By Michael G. Haas, MD
This blind, randomized, prospective, bilateral study investigated the efficacy of corneal collagen cross-linking at halting the progression of keratoconus. Not surprisingly, the results after 18 months of follow-up provide further evidence that cross-linking corneal collagen fibers with riboflavin and ultraviolet A appears to stop the progression of keratoconus without significant side effects, and improves visual and topographic parameters in some eyes. We are long overdue in the United States to have this phenomenal treatment approved by the Food and Drug Administration.
The authors conducted this study, which was published in November in the British Journal of Ophthalmology, due to the paucity of randomized prospective clinical studies on this topic. They designed the study to overcome some problems that can be encountered during clinical studies of keratoconus, including accurate assessment of outcome measures, the influence of contact lens wear and the variability in the natural history of the condition.
They recruited 24 subjects with early to moderate bilateral keratoconus with reported recent progression who were willing to remove hard lenses for three weeks prior to examinations. One eye of each subject was randomly assigned to undergo cross-linking following epithelial removal with riboflavin 0.1% and ultraviolet A (370 nm at 3 mW/cm2), with the other eye remaining untreated as a control during the follow-up period.
At 18 months, Orbscan II 3 mm, 5 mm keratometry and simulated astigmatism and cone apex power and wave-front measurements (Keraton Scout), including root mean square, coma and pentafoil, showed significant reductions from baseline in treated compared with untreated eyes (P = 0.04). In treated eyes, BSCVA was improved (P = 0.01), and Orbscan II-simulated keratometry (P < 0.001), 3 mm keratometry (P = 0.008), simulated astigmatism (P = 0.007), cone apex power (P = 0.002), root mean square, coma, spherical aberration, secondary astigmatism and pentafoil (P = 0.05) had decreased from baseline. No treated eyes appeared to progress during follow-up, with five (23 percent) showing consistent improvements. The only complication attributable to the treatment was transient recurrent corneal erosions in one eye.
In contrast, in untreated eyes there was significant worsening of refractive astigmatism. Three untreated eyes (14 percent) showed consistent deterioration in all parameters, which suggested progression. While there were improvements in BSCVA in both groups, the authors say this may be due to patients undergoing repeated refractive examinations every few months.