Objective: To report the morphological spectrum and outcome after laser treatment in posterior zone I retinopathy of prematurity.

Design: Retrospective, consecutive, interventional case series.

Methods: Review of charts and RetCam images of preterm infants with posterior zone I retinopathy of prematurity (defined as area within a circle, the radius of which extends from the center of the optic disc to the center of the macula) treated with confluent laser at a tertiary care referral institute between January 2006 and December 2015. Data was analyzed and tabulated using frequency and descriptive statistics to describe the demography, morphology, and outcome after laser treatment.

Results: Fifty-six eyes (28 infants) with a mean gestational age of 28.65 ± 2.18 weeks and birth weight of 1153.04 ± 251.51 g were analyzed. Forty-two (75%) eyes had persistent tunica vasculosa lentis and 25 (44.6%) had preretinal hemorrhages. All eyes had circumferential ROP and a poorly developed foveal vasculature. Four distinct morphological patterns were encountered: I - typical aggressive posterior retinopathy was seen in 36 (64.3%) eyes; II - atypical aggressive posterior retinopathy (14 eyes; 25%) had raised fibrovascular proliferation always on the nasal retina close to the optic disc; III - hybrid retinopathy of prematurity (4 eyes; 8.7%) had a mat-like fibrous proliferation on vascularized posterior retina; and IV - threshold retinopathy of prematurity seen in 2 (4.4%) eyes. An unfavourable outcome was seen in 44 (78.6%) eyes.

Conclusions: Retinopathy of prematurity in posterior zone I presents with atypical morphology and poor outcomes despite confluent laser photocoagulation.