Eyes with High Myopia Experience Greater Gaze-induced Optic Nerve Head Deformations Compared to Normal Eyes

Abstract

Purpose : To use finite element (FE) modeling and in vivo optical coherence tomography (OCT) imaging to estimate the effect of optic nerve traction on optic nerve head (ONH) deformations following horizontal eye movements in highly myopic (HM) eyes.

Methods : A FE model representing an emmetropic eye was constructed. A second model with a longer axial length (>26 mm) and thinner sclera thickness was constructed to represent structural changes in HM (Figure). To validate the FE models, 16 eyes from 9 HM subjects and 14 eyes from 8 non-HM subjects were imaged using OCT in primary gaze, 20° adduction and 20° abduction. Lamina cribrosa (LC) effective strains for all loading scenarios was measured using a 3-D strain tracking algorithm.

Results : ONH strains were greater in the HM vs. emmetropic FE model during horizontal eye movements. On average, ONH deformations in adduction were higher than in abduction. LC strains induced by adduction and abduction were both greater the HM (0.051 and 0.037, respectively) vs. the emmetropic model (0.035 and 0.025). In human subjects, 3-D strain tracking results showed LC strains in were significantly greater in HM vs. non-HM eyes for both adduction (0.060±0.040 vs. 0.039±0.021, p=0.039) and abduction (0.039±0.023 vs. 0.025±0.011, p=0.025).

Conclusions : ONH deformations following eye movements are greater in HM vs. control eyes. In both FE models and in vivo, ONH deformations were greater in adduction than in abduction. Larger LC strains in high myopia eyes may contribute to the increased risk of glaucoma in individuals with HM.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Figure. (A) An axial MRI scan of a high myopic eye. (B) Reconstructed geometry and FE mesh of the high myopia model, including boundary and contact definitions. (C) Detailed ONH structure and loading conditions.