Laser-assisted subepithelial keratectomy versus epipolis laser in situ keratomileusis for myopia: A meta-analysis of clinical outcomes

Methodological quality of the review: Medium confidence

Author: Daizong Wen, Jinhai Huang, Xuexi Li, Giacomo Savini, Yifan Feng, Qiaoya Lin MD, Qinmei Wang

Region: Turkey, Hong Kong, Ireland, USA, Spain, Germany

Sector: Myopia

Subsector: Myopia treatment comparaison

Equity focus: No

Study population: Adults

Type of programme: Treatment based

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: Photorefractive keratectomy was the first technique to employ the ophthalmic excimer laser for correction of refractive errors, and it has proved to be a predictable and safe method. Laser-assisted subepithelial keratomileusis (LASEK) and epipolis LASIK (Epi-LASIK) are recent advanced surface ablations that were developed to combine the advantages of photorefractive keratectomy and LASIK. Although many studies have compared the relative benefits of LASEK versus Epi-LASIK in myopic patients, the results are controversial. Some indicated an advantage for either LASEK or Epi-LASIK, whereas others found no significant differences between these two procedures.

Objectives: This study aimed to detect any differences in safety, efficacy, predictability, epithelial healing time and corneal haze formation between the two approaches.

Main findings: This review included six studies describing a total of 517 eyes with myopia ranging from 0 to -9.00 D (257 assigned to the LASEK group and 260 to the Epi-LASIK group). Three studies were RCTs, and the others were non-randomised cohort studies. Of the six studies, five used on-flap technique in the procedure, another one included both on-flap and off-flap groups, from which we only extracted the data of on-flap groups. The Jadad scale indicated a good quality of studies. Efficacity: Analysis showed no difference between the LASEK and Epi-LASIK groups. Predictability: there was no statistically significant difference between the LASEK and Epi-LASIK groups. Safety: there was no statistically significant difference between the LASEK and Epi-LASIK groups. Regarding healing time of the corneal epithelium, significant heterogeneity between study results was detected (I²=77%), but there was no significant difference between the LASEK and Epi-LASIK groups. Pain perception: a meta-analysis was not performed on these studies because of the different follow-up periods and the diversity of outcomes.

Methodology:

Inclusion criteria: i) study design: randomised, controlled studies (RCTs) and non-randomised, observational studies; ii) population: patients aged 18 to 60 years with any degree of myopia and of up to three dioptres (D) of astigmatism, no significant co-pathology, no history of previous ocular surgeries, or no systemic disease associated with impaired or abnormal wound healing; iii) intervention: eyes treated by LASEK versus Epi-LASIK, with the epithelial flap repositioned after ablation.

Authors conducted a search on Medline, Embase and the Cochrane Library for studies describing the comparative outcomes of LASEK and Epi-LASIK. Also, the search was performed in World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov to retrieve ongoing trials. The search was limited to English language papers. According to the current standard for reporting refractive surgery, efficacy, predictability and safety were assessed as the primary outcome parameters in our study. Two reviewers (DZW, JHH) independently extracted data and independently assessed the methodological quality. The quality of the trials was assessed according to Jadad scale for randomised, controlled studies and Newcastle-Ottawa Scale (NOS) for non-randomised cohort studies. Data for outcomes was entered into and analysed separately by the RevMan software (V 5.1, Cochrane Collaboration, Oxford, UK). Ninety-five per cent confidence intervals (CIs) were calculated for summary estimates. A P value less than 0.05 was considered statistically significant. Heterogeneity between studies was assessed by the chi-square and I² statistics.

Applicability/external validity: Regarding external validity, the authors just included six trials, which is not enough to analyse the outcome and very easy to produce bias. On the bias, the author reports some limitation which need to consider: the diversity of follow-up time ranging from three months to one year, which may be inadequate to determine the final visual outcomes from the procedures. Another limitation of this meta-analysis was the inclusion of non-randomised and retrospective observational studies, leading to potential bias and overestimating the effects of treatment. Furthermore, in this study, we only included on-flap procedures because we assumed that the different treatment of epithelial flaps may cause a potential influence to the combination of outcomes.

Geographic focus: Not discussed.

Summary of quality assessment:

Overall medium confidence was attributed in the conclusions about the effects of this review. Although authors used appropriate methods to analyse findings of included studies, methods used to identify studies for inclusion and the screening process were not rigorous enough to ensure biases were avoided.