THE RELATION BETWEEN VITAMIN A AND DARK ADAPTATION

Abstract

<h3>I. PURPOSE</h3> Night blindness and similar visual disturbances have long been associated with the nutritional state of the body. In recent years this connection has been traced to the vitamin A of the diet¹and has become understandable in terms of the chemical relation between vitamin A and the light-sensitive pigments of the retina.² After the establishment of vitamin A as a factor in the visual cycle, it seemed logical to use the properties of vision for the detection of early stages in vitamin A deprivation. Such tests were made by Edmund and Clemmesen³with visual intensity discrimination as an index and by Jeans and Zentmire⁴with dark adaptation as a criterion. Other investigations⁵followed and, though some of this work has been found to be perhaps more enthusiastic than critical,⁶it showed that the original idea is probably sound and that under properly