Comparison of femtosecond laser-assisted cataract surgery and conventional phacoemulsification on corneal impact: A meta-analysis and systematic review

Authors: Wang H, Chen X, Xu J, Yao K.

Geographical coverage: China, the USA, the UK, Germany, Italy, India, Singapore, Spain, Australia, Denmark, Japan, Greece, Hungary, Poland, and Switzerland

Sector: Cataract surgery

Sub-sector: Treatment comparison

Equity focus: Not reported

Study population: Patients with cataract

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: Cataract remains the leading cause of vision loss worldwide, with surgery being the only effective treatment. While phacoemulsification has long been the standard, femtosecond laser-assisted cataract surgery (FLACS) was introduced in 2008 to improve surgical precision. FLACS offers benefits such as enhanced capsulotomy quality and reduced ultrasound energy use.

Corneal endothelial cells are vital for corneal clarity but are highly susceptible to irreversible damage during surgery. Previous studies comparing FLACS with conventional phacoemulsification surgery (CPS) have reported inconsistent results due to limited outcome measures and methodological limitations. Earlier meta-analyses either lacked methodological rigour or excluded important indicators such as endothelial cell morphology. With the availability of new data, this review provides a comprehensive assessment of the corneal impact following FLACS and CPS.

Objective: To compare corneal impact and function after FLACS and CPS, providing evidence for clinical decision-making.

Main findings: The review included 42 studies (23 randomised controlled trials [RCTs] and 19 comparative cohort studies) published between 2012 and 2021. These studies were conducted across 15 countries on multiple continents, with China contributing a substantial portion, followed by the USA, UK, Germany, Italy, India, Singapore, Spain, Australia, Denmark, Japan, Greece, Hungary, Poland, and Switzerland.

Endothelial cell loss (ECL%) – Meta-analysis revealed that FLACS resulted in significantly lower ECL% at all evaluated postoperative time points:

• 1–3 days: Weighted mean difference (WMD) = -3.95, 95% confidence interval (CI): -6.70 to -1.21, p = 0.005
• 1 week: WMD = -3.09, 95% CI: -5.19 to -0.98, p = 0.004
• 1 month: WMD = -3.14, 95% CI: -4.17 to -1.57, p < 0.0001
• 3 months: WMD = -4.72, 95% CI: -7.62 to -1.82, p = 0.001
• 6 months: WMD = -1.60, 95% CI: -2.70 to -0.50, p = 0.004

However, endothelial cell density (ECD) and absolute ECL showed no statistically significant differences between FLACS and CPS at most time points, although a slight ECD advantage was observed in the FLACS group at 3 months (p = 0.002).

Central corneal thickness (CCT) – FLACS was associated with significantly lower CCT at:

• 1 week: WMD = -6.17, 95% CI: -12.29 to -0.06, p = 0.05
• 1 month: WMD = -6.86, 95% CI: -10.15 to -2.04, p = 0.002

This indicates faster resolution of corneal oedema in the FLACS group. No significant differences were found at earlier (1–3 days) or later (3 and 6 months) follow-up points.

Endothelial morphology – The percentage of hexagonal cells (6A) and the coefficient of variance (CoV) did not differ significantly between FLACS and CPS at any time point, suggesting comparable long-term morphological integrity regardless of the surgical technique.

Overall, FLACS provided greater early postoperative corneal endothelial protection and promoted faster recovery of corneal clarity.

Methodology:

Searches were conducted in PubMed, Embase, and the Cochrane Controlled Trials Register to identify RCTs and high-quality prospective comparative cohort studies comparing FLACS and CPS. Studies published in English or Chinese up to 31 December 2021 were included.

Two reviewers independently screened articles, with disagreements resolved by a third reviewer. Data extraction was conducted using a standardised form by one reviewer and verified by a second reviewer. Methodological quality was assessed using the Cochrane risk-of-bias tool for RCTs and the Newcastle–Ottawa Scale for cohort studies.

Meta-analyses were performed using fixed- or random-effects models depending on heterogeneity, which was assessed using the chi-square test and the I² statistic. Sensitivity analyses were conducted to evaluate the influence of individual studies on the pooled results.

Applicability/external validity: The inclusion of studies from diverse geographical regions supports broad applicability. However, the review only considered studies published in English and Chinese, and relied solely on published data. Follow-up was limited to six months due to the lack of longer-term data.

Geographic focus: Focus

No geographical limits were applied. The included studies represented a broad international distribution, with notable contributions from China, the USA, the UK, Germany, Italy, India, Singapore, Spain, Australia, Denmark, Japan, Greece, Hungary, Poland, and Switzerland.

Summary of quality assessment: Overall, there is medium confidence in the review’s conclusion. The literature search was comprehensive, with clearly defined inclusion and exclusion criteria. Valid and reliable tools were used to assess study quality, and findings were reported. Two reviewers screened the studies, and study characteristics were presented. The meta-analysis was conducted appropriately, and sensitivity analyses were performed. However, a list of excluded studies was not provided, the review was limited to English and Chinese publications, and there was no indication that reference lists were checked or that authors were contacted for further information.