Experimental photocoagulation of the human retina. II. Electron microscopic study.

Minimal retinal damage in xenon-arc photocoagulation lesions in man 14 hours to three days after exposure was confined to the retinal pigment epithelium (RPE) and consisted of accumulation of lysosome-related bodies in the cytoplasm. Slightly more intense damage consisted of dilation, vacuolization, and breakdown of the lamellae of the smooth-surfaced endoplasmic reticulum, preferentially around melanin-rich cell portions. Underneath more heavily vacuolated cells of the RPE, already in the periphery of ophthalmoscopically just-visible lesions, damage extended into the endothelial cells of the choriocapillaris and into the photoreceptor elements. Macrophages escaped from the choroidal circulation to appear on both sides of the Bruch membrane and within the subretinal space. More intense lesions showed features identical to those described in monkeys and are expected to show the same morphologic pattern of healing.