Choriocapillaris Flow Deficits and Outer Retinal Biomarkers in Early Macular Telangiectasia Type 2: A Multimodal Imaging Study

Background: Macular Telangiectasia Type 2 (MacTel Type 2) is a rare bilateral retinal disorder characterized by progressive neurodegeneration, Müller cell dysfunction, photoreceptor impairment, and secondary vascular remodeling. Although OCT and OCT angiography have improved the identification of structural and vascular abnormalities, the relationship between choriocapillaris impairment and early outer retinal degeneration remains incompletely defined. Methods: In this observational cross-sectional study, patients with early-stage MacTel Type 2 underwent multimodal imaging including spectral-domain OCT, OCT angiography, fundus autofluorescence, and microperimetry. Quantitative parameters included choriocapillaris flow deficit percentage, superficial and deep capillary plexus vessel density, ellipsoid zone disruption, central and parafoveal retinal thickness, hyporeflective intraretinal cavities, best corrected visual acuity, and mean retinal sensitivity. Analyses used linear mixed-effects models with a random intercept for patient to account for inter-eye correlation. Results: A cohort of 22 patients (40 eyes) with early non-neovascular MacTel Type 2 and 20 age-matched healthy control subjects (20 eyes) was analyzed. Mean age was 58.6 ± 7.9 years. Mean BCVA was 0.18 ± 0.11 logMAR, while mean retinal sensitivity was 24.1 ± 3.6 dB. Choriocapillaris flow deficits were increased in MacTel eyes compared with age-matched controls (18.7 ± 5.4% vs. 11.2 ± 3.8%; p < 0.001). Ellipsoid zone disruption was present in 55% of eyes, and greater EZ disruption length was significantly associated with reduced retinal sensitivity (standardized β = −0.61; p = 0.003). Choriocapillaris flow deficits were associated with greater ellipsoid zone disruption length (β = 0.58; p = 0.005), lower deep capillary plexus vessel density (β = −0.52; p = 0.013), and reduced retinal sensitivity (β = −0.49; p = 0.021). Conclusions: Early MacTel Type 2 was characterized by measurable OCTA-derived choriocapillaris flow impairment associated with outer retinal structural abnormalities and functional loss despite relatively preserved visual acuity. These cross-sectional associations do not establish temporal sequence or prognostic value; the utility of combined OCT/OCTA and microperimetric biomarkers for staging and monitoring requires prospective confirmation.