Optic Nerve Head Histopathology in High Axial Myopia.

Abstract

To describe particularities of the optic nerve head of axially highly myopic eyes. Measurements were obtained from enucleated globes and from population-based studies. Morphologic optic disc particularities in high axial myopia included enlarged disc size (secondary macrodisc), widening and temporal translocation of the papillary Bruch's membrane (BM) opening, parapapillary gamma and delta zone, elongation and thinning of lamina cribrosa and peripapillary scleral flange, steeper translamina cribrosa pressure gradient, decreased peripapillary choroid thickness, longer distance between peripapillary arterial circle and optic disc, optic cup flattening, presumably a stretching of the lamina cribrosa pores, and peripapillary intrachoroidal cavitations. These changes may be explained by growth of new BM in the retroequatorial region in the process of emmetropization or myopization as "overshooting" of the emmetropization process. The intrapapillary and parapapillary changes in the highly myopic optic nerve head may be reason for the increased susceptibility for glaucomatous optic nerve damage in high axial myopia. The widening of the papillary BM opening and the potential shift of the optic nerve head's 3 layer into temporal direction, both potentially leading to the development of parapapillary gamma zone may be of interest for elucidating the process of emmetropization/myopization.