Among all premature infants undergoing retinopathy of prematurity (ROP) screening examinations, approximately 12.5% develop severe ROP, occurring almost exclusively among infants of with a birth weight of less than 1,251g.

Researchers studied the incidence and early course of ROP in a large cohort representative of infants undergoing ROP screening. A secondary analysis of data from the Postnatal Growth and Retinopathy of Prematurity retrospective cohort included 7,483 infants who underwent serial ROP examinations.

Of these, 43.1% developed ROP, 6.1% and 6.3% developed type 1 and 2 ROP, respectively, 6.9% underwent treatment in one or both eyes and 2% had zone I disease. Moreover, 98.1% of the type 1 or 2 ROP cases occurred in infants with a body weight of less than 1,251g. Researchers found that 49.4% of the eyes were vascularized into zone III by 37 weeks postmenstrual age.

While more than 40% of at-risk premature infants develop some stage of ROP, most retinopathy regresses without treatment. The study concluded that its findings contribute to the knowledge of ROP screening as they included not just high-risk infants but all eligible infants.