Cataracts are the clouding and hardening of the crystalline, a natural lens which is part of the eye and which focusses images on the retina.
Cataracts are broken by using ultrasound and the pieces are absorbed through irrigation or suction. Once clean, the intraocular lens is implanted. The method is known as cataract phacoemulsification. If the intraocular lens is multifocal, trifocal or toric due to astigmatism, it becomes facorefractive.