The pathogenesis of papilledema: review of the literature and a new hypothesis
by David N. Levine and Ari I. Rapalino
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Papilledema, or swelling of the head of the optic nerve, occurs when intracranial pressure exceeds intraocular pressure to an abnormal degree. We conducted a biomechanical analysis of the effect of such excess pressure on the optic nerve. The stresses created in the nerve are: 1) a gradient of tissue pressure and 2) an axially oriented shear stress. Both are sharply localized to the region where the optic nerve exits the eye, and the excessive external pressure on the nerve begins. The gradient of tissue pressure liquifies the axoplasmic gel inside some of the axons – particularly those of large diameter located peripherally in the nerve cross-section - and displaces it towards the cell body, causing swelling of the optic nerve head.
High intracranial pressure displaces axoplasm from the extraocular portion of the optic nerve into the intraocular portion, causing swelling of the head of the optic nerve.
