目的:角膜交联(CXL)手术是阻止进行性角膜扩张和保持圆锥角膜视力的首选治疗方法。使用间歇脉冲紫外(UV)光开发脉冲交联(P-CXL),以减轻在标准交联方案(C-CXL)中连续UV暴露时发生的氧水平的消耗。本研究旨在探索P-CXL在圆锥角膜治疗中的应用,并确定P-CXL中氧的可用性是否具有优于C-CXL模式的疗效。
方法:本综述按照PRISMA指南进行。与两名独立的审稿人一起搜索了几个数据库,结果是29篇论文符合审查的纳入标准,选择14人进行荟萃分析。纳入论文评估的主要结果包括最大角膜曲率测量(Kmax),矫正视力和未矫正视力(CDVA,UDVA),次要结局包括中央角膜厚度(CCT),内皮细胞计数和分界线。对ReviewManager5.4进行了统计分析,荟萃分析采用了随机效应模型,它使用逆方差权重估计原始均值的加权效应大小。
结果:在12个月时,与基线相比,P-CXL在Kmax(-0.75D;p<0.001)和CDVA(-0.10logMAR;p<0.001)方面有统计学意义的显着降低。比较研究的荟萃分析确定了Kmax的平均差异,CDVA,UDVA,12个月后的Kmean和CCT在脉冲和连续交联组之间没有统计学意义。
结论:总体而言,P-CXL可有效改善圆锥角膜的视力和角膜曲率测量结果。meta分析显示P-CXL和C-CXL之间的Kmax和CDVA差异无统计学意义。表明P-CXL具有非劣效性。然而,荟萃分析的结果受到以下事实的限制:在某些研究中,与C-CXL相比,P-CXL使用了不同的能量水平和暴露时间,这使得它不适合确定CXL的功效是否通过使用脉冲光得到改善。
结论:什么是已知的•脉冲交联(P-CXL)在使用较高能量方案时使用间歇性紫外线来防止氧气消耗,不同于标准连续交联(C-CXL)中的连续UV暴露。•这在理论上应该通过维持对交联过程至关重要的较高氧气水平来增强治疗的功效。•没有系统评价或荟萃分析直接比较P-CXL与C-CXL的疗效或安全性。最新情况•荟萃分析显示,在12个月时具有等效注量(7.2J/cm2)的P-CXL和C-CXL组之间的角膜曲率测量差异无统计学意义(Kmax-0.04屈光度;p=0.84)。•荟萃分析显示,在12个月时,P-CXL和C-CXL组具有等效注量(7.2J/cm2)的视力差异无统计学意义(CDVA-0.01logMAR字母;p=0.57)。•在较高能量CXL方案中使用间歇性脉冲呈现与在等效注量(7.2J/cm2)下的连续光暴露在统计学上相似的结果。
OBJECTIVE: Corneal crosslinking (CXL) procedures are the treatment of choice in halting progressive corneal ectasia and preserving visual acuity due to keratoconus. Pulsed crosslinking (P-CXL) was developed using intermittent pulsing ultraviolet (UV) light to mitigate the depletion of oxygen levels that occurs with continuous UV exposure in standard crosslinking protocols (C-CXL). This study aimed to explore the use of P-CXL in the treatment of keratoconus and determine whether the availability of oxygen in P-CXL carries superior efficacy outcomes as an alternative to C-CXL modalities.
METHODS: This review was undertaken in accordance with PRISMA guidelines. A search of several databases conducted with two separate reviewers resulted in 29 papers meeting inclusion criteria for the review, 14 selected for meta-analysis. Primary outcomes assessed by the included papers included maximum keratometry (Kmax), corrected and uncorrected distance visual acuity (CDVA, UDVA), and secondary outcomes included central corneal thickness (CCT), endothelial cell count and demarcation line. Statistical analyses were carried out on Review Manager 5.4 and the meta-analysis employed a random-effects model, which estimated the weighted effect size of raw means using inverse variance weights.
RESULTS: At 12 months P-CXL showed statistically significant reductions in Kmax (-0.75 D; p < 0.001) and improvement in CDVA (-0.10 logMAR; p < 0.001) compared to baseline. The meta-analysis of comparative studies determined that mean differences in Kmax, CDVA, UDVA, Kmean and CCT after 12 months were not statistically significant between pulsed and continuous crosslinking groups.
CONCLUSIONS: Overall, P-CXL is effective in improving visual acuity and keratometry outcomes in keratoconus. The meta-analysis did not show a statistically significant difference in Kmax and CDVA between P-CXL and C-CXL, indicating a non-inferiority of P-CXL. However, findings of the meta-analysis are limited by the fact that different energy levels and exposure times were used for P-CXL in comparison to C-CXL in some studies, making it unsuitable to determine whether the efficacy of CXL is improved by the use of pulsed light.
CONCLUSIONS: What is Known • Pulsed crosslinking (P-CXL) uses intermittent UV light to prevent oxygen depletion when using higher energy protocols, unlike continuous UV exposure in standard continuous crosslinking (C-CXL). • This should theoretically enhance the efficacy of the treatment by maintaining higher oxygen levels that are crucial to the cross-linking process. • There are no systematic reviews or meta-analyses directly comparing the efficacy or safety of P-CXL to C-CXL. What is New • Meta-analysis revealed differences in keratometry between P-CXL and C-CXL groups with equivalent fluence (7.2 J/cm2) at 12 months were not statistically significant (Kmax -0.04 dioptres; p = 0.84). • Meta-analysis revealed differences in visual acuity between P-CXL and C-CXL groups with equivalent fluence (7.2 J/cm2) at 12 months were not statistically significant (CDVA -0.01 logMAR letters; p = 0.57). • The use of intermittent pulsing in higher energy CXL protocols renders statistically similar outcomes as continuous light exposure at equivalent fluence (7.2 J/cm2).