A meta-analysis of studies comparing standard and transepithelial corneal cross-linking showed that both techniques are safe, but the standard procedure was more effective at decreasing maximum keratometry.
A systematic search through PubMed, the Cochrane Library and Embase identified 1,018 potentially relevant studies, of which only three met the inclusion criteria established by the authors. They included 244 eyes, with 111 eyes treated by standard CXL and 133 eyes treated by transepithelial CXL. The follow-up was from 12 to 24 months.
Maximum keratometry data favored standard CXL, with significantly more reduction in Kmax. Keratometry, the authors noted, indicates the progression or improvement of keratoconus, and the weaker effect of the transepithelial procedure is likely to be the consequence of the lesser riboflavin penetration beyond the epithelial barrier. Because CXL happens through oxygen-dependent pathways, the epithelium may also act as a barrier to oxygen diffusion to the stroma.
“Considering all these factors, the actual transepithelial cross-linking effect may be less deep and less complete at all levels compared to what occurs with equivalent dosing with the epithelium removed,” the authors wrote.
As far as vision gain was concerned, the transepithelial CXL group of eyes had better corrected distance visual acuity improvement, but uncorrected distance visual acuity gain was similar in both groups.
Corneal thickness on the thinnest point was measured to assess safety. With both methods, a similar reduction in corneal thickness, within safety limits, was reported.
The authors said that the power of assessment of this analysis was limited by the low number of studies included and that more pragmatic randomized controlled trials are needed to draw conclusions. – by Michela Cimberle
Disclosures: The authors report no relevant financial disclosures.