AIM: To explore the morphological and functional parameters to evaluate the effectiveness of intravitreal injections of ranibizumab (IVR) in treating macular edema (ME) secondary to retinal vein occlusion (RVO). METHODS: This retrospective study involved 65 RVO patients (65 eyes) who received IVR and were followed-up for more than 3mo. ME was categorized into cystoid macular edema (CME), diffuse retinal thickening (DRT), and serous retinal detachment (SRD) according to optical coherence tomography (OCT) images. The comparison of best corrected visual acuity (BCVA; logMAR) and central macular thickness (CMT) among different follow-up points and those among 3 groups were performed by Kruskal-Wallis test. The correlation between BCVA and baseline parameters during treatment was analyzed using Spearman correlation analysis. RESULTS: BCVA tended to improve in all groups, with marked improvement in CME and DRT groups. CMT showed the greatest reduction after 1wk, and remained stable over the following 3mo. DRT patients had the worst BCVA and the highest CMT at baseline, but the differences became smaller after IVR treatment. CMT in SRD group was significantly better than in CME and DRT groups 3mo after IVR. Most patients of CME and SRD groups transitioned to a normal pattern at 3mo follow-up. DRT patients were most likely to transform into the other morphological groups, while SRD patients showed minimal transitions. BCVA at baseline was identified as the most important prognostic indicator in all 3 groups. Additionally, DRT patients with a longer clinical course, higher CMT and central retinal vein occlusion (CRVO) tend to exhibit worse BCVA after treatment. In addition, CRVO patients are more likely to have worse BCVA at 2 and 3mo follow-up compared with branch retinal vein occlusion (BRVO) patients in CME group. SRD patients with higher baseline CMT were prone to experiencing worse BCVA after treatment. CONCLUSION: The effectiveness of IVR is strongly correlated with baseline BCVA in all 3 groups. Baseline parameters including clinical course, CMT, and RVO position are also useful in predicting the BCVA at different time points after treatment.