Abstract
BackgroundThe purpose of the study was to determine the advantages and disadvantages of epi-on corneal cross-linking (CXL) techniques compared with standard epi-off CXL.MethodsWe searched MEDLINE and EMBASE for randomized controlled trials (RCTs) and non-randomized studies of interventions (NRSIs) and we evaluated the selected papers according to the Cochrane risk of bias tool. We considered, as primary outcomes, average Kmax flattening, changes in uncorrected and corrected distance visual acuity (UDVA and CDVA); as secondary outcomes, we considered changes in pachymetry values and endothelial cell density (ECD). We also investigated adverse events related to the treatments and treatment failure. Meta-analysis was conducted with a fixed or random-effects model using weighted mean difference (MD) with 95% confidence interval (CI) as the effect size.ResultsA total of 15 studies were included and among these 15 trials, 9 were RCTs and 6 were NRSIs, but only 4 studies showed no high risk of bias and were included in this meta-analysis. Our analysis revealed significant postoperative differences in CDVA (MD = 0.07; 95% CI 0.04 to 0.10; P < 0.001), and no significative differences in UDVA, Kmax, central corneal thickness (CCT) and ECD (P > 0.05). Epi-on CXL protocol was found to be significantly less prompt to have risks of delay in epithelial healing (P = 0.035) and persistent stromal haze (P = 0.026).ConclusionEpi-on CXL is as effective as epi-off CXL. Except for a higher significant improvement in CDVA with current epi-on protocols, our meta-analysis demonstrates that epi-on and epi-off CXL have comparable effects on visual, topographic, pachymetric, and endothelial parameters. Epi-on CXL has clinical advantages in terms of comfort and avoidance of complications as it reduces the risk of developing delay in epithelial healing and persistent stromal haze.
Highlights
The purpose of the study was to determine the advantages and disadvantages of epi-on corneal crosslinking (CXL) techniques compared with standard epi-off Corneal collagen cross-linking (CXL)
We investigated adverse events related to the treatments and treatment failure, such as keratoconus progression, loss of ≥ 2 lines of corrected distance visual acuity (CDVA), delay in epithelial healing, persistent stromal haze, sterile infiltrates and infections
Characteristics of included studies We identified a total of 15 studies where epi-on CXL outcomes of progressive keratoconus patients were compared to epi-off CXL outcomes
Summary
The purpose of the study was to determine the advantages and disadvantages of epi-on corneal crosslinking (CXL) techniques compared with standard epi-off CXL. After anesthetizing the eye, the central 8 mm of the corneal epithelium is removed to expose the collagen-rich stroma and riboflavin solution (0.1% riboflavin-5-phosphate and 20% dextran T-500) is applied to the surface of the cornea both 30 min before irradiation and at 5 min intervals during a 30 min exposure to 370 nm UVA with a fluence of 3 mW/ cm and a total irradiation dose of 5.4 J/cm2 [7]. The downside of epithelial removal is that it causes significant pain and discomfort in the early postoperative period; epi-off CXL carries a small risk of viral reactivation, haze, melting, infectious ulceration and the development of permanent stromal scars [8]. Considering these situations, several variations of the standard CXL procedure have been proposed since its introduction. To improve riboflavin penetration into the stroma via the intact epithelium, several approaches have been used and investigated to encourage riboflavin penetration to the stroma [9]
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