A clinicopathologic study of dye laser photocoagulation on primate retina.

Chorioretinal lesions produced by dye laser photocoagulation were examined on normal monkey retinas, using angiographic and histopathologic techniques. Retinal burns produced by green (514 nm), yellow (577 nm), orange (600 nm), and red (630 nm) laser lights were placed in the posterior pole between the fovea and the major vascular arcades. When examined histopathologically 24 hours after treatment, greater damage to the inner retina and deep choroid was noted with the red laser light than with the green, yellow and orange laser lights. These differences were not detectable 31 days after treatment. There were no appreciable acute differences among the lesions caused by green, yellow and orange irradiation. Laser light at four wavelengths of the orange spectrum (590, 595, 600, and 605 nm) produced comparable chorioretinal destruction in the juxtafoveal zone when examined 24 hours and 31 days after treatment. Retinal arterioles and venules treated with yellow (577 nm) and orange (600 nm) laser light demonstrated endothelial and pericytic cell damage. Changes in the outer retina, pigment epithelium, and choriocapillaris were also present beneath the photocoagulated vessels.