Relationships between distance from the fovea to the disc and macular retinal layer thickness differ between normal and glaucomatous eyes.

A multicenter cross-sectional study was conducted to investigate the magnification-corrected association between fovea-disc distance (FDD) and optical coherence tomography (OCT)-measured macular retinal layer thickness in eyes with and without primary open-angle glaucoma (POAG). A 12.0 × 9.0-mm-wide swept-source OCT scan, which includes both the macula and optic disc, was performed in 190 eyes from 124 healthy subjects (normal group) and 149 eyes from 117 POAG patients (POAG group). The FDD and thickness of the macular retinal nerve fiber layer (mRNFL), ganglion cell inner plexiform layer (GCIPL), and outer retina (OR, total retina minus (mRNFL plus GCIPL)) were measured and corrected for magnification effects. The mixed-effects models, accounting for potential confounding factors, revealed two significant associations between a longer FDD and retinal layer thickness: thinner mRNFL in the normal group (coefficients, -3.14, 95% confidence intervals (CI), -4.75 to -1.53; p = 0.0001) and thinner GCIPL in the POAG group (coefficients, -4.26; 95% CI, -6.85 to -1.67; p = 0.0013). The association between FDD and macular retinal layer thickness varies by retinal layer and the presence of POAG. FDD can significantly affect OCT-determined macular retinal layer thickness, especially GCIPL in POAG eyes and mRNFL in normal eyes.