Abstract: The invention relates to an ophthalmic surgery instrument (1; 101) for making a substantially circular cut in an internal part (110) of an eye (109), in particular for capsulorhexis, comprising a handle (2; 102) at the end of which there extends a rod (3; 103) carrying a blade (4; 104) designed to be introduced into the eye (109) via an incision (107) that has been formed in the latter, characterized in that the blade (4; 104) has a loop shape with dimensions substantially equal to those of the cut, and the instrument comprises means for passing the blade through the incision.