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Scanning electron microscopic (SEM) observations of the rabbit retinal pigment epithelium (RPE) are reported both for normal tissue and for tissue subjected to laser radiation. In normal RPE, cells were observed to be closely packed and to have the characteristic hexagonal shape. The microvilli were abundant and of two types. Suprathreshold lesions were produced with 0.4 musec pulses of high-intensity yellow light (585 nm.) from a dye laser. In the lased RPE, cells were denuded of their microvilli, and a number of cells with single discrete holes were observed. Hypertrophied cells were always present. Within 5 days of irradiation groups of small proliferating RPE cells were found in the lesion area.

Novel retinal irradiation techniques for laser damage studies are described; these are straightforward applications of the Fourier transform properties of an optical system. Interposing an appropriate diffracting screen between the laser source and the test eye enables one to simultaneously induce a number of discrete and precisely located retinal exposures with a known gradation of energy. Various kinds of diffracting objects are considered, and it is seen that transparent sinusoidal phase gratings offer the most promise for damage threshold studies. The method provides an objective measure of the ocular focal length at the time of the exposure. The production of arbitrary retinal irradiation patterns for more general research or clinical applications is possible with the extension of the technique by the use of simple holographic methods for forming the appropriate diffracting screens.