Early Peripapillary Choroidal Thinning during Myopia Development: A Potential Biomarker for Progressive Myopia Identified in Tree Shrews.

Purpose: The purpose of this study was to investigate longitudinal thickness changes of the peripapillary tissues in tree shrew eyes with induced high myopia from juvenile age to early adulthood.

Methods: Juvenile tree shrews were randomly assigned to either a control group (16 eyes, 8 animals) or a group with binocular -10 diopter (D) lens wear (18 eyes, 9 animals). Refraction, biometry, and optical coherence tomography scans centered on the optic nerve head (ONH) were obtained weekly for 19 weeks. Data were split into three temporal phases representing myopia onset (phase I, week 1), juvenile high myopia development (phase II, weeks 2-5), and sustained high myopia into early adulthood (phase III, weeks 6-19).

Results: Most eyes in the myopia group developed and maintained a spherical equivalent (SE) closely matching the lens power (-10.4 ± 2.03 D). Unexpectedly, two animals (n = 4 eyes) developed progressive myopia (-18.2 ± 2.9 D). Notably, eyes with progressive myopia showed rapid choroidal thinning compared to non-progressive eyes (-3.03 ± 0.6%/day vs. -1.64 ± 0.9%/day, P < 0.001) despite comparable SE and axial length changes during phase I. During phase III, these eyes exhibited accelerated thinning of sclera (-0.13 ± 0.01%/day vs. -0.02 ± 0.04%/day, P < 0.001) and choroid (-0.12 ± 0.03%/day vs. -0.02 ± 0.04%/day, P < 0.001). The observed chorioscleral thinning was more pronounced in sectors that are closer to the posterior pole.

Conclusions: Sustained negative lens wear can induce progressive myopia in tree shrews. Profound choroidal thinning during early myopia development is a potential biomarker for future chorioscleral thinning, axial elongation, and myopia progression. The asymmetric chorioscleral thinning may contribute to pathologic ONH remodeling and increased glaucoma risk later in life.