Independent-effect comparison of five crosslinking procedures for Progressive Keratoconus based on Keratometry and the ABCD Grading System using Generalized Estimating Equations (GEE)

Abstract

AbstractPurposeCorneal collagen crosslinking (CXL) is an effective treatment for progressive keratoconus. Multiple CXL modalities are clinically available. The present study compared the 1 year outcomes of five types of CXL procedures for progressive keratoconus in a Chinese population using generalized estimating equations (GEE).MethodsThis retrospective study included 239 eyes in 171 patients with keratoconus who underwent CXL and were followed up for 1 year. Five CXL procedures were assessed, includingAccelerated Transepithelial CXL,Iontophoresis CXLfor 10 min, CXL plus phototherapeutic keratectomy (CXL-plus-PTK),High-Fluence Accelerated CXL, andAccelerated CXL. Patients treated with theAccelerated CXLprocedure represented the reference group. Primary outcomes were visual acuity change, spherical equivalence, endothelial cell density, mean keratometry (Kmean), maximum keratometry (Kmax), minimum corneal thickness (MCT), and the ABCD Grading System, consisting ofA(staging index for ARC; ARC = anterior radius of curvature),B(staging index for PRC, PRC = posterior radius of curvature), andC(staging index for MCT) values 1 year postoperatively compared to baseline. Secondary outcomes were corrected GEE comparisons from each procedure versus theAccelerated CXLgroup.ResultsTheAccelerated Transepithelial CXLgroup had lower performance than theAccelerated CXLgroup according to Kmeanand Kmax. TheCXL-plus-PTKgroup performed significantly better than the reference group as reflected by Kmax(β = -0.935,P = 0.03). However, theCXL-plus-PTKgroup did not perform as well forBandC, and theIontophoresis CXLgroup performed better forC.ConclusionsTheCXL-plus-PTKprocedure was more effective than theAccelerated CXLprocedure based on Kmax, and theIontophoresis CXLprocedure performed better on theCvalue based on the ABCD Grading System.