bodies, form. Some cells or cell groups which are visible might represent histiocytes within the Bruch's membrane 35, 45, 68, and 92 h as well as 6 weeks after coagulation. They partly cross the outer layer of the Bruch's membrane and neighboring connective tissue of the choroid. According to our studies, pigment epithelial cells, choroidal histiocytes, and Müller's cells participate in the phagocytosis.