Comparative analysis of the development of collateral vessels in macular edema due to branch retinal vein occlusion following grid laser or ranibizumab treatment

PURPOSE: To evaluate the differences in the development of collateral vessels in patients with macular edema due to branch retinal vein occlusion (BRVO) after treatment with either grid laser or ranibizumab (RNB). METHODS: Comparative study including patients with macular edema due to acute BRVO and best-corrected visual acuity (BCVA) between 20/40 and 20/200. The sample was divided into two groups according to the treatment applied: laser group, including eyes treated with Argon laser when retinal hemorrhages were sufficiently absorbed to perform the treatment, and RNB group, including patients treated initially with one monthly intravitreal injection for a period of 3 months of RNB and more injections according to need thereafter. Before treatment patients in both groups, received a complete ophthalmic examination, including BCVA, fundus examination, optical coherence tomography, fundus color photography, and fundus fluorescein angiography (FA). This same protocol of examination was repeated in every visit after treatment, except FA that was only repeated every 3 months. The detection of the collateral vessels was done by two experienced examiners based on the analysis of the early phase of the FA. If there was a discrepancy in their judgment, the criterion of a third examiner evaluating the FA was considered. RESULTS: Mean baseline BCVA was 0.86±0.26 and 0.82±0.25 (logMAR [logarithm of the minimum angle of resolution]) in the RNB and laser groups, respectively (P=0.83). At the end of the follow-up, mean BCVA was 0.38±0.18 and 0.64±0.33 (logMAR) in the RNB and laser groups, respectively. The difference in the final BCVA between both groups was statistically significant (P=0.002). Collaterals developed in both groups; 66.67% of patients (14 out of 21 patients) developed collaterals at a mean time of 6.14±2.60 months after diagnosis in the RNB group, and 68.18% (16 out of 22 patients) developed collaterals in the laser group at a mean time of 6.2±1.97 months after diagnosis. No statistically significant differences between groups were found in the number of cases developing collateral vessels (P=1.00) as well as in the time required for such development (P=0.947). CONCLUSION: The use of RNB for the treatment of macular edema due to BRVO does not seem to alter the development of collateral vessels. Future studies with larger samples are required to confirm these outcomes.