Dye laser photocoagulation through experimentally induced retinal hemorrhage.

The histological effects of photocoagulation obtained by using each of 4 wavelengths of the dye laser (577, 590, 610, and 630 nm) on experimentally induced retinal hemorrhage in cat eyes were examined. Energy from 577, 590, and 610 nm laser was directly absorbed by red blood cells in the retinal hemorrhage and destroyed the inner layers of the retina. Red blood cells were not directly coagulated with the use of 630 nm laser, and the retinal pigment epithelial cells (RPE cells) and choroidal melanocytes were coagulated. These results suggest that the use of yellow or orange dye lasers for photocoagulative therapy in a retinal hemorrhage is dangerous, because of the risk for destruction of the inner layers of the retina. A 630 nm dye laser is useful for photocoagulation of a retinal hemorrhage, while the laser energy is unable to reach the RPE cells and the choroid with the use of other wavelengths.