Eyelids

The anterior covering of the eye; thatportion of movable skin with which the eyeballis cpvered or uncovered at will, protecting it from injury by their closure.

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.