Glenn A M, Fishman G A, Gilbert L D, Derlacki D J
Department of Opthalmology and Visual Sciences, University of Illinois at Chicago, College of Medicine 60612.
Retina. 1994;14(1):27-30. doi: 10.1097/00006982-199401000-00006.
Prolongation in recovery of rod thresholds has been demonstrated in Stargardt's dystrophy. One possible explanation for this finding includes an impairment of vitamin A transport by the retinal pigment epithelium (RPE). By delivering an increased amount of vitamin A to the RPE, it might be possible to overcome a relative deficiency of vitamin A utilization or transport, and thus improve rod dark adaptation.
Baseline dark-adapted rod final thresholds were measured for five patients with Stargardt's dystrophy after 60 minutes of dark adaptation. A full dark-adaptation curve was then measured after exposure to a bleaching light for 5 minutes. Time of recovery to within 0.2 log units of the prebleach dark-adapted rod threshold was determined. Each subject then took a 14- to 18-day course of oral vitamin A, 50,000 IU daily. Dark adaptation was then reassessed using the same pretreatment protocol.
Before treatment, all five patients had a prolongation of their rod recovery curve. There was no statistically significant difference between subjects in mean time taken to reach prebleach rod baseline thresholds before and after vitamin A treatment.
These findings do not rule out the possibility that a delay in rod dark adaptation in Stargardt's dystrophy results from an inability to transport vitamin A from the RPE to photoreceptor cells. Nevertheless, a high dose of oral vitamin A taken for at least 14 days did not provide any objective improvement in dark-adaptation function in five such patients.
