Convex

That which has a rounded and elevatedsurface. The surface, if continued at the sameradius of curvature, would form a completecircle, or sphere.

Source: Ophthalmic Dictionary including pronunciation, derivation and definition of the words used in Optometry and Ophthalmology by James J. Lewis, Oph. D. Professor of Optometry in the Northern Illinois College of Ophthalmology and Otology, Chicago.