Background adaptation in children with a history of mild retinopathy of prematurity

PURPOSE. in children with a history of mild retinopathy of prematurity (ROP ), test the hypothesis that elevation of the parafoveal over peripheral dar k-adapted threshold is due to photoreceptor rather than postreceptor dysfun ction. METHODS. A forced choice procedure was used to measure thresholds for detec tion of 2 degrees diameter, 50 msec, blue stimuli presented 10 degrees (par afoveal) or 30 degrees (peripheral) eccentric in the dark and in the presen ce of steady red backgrounds (-4 to +2 log scot td). Four ROP and four cont rol subjects were tested at both eccentricities. A model of the increment t hreshold function was fit to the data to calculate the eigengrau and dark-a dapted threshold. RESULTS. Both ROP subjects with elevated parafoveal thresholds also have el evated parafoveal eigengraus On the other hand, parafoveal and peripheral e igengraus are equal in ROP subjects without parafoveal threshold elevation. Nevertheless, the dark-adapted thresholds of all ROP subjects are higher t han those of any control subject at both sites, CONCLUSIONS. The parafoveal threshold elevation is due to rod dysfunction. There is also evidence of peripheral rod photoreceptor involvement in the s ubjects with ROP.