The age at which retinopathy of prematurity was first seen was determined in 143 infants. In all, the initial ophthalmological examination was normal. Birth weights varied from 630 to 2700 g and gestational ages from 24.5 to 40.0 weeks. The median postnatal age at which acute retinopathy of prematurity was first seen was 51 and 40 days for those less than 28 and greater than or equal to 28 week...