Effects of high myopia on in vivo compliance of anterior scleral canal opening and lamina cribrosa depth in juvenile tree shrews

Abstract

Purpose : To investigate in vivo effects of high myopia on the deformation response of the anterior scleral canal opening (ASCO) area and lamina cribrosa (LC) depth with acute changes in IOP.

Methods : Juvenile tree shrews were randomly assigned to two groups: normal visual experience (n = 6) and monocular -10D lens treatment to induce high myopia (n = 6). Lens treatment started at 24 days of visual experience (DVE). At 59 DVE, eyes were canulated and the optic nerve head was imaged via optical coherence tomography (Spectralis OCT2, Heidelberg Engineering) at four IOP levels (5, 15, 30, 45mmHg) with at least 5 minutes rest after IOP changes. A deep learning algorithm (Reflectivity, Abyss Processing) was trained with 489 manually segmented OCT scans and used for auto-segmentation of the anterior LC surface. ASCO points were manually segmented. ASCO area and central LC depth were computed in 3D and analyzed after nonlinear distortion correction (Grytz R, et al. IOVS 2020; 61: ARVO E-Abstract 4778) from 48 radial B-Scans per OCT scan. Mixed design analysis of variance split-plot ANOVA and Wilcoxson analysis were used to test for significant IOP-group interactions and group differences at each IOP level, respectively.

Results : ASCO deformations were small across all groups with significant changes in IOP-group interactions between treated and control eyes. For IOPs 30 and 45 mmHg, ASCO area changes were significantly higher in treated vs control eyes (p < 0.05). In a large number of eyes, ASCO area was decreasing with IOP (9/12 normal, 5/6 control, 3/7 treated). No significant differences were found for central LC depth changes.

Conclusions : Our results suggest that high myopia has a small but measurable effect on ASCO area changes with IOP in juvenile tree shrews. This increase in optic nerve head compliance during juvenile myopia may contribute to subsequent ONH remodeling and increased risk of glaucoma later in life.

This is a 2021 ARVO Annual Meeting abstract.

 

A: Representative OCT scan showing segmented ASCO points and anterior LC surface. Central LC depth was calculated as the normal distance between the best fit ASCO plane and anterior LC surface. B,C: Mean ASCO area and central LC depth changes with IOP. Error bars represent SEM. * represents p < 0.05.

 

IOP-group interaction results. T: treated, C: control, N: normal. * represents p < 0.05.