Peripapillary Suprachoroidal Cavitation, Parapapillary Gamma Zone and Optic Disc Rotation Due to the Biomechanics of the Optic Nerve Dura Mater

It was with great interest that we read the article by Wang and colleagues,¹ in which they formed a biomechanical model of the optic nerve head and calculated that the optic nerve head strains following a lateral eye movement of 13° were as high as or higher than those resulting from an intraocular pressure of 50 mm Hg. This example may show the importance of the biomechanics of the optic nerve dura mater for the physiology and pathophysiology of the optic nerve head. To cite an example, peripapillary suprachoroidal cavitations found in highly myopic eyes with a prevalence of approximately 17% are usually located in the inferior peripapillary region.^2,3 They are associated with an optic disc rotation around the vertical axis and high axial myopia. The fact that the pull of the optic nerve dura mater may exert traction on the temporal and inferior peripapillary sclera has been discussed.⁴ This traction may be stronger on the temporal optic nerve head side than on its nasal side, as the optic nerve dura mater originates in the nasal upper region of the orbit. Subsequently, the pull may be most marked in eyes with a longer axial diameter (i.e., highly myopic eye) in adduction. These reflections fit well with the model described by Wang et al.¹ in their study. We would therefore like to ask Dr. Wang and associates¹ whether their model could also explain the forces exerted by the optic nerve dura mater pull on the temporal peripapillary sclera and peripapillary scleral flange, also including the development and enlargement of parapapillary gamma zone and increasing vertical optic disc rotation in highly myopic eyes.