SCOTOPIC THRESHOLDS AND PLASMA RETINOL IN CYSTIC-FIBROSIS

  • 1 January 1982
    • journal article
    • research article
    • Vol. 23  (3) , 364-370
Abstract
Patients with cystic fibrosis (CF) often have low plasma concentrations of vitamin A. Dark-adapted scotopic thresholds of 56 patients with CF, aged 4-34 yr, either with a 2-alternative forced-choice procedure or as the final threshold after a full dark-adaptation curve, were measured. Fasting plasma vitamin A alcohol (retinol) was measured in 34 of the 56 patients. The average thresholds were higher and retinol values lower in patients than in controls. In 2 patients with very low (< 7 .mu.g/dl) initial retinol levels and elevated thresholds, decreased rhodopsin densities were observed; rhodopsin density and thresholds returned to normal after treatment with oral vitamin A. Rhodopsin density and log sensitivity were linearly related. Only marked decreases in plasma retinol were associated with elevations of dark-adapted threshold and decreases in rhodopsin density; the tissues of patients with CF may sequester vitamin A to maintain retinal function.