Rates and Risk Factors for Failure After Corneal Collagen Crosslinking for Keratoconus: An IRIS Registry Analysis.

Purpose: To investigate rates and risk factors for corneal collagen crosslinking (CXL) failure in patients with progressive keratoconus (KCN) using a large national clinical registry.

Methods: Patients with treatment-naïve KCN (International Classification of Diseases [ICD]-9/10: 371.6x/H18.6x) who underwent CXL (Current Procedural Terminology [CPT]: 0402T) between 2016 and 2022 and had at least 6-month follow-up after CXL in the American Academy of Ophthalmology IRIS Registry (Intelligent Research in Sight) were included. The primary outcome was the Kaplan-Meier estimated rate of CXL failure within 3 years, defined as undergoing repeat CXL, penetrating keratoplasty (PK), or deep anterior lamellar keratoplasty (DALK) after initial CXL. Associations between CXL failure and age, sex, race, ethnicity, insurance status, allergic and atopic disease, best recorded visual acuity, and procedure laterality were evaluated using a mixed-effects Cox proportional hazards model.

Results: From 2016 to 2022, 11,731 eyes from 8568 patients underwent CXL for KCN. A total of 148 eyes (1.3%) from 143 (1.7%) patients experienced CXL failure, of which 54 eyes (52 patients) underwent PK or DALK. The estimated 3-year and 5-year CXL failure rates were 2.0% (95% confidence interval [CI], 1.5%-2.4%) and 4.5% (95% CI: 3.4%-5.6%), respectively. Multivariable Cox regression demonstrated that age <18 years (hazard ratio [HR]: 2.02; 95% CI, 1.03-3.97; P = 0.04) and unilateral CXL (HR: 1.54; 95% CI, 1.06-2.24; P = 0.02) were associated with higher CXL failure rates.

Conclusions: Approximately 1 in 50 eyes with KCN that underwent CXL had repeat treatment or keratoplasty within 3 years in a large national clinical registry. Patients younger than 18 years of age were at greatest risk.