Schematic representation of the principles of a microkeratome. A, The suction ring serves as a platform for the microkeratome head, gripping the conjunctiva and sclera adjacent to the limbus. B, Simplified cross-section schematic of a typical microkeratome head. C, Creation of the flap. When the microkeratome head passes across the cornea, the applanating surface of the head flattens the cornea in advance of the blade.