Structural Characteristics of Parapapillary Choroidal Microvasculature Dropout in Primary Open-Angle Glaucoma: Comparison Between Width and Area

Purpose: To compare the circumferential width and area of parapapillary choroidal microvasculature dropout (CMvD) and investigate their correlation with clinical characteristics in eyes with primary open-angle glaucoma (POAG). Subjects and methods: This retrospective cross-sectional study included 121 POAG eyes with localized retinal nerve fiber layer (RNFL) defects (84 eyes with CMvD and 37 without CMvD). CMvD was defined as focal sectoral capillary hypoperfusion or nonperfusion in the parapapillary choroid identified using optical coherence tomography angiography. Circumferential CMvD width (in degrees) and area were quantitatively measured, and their relationships with clinical factors were analyzed. Results: CMvD was present in 84 of 121 eyes (69.4%). Although CMvD width and area were strongly correlated ( P < 0.001), they showed distinct clinical associations. A larger CMvD width was significantly associated with a thinner global RNFL thickness ( P =0.046), worse visual field mean deviation ( P =0.049), and larger β-zone parapapillary atrophy (PPA) area ( P= 0.013). Conversely, larger areas of β-zone and γ-zone PPA were related to a larger CMvD area ( P =0.001 and P < 0.001, respectively). Conclusion: Although circumferential CMvD width and area were highly correlated, their associated clinical factors differed. The CMvD width, reflecting the extent of optic disc margin involvement, serves as a more robust indicator of glaucomatous damage severity than the CMvD area, which may be influenced more by myopia-related anatomical variation.