Angular Location of Retinal Nerve Fiber Layer Defect: Association With Myopia and Open-Angle Glaucoma

PURPOSE. To compare retinal nerve fiber layer (RNFL) defects' angle measurements determined from the center of the optic disc and Bruch's membrane opening (BMO), as a function of myopia and open-angle glaucoma (OAG) subtypes. METHODS. In total, 118 patients with OAG were grouped by axial length (AL; high myopia, AL >26 mm; mild to moderate myopia, 24 <= AL <= 26 mm; nonmyopia, AL <24 mm) and OAG subtype (normal-tension glaucoma [NTG], high-tension glaucoma [HTG]). The disc and BMO centers were determined by a merged image of red-free fundus photography and spectral-domain optical coherence tomography. The angular location of the RNFL defect close to the fovea (angle a) was measured from the disc center and BMO center, respectively (angle alpha(disc) and angle alpha(BMO)). The difference between angle alpha(disc) and alpha(BMO) (Delta(a)), as well as the RNFL defect width (angle gamma), was evaluated. RESULTS. Angle alpha(disc) was smaller in myopic eyes and correlated significantly with AL (P = 0.001), whereas it did not differ among OAG subgroups. Angle alpha(BMO) and angle gamma were not different in the myopic and OAG subgroups. The Delta alpha was larger for eyes with higher degree of myopia and had significant correlation with AL (P < 0.001) and was larger in NTG eyes than in HTG eyes (P = 0.023). CONCLUSIONS. The angular location of the RNFL defect measured from the disc center, but not from the BMO center, was closer to the fovea for glaucomatous eyes with higher values of AL. The present study may facilitate understanding of the characteristic locational pattern of the RNFL defect in myopic glaucomatous eyes.