Abstract: Objective To explore the clinical efficacy of intravitreal chemotherapy for retinoblastoma with vitreous seeding. Design  Retrospectvie case series. Participants 18 patients (18 eyes) unilateral group cT2 retinoblastoma patients diagnosed and treated at Beijing Children’s Hospital from October 2019 to October 2020 were recruited. Methods According to the morphological characteristics of vitreous implant lesions, the patients were divided into type 1 (dust-like) and type 2 (spherical). All the patients received intravitreal injection of melphalan. Number of intravitreal injection, time to regression of vitreous seeds, follow-up time, complications related to surgery and extraocular extension were recorded. Globe salvage rate were computed. Number of intravitreal injection and time to regression of vitreous seeds in different group were compared with rank sum test. Main Outcome Measures The Times of intravitreal chemotherapy, the regression time of vitreous implantation tumor, the follow-up time, the occurrence of surgery-related complications, the presence of extraocular metastasis of tumor, and the eye preservation rate. Results Among 18 patients (18 eyes) unilateral group cT2 retinoblastoma patients, the morphologic feature of vitreous seeds was dustlike (type1) in 10 patients (10 eyes), was spherelike (type 2) in 8 patients (8 eyes). Vitreous seeds of all patients regressed after intravitreal injection of melphalan. During the treatment and follow-up period, 8 eyes (44.4%) had pepper-and-salt retinopathy close to the injection location in the retina and 2 eyes(11.1%) had mild vitreous hemorrhage. No patient died or had extraocular extension. The follow-up time was （21.08±2.18）months. The median number of intravitreal injection for type 1 and type 2 was 2.5（2, 3） and 5.5（5, 6）, respectively (Z=-3.679, P<0.05). The median time to regression of vitreous seeds for type 1 and type 2 was 1.875 months（1.56，2.00） and 3.875 months（3.50, 4.06）, respectively (Z=-3.586, P<0.05). Conclusion Intravitreal chemotherapy is the very effective treatment modality for retinoblastoma with vitreous seeds. (Ophthalmol CHN, 2024, 33: 47-51)

Key words: retinoblastoma, intravitreal chemotherapy