Vitamin A Supplementation Effects on Photopic and Scotopic Visual Function andMeasures of Vitamin A Status

摘要

We investigated the effects of vitamin A supplementation in an individual withabnormally low vitamin A-containing transthyretin-bound retinol binding protein (RBP). Measures of spectral dark adaptation and spatial contrast sensitivity suggest a differential return of parafoveal and foveal receptor systems during supplementation. Parafoveal cone systems appear to return more rapidly than foveal cones and rods. Post-supplementation measures of spectral dark adaptation demonstrated a crossing of spectral dark adaptation functions at 6.5 minutes, close to the appearance of the rod cone break attributed to achromatic measures of dark adaptation. Contrast sensitivity for the finest spatial frequency showed a delay of dark adaptation. Contrast sensitivity for the finest spatial frequencies. While measures of serum retinol, total RBP, and free RBP increased during supplementation, transthyretin-bound RBP failed to show any increase relative to its abnormally low presupplementation level. Bodily stores of vitamin A either require more time to return to normal levels than retinol delivered to the retina or this individual possessed a specific genetic deficiency in the bodily mechanism responsible for storing vitamin A. Keywords: Night vision; Vitamin A; Retinol binding protein; Dark adaptation; Vitamin A deficiency; Contrast sensitivity; Supplementation. (kr)