Abstract
Purpose :
To evaluate the slowing effect of scleral crosslinking (SXL) on experimental myopia in tree shrews using sub-Tenon’s injections of genipin (GEN) at different concentrations and number of injections.
Methods :
Three or five sub-Tenon’s injections of 0.4 ml/15min 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 (DVE). Form-deprivation (FD) was induced in the injected eye between 24 and 35 DVE while the fellow eye served as control. Tree shrews were randomly assigned to 6 experimental groups: normal visual experience (n=6); FD (n=6); FD + 3 GEN injections at 10 mM (n=6) and 20 mM (n=5); FD + 5 GEN injections at 20 mM (n=5); and FD + 5 sham injections (n=3). Refractive state and ocular dimensions were measured daily in awake animals. A significant treatment effect with respect to the FD group was reported when significant differences (treated vs. control, t-test, p<0.05) were identified for at least three consecutive days.
Results :
Lens thickness remained unaffected in all groups. The low concentration group (FD + 3 x 10 mM GEN) showed no treatment effect on refractive error, axial length, posterior chamber depth or corneal thickness, but had a reduced anterior chamber depth (Figure). Compared to FD, the high concentration group (FD + 3 x 20 mM GEN) showed significantly lower refractive error, axial length, anterior chamber depth, vitreous chamber depth; and significant corneal thickening. In general, these treatment effects increased by injecting the high concentration GEN 5 times. Some treatment effects were transient as the final slope of axial lengthening and vitreous chamber deepening was similar between all GEN groups and the FD group. The sham injections significantly attenuated FD-induced axial length and vitreous chamber elongation.
Conclusions :
We have shown that SXL using GEN can slow axial elongation and FD myopia in tree shrews. The extent and duration of this treatment effect seems to be dose dependent. Some results were unexpected (corneal thickening, reduction of the anterior chamber depth, sham effect) and need further evaluation. A sustained delivery of GEN may be needed for a prolonged treatment effect.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.