The cornea is the clear part in the front of the eye. It allows light to pass through to the retina unobstructed. The curvature of the cornea bends the light rays and focuses them on the retina, producing clear images in normal vision.
Disease or trauma to the cornea can alter its structure and cause vision loss. Changes in corneal shape, thickness, or clarity cause poor vision that can often be corrected with a corneal transplant.