We describe a new type of caliper to optimize the size, shape, and centration of the capsulorhexis during intraocular lens (IOL) surgery. This flexible, ring-shaped tool is positioned on the anterior capsule surface, where it is kept in place by an ophthalmic viscosurgical device. When in place, the caliper provides an ideal guide for the surgeon to follow and facilitates optimal capsulorhexis shape and centration.