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Rafael Grytz, Mustapha El Hamdaoui; Computational Modeling of Vision-Guided Remodeling and Age-Dependent Growth of the Tree Shrew Sclera During Normal Development and Lens-Induced Myopia. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5530. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To computationally investigate the hypothesis that scleral growth is controlled by genetic factors while scleral remodeling is primarily driven by environmental factors such as visual defocus.
We developed a multi-scale computational model to simulate scleral growth and remodeling (G&R) in tree shrews based on the following assumptions: (i) the sclera deforms due to external loading (IOP) and G&R; (ii) scleral G&R ceases with age; and, in addition, (iii) scleral remodeling is modulated by the eye's refractive error. We define growth as a mechanism that changes the volume of a tissue while remodeling involves internal deformations and restructuring of the extracellular micro-structure that are volume-preserving at the macro-scale. A simplified model of the eye's optical system was used to translate the axial length of our axisymmetric finite element (FE) model of the tree shrew eye into refractive error. We fitted our model against new and previously published tree shrew data (Norton et al., Vision Res. 2010;50:564) consisting of one new normal group (n=7) and 6 groups of monocular -5D lens treated animals (n=5), where lens wear started at 11, 16, 24, 35, 48, or 100 days of visual experience (DVE). Lens treatment was 11 days in all except the oldest group (41 days).
The computational model was able to replicate the age- and vision-dependent response of the tree shrew experiments (Fig. 1). Scleral growth ceased at younger age than scleral remodeling (Fig. 2A). During normal development, scleral remodeling occurred at maximum rate first (until 15 DVE) and slowed afterwards as the eye emmetropized. The model predicted the highest susceptibility to scleral remodeling and myopia at 31 DVE (Fig. 2B), which was in good agreement with experimental data that were not used to fit the model (Siegwart and Norton, Vision Res. 1998;38:3505).
This is the first model that distinguishes scleral growth from remodeling during eye development. The good agreement of our results with experimental data supports the notion that scleral growth and remodeling are two independently controlled mechanisms during postnatal eye development.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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