Finite Element Analysis Predicts Large Optic Nerve Head Strains During Horizontal Eye Movements

Abstract

Our models predicted high ONH strains during eye movements, which were aggravated with stiffer optic nerve sheaths. Further studies are needed to explore links between ONH strains induced by eye movements and axonal loss in glaucoma.

Factors Influencing Lamina Cribrosa Microcapillary Hemodynamics and Oxygen Concentrations

“…This is not biologically accurate as the LC has a thickness of approximately 270 lm. 58 Considering that the LC may exhibit highly heterogeneous stresses (induced by IOP, the retrolaminar pressure, or during eye movements 59 ), it would be logical to observe variations in LC hemodynamics and oxygen concentrations through the thickness of the LC, as predicted by Causin et al 20 LC thickness has also been shown to change with glaucoma progression, which may in turn compromise blood flow further in glaucoma subjects. 8 While using 'surface-like' LCs (as performed herein) should provide a first degree of understanding of LC hemodynamics, future improvements to our models should prioritize on incorporating LC thickness and interactions with LC stresses.…”

Predictions of Optic Nerve Traction Forces and Peripapillary Tissue Stresses Following Horizontal Eye Movements

“…16 Briefly, the optic nerve, orbital fat, and eye globe were reconstructed from MRI images of a healthy subject. The ONH geometry, including the peripapillary sclera, scleral flange, prelaminar neural tissue, lamina cribrosa, postlaminar neural tissue, pia, and dura, was embedded within an ''idealized'' spherical corneoscleral shell.…”

“…Detailed geometric parameters of these tissues can be found in the recent literature. 16 We further included the choroid and BM into the model to increase its biofidelity and to estimate stresses in the regions in which peripapillary zones typically develop. The thickness of the choroid and BM were 134 lm 19 and 5 lm, 20 respectively.…”

“…16 A scleral fiber ring with thickness of 0.5 mm was included ( Fig. 1) to account for the circumferential alignment of collagen fibers within the scleral flange and around the scleral canal.…”

“…13 Recently, there has been renewed interest in the effects of eye movements on the optic nerve and ONH deformations and their possible links to optic neuropathies. Specifically, studies that used optical coherence tomography (OCT), [13][14][15] finite element (FE) modeling, 16 and magnetic resonance imaging (MRI), 17 all converge to the single fact that horizontal eye movements considerably deform the ONH tissues (through the ''strong'' optic nerve [including its sheath] traction imposed on the ONH), and that these deformations can be as large (or significantly larger) than those induced by a substantial IOP elevation. 14,16 Because eye movements appear to have a strong impact on the ONH tissues, and can even alter the axial length of the eye, 18 we aimed to understand if there could exist a link between eye movements and the development of peripapillary zones.…”