The cornea is the clear watch glass covering in the front of the eye. The cornea works with the lens of the eye to focus images on the retina. The retina is the internal layer of the eye that receives and transmits focused images. The retina is normally red due to its rich blood supply.
Review Date 2/28/2019
Updated by: Franklin W. Lusby, MD, ophthalmologist, Lusby Vision Institute, La Jolla, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.