The effects of laser photocoagulation in the retinal capillaries.

Using ruby and argon lasers, we produced multiple lesions on normal rhesus monkey retinas. The clinically used energy levels of both lasers produced identical cellular changes in the retina. Neither laser directly produced obliteration of capillaries. However, after the cellular damage in each burn lesion was repaired, we observed delayed degeneration of capillaries in a small segment at the burned areas. The marked reduction of active retinal cells that reduce vascular activity may beneficially affect laser treatment of diabetic retinopathy. The retinal tissue appears to have excessive photoreceptor cells and the horizontal connection of other cells seems to compensate for visual function after loss of many photoreceptor cells. We demonstrated severe damage in the ganglion cells by argon laser when it was aimed at the thick blood films in the vitreous cavity. Certain precautions must be taken when peripapillary neovascularization is treated by laser beam.