[Retinopathy of prematurity in extremely low birth weight infants: a Tokyo multicenter study].

Objective: To investigate how the increase in survival rate in extremely low birth weight (a birth weight of 1,000 g or less) infants had affected the incidence of retinopathy of prematurity (ROP) and the frequency of laser treatment.
Methods: We retrospectively reviewed the medical records of 122 surviving premature infants with birthweights less than 1,000 g to determine the severity of ROP observed at 16 neonatal intensive care units in Tokyo between April and October 2002.
Results: The survival rate was 85.6%. The mean gestational age was 26.74 weeks and the mean birth weight was 782.25 g. One-hundred-and-five infants (86.1%) developed ROP, fifty (41.0%) received laser treatment, and six (4.9%) had retinal detachment. The median postmenstrual age (gestational age at birth plus chronological age in weeks, PMA) at the onset of ROP was 32.5 weeks, and the first laser treatment was performed at the median PMA of 35.7 weeks.
Conclusions: In these extremely low birth weight infants, there was an increase in the survival rate and in the incidence of severe ROP that progressed to the stage that required treatment.