Hydrodissection is a technique in which balanced salt solution is injected through a cannula into various layers of a cataractous lens to separate the lens lamella in a nonspecific location. Selective hydrodissection allows separation of the lens lamella at different desired anatomical layers. The technique allows the smallest possible nucleus, ie, the hard-core nucleus, to be hydroexpressed as a separate entity, requiring, correspondingly, a relatively small capsulorhexis and limbal incision. Then, in a second maneuver, the epinucleus, which engulfs the hardcore nucleus to form the adult nucleus, also can be aspirated or hydroexpressed as a whole. Selective hydrodissection permits scleral incision and stitchless surgery in planned extracapsular cataract extraction and also may serve as an intermediate step for surgeons who wish to convert to or learn phacoemulsification techniques.