Riboflavin dosing regimens safely improve visual acuity in keratoconus, corneal ectasia
Both the 2- and 5-minute riboflavin dosing regimens are safe and confer similar reduction in the maximum keratometry value in patients with keratoconus or corneal ectasia, reports a new study.
The mean reductions in maximum keratometry from baseline were 0.97 and 0.76 dioptres with 2- and 5-minute riboflavin dosing intervals at 6 months, respectively (90 percent CI for treatment difference, –0.23 to 0.66; per-protocol population).
At 6 months, both dosing intervals led to a mean improvement in corrected distance visual acuity (CDVA) of 0.07 logarithm of the minimum angle of resolution or 3.5 letters. Of the 635 study and fellow eyes examined at 6 months, 134 (21 percent) gained and 32 (5 percent) lost two or more lines of CDVA.
Three eyes (0.4 percent) developed sterile infiltrates, three (0.4 percent) had recurrent epithelial defects, and one (0.1 percent) had delayed epithelial healing with dendrites. Retreatment was performed in three eyes (0.4 percent).
A total of 510 patients with progressive keratoconus or ectasia after refractive surgery were included in this prospective, randomized, single-centre equivalence trial. One eye per patients was randomly assigned to 2- or 5- minute riboflavin dosing intervals with standard corneal crosslinking (epithelial removal and 30-minute irradiation with 3 mW/cm2 ultraviolet A light).
Block randomization led to comparable representation of keratoconus and ectasia following refractive surgery in the two treatment arms. The two one-sided test was used to assess treatment equivalence. The authors treated fellow eyes (n=207) with 5-minute dosing and considered these in the safety analysis.
The equivalent change in the topography-deprived maximum keratometry value from baseline to 6 months was the primary hypothesis. A ±0.75-dioptre margin of equivalence for the treatment difference between 2- and 5-minute dosing regimens was considered clinically relevant.
The authors also assessed adverse events and changes from baseline to 6 months in CDVA, uncorrected distance visual acuity and minimum corneal thickness.