Visual differences in topography-guided versus wavefront-optimized LASIK in the treatment of myopia: a meta-analysis

Authors: Hu PC, Li L, Wu XH, Li YQ, Li KW.

Geographical coverage: China, India, South Korea, Turkey and Egypt.

Sector: Biomedical

Sub-sector: Treatment

Equity focus: None specified

Study population: Adult patients undergoing corneal surgery (TG-LASIK or WFO-LASIK.

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: LASIK is the most common surgery for myopia correction, but it falls short in meeting modern visual quality standards. TG-LASIK, used for abnormal corneal astigmatism and eccentric ablation, has proven safe and effective for primary surgeries. WFO-LASIK is also employed to enhance patients’ visual quality. Recent studies have compared these two customised ablation methods for myopia treatment, but their small sample sizes and contradictory results limit their conclusions.

Objectives: To investigate the potential differences between topography-guided (TG) and wavefront-optimised (WFO) laser in-situ keratomileusis (LASIK) for the treatment of myopia.

Main findings:

Authors found that both TG-LASIK and WFO-LASIK are safe, effective, and predictable for correcting myopia. TG-LASIK may produce fewer aberrations and is more precise than WFO-LASIK.

In total, eleven studies were included in the review: eight prospective comparative studies, two RCTs and one retrospective study. These enrolled a total of 1,425 eyes in 11 studies, of which 701 eyes (49.19%) were TG-LASIK, and 724 eyes (50.81%) underwent WFO-LASIK. The follow-up period after surgery was three to six months. Included studies were conducted in China (4), India (3), South Korea (2), Turkey (1), Egypt (1).

Based on the Jadad scale criteria, the authors identified two randomised controlled trials (RCTs) as high quality, with scores of 3 or above. The quality of the cohort was assessed using the Newcastle-Ottawa Scale (NOS). All cohorts had a total score exceeding 5, indicating they are considered high-quality research.

The authors found no significant differences between TG and WFO ablation in terms of the proportion of eyes achieving an uncorrected distance visual acuity (UCVA) of 20/20 or better (p = 0.377), gaining one line or more (p = 0.05), postoperative cylinder (p = 0.40), vertical coma (p = 0.593), and horizontal coma (p = 0.957). Following TG ablation, a significantly higher proportion of patients’ eyes had postoperative refraction within ±0.5 dioptre of the target refraction compared to those undergoing WFO (p = 0.003). In contrast to the WFO group, the TG group had a lower manifest refraction spherical equivalent (MRSE; p = 0.000) and better UCVA (p = 0.005). The TG group also had significantly lower higher-order aberrations (HOAs; p = 0.000), spherical aberration (p = 0.000), and coma (p = 0.000). The cumulative meta-analysis showed that the proportion of eyes achieving UCVA of 20/20 or better, postoperative refraction within ±0.5 dioptre, and MRSE remained steady between the two groups. No publication bias was detected.

Authors note the need for additional randomised, prospective contralateral eye studies to measure the long-term differences between TG and WFO treatments.

Methodology:

Inclusion criteria set by the authors were as follows: 1) RCTs and non-randomised comparative studies Non-RCFs; 2) adult patients with the stable refractive state, no systemic disease likely to affect or cause abnormal wound healing, no history of ophthalmic surgery; 3) patients undergoing corneal surgery (TG-LASIK or WFO-LASIK); 4) a minimum follow-up period of three months; and 5) original clinical publications with accessible data. There were no language or date restrictions.

Two authors independently searched PubMed, Cochrane, Web of Science, EMBASE and Chinese databases (i.e., CNKI, CBM, Wanfang and VIP) to compare the records of TG-LASIK and WFO-LASIK in the treatment of myopia, and the last search was on 18 August 2020. Titles and abstracts were selected independently by two reviewers. Differences between reviewers were resolved through deliberations.

Two researchers independently extracted data and performed a quality assessment of the articles using standardised forms. The quality of RCTs was measured by the Jadad scale. Non-RCTs were evaluated using the NOS. The NOS evaluated article quality. The total score was 9, and studies with a score of 6 or higher were deemed to be of high quality.

Data was statistically analysed using Stata. Continuous variables were calculated by weighted mean difference (WMD) or standard mean difference (SMD), and dichotomous outcomes by odds ratio (OR). A 95% confidence interval (CI) was used, with outcomes deemed statistically significant when p < 0.05. In cases of heterogeneity (I2 > 50% or p < 0.10), a random effects model (REM) was used, otherwise a fixed-effects model (FEM) was adopted. Subgroup analysis was conducted for different follow-up periods. Publication bias was assessed using funnel plots, Egger tests, Harbord tests, and Peters tests. Sensitivity analysis was performed to evaluate result robustness by removing individual studies and assessing their impact on pooled estimates. A cumulative meta-analysis was also conducted to assess the effect of time on result robustness.

Applicability/external validity: The authors acknowledge several constraints that could restrict the relevance of the study, such as the consideration of only a brief follow-up period.

Geographic focus: All included studies were undertaken in LMICs. Authors do not specifically consider how findings may vary in different geographic contexts.

Summary of quality assessment:

The methods used to identify, include, and critically appraise studies were generally robust, with two authors undertaking all key activities. However, no attempt was made to include unpublished material in the review or to contact relevant experts. The approach to the analysis of the data was generally thorough; however, there was no discussion of unit of analysis issues, as pertaining to the inclusion of multiple eyes or RCTs. In addition, no analysis was undertaken on the basis of the quality and risk of bias of the included studies – although we appreciate that this would have been difficult in practice, given the small number of studies involved. For these reasons, we attributed a medium confidence in the findings of this review.