Canthaxanthine-induced retinal pigment epithelial changes in the cat.

Canthaxanthine retinopathy in humans is a retinal crystalline deposition associated with ingestion of canthaxanthine, an over-the-counter oral tanning agent. In this study cats were fed doses of canthaxanthine varying from 2 mg/kg/day (an equivalent standard human dose) to 16 mg/kg/day for up to six months. Indirect opthalmoscopy showed progressive development of an orange sheen in the retina overlying the tapetum lucidum without evidence of crystal formation. Electroretinograms performed at one and two months showed no significant change from baseline examination. On light and transmission electron microscopic examination, the retinal pigment epithelium of the experimental animals showed an increase in cell height and a regional vacuolization due to an enlargement and disruption of some phagolysosomes and the development of cytoplasmic spaces. These observations suggest that further studies should be conducted on humans who ingest canthaxanthine to assess structural and functional alterations, especially in the pigment epithelium.