Eighteen adults with night vision complaints showed significantly increased final rod thresholds as compared to their age and sex-matched controls, but vitamin A and zinc levels did not differ between the two groups. Vitamin A supplementation of three subjects produced changes in final rod thresholds and serum vitamin A levels, but these changes did not produce subjective improvements in night vision. It is concluded that patients with complaints about night vision often have increased final rod thresholds, but that actual vitamin A or zinc deficiencies are not common in these patients. Supplementation of selected patients may not improve night vision function to a degree noticeable by the patients and may produce unwanted side effects.
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