Corneal collagen crosslinking (CXL) has been a success for years—but it’s a lengthy procedure. Current CXL protocol development efforts involve reducing overall treatment time while maintaining ability to halt the progression of keratoconus.

A recent study compared the relative 12-month efficacy of the standard Dresden protocol (3mW/cm² for 30 minutes, 5.4 J/cm²) with an accelerated protocol with the equivalent total irradiance (9mW/cm² for 10 minutes, 5.4 J/cm²) and an accelerated protocol with an increased total irradiance (30mW/cm² for 4 minutes, 7.2 J/cm²). The researchers found that all protocols had similar visual acuity, refractive outcomes and proportion of total patients who experienced stabilization of disease at 12 months; however, more parameters showed significant improvements at 12 months with the standard protocol compared with either accelerated protocol and had significantly better improvements in some of the keratoconus indices.

When determining whether changes in any variable correlated well with changes corrected distance visual acuity (CDVA) outcomes, only asphericity, Kmean and central keratoconus index were satisfactorily correlated with changes in CDVA, and neither was consistently correlated for any protocol. Also, Kmax had poor correlation with CDVA in the study.

Researchers propose that the lack of correlation between measured variables and change in CDVA could be that the currently available tools measure changes in the anterior stroma that are indirect consequences of the actual biomechanical disease process. They believe their results help highlight the need for not only a better understanding of the effects of accelerated crosslinking protocols but also an optimal metric to evaluate such effects consistently in vivo. For now, they believe it is important to consider many different variables other than just Kmax when studying different CXL protocols.