Screening for retinopathy of prematury: how can we do better?

Retinopathy of prematurity (ROP) is a disease of the retina associated with preterm birth, particularly very low birth weight/very preterm infants, in which retinal blood vessels fail to grow and develop normally. In spite of major advances in the understanding of postnatal risk factors for the development of ROP, it continues to be one of the leading causes of childhood blindness in high-income countries. With the improved access to neonatal technologies and survival of premature infants, the incidence of severe ROP has begun to emerge as a major cause of blindness in low-income countries, as well. ROP incidence varies considerably from country to country and even from neonatal unit to unit. While most cases are mild and resolve spontaneously, a small proportion does progress to severe ROP which, left untreated, can result in irreversible vision loss. To avoid this grim outcome, screening programs for detecting treatment-requiring ROP have been established worldwide. Infants at risk for ROP are identified using recommended birth weight (BW) and gestational age (GA) criteria. According to the current Portuguese Pediatric Society, all infants with GA ≤32 weeks (w), BW ≤ 1500 g, BW<2000 g with prolonged exposure to oxygen and selected infants that are at higher risk of ROP for having severe disease or who have undergone major surgery in the opinion of the attending neonatologist or pediatrician should undergo screening for ROP. Although the currently recommended guidelines have high sensitivity for detection of ROP, their specificity is low, as successive retinal examinations are necessary to reliably detect severe ROP in time for intervention. This is done at the cost of repeatedly subjecting infants, many of whom develop no or mild retinopathy to stressful, resource-intensive, serial diagnostic eye examinations. Due to the low diagnostic yield of current screening guidelines, the identification of additional predictive factors for ROP may help identify infants at high ROP risk and to best manage and allocate resources for those at higher risk while sparing those at lower risk. The main objective of this thesis was to establish a set of strategies that could help improve screening of preterm infants in Portugal. To this end, 3 retrospective and 2 prospective cohort studies were undertaken. In recent years, prediction algorithms have proven to be useful in some populations. To test their applicability in Portuguese cohorts, two retrospective studies were performed. The first study performed a comparison between the WINROP model and the G-ROP model for their sensitivity and specificity for Type 1 ROP and concluded that both models had similar sensitivities but none was suitable as an alternative to the current screening modality. If restricted to GA