Diagnosis of night blindness and serum vitamin A level: a population-based study.

In a cross-sectional survey of 5420 children in northern Bangladesh, 124 were reported to have night blindness by their parents. Of these, 105 cases along with controls matched for age, sex, and neighbourhood had their scotopic vision examined under standard condition using a luxometer, underwent an ophthalmological examination, and had their serum vitamin A level determined. The mean serum vitamin A level was lowest among children identified as night blind by both their parents and the investigators (16.3 micrograms/dl; 95% confidence interval (CI), 13.9-18.7) and highest among those identified as not night blind by both their parents and the investigators (23.6 micrograms/dl; 95% CI, 21.3-25.9). The results show that parents' report of their children's night blindness had low sensitivity compared with diagnosis using standard observations of scotopic vision with a luxometer.