[Retinal degeneration after intravitreal injection of ornithine. 1. Early change after administration]

Retinal damage 1 to 7 days after intravitreal injection of 1-ornithine hydrochloride solution into monkey eyes was investigated. Clinically the retinal pigment epithelium (RPE) showed edema, and hyperfluorescence on fluoroangiograms, predominantly in the equatorial region at 3 to 7 days. No retinal changes were seen at the posterior pole. Histopathologically, RPE in the equatorial region showed severe damage 24 hours after injection, becoming liquefactively necrotic and degenerated at 3 to 7 days. Early changes in RPE consisted of an increase in the number of secondary lysosomes, disappearance of basal infolding, destruction of most of the smooth endoplasmic reticulum, shortening of microvilli, and marked swelling of mitochondria. These RPE changes were seen slightly in the posterior pole. There were slight changes in the inner retina including photoreceptors. In eyes injected intravitreally by hi-osmosis of 3.5% NaCl solution, with equivalent osmolarity to ornithine solution, mild changes of microvilli and mitochondria were seen, but not necrotic changes. Our experiment showed that intravitreal injection of a small amount of 1-ornithine hydrochloride induced severe RPE damage. Selective toxicity of ornithine to RPE appeared mainly in the equatorial region.