In Vivo 3-Dimensional Strain Mapping Confirms Large Optic Nerve Head Deformations Following Horizontal Eye Movements

Abstract

Our results confirm that horizontal eye movements generate significant ONH strains, which is consistent with our previous estimations using finite element analysis. Further studies are needed to explore a possible link between ONH strains induced by eye movements and axonal loss in optic neuropathies.

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

“…However, the difference in ppS stresses was relatively large (ppS stress in adduction was 16% higher than in abduction). This trend was similar to our previous studies, 14,16 in which LC strains in adduction were higher than those in abduction. Other independent studies also concluded that ONH deformation was more affected by adduction.…”

“…41 The shearing deformation observed in this study (Fig. 2) and other OCT observations [13][14][15] might be able to explain the optic disc rotation about the vertical axis (axis along the superior-inferior direction) observed in myopic eyes. 42 It is plausible that continuous stretching of peripapillary tissues following repeated eye movements might contribute to the development of rotated optic discs and peripapillary zones simultaneously through a tissue remodeling process.…”

“…This deformation pattern is in agreement with that observed in three recent OCT studies. [13][14][15] Furthermore, LC strains (see Supplementary Material SC) in this study were on the same order of magnitude as those measured in vivo.…”

“…Note that the links between mechanical stress/strain and peripapillary zones are speculative; further experimental or clinical studies may aid in understanding their potential relationships. In our previous study using in vivo OCT imaging, 14 we observed on average larger gaze-induced ONH deformations in subjects with peripapillary zones. That study was, however, limited to a small sample size (5 eyes without peripapillary zones versus 11 eyes with peripapillary zones), and repeating such work with a larger sample size may provide a better understanding of the correlation between eye movements and peripapillary zones.…”

“…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.…”