The cornea does most of the focusing of the light onto the retina, and the lens allows for more accuracy of focusing.
The cornea is the outer transparent some-shaped structure that covers the iris and the pupil. The cornea directs light rays into the eye and helps focus them on the light-sensitive retina at the back of the eye, providing sharp, clear vision. The cornea provides 65-75% of your eye's focusing power. The cornea does not contain any blood vessels, but instead contains many nerve endings that make it extremely sensitive and that is the reason why s scratch or even a loose eyelashes is so painful.
The lens on the other hand, is composed of transparent, flexible tissue and is located directly behind the iris and the pupil. Light passes through the pupil to the lens. Small muscles attached to the lens can make the lens change shape, allowing the eyes to focus on near or far objects. The lens provides 25-35% of the eye's focusing power.
