The 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. We 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. A 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). Epi-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.

中文翻译：

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角膜胶原交联上皮与上皮关闭：系统评价和荟萃分析

该研究的目的是确定外延角膜交联 (CXL) 技术与标准外延 CXL 相比的优缺点。我们在 MEDLINE 和 EMBASE 中搜索了随机对照试验 (RCT) 和非随机干预研究 (NRSI)，并根据 Cochrane 偏倚风险工具评估了所选论文。我们将平均 Kmax 变平、未矫正和矫正远视力（UDVA 和 CDVA）的变化视为主要结果；作为次要结果，我们考虑了厚度测量值和内皮细胞密度 (ECD) 的变化。我们还调查了与治疗和治疗失败相关的不良事件。Meta 分析采用固定或随机效应模型，使用加权平均差 (MD) 和 95% 置信区间 (CI) 作为效应大小。共纳入 15 项研究，在这 15 项试验中，9 项为 RCT，6 项为 NRSI，但只有 4 项研究显示无高偏倚风险并被纳入本荟萃分析。我们的分析显示术后 CDVA 存在显着差异（MD = 0.07；95% CI 0.04 至 0.10；P < 0.001），UDVA、Kmax、中央角膜厚度（CCT）和 ECD 无显着差异（P > 0.05）。发现 Epi-on CXL 协议显着降低上皮愈合延迟 (P = 0.035) 和持续基质混浊 (P = 0.026) 的风险。Epi-on CXL 与epi-off CXL 一样有效。除了使用当前外延方案对 CDVA 的显着改善外，我们的荟萃分析表明外延和外延 CXL 对视觉、地形、厚度和内皮参数的影响相当。