Abstract
Purpose :
As myopia develops, the ocular globe undergoes physical changes, such as elongation, and the sclera also undergoes remodeling. How the sclera is remodeled at a microstructural level and how the organization of collagen fibers is affected by pharmacological myopia treatments is still not well understood.
Methods :
Myopia was induced in one eye in guinea pigs (n=5; 2 weeks old at start) via form deprivation (60% transmitted light) over a period of 70 days, leaving the fellow eye (FE) uncovered. Myopia was allowed to develop for 7 days, and one pharmacological intervention (daily drop 1% atropine(AT), n=1; 0.005% latanaprost(LA) n=2) or sham intervention (n=2) was applied for the remaining 63 days concurrently with diffuser wear. After the 70 days, the animals were euthanized (anesthesia overdose) and eyes extracted. Superior nasal/temporal and inferior nasal/temporal scleral strips were collected. For each strip, five image stacks were captured using a custom-built Second Harmonic Generation (SHG) microscope. Scleral collagen organization was quantified using an order coefficient (OC) metric (Germann et al., 2018). The signal level collected in the forward and backward scattering (FSHG&BSHG) directions was also recorded. Statistical significance between averages was determined with a Student T-Test (p-value<0.05 level).
Results :
OC value was significantly different between sham treated myopic and non-myopic FE (4.6% and 2.9% increase). In contrast, there was no significant difference in average OC value between the LA- or AT-treated myopic eyes and non-myopic FE. Also, FSHG signal was reduced in the sham-condition (19.4% and 10.5% decrease) and increased in the AT-condition (57.8% increase) with respect to the non-myopic FE, while LA did not induce systematic differences. BSHG signal did not capture differences across conditions.
Conclusions :
SHG microscopy scleral imaging revealed significant changes in scleral collagen organization of form-deprived myopic guinea pig eyes. Pharmacological treatments (AT and LA) are able to prevent substantial changes to collagen fiber organization in the sclera at a microscopic level, in agreement with reported scleral biomechanical differences. Differences in FSHG levels between AT-treated and LA-treated myopic eyes suggest that the two myopia-control treatments operate under different mechanisms and possibly different time courses on scleral tissue.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.