Effects of SMILE on intraocular pressure and corneal biomechanics: a systematic review and meta-analysis

Abstract

Abstract Purpose Small incision lenticule extraction (SMILE) is a popular flapless refractive procedure for myopia and myopic astigmatism, although postoperative corneal biomechanical changes may affect intraocular pressure measurements and glaucoma assessment. This systematic review and meta-analysis aimed to quantify the postoperative underestimation of IOP and changes in corneal biomechanical parameters following SMILE. Materials and methods A comprehensive literature search of PubMed, Cochrane Library, ScienceDirect, and Scopus databases was performed up to April 30, 2026, according to PRISMA guidelines. Observational studies reporting preoperative and postoperative IOP measurements after SMILE using Goldmann applanation tonometry (GAT), Ocular Response Analyzer (ORA), or Corvis ST were included. Secondary outcomes included changes in corneal hysteresis (CH) and corneal resistance factor (CRF). Results Seventeen studies involving 1177 eyes were analyzed. Postoperative IOP was significantly reduced across all tonometric modalities. The pooled mean reduction was greatest with GAT (MD: 3.47 mmHg; 95% CI 2.85–4.10), followed by ORA (MD: 2.50 mmHg; 95% CI 2.06–2.94) and Corvis ST (MD: 1.52 mmHg; 95% CI 0.62–2.42) (all p < 0.001). Significant postoperative reductions were observed in CH (MD: 1.84 mmHg) and CRF (MD: 3.01 mmHg), indicating decreased corneal biomechanical stability after SMILE. Conclusions SMILE leads to significant underestimation of IOP measurements and measurable biomechanical weakening of the cornea. Clinicians should interpret postoperative IOP values cautiously, even when using biomechanically corrected tonometric devices.