Purpose
To evaluate the effect of scleral crosslinking (SXL) on slowing experimental progressive myopia in tree shrew eyes using sub-Tenon's injections of genipin (GEN) at different concentrations and number of injections.
Methods
Three or five sub-Tenon's injections of GEN at 0 mM (sham), 10 mM, or 20 mM were performed in one eye every other day starting at 18 days of visual experience. Form deprivation (FD) myopia was induced in the injected eye between 24 and 35 days of visual experience; the fellow eye served as control. Tree shrews were randomly assigned to five experimental groups: FD (
n
= 8); FD + 5 × sham injections (
n
= 6); FD + 3 × GEN injections at 10 mM (
n
= 6) and 20 mM (
n
= 6); and FD + 5 × GEN injections at 20 mM (
n
= 6). Refractive state and ocular dimensions were measured daily.
Results
Compared with the FD group, the sham-injected group showed a transient effect on slowing vitreous chamber elongation. With increasing GEN dose, SXL had an increasing treatment effect on slowing vitreous chamber elongation and myopia progression. In addition, SXL led to a dose-dependent shortening of the aqueous chamber depth and corneal thickening. Lens thickening was observed in the group with the highest concentration.
Conclusions
We have shown that SXL using GEN can slow axial elongation and myopia progression in tree shrews. The extent of this treatment effect was dose dependent. Several unexpected effects were observed (corneal thickening, decrease of the anterior chamber depth, and lens thickening), which require further optimization of the GEN delivery approach before clinical consideration.
Translational Relevance
The results of this preclinical study suggest that scleral crosslinking using genipin can slow myopia progression.
Several tests for heteroscedasticity in a two-group between-subject variances were compared with a simulation study. Two common rank-based procedures inflated test size with skewed error distributions. Nonparametric Levene test performed well but has notable limitations. Tests based on the absolute value of OLS residuals also inflated test size with skewed error distributions. Procedures based on squared OLS residuals performed better; however, the original Breusch-Pagan and Variance Function Regression are sensitive to even slight departures from the normality assumption. The Brown-Forsythe test based on taking the absolute value of median centered data performed the best; however, generalization to more complex analyses would not be straightforward.espite decades of research, there does not seem to be a consensus for a single procedure for testing for heteroscedasticity that works uniformly well across common data scenarios. In betweensubjects ANOVA, testing for heteroscedasticity reduces to testing whether the J groups have identical variances with the following null hypothesis:
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