PURPOSE: To compare the incidence, type, interval for reactivation, and structural outcomes in infants with aggressive retinopathy of prematurity (A-ROP) treated with ranibizumab or bevacizumab. METHOD: It is a single-center, retrospective, consecutive, case series. We included infants with A-ROP which were initially treated with either intravitreal ranibizumab (IVR, 0.25 mg) or intravitreal bevacizumab (IVB, 0.625 mg) between January 2017 and December 2023. The infants were followed up for reactivation. The demographic and clinical data were collected. The time, zone, type of reactivation, its treatment, type of final structural outcome, and factors associated with reactivation were analyzed. RESULTS: One hundred eight among the 322 infants with A-ROP were included in the study. Fifty-five received IVR, while 53 received IVB. Infants treated with IVR had higher incidence of reactivation (92.7% vs 52.8%, P <
0.001) at an earlier interval than IVB (7.7 weeks vs 12.8 weeks, P <
0.001). Infants treated with IVR had approximately 3.3 times higher possibility of reactivation than those treated with IVB. Three infants (5.9%) in the IVR group and five (9.4%) in the IVB group attained complete vascularization of the retina ( P = 0.72). More infants treated with IVB had regression with a persistent avascular retina (PAR) than IVR (52.8% vs 15.7%, P <
0.001). Infants in the IVB group had 10 times higher possibility of regression with PAR. CONCLUSION: Infants of A-ROP treated with IVR have a higher incidence and earlier reactivation, while those treated with IVB have less incidence and delayed reactivation, albeit with a higher possibility of regression with a PAR.