A keratome includes a cutter head with a reciprocating blade and a cutting edge extending below a sole surface of the cutter head, an automated drive unit for powered translational movement of at least the cutter head thereof, and a suction ring adapted to be secured to an eye by suction and defining a cornea aperture for presenting the outer layer of the cornea of the eye for cutting. The suction ring has a shoe from which the eye ring extends defining a cutting guideway configured for receiving the cutter head in precision mating sliding engagement when the cutting edge of the blade is positioned over the cornea aperture of the eye ring, and an entrance guideway extending from and generally aligned with the cutting guideway configured for receiving the cutter head in orienting sliding engagement and positively positioning the cutter head for precision mating sliding engagement with the cutting guideway.