Corneal Thickness Effects using Riboflavin/Dextran versus Hypotonic Riboflavin during Corneal Collagen Crosslinking

Abstract

Purpose: : To investigate the use of Riboflavin 0.1% in 20% dextran solution versus its hypotonic formulation during ultraviolet light exposure in corneal collagen crosslinking (CXL) for keratoconus (KC) and ectasia.

Methods: : In a prospective, controlled clinical trial, 21 eyes underwent CXL for KC or ectasia (14 and 7 eyes respectively). CXL was performed using the UVX system (Peschke Meditrade GmbH). All eyes underwent pre-treatment with Riboflavin 0.1% in 20% dextran solution every 2 minutes for 30 minutes. If the cornea was <400 microns thick, then hypotonic riboflavin was administered until the cornea swelled beyond 400 microns. Eyes were then randomized to receive either Riboflavin 0.1%/dextran (RIBO) or hypotonic (HYPO) riboflavin every 2 minutes for the 30 minute duration of UV exposure (UVA 365nm light for 30 minutes at an irradiance of 3mW/cm²). Corneal thickness was measured using ultrasound pachymetry (Sonogage).

Results: : Mean initial corneal thickness was 435.7µm (ranging 318 to 526) and 445.4µm (ranging 327 to 532) for RIBO and HYPO eyes respectively. Following debridement, mean thickness was 392.1µm (ranging 304 to 463) for RIBO eyes and was 402.9µm (ranging 330 to 454) for HYPO eyes. After pre-treatment with riboflavin 0.1%/dextran, mean thickness was 417.2µm (ranging 323 to 535) for RIBO eyes and 417.0µm (ranging 317 to 468) for HYPO eyes. Three eyes (2 RIBO; 1 HYPO) required the use of hypotonic riboflavin to achieve the minimum corneal thickness of 400µm prior to UV irradiance. Mean corneal thinning during UV exposure was 133.8µm (SD 33.2)(p<0.0001) and 94.6µm (SD 48.0)(p=0.002) for RIBO and HYPO eyes respectively. Mean corneal thinning with UV exposure was significantly greater for RIBO eyes compared to HYPO eyes (p=0.04) At the conclusion of CXL treatment, mean thickness was 294.4µm (ranging 238 to 345) and 335.3µm (ranging 271 to 398) in RIBO and HYPO eyes respectively.

Conclusions: : The use of hypotonic riboflavin appears to better maintain consistent corneal thickness during UV administration. Whether better maintenance of corneal thickness potentially may result in improved consistency, reproducibility and/or safety of the CXL procedure requires further follow-up.

Clinical Trial: : http://www.clinicaltrials.gov NCT01152541

Keywords: keratoconus • clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled clinical trials