Epipolis-laser in situ keratomileusis versus photorefractive keratectomy for the correction of myopia: a meta-analysis

Methodological quality of the review: Medium confidence

Author: Wenjing Wu; Yan Wang; Lulu Xu

Region: USA, Korea, UAE, Ireland

Sector: Myopia

Subsector: Myopia treatment

Equity focus: No

Study population: Adults

Type of programme: Hospital

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: Currently, LASIK is the main procedure of corneal refractive surgery to treat myopia. However, surface corneal refractive surgery is still an effective and safe choice for some special patients, especially for corneal epithelial basement membrane lesions, thin cornea with high myopia, and patients with flap complications post-LASIK. This procedure has become popular for correcting refraction errors. However, Epi-LASIK cannot avoid pain or haze. It was reported that patients who underwent Epi-LASIK showed superior refractive efficacy compared to PRK. However, several previous studies suggested that Epi-LASIK and PRK did not show any difference in terms of efficacy and predictability. Meanwhile, several studies compared the side effects, such as pain and haze, between Epi-LASIK and PRK; the results were different from study to study.

Objectives: This meta-analysis aims to examine some possible differences in the efficacy, predictability and side effects, such as pain and haze, between these two techniques.

Main findings: Seven articles with a total 987 eyes were suitable for the meta-analysis. The results included efficacy outcomes (percentage of eyes with 20/20 uncorrected visual acuity post-treatment), predictability (proportion of eyes within ±0.5 D of the target refraction), epithelial healing time, and the incidence of significant haze and pain scores after surgery. There is no statistical significance in the predictability between Epi-LASIK and PRK; the risk ratio (RR) is 1.03, 95 % confidence interval (CI) [0.92, 1.16], P=0.18; with respect to efficacy, the odds ratio is 1.43, 95 % CI = [0.85, 2.40], P=0.56 between Epi-LASIK and PRK, there is no statistical significance either. The epithelial cell layer healing time and the pain scores and the incidence of significant haze showed no significance between these two techniques, although more pains can be found in Epi-LASIK than PRK at the early-stage post-operation. According to the above analysis, Epi-LASIK has good efficacy and predictability as PRK. In addition, both techniques have low pain scores and low incidence of significant haze.


As Epi-LASIK was a relatively new operation technique, there were limited literatures reporting the comparisons between Epi-LASIK and PRK. Therefore, the prospective and retrospective clinical studies were also included for the meta-analysis. In addition, outcome measures based on a standardised format proposed by Reinstein and Waring, and efficacy measures, used the standard according to the United States Food and Drug Administration (FDA) refractive surgery clinical trials. If the outcome was not possible for all, one of the outcome measures was required at least.

Reports of clinical trials comparing the postoperative outcomes of Epi-LASIK and PRK were identified through a systematic search in PubMed, the Cochrane Library and Embase. The language was restricted to English. Epi-LASIK, epipolis-laser in situ keratomileusis, PRK, and photorefractive keratectomy were the terms for sensitive searches. Also, the reference lists of every article were scrutinised for information about additional trials. Analysis: Related data included study population characteristics (age, eyes and location), design methods, outcome variables, and duration of the study. The quality of each article was assessed by the Jadad et al. score with a scale of 0 to 5. The refractive outcome was compared with the efficacy and predictability. Efficacy is the percentage of all eyes in which the target refraction was zero that reached uncorrected distance visual acuity (UCVA) equal or higher than 20/20. As the variety of follow-up time, which ranged from four days to 12 months, data provided at the end of the follow-up was used for comparison. For the continuous outcomes, we calculated the weighted mean difference (WMD) with 95 % confidence interval (CI). A pooled odds ratio (OR) was calculated for the dichotomous outcomes. Heterogeneity was assessed using the chi-square test and I2. P value less than 0.05 was considered statistically significant. All statistical analyses were performed by RevMan software (version 5.0, Oxford, United Kingdom).

Applicability/external validity: Regarding external validity, the authors reported some important limitations which need to be considered when applying the results to other settings: first, language and type of publication restriction; second, the follow-up durations were different among studies; third, changes in technology may impact the results significantly, which is a problem with meta-analysis of a surgical technique in evolution.

Geographic focus: They used the United States Food and Drug Administration (FDA) refractive surgery clinical trials for efficacy measurement. This efficacy measurement can be different according to setting (Europe, Asia, etc.).

Summary of quality assessment: Overall, medium confidence was attributed to the review findings. The review has a low robustness – we noted that there were language and type of publication restrictions which led to just seven studies being included. In addition, the authors did not specify the period of search and also no clear mention was made of the number of researchers who did the studies screening and data extraction.

Publication Source:

Wu W, Wang Y, Xu L. Epipolis-laser in situ keratomileusis versus photorefractive keratectomy for the correction of myopia: a meta-analysis. Int Ophthalmol. 2015 Oct;35(5):757-63.