Quantification of Corneal Collagen Cross-Linking in Keratoconus with Inverse Spectroscopic Optical Coherence Tomography

Abstract

Purpose : Optimization of corneal collagen cross-linking (CXL) is hindered by the inability to immediately measure treatment effects. Inverse spectroscopic optical coherence tomography (IS-OCT) is an emerging technique capable of non-invasively detecting nanoscale ultrastructural changes. The IS-OCT output measure D was previously found to increase with increased collagen cross-linking in vitro. We performed a pilot study to measure changes in keratoconus patient eyes before and after CXL by IS-OCT in vivo.

Methods : With IRB approval, keratoconus patients scheduled to undergo CXL were consented and enrolled. Standard epi-off CXL was performed in one eye (Glaukos, San Clemente, CA). Immediately preceding, and one month after unilateral CXL, both central corneas were imaged with dual channel visible and near-infrared light OCT. D was calculated and compared between eyes. A two-tailed paired Students t-test was used for statistical analysis.

Results : The change in corneal D before and after CXL was +1.78 ± 0.36 (n = 3), compared to -0.22 ± 0.34 (n = 3) in the contra-lateral non-CXL cornea (p = 0.03). Delta D in the anterior half of the cornea was +1.83 ± 0.12 in CXL eyes vs. -0.21 ± 0.68 in non-CXL eyes (p=0.047). Delta D in the posterior half of the cornea was +1.68 ± 0.47 in CXL eyes vs. -0.19 ± 0.37 in non-CXL eyes (p=0.03). The increase in D after CXL appeared more consistently higher in the anterior corneal stroma and diminished in the posterior-most region (Figure 1).

Conclusions : In this preliminary study, we found that IS-OCT can be used to image corneas quickly and non-invasively in patients. D was increased in corneas following CXL. IS-OCT could help quantitate CXL in vivo, but further study with additional patients and methods for improved data normalization are needed to validate these preliminary results.

This is a 2021 ARVO Annual Meeting abstract.

 

Figure 1: Mean and standard error of the change in D, relative to the minimum value of D (min(D)), in both eyes of keratoconus patients from baseline to one month after unilateral CXL, as a function of corneal depth.