Microvascular changes in treatment naïve non-exudative macular neovascularization complicated by exudation

Purpose: To assess differences in choriocapillaris (CC) and macular neovascularization (MNV) optical coherence tomography angiography quantitative parameters between long-term persistently nonexudative MNVs (NE-MNVs) and long-term activated NE-MNVs in age-related macular degeneration. Methods: Age-related macular degeneration patients with treatment-naïve NE-MNVs with >2 years of follow-up and no evidence of exudation within the first 6 months from diagnosis were retrospectively recruited. Two groups were considered according to the occurrence (EX group) or not (NE group) of exudation within the first 2 years of follow-up. Segmentation of the MNV and of the perilesional CC were obtained from enface optical coherence tomography angiography acquisitions at diagnosis and at 6-month follow-up. OCT B-scan images of the MNV were also collected. Fractal ratio was defined as the ratio between MNV fractal dimension (FrD) and CC FrD. Results: Fifty (50) eyes were included (20 EX group and 30 NE group). EX group showed higher flow deficit density and flow deficit number at the 6-month follow-up. It also showed higher MNV FrD, lower CC FrD, and higher fractal ratio at the 6-month follow-up. The fractal ratio significantly increased at 6-month acquisitions in the EX group, showing an area under the ROC curves of 0.887 (95% CI 0.869–0.922). Conclusion: Fractal ratio at 6 months can predict exudation risk of MNV within 2 years from diagnosis. This suggests increased structural complexity of the NE-MNV accompanied by progressive capillary rarefaction of the perilesional CC as a key driving factor for the development of exudation in NE-MNV.