Does Foveal Position Relative to the Optic Disc Affect Optical Coherence Tomography Measurements in Glaucoma?

Abstract

Objectives: To determine interindividual variability in the angle between the anatomic axis connecting the fovea and optic disc centerand the horizontal meridian using spectral domain optical coherence tomography (OCT).Materials and Methods: A total of 260 eyes of 133 subjects (81 women, 52 men) with glaucoma or suspected glaucoma wereincluded in the study retrospectively. Fovea-disc angle (FoDi angle) measurements, determined as the angle between the horizontalmeridian passing through the Bruch’s membrane opening (BMO) center and the line connecting the fovea and BMO center, wererecorded from spectral domain-OCT scans performed by the same investigator. FoDi angle was defined as negative if the fovea was locatedbelow the horizontal meridian through the BMO center and positive if the fovea was located above it.Results: The mean age of the participants was 56.5±14.6 years (27-83 years). The mean FoDi angle was -6.43±4.96° (range: -24.40° to+11.60°). Absolute deviation of the fovea BMO axis from the horizontal axis was 0-5° in 83 eyes (31.92%), 5-10° in 124 eyes (47.69%),10-15° in 41 eyes (15.76%), 15-20° in 10 eyes (3.84%), and greater than 20° in 2 eyes (0.79%).Conclusion: Most OCT devices currently used in the treatment and follow-up of glaucoma patients provide peripapillary retinal nervefiber layer (RNFL) thickness measurements that are made based on a clinical axis in reference to the horizontal meridian passing throughthe optic disc center. The results of our study reveal interindividual variation in FoDi angle as well as intraindividual differences in FoDiangle between fellow eyes in the same individual. Disparity between clinical and anatomic quadrants could impact RNFL thicknessmeasurements, which may lead to errors in the diagnosis of glaucoma.