A method for measuring the intraocular pressure (IOP) of an eye docked to an ophthalmic surgical laser system via a patient interface assembly. While the eye is docked to the laser system, and as the vertical force exerted on the eye by the patient interface fluctuates as the patient breaths and moves, the amount of corneal deformation is continuously measured by an optical coherence tomography device of the laser system and the force exerted on the eye is continuously measured by force sensors integrated in the patient interface assembly. Based on the real-time force signal and real-time corneal deformation signal, a controller calculates a linear relationship between force and corneal deformation, and determines the IOP of the docked eye by comparing a slope of the linear relationship against a pre-established slope vs. IOP calibration curve. The IOP of the docked eye can be used when setting laser treatment parameters.