CXL using riboflavin with methylcellulose appears effective for keratoconus

This prospective randomized study examined the efficacy of conventional and accelerated corneal collagen crosslinking (CXL) using riboflavin with hydroxypropyl methylcellulose.

Study design

Forty patients with keratoconus (40 eyes) were randomized to either CXL using conventional 3 mW/cm² ultraviolet A (UVA) irradiation for 30 minutes or accelerated 9 mW/cm² UVA irradiation for 10 minutes. In both groups, surgeons used a solution of 0.1% riboflavin with 1.1% hydroxypropyl methylcellulose (methylcellulose–riboflavin). Uncorrected and corrected distance visual acuity and Scheimpflug tomography were performed at baseline and after 24 months.

Outcomes

Both groups showed statistically significant improvement in CDVA and maximum keratometric reading from baseline; however, there were no differences between groups. Neither group exhibited any significant changes in keratometry readings (flattest, steepest or mean) or endothelial cell density after 2 years.

Limitations

This study was limited by a lack of a dextran–riboflavin control group. There were 8 patients out of 40 that did not complete the 2-year follow-up, a dropout rate of 20% with an already small sample size. Measurements of depth of demarcation line were not undertaken in this study, though the authors reference their prior work demonstrating a deeper demarcation line with the methylcellulose-riboflavin solution.

Clinical significance

Both standard and accelerated CXL showed similar improvements in visual acuity and maximum keratometric reading 2 years postoperatively when using riboflavin with methylcellulose. Contrary to the use of riboflavin with dextran, which has been shown to cause thinning of the cornea during CXL, the potential benefit of methylcellulose–riboflavin is that it stabilizes intraoperative corneal thickness while providing a faster diffusion rate.