Vitamin A is present as retinol in the tears of humans and rabbits

Abstract

Vitamin A is required for the normal growth maintenance and maturation of the corneal epithelium and is effective in the treatment of xerophthalmia and experimental corneal epithelial wounds when applied topically as retinoic acid. The normal route of delivery of vitamin A to the cornea has remained undefined. We collected tears from normal and vitamin A deficient rabbits and from humans and analyzed them by high pressure liquid chromatography. A peak corresponding to a retinol standard was eluted from normal rabbit and human tears but was absent from the vitamin A deficient rabbit tears. The retinol concentration in rabbit tears was 69 ng/ml (0.2 × 10⁻⁶M) and in human tears was 16 ng/ml (0.5 × 10⁻⁷M). This demonstration that vitamin A is present in the tears as retinol establishes the rationale for treatment of corneal disease with topical vitamin A.