We present a real.time simulation of the phaco-emulsification task in a virtual reality training system for cataract surgery. Phaco.emulsification consists in breaking in small fragments and completely removing the eye crystalline lens by employing an ultra.sound tool called phaco.emulsificator. Our approach employs a mesh-less shape. based dynamic algorithm integrated with a simplex geometry representation in order to efficiently handle the rendering process and the continuous modifications involved by the surgical tool interaction, and with a smoothed particle hydrodynamics scheme with spatial ordering for handling fragments interactions. The complete training system also simulates other tasks involved in cataract surgery, like the corneal incision and the capsulorhexis. The simulator runs on a multiprocessing PC platform and provides realistic physically-based visual simulations of tools interactions. The current setup employs SensAble PHANToM for simulating the interaction devices, and a binocular display for presenting images to the user.