Ruby laser effects on the monkey eye.

Laser pulses of vioderate energy but of large retinal subtense produce significantly different retinal lesions than a clinical type of exposure of high energy density and small retinal subtense. A retinal photocoagulation that leads to a satisfactory retinal adhesion, whether produced by white light or laser, is characterized by sharp boundaries, coagulation necrosis of the entire retinal exposure area, and migration of pigment into the area of insult. A low energy density retinal burn of large retinal area is frequently not visible ophthalmoscopically. Histologically, the lesion is not demarcated by sharp boundaries, little coagulation necrosis is seen, and eventually the entire retina becomes involved. Pulsed ruby laser radiation was presented in Maxwellian view to the intact monkey eye. The pulse duration was about 2.0 msec, and the flash energy was varied between 1 and 250 joules. Gross damage to the globe was characterized by cornea! pitting, lenticular disruption, bubbles and hemorrhage in the vitreous, and loss of light reflex. Energy levels above 100 joules produced a marked degree of periorbital edema. Histological observations revealed extensive primary damage in the pigment epithelium and choroid and secondary retinal detachment and degeneration peripheral to the area exposed. Progressive retinal detachment and dedifferentiation secondary to the laser lesion are found to occur for a considerable time post exposure.