These procedures take place in the operating theatre. Topical anesthesia is used in adults (anesthetic drops on the ocular surface). These are performed in day surgery. Through a small incision in the cornea an ultrasound probe is introduced into the eye (Phacoemulsifier) which breaks up the lens and suctions the fragments. The intraocular lens is inserted in the same incision. The possibility of replacing the lens with an intraocular lens corrects pre-existent refractive errors. Before surgery it is important to evaluate the correct power of the intraocular lens.