Optical Coherence Tomography Angiography Characterization of Vascular Alterations in Macular Telangiectasia Type 2

Purpose: To investigate retinal microvascular and choriocapillaris changes across the newly proposed seven-step classification for macular telangiectasia type 2 (MacTel) using swept-source optical coherence tomography angiography (SS-OCTA). Methods: Cross-sectional, observational study including 111 eyes with MacTel (56 patients) and 120 matched control eyes (60 subjects). Participants underwent comprehensive ophthalmic examinations, including macular 6 × 6-mm SS-OCTA. MacTel eyes were categorized into one of seven grades (0-6) using multimodal imaging. SS-OCTA scans were processed to measure vessel density (VD), vessel skeletonized density (VSD), foveal avascular zone (FAZ) metrics, and choriocapillaris flow deficit percentage (CCFD%). Differences between groups were assessed using Mann-Whitney U, Kruskal-Wallis tests, and generalized mixed-effects models. Cluster analysis assessed the agreement between clinical grades and OCTA-based clusters. Results: Of the MacTel eyes, 32% were grade 0, 9% grade 1, 18% grade 2, 5% grade 3, 15% grade 4, 13% grade 5, and 8% grade 6. MacTel eyes exhibited significant alterations in VD and VSD, particularly in the central 1-mm circle and temporal/inferior sectors, alongside consistently higher CCFD% across all macular regions. Advanced grades (5-6) showed pronounced differences in VD, VSD, and CCFD% compared to early grades (0-2). Agreement between MacTel grading and OCTA-based clusters was fair to moderate (Adjusted Rand Index = 0.233), with higher concordance for grades 0 and 4 to 6. Conclusions: SS-OCTA reveals significant retinal vascular and choriocapillaris impairment in MacTel, with pronounced alterations in advanced disease grades. The observed vascular damage, extending beyond the MacTel area, underscores the value of OCTA in identifying disease severity and aiding in its classification.