The cornea's primary function is to focus and control the entrance of light into the eye. It is a vital part of the eye and acts as the eye's outermost lens.
The cornea is a clear covering over the surface portion of the eye. It is very strong and durable and helps protect the eye from invasive dust, germs and foreign matter. The cornea also focuses images and light onto the retina, which then begins translating them to vision for transmission to the brain through the optical nerve. In total, the cornea accounts for around 65 to 75 percent of the eye's focusing ability.