Cornea

n. transparent external coating of the eye

n. horny outer layer of the epidermis

The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eye's optical power. Together with the lens, the cornea refracts light, and as a result helps the eye to focus, accounting for approximately 80% of its production to 20% of the lens focusing power. The cornea contributes more to the total refraction than the lens does, but, whereas the curvature of the lens can be adjusted to "tune" the focus depending upon the object's distance, the curvature of the cornea is fixed.
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Cornea /cor·nea/ the transparent anterior part of the eye. cor´neal conical cornea keratoconus. cor·ne·a n. [more]Cornea - Community and Resources

Noun
1. transparent anterior portion of the outer covering of the eye; it covers the lens and iris and is continuous with the sclera
(hypernym) membrane, tissue layer
(hyponym) arcus, arcus senilis
(part-holonym) eye, oculus, optic

n. cornea, transparent external coating of the eye

adj. horny, made of horn; resembling horn