Finite element simulation and experimental test of ovine corneal tissue cutting process in cataract surgery operation

Abstract

The modeling of corneal tissue cutting is essential in developing haptic training simulators and robotassisted surgeries. A finite element model was developed in this study for the ovine corneal cutting process and validated with an experimental setup for the first time. The experimental setup forces are measured in pre-cutting, cutting, and relaxation phases. The mechanical behavior of corneal incision was modeled by the finite element method. A test setup was built to conduct experiments on 32 fresh and well-preserved ovine cornea. Force was recorded with the sampling rate of 200 Hz. The tests were performed for intraocular pressures from 15 mm-Hg to 18 mm-Hg, and keratome velocities of 1 mm/s and 2 mm/s. The finite element model characterized the nonlinear behavior of the ovine corneal tissue. In the pre-cutting phase, the force is increased until the instrument tip penetrates. A 12.3% (2 mm/s) and 19.1% (1 mm/s) reduction in force indicated the onset of the cutting phase after which force remained constant. At the relaxation phase, force returned to zero. The cutting force values varied by pressure between 0.183N and 0.287 N for 1 mm/s and between 0.211 N and 0.281 N for 2 mm/s of keratome velocity, respectively. The finite element simulations show that the maximum force errors predicted by the model is 0.042 N for 2 mm/s of keratome velocity. The root mean square of force error between the finite element simulations and the experiments is 0.025 N.