Abstract: A surgical knife, especially for use by ophthalmic surgeons for performing radial keratotomy, comprises an elongate body and a head portion which receives a diamond blade and within which the blade is displaceable forwards and backwards lengthwise of the knife along a line extending at an angle of inclination to the axis of the knife body. The angle of inclination is preferably about 20.degree.. The knife preferably incorporates a micrometer setting mechanism, adjustment of which is transmitted through the knife body to a piston located in the head portion and arranged to make contact with a knife holder for the blade. The transmission chain from micrometer to piston may include a cranked element acting on the piston.

Abstract: A surgical knife, particularly for use in radial keratotomy, comprises a blade, such as a diamond, which is movable for adjustment of the depth of cut by an invariant coupling to a micrometer mechanism, without provision for full retraction of the blade, and a removable protective end cap adapted to encompass the blade when the knife is not in use. The invariant coupling of the blade to the micrometer mechanism is via a mechanical linkage which incorporates a rotatable spindle having two axially separate screw-thread connections. The end cap is provided with holes for the passage of sterilizing fluid to and around the blade.