Abstract
Purpose :
Recently, the riboflavin/UV-A collagen cross-linking (UV-CXL) clinical technique to treat corneal keratoconus has been applied locally in the cornea for patient-specific treatment. We hypothesize that a confocal air-coupled ultrasonic optical coherence elastography (ACUS-OCE) system can detect local changes of corneal elasticity in vivo under localized and global UV-CXL in rabbits.
Methods :
ACUS-OCE measurements were made in four Dutch-Belted rabbits (n = 8 corneas) in the following protocol: (1) the left cornea was measured before (untreated: UT) and after half-treated (HT) UV-CXL; and (2) the right cornea was measured before and after full-treated (FT) UV-CXL. The ACUS-OCE setup includes a spectral-domain optical coherence tomography system coaligned with an air-coupled 1 MHz ultrasonic transducer that produced mechanical excitation (Lamb waves) at the apex of the corneas. Corneal thickness and Lamb wave speed were measured along four meridians: superior, inferior, nasal, and temporal. Finally, a modified Rayleigh-Lamb equation was used to convert wave speed into shear modulus.
Results :
Lamb wave speed maps (Fig. 1a) along the inferior-superior direction are shown for the UT, HF, and FT corneas with UV-CXL. The inferior meridian (i.e., UV-CXL treated) in the HT cornea case was stiffer (~7.14 m/s) than its superior (untreated) meridian (~5.88 m/s). Moreover, the speed map for the FT case was symmetric and showed a marked speed elevation (~7.66 m/s) compared to the UT case (~5.31 m/s). There was a significant increase in the shear modulus in the inferior meridian of the left HT corneas (p < .001) after localized UV-CXL (Fig. 1b). Similarly, for the right FT corneas, there is a significant increase in shear modulus (p < .001) in all meridians after full UV-CXL.
Conclusions :
In this work, we have demonstrated that ACUS-OCE can detect localized untreated and UV-CXL treated regions in the same cornea in vivo. This technology shows great potential for the monitoring and customization of patient-specific UV-CXL treatment.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.