Changes of choroidal thickness and choroidal vascularity index in patients with macular edema secondary to branch retinal vein occlusion after intravitreal ranibizumab.

Background: To observe the changes of choroidal thickness (CT) and choroidal vascularity index (CVI) in patients with macular edema secondary to branch retinal vein occlusion (BRVO) after multiple intravitreal injections of ranibizumab.

Methods: A retrospective cohort study was conducted on 91 patients (91 eyes) with unilateral BRVO treated with a 3 + PRN (pro re nata) regimen of ranibizumab from January 2022 to March 2023. Optical coherence tomography (OCT) was used to measure central retinal thickness (CRT). Enhanced depth imaging OCT (EDI-OCT) was used to measure subfoveal CT (SFCT), nasal CT (1.5 mm from the fovea), and temporal CT (1.5 mm from the fovea) to calculate the mean CT. Choroidal images were binarized using ImageJ software to quantify the luminal area (LA), stromal area (SA), and total choroidal area (TCA), from which CVI (LA/TCA) was calculated. These parameters were evaluated at baseline and 1 month after each injection and were compared across different types of macular edema and between the acute and stable phases of BRVO.

Results: At baseline, the cystoid macular edema (CME) group had significantly lower CRT and SFCT compared to the diffuse retinal thickening (DRT) and mixed-type groups (P < 0.01); however, best-corrected visual acuity (BCVA) and CVI did not differ significantly among the groups. In BRVO-affected eyes, CT, LA, SA, TCA, and CVI were all significantly higher than in contralateral eyes (P < 0.01). Compared to baseline, CT decreased significantly after the first injection and stabilized after the second (P < 0.01). CVI decreased significantly after the second injection and remained stable thereafter (P < 0.01). These changes persisted for at least six months after the final injection.

Conclusions: BRVO affects both retinal and choroidal structures. BRVO-affected eyes exhibit choroidal vasodilation, stromal thickening, and have higher CT and CVI values compared to unaffected eyes. Anti-VEGF therapy effectively reduces CT and CVI during the acute phase, leading to a stable state. CVI values do not appear to differ based on the morphological type of macular edema.

Trial registration: ChiCTR2400090054. Registered on 13 November 2023, retrospectively registered.