Objective:To evaluate the efficacy and safety of reduced-dose intravitreal ganciclovir for the treatment of acquired immunodeficiency syndrome (AIDS) patients with cytomegalovirus retinitis (CMVR).Methods:A prospective observational cohort study observed 15 AIDS patients (28 eyes) who suffered from CMVR onset between January 2016 and December 2018 at Nanning Aier Eye Hospital. Among this 28 eyes, BCVA of 6 eyes (21.4%) were between moving hand to counting finger, 15 eyes (53.6%) were between 0.02 to 0.1 and 7 eyes were better than 0.1 (25.0%). All eyes received intravitreal injection 0.1 ml of ganciclovir at 4 mg/ml (contain ganciclovir 0.4 mg). The induction regimen was twice weekly for 2 weeks and a maintenance period of the same dose weekly. The mean number of injections was 7.1±1.7 times. For hospitalized patients who had no contraindicated received a 14-day twice daily intravenous ganciclovir (IVG) 5.0 mg/kg·d until complete resolution of CMVR. All patients were divided into intravitreal ganciclovir (IVTG) group and IVTG+IVG group according to different treatment plans, which were 5 cases with 8 eyes and 10 cases with 20 eyes, respectively. The follow-up was more than 6 months. BCVA, complete resolution or stable of the lesion and complications were observed.Results:Six months later, 20 eyes (71.4%) had a obvious reduced or disappeared of the anterior chamber and vitreous inflammation, and the retinal lesions became stable or complete resolution. 24 eyes showed improvements of BCVA and 4 eyes showed stable. 2 eyes (7.1%) presented with BCVA ≤ counting finger, 7 eyes (25.0%) were 0.02- 0.1 and 19 eyes were ≥ 0.1 (67.9%). Compared with before treatment, the ratio of BCVA that less than or equal to counting finger and between 0.02 to 0.1 decreased(21.4% vs 7.1% and 53.6% vs 25.0%, respectively), but the ratio of BCVA better than 0.1 increased (25.0% vs 67.9%). When IVTG+IVG group was compared with IVTG group, the average time-to-resolution of CMVR were 83.2±25.2 and 85.3±24.4 days respectively. There was no significant difference in resolution times( Z=0.17, P=0.87). The ratio of retinal lesions became stable or complete resolution were 75.0% (15 eyes) and 62.5% (5 eyes), there was no evident difference in time-to-resolution between the two groups ( F=0.42, P=0.51). No recurrence was seen during the follow-up period. In cases of unilateral CMVR, there were no patients with a second eye involvement during the follow-up period. No endophthalmitis, vitreous hemorrhage, retinal detachment were found in our study. Conclusion:Reduced-dose intravitreal ganciclovir is a safe and effective treatment option for CMVR.