Prognostic Relevance of Relative Ellipsoid Zone Reflectivity for Ellipsoid Zone Loss in Macular Telangiectasia Type 2.

Purpose: The relative ellipsoid zone reflectivity (rEZR) is an innovative biomarker for photoreceptor alterations and showed association with disease staging in macular telangiectasia type 2 (MacTel). However, its prognostic relevance for the ellipsoid zone (EZ) loss is unclear. Methods: Longitudinal spectral-domain optical coherence tomography (SD-OCT) imaging of patients with MacTel from an observational natural history study was used for en face determination of manifest EZ loss. The rEZR was assessed globally (mean rEZR/SD-OCT volume scan) and topographically (spatially refined). Logistic and linear-mixed effect models were used to investigate the rEZR's association with EZ loss onset and the (square-root transformed) progression rate of existing EZ loss. Results: A total of 97 eyes of 70 patients (39 women, mean age = 60.3 ± 8.9 years) were included and reviewed in a median observational period of 28.7 months (range = 20.3-49.9 months). Whereas 65 eyes of 44 patients showed manifest EZ loss (mean ± SD area = 0.44 ± 0.57 mm2) at baseline, 14 eyes of 14 patients developed EZ loss over time. Significant associations of the rEZR were only found in the topographical analyses indicated by lower rEZR values and a higher risk for EZ loss onset (odds ratio [OR] = 0.34, 95% confidence interval [CI] = 0.29 to 0.39, P < 0.001) as well as a faster EZ loss progression (coefficient estimate = -0.002, 95% CI = -0.0046 to 0.0001, P = 0.038). Conclusions: This study demonstrates the prognostic relevance of spatially refined rEZR changes before and beyond already existing EZ loss for both its onset and progression over time in MacTel. Further analyses of the rEZR are warranted to achieve both a more tailored patient selection and a novel end point identification for clinical trials in MacTel.