A radial OCT scans at the optic disc were obtained. White arrowheads show Bruch's membrane opening (BMO). Dotted line shows BMO reference plane. Black arrowhead shows the anterior surface of the lamina cribrosa (LC). The distance between BMO reference plane and anterior LC (α), prelamina tissue thickness (β) at the center of BMO reference plane, and the diameters of the BMOs (γ) are also indicated.