Low incidence of sight-threatening retinopathy of prematurity in infants born before 28 weeks gestation at a neonatal intensive care unit in Japan.

Improvement in neonatal care has led to increased survival rates of very premature infants. Accordingly, there are now more extremely preterm infants who are at risk of developing retinopathy of prematurity (ROP). ROP is a disorder of low birth-weight preterm infants and may lead to blindness. However, the prevalence of ROP varies globally, depending on different neonatal and ophthalmic care. Therefore, we studied the incidence and progression of ROP in extremely preterm infants in Japan. In addition, we investigated the characteristics and the clinical courses of the infants who progressed to sight-threatening ROP. A total of 3,154 infants were born at the Japanese Red Cross Sendai Hospital between 2009 and 2011, including 53 live-born infants born before 28 weeks' gestation. Two extremely preterm infants died before the first ROP examination. Among the survived 51 infants (the birth-weight ranged from 309 to 1,354 g, mean 779 g), 36 infants (70.6%) developed ROP: 18 infants with mild ROP and 18 infants with severe ROP. Eight out of the 51 infants (15.7%) underwent laser treatment. None of the infants born at older than 27 weeks 0 day of gestation required any treatment for ROP. In conclusion, most of extremely preterm infants develop some degree of ROP. However, in the majority of these infants the ROP never progressed beyond mild disease and resolved spontaneously without treatment. Sight-threatening ROP was rare. The present study clarifies the natural history of ROP in extremely preterm infants with active perinatal care.