Abstract
Purpose :
Scleral cross-linking has been proposed as a potential treatment for halting the progression of myopia. In this study, we test whether the Rose Bengal-Green Light collagen cross-linking (RGX) treatment that has been previously tested in the cornea (Cherfan et al.,IOVS 2013) can be translated to the sclera.
Methods :
The outer tissue was removed from the sclera of ten porcine ocular globes (24-48h post-mortem).After removing the epithelium, globes were treated with RGX on the nasal (NR) and temporal (TR) regions, where one side was treated and the other kept as control. RGX treated regions were partially immersed in 0.1%(w/v) Rose-Bengal solution for 120s, irradiated by green light (532nm 0.5mW/cm2) for 200s, immersed again for 30s, and irradiated for an additional 200s. Anterior and posterior scleral strips (20×4 mm approx) were collected from the NR and TR, both from RGX and untreated areas of each eye. Strips were mounted in an uniaxial stretcher (CellScale, Canada) to determine the Young’s modulus (YM) at 8%, 10% and 12% strain. Sample cross-sections were measured with a custom spectral OCT system. T-test was used to test regional and RGX-induced differences in scleral biomechanics.
Results :
All stress-strain curves of scleral tissue showed an exponential behavior. In untreated regions, anterior was stiffer than posterior sclera (7.35±3.31 vs 3.29±1.62 MPa at 8% and 16.11±8.00 vs 7.54±3.79 MPa at 10% strains).In the anterior sclera, the mean YM for the untreated regions was 7.40±4.01 (NR) and 7.29±2.42MPa (TR), and for the RGX regions, the average YM was 4.83±3.73 (NR) and 5.84±2.33MPa (TR), at 8% strain. In the posterior sclera, the average YM for untreated regions was 4.04±1.72 (NR) and 2.55±1.08MPa (TR), and for the RGX regions YM was 2.65±1.41 and 3.57±1.98MPa. At all strains, RGX produced a highest increase in stiffness in the posterior temporal sclera by 40.07%, compared with untreated sclera in the same region (T-Test,P<0.001 two-tailed), although it decreased in the posterior nasal sclera by 34.81% (T-Test,P<0.001 two-tailed).
Conclusions :
RGX treatment significantly stiffened the posterior temporal sclera of the porcine ocular globe, making this zone a prime candidate for myopia treatment. Interestingly, other regions saw a decreases in stiffness after RGX, suggesting that a separate process may compete to RGX stiffening, which may include optic nerve head traction or dehydration or swelling in samples ex vivo.
This is a 2020 ARVO Annual Meeting abstract.