Abstract
Purpose :
To investigate the effect of sustained experimental high myopia on IOP-induced peripapillary tissue thinning in adult tree shrews.
Methods :
A total of 12 adult tree shrews were randomly assigned to two groups: experimental high myopia (n=7; refraction=-13.6±4.3D; axial length=8.2±0.2mm; age=0.93±0.17years) or normal vision (n=5; refraction=0.4±0.9D; axial length=7.98±0.01mm; age=0.99±0.06years). High myopia was induced at juvenile age and sustained until the experimental endpoint by continuous -10D lens wear. Animals were anesthetized and the anterior chamber was cannulated to control IOP. Optical coherence tomography scans of the optic nerve head (ONH) were obtained at four IOP levels: 5, 15, 30, 45 mmHg. The sclera, choroid-retinal pigment epithelium complex (Ch-RPE), retinal nerve fiber layer (RNFL) and remaining retinal layers (RRL) were automatically segmented and reconstructed in 3D after nonlinear distortion correction. The peripapillary tissue thickness was calculated over a 50µm circular band located 1000µm away from the ONH center. Differences in IOP-induced tissue thinning were tested across groups and tissues using a linear mixed effects model with a fixed intercept and random slope. The significance level was set to 0.05.
Results :
High myopic eyes exhibited higher IOP-induced thinning in all tissues compared to normal. However, this thinning was only significantly different in the RRL and sclera (Fig. 1). Across both groups, relative IOP-induced thinning was significantly lower in the retinal layers compared to Ch-RPE and sclera. A sectorial analysis (Fig. 2) showed that high myopia introduced an asymmetric thinning pattern to the sclera with significantly more thinning in sectors that were close to the posterior pole. A similar pattern was seen in the RRL but was not in RNFL and Ch-RPE.
Conclusions :
Sustained experimental high myopia until adulthood leads to thinning of peripapillary tissues in response to an IOP challenge that is similar to the response at juvenile age (Grytz R, et al. IOVS 2023;64:ARVO E-Abstract 2856). At the here tested adult age, high myopia increases the susceptibility to IOP-induced scleral thinning and introduces an asymmetric thinning pattern across sectors. The retina remains mostly protected against IOP-induced thinning as seen at juvenile age. These changes may have long-term effects and contribute to increased risk for glaucoma.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.