RESUMO
Monkey retinas were studied histopathologically to assess the relative effects of immediate versus delayed repetitive photocoagulation with the argon laser. Immediate retreatment adds relatively little damage to that created in the retinal nerve fiber layer by the initial photocoagulation. Delayed retreatment increases destruction of all retinal layers, including the nerve fiber layer, and also increases the chance of inducing hemorrhage. When argon laser retreatment of a retinal locus is necessary, it is much safer to do so immediately (within a few hours) rather than after days or weeks.
Assuntos
Argônio , Terapia a Laser , Lasers/efeitos adversos , Retina/patologia , Retina/cirurgia , Animais , Haplorrinos , Fotocoagulação/métodos , Macaca mulatta , Fatores de TempoRESUMO
Eight rhesus monkeys were photocoagulated with varying intensities of argon laser energy to determine the effects on the retinal nerve fiber layer. Photocoagulation of arterioles and venules always resulted in largely irreversible and permanent perivascular axonal destruction. Photocoagulation of areas free of major vessels showed variable responses to identical dosages, ranging from minimal destruction of the outer part of the retina to full-thickness destruction involving the nerve fiber layer. Variations in retinal thickness, vascularity, pigment epithelial pigmentation, and focus of the laser beam are responsible for differences in severity of each burn. Even when major vessels are avoided, it is impossible to predict accurately the degree of damage. However, our studies suggest that much of the initial damage is extracellular, sparing nerve fiber layer axons. Therefore, some acute damage might be reversible following resorption of the edema.
