The clear dome or "window" that covers the front of the eye, it provides a large part of the focusing ability of the eye.
The cornea is the clear dome that covers the front of the eye. It starts to focus light onto the lens. If the eye is like a camera, consider the cornea to be like a UV (ultraviolet) filter screwed onto the end of the camera lens. This is the part of the eye that undergoes vision-correcting LASIK surgery.