Retinal Laser Damage Thresholds as a Function of Image Diameter

The eyes of rhesus monkeys were exposed to argon (514.5 nm) and ruby (694.3 nm) laser irradiation using various retinal image diameters which were estimated by microphotometric techniques. The experimental design for both wavelengths produced image diameters of 40μ to 50μ for the “minimal” case and approximately 500μ to 1,000μ for the larger irradiance series employed. Extramacular retinal exposure sites were examined by ophthalmoscopic and histopathological techniques. Flat preparations of the pigmented epithelium and sensory layers of the retina were utilized in the confirmation of damage at low power levels. All data were statistically analyzed to establish trends, and results were compared for the wavelengths employed. Results indicate that retinal damage is primarily dependent on energy distribution as a function of image diameter and exposure duration.