The cornea is the transparent, dome-shaped outer layer of the eye that covers the front portion, including the iris and pupil. It plays a crucial role in focusing light onto the retina by refracting (bending) incoming light rays. The cornea is composed of several layers, including an outer epithelial layer, a middle stromal layer, and an inner endothelial layer. Its clarity and curvature are essential for sharp vision, and any damage or irregularities in the cornea can lead to vision problems.