Correlation of Dark Adaptation Test Results with Serum Vitamin A Levels in Diseased Adults

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Abstract
Dark adaptation is a reliable and highly reproducible indicator of vitamin A nutritional status in terms of function. Abnormal dark adaptation occurs over a fairly wide range of serum vitamin A values; however, the lower limit of serum vitamin A which is related to normal ocular function has not been determined. We studied dark adaptation in 67 patients with a variety of hepatic and gastrointestinal diseases or with chronic alcoholism. We found that a serum vitamin A level ≥40 µg% predicted normal dark adaptation 95% of the time, a serum vitamin A level ≥30 µg predicted normal retinal function 68% of the time and a level ≥20 µg% predicted normal function 27% of the time. Thus, in individual patients with serum vitamin A levels <40 µg% one can be sure of vitamin A sufficiency only if a normal dark adaptation response is elicited.