Displacement of the Optic Nerve Head

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Abstract
• Mechanical compression of axons within the lamina scleralis has been suggested as a mechanism of damage in glaucoma. Movement within the optic nerve head was studied after acute intraocular pressure elevation in the enucleated primate eye. Fine platinum wire was positioned within the lamina scleralis and displacement characterized after IOP elevation. These studies demonstrate the following: (1) retrodisplacement increases significantly with increasing pressure, (2) maximum retrodisplacement occurs at the center and minimum retrodisplacement occurs at the periphery of the optic nerve, (3) retrodisplacement at the position of minimum movement in the optic nerve is indistinguishable from that in the sclera, (4) 67% of the net retrodisplacement occurs after a 15-mm Hg increase in IOP, and (5) tangential displacements within the lamina scleralis also increase with increasing pressure but are only 50% of the magnitude of retrodisplacements.