Definition: The transparent anterior portion of the fibrous coat of the eye consisting of five layers: stratified squamous epithelium, Bowman's membrane, stroma, DESCEMET'S MEMBRANE, and mesenchymal endothelium. It serves as the first refracting medium of the eye. It is structurally continuous with the sclera, is avascular, receiving its nourishment by permeation through spaces between the lamellae, and is innervated by the ophthalmic division of the trigeminal nerve via the ciliary nerves and those of the surrounding conjunctiva which together form plexuses. (Cline et al., Dictionary of Visual Science, 4th ed)