Chloroquine retinopathy in the rhesus monkey.

Chloroquine was administered intramuscularly 5 days a week to rhesus monkeys for as long as4 V3 years. No clinical, fluorescein angiographic, or electrophysiological evidence of retinaldamage was observed. Yet chloroquine/chloroquine byproduct analysis of the ocular tissuesrevealed an enormous binding capacity of the pigmented, tissues of the eye (choroid plus RPE,ciliary body, and iris) with eventual accumulation observed, in the retina. Despite the normalophthalmic appearance and function, extensive pathological changes occurred in the retinasand choroids of these experimental monkeys. The chloroquine caused an initial dramatic effecton the ganglion cells, with the photoreceptors affected shortly thereafter. Patchy degenerationof the ganglion cells and photoreceptors then progressed over several years, with the choroidand pigment epithelium ultimately deteriorating as well.Key words: chloroquine, rhesus monkeys, retinopathy, electro re tinogram,chemical analysis, electron microscopy, membranous cytoplasmic bodies,photoreceptors, ganglion cells, retinal pigment epithelium, choroid