Endothelial repair following Nd:YAG laser injury

Effects of different energy levels (1.2, 2.0, 2.8, 4.0 mj) of a mode-locked Nd:YAG laser beam focused directly on the corneal endothelium were evaluated in rabbit, cat, and owl monkey. The endothelial lesion observed by specular microscopy at 10 min; 8, 16, and 24 hr; 3, 5, 7, and 21 days measured up to 0.8 mM in diameter. It showed focal destruction of Descemet's membrane and a larger area of endothelial denudation corresponding probably to the shock wave generated by the plasma. The size of the defect correlated with the amount of energy delivered. Even though healing was characterized by a phase of rapid endothelial migration during the first 24 hr, only about one-half of the defect was covered after 1 week in all animals. This lesion persisted with minimal endothelial proliferation for 3 weeks in the rabbit and for 3 months in the cat. The monkey was followed for only 1 week. Our findings indicate that the laser-tissue interaction is different from mechanical or thermal modes of injury and interferes with the specific endothelial functions in repair.