Abstract： Objective To observe the efficacy and safety of intravitreal injection of ranibizumab (Lucentis) to treat idiopathic choroidal neovascularization (ICNV).Methods Fifty-four eyes from 54 patients with ICNV were included in this study.There were 24 males and 30 females.The patients aged from 21 to 49 years with a mean age of 32.57 ± 7.06 years,The course of disease ranged from 6 days to 3 months with an average of 1.07±0.65 months.The examinations of best corrected visual acuity (BCVA)included Snellen chart and ETDRS visual acuity of ETDRS chart.Indirect ophthalmoscopy,fundus fluorescein angiography (FFA) and optic coherence tomography (OCT) were performed.The BCVA was hand motion - 0.6.The average score of ETDRS chart was 32.00± 16.41,and the average CRT (337.31±76.91) μm before treatment.All of the patients received an initial intravitreal injection of ranibizumab (0.5 mg,0.05 ml) and repeated treatments after the one-month follow-up if needed.The average follow-up period was 15.56±6.54 months.The changes of BCVA,ETDRS visual acuity,CRT and leakage of CNV before and after treatment were observed.Results One month after first injection,the mean number of ETDRS chart letters increased 16.81 to 48.81 ± 16.96 with a significant difference (t=- 11.991,P＜0.01),in which 25 eyes increased more than 15 (46.30 ％),while 2 eyes decreased more than 1 (3.70％).The mean CRT was (227.67± 91.41) μm,which significantly decreased compared with before treatment (t=12.021,P＜0.01).At the end of the follow-up period the number of repetitive intravitreal injections of ranibizumab was 1 - 4 times,with the mean of (1.59±0.71) times/eye.The mean number of ETDRS chart letters increased 17.20 to 49.20 ± 16.60 with a significant difference (t =-11.390,P＜0.01),in which 27 eyes increased more than 15 (50.00％),while 3 eyes decreased more than 1 (5.56％).The mean CRT was (227.69± 89.30) μm,which significantly decreased compared with before treatment (t =10.872,P＜0.01).There was complete CNV closure in 35 eyes (64.81 ％),partial closure in 11 eyes ( 20.37 ％),no change or expansion in 6 eyes (11.11 ％),and new CNV in 2 eyes (3.70％).No ocular or systemic adverse events were found after intravitreal injection of ranibizumab during the follow-up duration.Conclusions Intravitreal injection of ranibizumab is safe and effective for idiopathic choroidal neovascularization.It may improve the visual acuity and macular edema.However,long-term efficacy and safety remain to be further studied.