Time-resolved detection of corneal UV Collagen Cross-linking (CXL) using Non-contact Optical Coherence Elastography (OCE)

Abstract

Purpose : While many current methods measuring CXL efficacy are indirect or invasive, Optical Coherence Elastography (OCE) can measure the biomechanical properties of the cornea without contact. The purpose of this study is to measure CXL effectiveness in ex-vivo porcine and human cornea while subject to UV-illumination.

Methods : An air-coupled ultrasound transducer was paired with phase-sensitive Optical Coherence Tomography (PhS-OCT) to generate and track mechanical waves in porcine and human cornea tissue inflated to 15mmHg using an artificial anterior chamber. Using standard CXL protocols, corneas were subject to epithelial debridement and one 50μL drop of .1% riboflavin in 20% dextran solution was applied every 2 minutes for 30 minutes. The corneas were then exposed to 3mW/cm² of 365 nm UV light and riboflavin/dextran drops were continued every 5 minutes for 30 minutes. Corneas were scanned prior to and post epithelial debridement, post riboflavin/dextran solution exposure, and every 2 minutes during the 30-minute UV light exposure to analyze temporal changes in mechanical wave speed (directly related to tissue elastic modulus, thus the stiffness) that can potentially monitor treatment efficacy.

Results : OCE scanning during treatment was able to monitor CXL efficacy, demonstrating a post-treatment increase in mechanical wave group velocity of ~80% and ~10% relative to baseline in porcine and human cornea, respectively. Early results indicate a ‘saturation’ point in human corneal stiffness (Figure 1) well before the standard 30-minute mark.

Conclusions : This experiment strongly suggests that non-invasive OCE imaging can quantitatively monitor CXL-induced changes in corneal elasticity to provide a framework for comparing the effectiveness of various CXL protocols. This method shows promise as a potential technique to provide patient-specific feedback during surgical intervention.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Figure 1. Mechanical wave group velocity map (indication of stiffness) (a) before, and (b) after CXL treatment of human cornea. White arrow denotes AuT location. Dashed box denotes region used to calculate (c) mean group velocity, and (d) thickness during treatment. Black dashed line denotes UV illumination period. The period without data between baseline measurements and UV illumination represents epithelial debridement and the initial 30 min riboflavin application.