Comparison of optical coherence tomography angiography features in type ۱ versus type ۲ choroidal neovascular membranes secondary to age-related macular degeneration

Abstract Background: Optical coherence tomography angiography (OCTA) is an advanced imaging modality that provides high resolution images at the level of different retinal layers. This study aime to evaluate choroidal neovascular membranes (CNVMs) secondary to age-related macular degeneration (AMD) quantitatively and qualitatively, according to their classification, morphological features, and flow areas, using OCTA. Methods: In this descriptive, comparative, cross-sectional study, CNVMs were divided into ۲ groups according to their classification as type ۱ or type ۲ neovascularization. Mixed CNVMs were excluded from the study. The size (mm۲) and the flow area (mm۲) of the CNVMs were calculated via OCTA and the presence of the perivascular halo and loop anastomoses were analyzed. The morphological appearance of the CNVMs were classified as: medusa, sea-fan, lacy-wheel, glomerular, dead tree, and mature vascular networks. Results: Of the ۸۵ eyes assessed for eligibility, ۴۵ eyes of ۳۴ individuals with CNVM were enrolled in this retrospective study. Twenty-eight eyes had type ۱ and ۱۷ eyes had type ۲ CNVMs. The mean size and flow area were greater in type ۱ than in type ۲ CNVMs (mean ± standard deviation [SD], ۶.۶۹ ± ۴.۵۴ and ۳.۶۱ ± ۳.۵۶ mm۲ versus ۳.۰۴ ± ۱.۹۸ and ۱.۷۷ ± ۱.۶۲ mm۲; P = ۰.۰۴۴ and ۰.۰۴۶, respectively). Among the ۲۲ eyes with type ۱ CNVMs and the ۹ eyes with type ۲ CNVMs, ۳۱ eyes had exudative membranes. Among the eyes with exudative CNVMs, ۲۲ eyes had a perivascular halo and ۲۲ eyes had loop anastomoses; this was significantly more than in the non-exudative eyes (P = ۰.۰۴۲ and ۰.۰۴۱, respectively). The lacy-wheel (۳۸.۷%) and dead tree (۷۱.۴%) patterns were the most frequent morphological appearance of the CNVMs in the exudative and non-exudative membranes, respectively. Conclusions: OCTA provides objective documantation about CNVMs. A perivascular dark halo around CNVMs could be a criterion to define exudative membranes activity.