Corneal collagen crosslinking (CXL), first used on humans about 20 years ago, is quickly becoming an important part of the keratoconus treatment protocol. Despite its success, researchers continue to search for ways to improve the standard, or Dresden, protocol. Even with up to eight different combinations of CXL, the tried-and-true Dresden protocol still provides the best changes of controlling keratoconus progression.  

Researchers examined the one-year outcomes for 670 eyes of 461 patients with progressive keratoconus treated with various CXL techniques, including: epi-on or epi-off, conventional 3mW/cm² or accelerated 9mW/cm² and seven different riboflavin formulations. Standard CXL served as the reference for the study. 

When comparing all eight combinations, the researchers found the epi-on technique performed significantly worse based on maximum keratometry (Kmax) and mean keratometry (Kmean) readings compared with those who had the standard CXL protocol. Likewise, patients treated with a specific riboflavin formulation called Meran, and those who underwent an accelerated protocol, also experienced worse Kmax and Kmean at the one-year follow-up.

The Meran riboflavin group also had poorer post-op corrected distance visual acuity; none of the other combinations showed any statistical difference in visual acuity from the reference group. 

Although only 2.1% of all treated eyes required retreatment, most of those 2.1% were in the epi-on group, the researchers found. 

Even if the standard protocol is less comfortable and more time-consuming that some of the newer techniques, “we believe that epi-off CXL combined with a UVA intensity of 3 mW/cm² is the preferred treatment protocol for patients with progressive keratoconus,” the researchers concluded in their paper on the study.