Abnormal dark adaptation in sickle cell anemia.

Patients with sickle cell anemia may be zinc-deficient. Zinc deficiency has been reported to cause delayed dark adaptation. We have studied dark adaptation in 13 patients with homozygous sickle cell anemia. Six patients had delayed dark adaptation. Their mean plasma and neutrophil zinc levels were 93.83 +/- 8.26 micrograms/100 microliters and 37.33 +/- 11.88 micrograms/10(10) cells, respectively, compared to the corresponding mean values for seven patients with normal dark adaptation of 105.86 +/- 13.31 and 86.71 +/- 19.53. For the six patients with delayed dark adaptation, the lower neutrophil zinc value, but not the plasma value, was significant (p less than 0.01). Three of the six were treated with oral zinc, with improvement in their dark adaptation. Neutrophil zinc levels correlated inversely (r = -0.77, p less than 0.01) with log relative threshold at 30 min. We conclude that patients with sickle cell anemia may show decreased ability to dark-adapt that is related to zinc deficiency.