Introduction: The survival rate of extremely premature infants has increased. No recent study has investigated the characteristics of retinopathy of prematurity (ROP) or the incidence of threshold ROP in the most severely premature infants. We undertook this study to determine the risk of developing ROP and threshold ROP in the growing sub-population of infants <25 weeks' estimated gestational age (EGA).
Methods: A retrospective review of infants born before the 25th week of gestation between the years 1994 and 1997 was performed. Of 49 infants examined (97 eyes), 42 were born in the 24th week of gestation and 7 were born in the 23rd week. Mean follow-up was 6.3 months (range, 2.5-37 months). Ophthalmology screening examinations were initiated at 5 weeks of age and continued until the infants were no longer at risk for serious ROP.
Results: ROP developed in all (97) eyes. Thirty-nine of 97 (40%) eyes in 20 of 49 (41%) infants developed threshold ROP, diagnosed at a mean post-conceptional age of 34 weeks. Thirteen (13%) eyes of 7 (14%) patients developed prethreshold disease and regressed without treatment.
Conclusion: There is an increased incidence of threshold disease in infants </=25 weeks' EGA compared with children of greater EGA. Threshold disease may occur at an earlier post-conceptional age in this subgroup of neonates.