Fig. 4 A. Anterior and posterior diagram of the corneal edges showing the elliptic shape anteriorly and the round shape posteriorly. Also noted are the vertical and horizontal diameters of the anterior and the posterior cornea; the radius of curvature of the cornea and of the sclera (B); the corneal height and the central 4 mm of the cornea, which is optically important; and the comparative thickness of the central and peripheral cornea (C). (Hogan M, Alvarado J, Weddell J: Histology of the Human Eye—An Atlas and Textbook. Philadelphia: WB Saunders, 1971:61)