Introduction: Patients with zone I retinopathy of prematurity (ROP) have poor outcomes despite treatment. We analyze the clinical characteristics and treatment outcome of patients with zone I disease and compare them with patients with zone II disease.
Methods: Preterm infants weighing less than 1500 g at birth were screened by the authors at age 4 to 6 weeks (group A). Group B was composed of referral patients that had been screened elsewhere. Findings were recorded according to the International Classification of Retinopathy of Prematurity. We classified all patients as either zone I, zone II, or zone III disease. If a retinopathy spanned 2 zones in one eye, it was classified in the most posterior zone as indicated by the International Classification of Retinopathy of Prematurity. Threshold was defined as in the Cryotherapy for Retinopathy of Prematurity study. Indirect diode-laser treatment was used to ablate the avascular retina. At the 3-month follow-up, outcome was judged according to Cryotherapy for Retinopathy of Prematurity criteria. Differences between eyes with zone I or zone II ROP were analyzed.
Results: Group A was composed of 222 infants; 2 presented with zone I ROP. Of 63 patients comprising group B, 9 had zone I ROP: a total of 11 infants with zone I ROP, 22 eyes. At 3 months, 8 of 20 eyes with zone I ROP that were included in follow-up had an unfavorable outcome (40%). Mean birth weight and gestational age were similar in zone I and zone II cases, but mean gestational age at treatment was significantly different (35.2 weeks in zone I cases vs 37.2 weeks in zone II cases, P =.006). Unusual signs such as a demarcation vessel between vascular and avascular retina and excessive intraretinal neovascularization were observed in zone I eyes but not observed in eyes with zone II or zone III ROP.
Discussion: Zone I ROP appears to be different from zone II ROP. Earlier treatment age suggests either an early start, faster progression, or both. Special attention should be given to atypical morphology present in zone I ROP.