Fig. 1. Image formation by a convex mirror. Keratometry and keratoscopy utilize the property of the anterior corneal surface to reflect light, forming a virtual erect image within the anterior chamber. O, object; I, image; F, focal point; C. center of curvature of cornea; u, distance of object from cornea; v, distance of image from cornea; r, radius of curvature of cornea. (Corbett MC, Rosen ES, O'Brart DPS: Corneal Topography: Principles and Applications. London, BMJ Books, 1999.)