An Experiment in Human Dietary Night-Blindness

Effect of Anoxemia on the Dark Adaptation of the Normal and of the Vitamin a-Deficient Subject

“…The cone threshold was studied by inserting a red filter in the beam of the test flash, and, as figure 2 shows, only the cone part of the adaptation curve is recorded. The effect of anoxemia was to raise the threshold by a factor of 2.5 (an upward displacement of 0.4 unit i" the intensity plot on the logarithmic scale).…”

The Occurrence of Abnormal Dark Adaptation and Its Relation to Vitamin a Metabolism in Patients With Cirrhosis of the Liver

“…After a 4-minute exposure to white light 4700 millilamberts, the first phase (a) of cone adaptation takes place, to be followed by the rod phase (b). If the normal person is subjected to a diet low in vitamin A for a sufficient length of time, the final threshold becomes raised not only for the rods but also for the cones (20,21,22). The cone changes were noted originally in cases of liver cirrhosis (14).…”

A STUDY OF DIET IN RELATION TO HEALTH. DARK ADAPTATION AS AN INDEX OF ADEQUATE VITAMIN A INTAKE : II. A New Photometer for Measuring Rate of Dark Adaptation

“…But in many cases, those who adapted slowly showed the delay only at the end, at apertures 3 and 2, and were within the normal range to aperture 4. Wald, Jeghers and Arminio (1938), on the other hand, consider that adaptation is complete in from 30 to 45 minutes and that judgment should be based on the light threshold at that time. When their subject was on a diet of low vitamin A content, they found the threshold " at complete dark adaptation " to be 50 times that when he was taking a normal diet with a supplement of a vitamin A concentrate.…”