Intrastromal Corneal Ring Segments in Previously Cross-Linked versus Virgin Keratoconic Corneas: A Multi-Parameter Propensity Score Matched Analysis.

Purpose: To compare outcomes of intrastromal corneal ring segments (ICRS) insertion in crosslinked (CXL) versus non-CXL keratoconic eyes, using a multi-parameter propensity score matching (PSM).

Setting: American University of Beirut Medical Center, Beirut, Lebanon.

Design: Retrospective case series.

Methods: A total of 198 eyes with mild to moderate keratoconus who underwent ICRS insertion were included. Our data were divided into two groups, based on whether CXL was performed before ICRS insertion. A PSM was used to balance the following covariates: age, gender, ICRS segment thickness, arc size, optical zone, topographic data and total corneal coma. Visual, refractive, topographic and total corneal aberrometric data were measured preoperatively and at 6 months post-ICRS implantation.

Results: After 1:1 PSM, 32 eyes from 27 patients with prior CXL were matched to 32 untreated eyes from 30 patients. Preoperative parameters were not statistically different between the groups (ps>.05). Both groups displayed a statistically significant improvement in visual, refractive, and topographic (simulated keratometry, maximum axial keratometry, and keratometric astigmatism) and total corneal aberrometric (total higher order aberrations and coma) outcomes 6 months after ICRS insertion (all ps<.05). The changes in all reported visual, refractive, topographic and total corneal aberrometric outcomes were not statistically different between CXL and non-CXL eyes (all ps>.05).

Conclusions: When properly matched for preoperative disease type and severity, ICRS insertion had a similar improvement in eyes with and without CXL.