Abstract: Apparatus to retain a disc obtained from a human cornea during a cutting operation to alter the surface of the disc. The apparatus includes a plurality of plunger-like moldings, any one of which can support the corneal disc. The molding is interchangeably supported in a recess provided in a support member. The support surface of the molding is concave or convex with a predetermined curvature and gaspervious openings communicate with an evacuation chamber so that a corneal disc can be sucked against the corneal support surface by a negative pressure. A pressure ring engages the edge of the corneal disc for clamping it between the pressure ring and molding. A guideway for a transversely-movable cutting device ring and molding. The molding can be formed with a number of bores or constructed of porous material. The apparatus is used by selecting a particular molding with a corneal disc-receiving surface that is either convex when minus values are required or concave when plus values are required.