Quantitative Assessment Of Corneal Biomechanical Changes In Vivo After PiXL With Different Ultraviolet-A Energy Doses Using Optical Coherence Elastography

Purpose:Photorefractive intrastromal corneal crosslinking(Pi XL)treatment corrects myopia by enhancing localized central corneal biomechanics.However,the dose-effect relationship between the changes in corneal biomechanics and alternations in corneal curvature remains unclear.In this study,we developed an acoustic radiation force optical coherence elastography(ARF-OCE)technique and used it to investigate the dose-effect relationship in Pi XL.Methods:Pi XL treatments with five ultraviolet-A(UVA)energy doses(5.4–45 J/cm~2)were administered to rabbit corneas in vivo(n=15).ARF-OCE measurements and corneal topography were performed three days before and one week after Pi XL treatment.Depth-resolved Young’s modulus images of the in vivo corneas were obtained based on the phase velocity of the Lamb wave.Then,the Young’s modulus of the anterior corneal stroma was averaged to quantitatively assess the changes in corneal biomechanics.Results:The corneal Young’s modulus increased with increasing UVA energy dose.As the UVA dose increased from Group I(5.4 J/cm~2)to Group V(45 J/cm~2),the mean value of percentage change in Young’s modulus(ΔE%)also increased.The values ranged from 0.26 to 1.71.Similarly,the mean value of change in the mean keratometry(ΔKm)increased with increasing UVA dose from Group I to Group IV(35 J/cm~2),ranging from 0.40 diopters(D)to 2.10 D.Furthermore,there was a statistically significant positive correlation betweenΔE%andΔKm in Groups I to IV.Conclusion:In this work,we demonstrated that ARF-OCE could be applied to quantitatively analyze depth-related changes in corneal biomechanics in vivo.This technique shows great potential in helping to accurately determine the dose-effect relationship in Pi XL.