Fig. 9. Mean ± standard error (SE) decline from baseline in 30-Hz electroretinogram (ERG) amplitude by total vitamin A intake (diet plus capsules) irrespective of randomization assignment for all patients in the higher amplitude cohort. The mean decline was calculated as the mean of screening and baseline minus the mean of all follow-up visits by quintile of total vitamin A intake averaged over all visits. Sample sizes were 69, 72, 74, 65, and 74 for the lowest to highest quintiles of total vitamin A intake. Vertical bars indicate SEs. (From Berson EL, Rosner B, Sandberg MA et al. A randomized trial of vitamin A and vitamin E supplementation for retinitis pigmentosa. Arch Ophthalmol 1993;111:761.)