Effect of Vitamin A-Deficiency on the Dark Adaptation of the Pigeon

Abstract

GRANIT¹ has stressed the uniformity of the Purkinje shift in various kinds of eye, and concludes that there must be a chemical correlation between the rod and cone substances. Since vitamin A-deficiency is known to reduce the amount of visual purple in the retinal rods and to diminish the ability of the animal to become dark-adapted, it is of interest to see what effect vitamin A-deficiency has on the retinal function of an animal the retina of which is made up almost wholly of cones. I have measured the dark adaptation of normal and vitamin A-deficient pigeons by determining the height of the b-wave of the electroretinogram using a light of constant brightness, and also by measuring the minimum intensity of light required to elicit an electrical response from the eye. Similar experiments on animals the retinæ of which are made up almost wholly of rods^2,3 have shown the sensitivity of the retina to be greatly reduced during deficiency and to be restored to normal on giving vitamin A concentrate.