Comparison of VISUMAX 800 and VISUMAX 500 Femtosecond Laser Systems for Myopia: A Systematic Review and Meta-Analysis

Objectives: The VISUMAX 800 (Carl Zeiss Meditec) is the second-generation femtosecond laser for small incision lenticule extraction (SMILE), featuring faster pulse rates, automated cyclotorsion compensation (OcuLign), and automated centration (CentraLign) versus the VISUMAX 500. This systematic review and meta-analysis compared their clinical outcomes in myopia correction. Methods: Following PRISMA 2020 guidelines, we searched PubMed, EMBASE, and Web of Science through March 2026 for studies comparing the two platforms in myopia or myopic astigmatism with extractable data. Primary outcomes were predictability (SE ± 0.50 D) and astigmatism (CYL ≤ 0.50 D). Secondary outcomes included UDVA ≥ 20/20, safety (CDVA loss ≥ 1 line), R² values, surgically induced astigmatism, axis alignment (±5°), and higher-order aberrations. Risk of bias was assessed using the ROBINS-I tool for all included studies, as no randomized controlled trials were available. Publication bias was evaluated via funnel plots, Egger's test, and Begg's test, with appropriate caution noted regarding the limited number of studies. Sensitivity analysis used the leave-one-out method. Results: Nine studies (1672 eyes: 646 VISUMAX 800, 1026 VISUMAX 500) were included. For SE ± 0.50 D, the pooled risk ratio (RR) was 1.065 (95% CI: 0.997-1.137, p = 0.061) with substantial heterogeneity (I² = 64.7%, p = 0.004). For CYL ± 0.50 D (eight studies, 1585 eyes), the pooled RR was 1.022 (95% CI: 0.978-1.068, p = 0.333, I² = 51.7%). Astigmatism axis within ±5° significantly favored VISUMAX 800 (RR = 1.157, 95% CI: 1.071-1.250, p = 0.0002, I² = 0%). No statistically significant differences were observed for UDVA ≥ 20/20, safety, SEQ R², cylinder R², TIA, SIA, total HOAs, spherical aberration, or coma RMS. Publication bias tests showed no significant asymmetry for the primary outcomes, though these tests have limited power with fewer than 10 studies. ROBINS-I assessments classified most studies as having "serious" risk of bias due to their non-randomized designs. Conclusions: Both platforms yield comparable predictability, safety, and visual outcomes. VISUMAX 800 offers superior astigmatism axis alignment, likely due to automated compensation and centration. The borderline SE predictability warrants further randomized investigation.