ObjectiveTo observe the clinical characteristics and therapeutic effect of reactivation of retinopathy of prematurity (ROP) patients after intravitreal injection of ranibizumab (IVR). MethodsA retrospective case series study. Eleven children with ROP (21 eyes) who were reactivated after IVR in Shenzhen Eye Hospital from January 2019 to October 2021 were included in the study. Among them, there were 6 males (11 eyes) and 5 females (10 eyes), with the gestational age of (27.6±2.2) weeks and birth weight of (1 034.6±306.5) g. At the first IVR treatment, 14 eyes (63.7%, 14/22) had acute ROP (AROP), 8 eyes (36.3%, 8/22) had threshold lesions. Post-reactivation treatments include IVR, retinal laser photocoagulation (LP), or minimally invasive vitrectomy (MIVS). The follow-up time after treatment was 12 to 18 months. Birth gestational age, birth weight, treatment method, corrected gestational age at treatment, lesion stage before and after treatment, lesion reactivation and regression time were recorded. The clinical characteristics and efficacy were observed and analyzed. ResultsThe time from initial IVR treatment to reactivation was (8.2±3.5) weeks. The corrected gestational age of the child was (43.62±4.08) weeks. In 21 eyes, AROP, threshold lesion, pre-threshold lesion, and stage 4 lesion were in 2, 4, 12, and 3 eyes, respectively. The patients were treated with IVR, LP, IVR+LP, IVR+MIVS in 2, 13, 4 and 2 eyes, respectively. After the first reactivation treatment, the time of regression and stability was (8.4±4.9) weeks after treatment. There were 5 eyes with secondary reactivation of the lesion, and the lesion stages were stage 3, stage 4a and stage 5 in 2, 1 and 2 eyes, respectively. The mean reactivation time was (19.3±6.0) weeks after the last treatment. The patients in stage 3, stage 4a and stage 5 were treated with LP, LP+MIVS and IVR, respecitively, and the lesions subsided steadily during follow-up. At the last follow-up, 19 out of 21 eyes showed complete regression of the lesions, stable photocoagulation, regression of crista-like lesions, no additional lesions, and retinal leveling. All retinal detachment was "funnel-shaped" in 2 eyes. ConclusionsThe lesion reactivation of AROP after IVR treatment is more common. The early reactivation rate is higher after treatment. There is a possibility of reactivation twice after re-treatment.