Progression patterns in foveal-sparing geographic atrophy with double-layer sign due to neovascularization or basal laminar deposits

PURPOSE. The purpose of this study was to analyze the prognostic significance of double-layer sign (DLS) in eyes with foveal-sparing geographic atrophy (GA) secondary to age-related macular degeneration. METHODS. This retrospective, observational cohort study analyzed 46 eyes (46 patients) with foveal sparing GA and associated DLS, using fundus autofluorescence (FAF), near-infrared reflectance (NIR), optical coherence tomography (OCT), and OCT angiography (OCTA). DLS was defined based on OCTA findings as either thick basal laminar deposits (BLamD) or non-exudative macular neovascularization (NE-MNV). The area of GA and foveal sparing were estimated on both FAF and NIR at different time points. Centrifugal and centripetal GA growth rates referring to the lesion expansion away from and toward the fovea, respectively, were evaluated using a mathematical formula. RESULTS. Of the 46 eyes enrolled, 25 had thick BLamD, whereas 21 had type 1 NE-MNV. The NE-MNV eyes showed significantly thicker DLS than those with BLamD (90.4 ± 39.8 μm vs. 57.0 ± 27 μm, 95% confidence interval [CI] = 0.34 to 0.78, P < 0.001). GA areas were smaller on FAF than NIR (95% CI = −0.89 to −0.03, P = 0.03) in the BLamD group, whereas no difference was observed in the NE-MNV group (95% CI = −0.37 to 0.64, P = 0.60). Despite similar GA areas, the NE-MNV eyes exhibited larger foveal sparing (95% CI = 0.02 to 1.21, P = 0.04). The foveal sparing area remained stable (F(1.2, 11 = 4.15, P = 0.06, ω2 = 0.02) in the NE-MNV group, whereas a significant reduction was observed in the BLamD subgroup (F(1.39, 20.9) = 7.5, P < 0.001, ω2 = 0.09). CONCLUSIONS. OCTA has provided valuable insights into the pathogenic interpretation of the DLS signature. Our findings confirm that a neovascular DLS protects the retinal pigment epithelium and outer retina, contributing to prolonged foveal preservation.