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Michael J A Girard, Liam K Fisher, Dan Milea, Jost B Jonas, Xiaofei Wang; Predictions of Optic Nerve Traction Forces and Optic Nerve Head Tissue Stresses Following Horizontal Eye Movements. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3171. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To use finite element (FE) analysis to predict: (1) the optic nerve traction forces that act on the optic nerve head (ONH) following horizontal eye movements; and (2) the resulting stress levels in the peripapillary connective tissues of the ONH (Bruch’s membrane [BM] and scleral flange).
A FE model of a healthy eye was reconstructed in primary gaze position that included details from the orbital tissues (visualized with magnetic resonance imaging) and from the ONH tissues (using measurements from the literature). Optic nerve traction forces and peripapillary tissue stresses in both adduction and abduction (13°) were computed using nonlinear FE analysis. The peripapillary tissue stresses were also compared with those resulting from an intraocular pressure (IOP) of 50 mmHg (simulated in primary gaze position).
Our models predicted that, following horizontal eye movements, the ONH was sheared in the transverse plane due to the pulling action of the optic nerve. The estimated optic nerve traction forces were 90 mN in abduction and 150 mN in adduction. Peripapillary tissue stresses were typically concentrated in the nasal and temporal quadrants and were at most 2.3x higher than those induced by an IOP of 50 mmHg. In adduction, scleral stresses were highest in the temporal region, while BM stresses were highest in the nasal region. This trend was reversed in abduction.
Following horizontal eye movements, our models predicted high optic nerve traction forces that were of the same order of magnitude as extraocular muscle forces. Optic nerve traction resulted in large peripapillary tissue stresses (concentrated in the nasal and temporal quadrants), and thus may have a role to play in the development and progression of peripapillary atrophy and glaucoma.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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