Vascular geometry and network topology reveal vascular remodelling beyond density measures across Chew grades in macular telangiectasia type 2

Background/Objectives: Previous OCTA studies across MacTel severity levels have primarily characterised perfusion- and density-based vascular changes. Whether graph-derived network architecture provides complementary information on severity remains unclear. We therefore tested whether lower Chew grades already show architectural abnormalities despite comparatively preserved global vessel density. Subjects/Methods: This cross-sectional study included 62 MacTel and 64 healthy control eyes. Fovea-centred 3x3-mm high-resolution swept-source OCTA acquired with the DREAM platform was analysed with OCTAVA. Whole-image vessel length density (VLD), regional vessel area density (VAD), peri-FAZ perfusion, foveal avascular zone (FAZ) geometry and network topology were assessed using mixed-effects models adjusted for age, sex and axial length. Results: Grades 0-2 already showed greater FAZ acircularity than controls in the superficial (SCP; +0.132; q<0.001) and deep capillary plexus (DCP; +0.073; q=0.034), with lower SCP branchpoint density (q=0.022). Across MacTel grades, DCP VLD decreased by 0.352 mm-1 per grade (95% CI -0.583 to -0.121; Holm P=0.007), whereas the SCP slope was not significant (Holm P=0.071; plexus interaction P=0.160). DCP parafoveal VAD declined by 0.593 percentage points per grade (95% CI, -0.943 to -0.242; q=0.007), with no comparable decline in foveal VAD. Visual acuity worsened by 0.071 logMAR per grade (P<0.001). Conclusions: OCTA suggests two complementary components of the MacTel vascular phenotype: geometric and topologic remodelling in lower grades, with additional regional and global capillary rarefaction in higher grades. Vascular geometry and network topology, therefore, provide complementary information not captured by vessel density alone.