Vitreous humor exhibits complex biomechanical properties and determination of these properties is essential for designing ophthalmic biomedical microdevices. In this paper, the viscoelastic properties of porcine vitreous humor were studied based on ex vivo creep experiments, in which a microrobot was magnetically actuated inside the vitreous. A three-dimensional (3D) finite element (FE) model was proposed to simulate the viscoelastic interaction between the microrobot and porcine vitreous humor. An optimization-based method was employed to estimate the viscoelastic parameters of the vitreous humor. The proposed model successfully validated the experimental measurements. The estimated parameters were compared with published data in literature. The model was then used to study the shape-dependent interaction of the microrobot with the vitreous humor. The methods presented in this paper can be used for the optimization of ophthalmic microrobots and microsurgical tools.