Abstract: A medical instrument including (a) a handle; (b) a cautery for burning a lens capsule of an eye at the periphery of a portion of the capsule to be removed during surgery, the cautery including a retractable-extendible cautery portion being retractable into and extendible from the handle, so as to permit insertion of the cautery portion through a small incision formed in the eye when retracted and thereafter to correspond to a peripheral extent of the portion of the capsule to be removed when extended; (c) a mechanism for retracting and extending the cautery portion, the mechanism being engaged by the handle; and (d) an arrangement for connecting the cautery with an electrical apparatus for heating the cautery portion, whereby the peripheral extent of the capsule portion to be removed is searable by the cautery portion when extended and heated.