What is the primary function of the cornea?

• A. Focus or refract light
• B. Produce tears
• C. Control eyelid movement
• D. Generate optic nerve signals

Answer: (A)

The cornea’s primary function is to refract light as it enters the eye, beginning the process of focusing the image on the retina. Its curved, transparent front surface provides most of the eye’s focusing power—about 40 diopters, roughly two-thirds of what’s needed to form a sharp image—while the lens supplies the remainder. Tears are produced by the lacrimal glands, eyelid movement is controlled by the eyelid muscles, and optic nerve signals come from the retina and travel to the brain; the cornea itself does not perform those roles.