Abstract
Purpose :
Corneal ectasias are progressive, degenerative ocular diseases defined by abnormal structural changes in the cornea, leading to distortion of vision and substantial reduction in quality of life. Corneal collagen cross-linking (CXL) increases the biomechanical rigidity of the cornea and can halt ectatic processes. The established CXL protocol requires removal of the corneal epithelium, however, some surgeons have proposed transepithelial approaches to minimise adverse events and enhance recovery. The purpose of this study is to review the evidence on transepithelial CXL and compare it to the epithelium-off protocol.
Methods :
We performed a systematic review and meta-analysis. We searched 16 electronic databases including MEDLINE, Embase, and the Cochrane Library from inception until October 5, 2018 for randomised trials comparing transepithelial and epithelium-off CXL for any corneal ectasia. Our database search was supplemented with screening of the grey literature, reviewing conference proceedings, and hand-searching. Our primary outcome was change in maximal keratometry (Kmax) 12 months after treatment and we examined additional patient- and procedure-specific outcomes. We summarised our analyses by calculating relative risks (RRs) with 95% confidence intervals (CIs) for dichotomous outcomes and weighted mean differences (MDs) with 95% CIs for continuous outcomes.
Results :
10 trials (totalling 615 eyes) fulfilled our inclusion criteria. The change in Kmax at 12 months (MD 0.73, 95% CI: 0.14–1.32, p=0.02) and latest follow-up (MD 0.87, 95% CI: 0.34–1.40, p=0.001) significantly favoured conventional CXL. The mean Kmax was lower at 12 months in the conventional group than the transepithelial group. Changes in corrected distance visual acuity (MD -0.04, 95% CI: -0.11–0.02, p=0.20) and uncorrected distance visual acuity (MD -0.01, 95% CI: -0.10–0.08, p=0.78) at 12 months were comparable between the two protocols. Notably, we found a significant reduction in the incidence of complications with transepithelial CXL (RR 0.23, 95% CI: 0.06–0.95, p=0.04).
Conclusions :
Our work suggests that transepithelial CXL is safer than the conventional approach, however, its efficacy remains inferior. Surgeons should seek to further refine the transepithelial protocol to yield a procedure that is both safe and effective in arresting ectasia.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.