Comparative Contralateral Randomized Clinical Trial of Standard (3 mW/cm 2 ) Versus Accelerated (9 mW/cm 2 ) CXL in Patients With Down Syndrome: 3-Year Results

Abstract

PURPOSE: To compare the long-term results of accelerated corneal cross-linking (CXL) (9 mW/cm 2 , 10 min) with standard CXL (3 mW/cm 2 , 30 min) in patients with Down syndrome who had keratoconus. METHODS: In this contralateral randomized clinical trial, 27 patients with Down syndrome aged 15.78 ± 2.46 years (range: 10 to 19 years) were enrolled. CXL was performed using the KXL System (Avedro, Inc) under general anesthesia, and patients were followed up for 3 years. The main outcome measure was a change in average keratometry in the 3-mm zone around the steepest point (zonal Kmax-3mm). Secondary outcomes were changes in Corvis ST (Oculus Optikgeräte GmbH) biomechanical parameters and vision, refraction, and corneal tomography measurements. RESULTS: Mean 3-year changes in zonal Kmax-3mm were not significantly different between the accelerated and standard groups (−0.06 ± 0.75 and −0.35 ± 0.94 diopters [D], respectively, P = .727). Despite the contralateral design of the study, based on most baseline biomechanical indices, corneas in the standard group were weaker before treatment. The standard group also showed significantly fewer 3-year changes in the stress-strain index (−0.11 ± 0.21 vs −0.30 ± 0.32), integrated radius (+0.99 ± 3.48 vs +3.14 ± 2.84), and deformation amplitude ratio-2mm (−1.38 ± 1.33 vs +0.30 ± 1.75) (all P < .0167). Corneal stiffness in the accelerated group was stable for 2 years, and the decline mainly occurred during the third year. CONCLUSIONS: In young patients with Down syndrome who had keratoconus, accelerated and standard CXL showed a similar flattening effect. Standard CXL is better able to maintain corneal stiffness in weaker corneas. With accelerated CXL, despite stable results for 2 years, there was decreased corneal stiffness in the third year. Longer follow-up periods are warranted to study the decreased efficacy on keratoconus progression. [ J Refract Surg . 2022;38(6):381–388.]