[Characterization of collateral circulation after anti-VEGF treatment for retinal vein occlusion]

Objective: To observe the formation time, location, and influencing factors (including treatment regimens and systemic factors) of collateral vessels in retinal vein occlusion (RVO) patients following anti-VEGF therapy. Methods: A retrospective cohort study was conducted among patients diagnosed with RVO at the Ophthalmology Departments of Beijing Tsinghua Changgung Hospital and Zhangjiakou Fourth Hospital between December 2017 and December 2019. Patients with macular edema were treated with anti-VEGF ranibizumab (Lucentis). Based on treatment preferences, patients were divided into three groups: no-injection group, 1+PRN group (one initial injection followed by pro re nata treatment), and 3+PRN group (three monthly injections followed by pro re nata treatment). All patients were followed up for two years, with regular collections of fundus imaging data. The primary outcome measure was the formation of retinal collateral circulation, which was assessed jointly by two senior ophthalmologists using color fundus photography and fluorescein angiography. The presence, timing, and characteristics of collateral circulation were recorded, and the effects of different treatment regimens and systemic factors were analyzed. Statistical analysis was performed using SPSS 27.0, with between-group comparisons conducted using the Chi-square tests or Fisher's exact test. A p-value<0.05 was considered statistically significant. Results: A total of 157 patients (157 eyes) with RVO were included, comprising 87 cases of branch retinal vein occlusion (BRVO) and 70 cases of central retinal vein occlusion (CRVO). Among BRVO patients, 62.1% (54/87) developed collateral circulation, with a median formation time of 172.0 (253.0, 124.3) days. Among CRVO patients, 18.6% (13/70) developed collateral circulation, with a median formation time of 333.5 (369.0, 256.3) days. In BRVO patients, the rates of collateral circulation formation in the non-injection, 1+PRN, and 3+PRN groups were 9/14, 62.8% (27/43), and 90.0% (18/20), respectively. The Chi-square test indicated no statistically significant difference among the groups (χ²=5.102, P=0.078). In CRVO patients, the rates were 3/5, 19.4% (6/31), and 11.8% (4/34) in the three groups, respectively. The Fisher's exact test revealed a statistically significant difference in collateral circulation formation rates among the treatment groups (P=0.022). The Chi-square test results showed that in BRVO patients, the presence of diabetes (χ²=2.67, P=0.10) and hypertension (χ²=0.79, P=0.37) had no statistically significant impact on the establishment of retinal collateral circulation. Similarly, in CRVO patients, the presence of diabetes (χ²=1.33, P=0.249) and hypertension (χ²=0.13, P=0.720) showed no statistically significant influence on collateral circulation formation. Conclusions: Anti-VEGF therapy significantly suppressed the collateral vessel formation in patients with CRVO but had no significant effect on patients with BRVO. Systemic factors had no significant effect on the collateral formation in either group.