Sequential Morphologic Alterations in the Foveola and Cornea of Nonhuman Subjects after Exposure to Coherent Light.

Abstract : Serial light microscopic and ultrastructural sections were prepared through well-fixed marker and experimental macular retinal lesions in both eyes of a rhesus monkey, sacrificed seven days after exposure to a neodymium-YAG dye laser tuned to 900 nm (gallium arsenide). Each laser exposure was 50 microns in diameter and of 20 nanosecond pulse duration. The marker lesions were produced by 120 pulses (average 30.6 microjoule/pulse) and the experimental lesions by a single 30.6 microjoule pulse (average) in the left eye and a single 9.5 microjoule pulse (average) in the right eye. The morphologic changes in the marker and experimental lesions were qualitatively similar but differed in the extent of tissue response. The left eye experimental single pulse laser exposures showed histologic evidence of significant tissue disruption, primarily involving the retinal pigment epithelium, outer segments of the rods and cones and outer nuclear layer. The experimental lesions in the right eye contained only equivocal histologic evidence of tissue damage, suggesting either that a 20 nanosecond 50 micron diameter laser exposure of 9.5 microjoules is not of sufficient magnitude to produce a lesion, or that the lesions were present but missed. This contractor prepared light and electron microscopic sections through three un-irradiated one laser irradiated (helium-cadmium 44.1 nm) turtle retinal eye cup preparations. Originator supplied keywords include: Gallium arsenide laser, Focal retinal lesions, Intracardiac perfusion, Marker and experimental lesions.