摘要： Importance: Intraocular pressure is often reduced following cataract surgery. Postoperative changes in corneal stiffness are likely to be at least partly responsible for any reduction in IOP measured with applanation tonometry. Background: To determine the effect of cataract surgery and corneal incision size on corneal biomechanics. Design: Prospective randomised trial Participants: One-hundred prospectively enrolled patients qualifying for cataract surgery Methods: Participants were randomised to clear corneal incisions with a 2.20 or 2.85mm keratome. Corvis-ST tonometry and dynamic corneal response measurements were obtained preoperatively, and 3-months postoperatively. Multiple regression analysis was completed using R software. Main Outcome Measures: Corvis-ST biomechanical parameters Results: Ninety-three eyes of 93 patients were included in the final analysis. Mean Corvis-ST biomechanically corrected intraocular pressure decreased by 3.63 mmHg postoperatively (95% confidence interval = 2.97 – 4.35, P ≤0.01), and central pachymetry increased by 6.96μm (4.33 – 9.59, P ≤0.01). Independent of IOP and pachymetry changes, mean (± standard error) corneal first applanation stiffness parameter reduced by 9.761±3.729 (P = 0.01) postoperatively. First applanation velocity increased by 0.007±0.002ms, second applanation velocity increased by 0.012±0.004ms (P ≤0.01), the first applanation deformation amplitude increased by 0.008±0.002mm (P ≤0.01), and the deflection amplitude at highest concavity increased by 0.030±0.069 (P ≤0.01). There were no significant differences between different incision size groups. Conclusions and Relevance: Corneal stiffness is reduced three months following cataract surgery and is associated with falsely low intraocular pressure measurements. This finding may be important for glaucoma patients and in particular when assessing the effectivity of Minimally Invasive Glaucoma Surgery devices.