Evaluation of the effects of intravitreal bevacizumab treatment on retinal and choroidal structures in neovascular age-related macular degeneration

Aim: To evaluate retinal and choroidal structural changes in naïve neovascular age-related macular degeneration patients treated with bevacizumab over a 3-month period. Materials and Methods: The study was designed prospectively, included 50 eyes of 50 treatment-naïve patients. A comprehensive ophthalmological examination was performed. Central macular thickness (CMT) and nasal, temporal, and subfoveal choroidal thicknesses (SFCT) measured by enhanced depth imaging mode of optical coherence tomography (EDI-OCT). Thickness of retinal layers obtained through macular OCT segmentation. The ImageJ software was used to binarize OCT scans and measure total choroid area (TCA), luminal area (LA), and stromal area (SA). Choroidal vascularity index (CVI) was defined as the ratio of LA to TCA. Patients received three doses of bevacizumab injections at monthly intervals. Measurements were performed before injection, one month after the 1st, 2nd, and 3rd injections. Results: CMT significantly decreased from 355.6±96.81 μm to 296.24±74.94 μm and SFCT showed a significant reduction after treatment from 226.02±82.32 μm to 220.02±80.83 μm (p<0.05). A significant improvement in best-corrected visual acuity was observed compared to baseline (p<0.05). Significant reduction was noted in the retinal nerve fiber layer, inner nuclear layer, and outer nuclear layer compared to pre-treatment values (p<0.05). However, no significant changes was observed in other layers of retina (p>0.05). TCA, which was 0.38±0.12 mm² at baseline, significantly decreased to 0.36±0.12 mm² in the post-treatment period (p=0.007), and LA, which was 0.24±0.08 mm² at baseline, significantly decreased to 0.23±0.08 mm² at the end of treatment (p=0.021). No significant differences were found in CVI, SA, or LA/SA values between pre- and post-treatment periods (p>0.05). Conclusion: The significant reduction observed in SFCT, TCA, and LA, along with the decrease in CMT and retinal layers, indicates that bevacizumab is effective not only on retinal layers but also on choroidal structures in the short term period. Keywords: Anti-VEGF, Choroidal vascularity index, Image binarization, Segmentation, Subfoveal choroidal thickness