Vitamin a Deficiency and Dark Adaptation

Night blindness or hemeralopia as the result of qualitatively inadequate dietaries has been recognized from the time of Hippocrates.¹However, for many years this condition was considered of rare occurrence except in certain communities or during periods of fasting, famine or war. The recent reports by Jeans and his co-workers,²Jeghers,³Park,⁴Corlette and his associates,⁵Barborka⁶and others suggest that this condition is relatively frequent. The literature is in agreement as to the infrequency of frank cases of night blindness associated with xerophthalmia, xerosis and keratomalacia in the United States. Each of these workers was tested for impaired dark adaptation by means of an instrument designed for clinical use and known as the biophotometer. This instrument purports to determine vitamin A deficiency by measurement of the degree of impairment of the light threshold and the rate and degree of dark adaptation. Other means