A safety knife for ophthalmic surgical procedures has handle to which a blade holder is attached at one end, holding a pre-installed surgical blade. Compositions, medicaments, and therapeutic methods related thereto are also disclosed. The contact bridge is movable via a guide along a direction of movement. It is further configured such that in addition to a time on which the abnormality occurred, the information is stored in an external memory together with a parameter indicative of the quantity of state.