The ultraviolet light from the sun can damage the retina, which is the back of the eye where rods and cones make visual images. Long-term, unprotected exposure can also cause the development of cloudy bumps along the edge of the cornea, which can grow over the cornea and prevent clear vision. Moreover, UV light from the sun is also a factor in the development of cataracts.
Moreover, the worst consequence of long-term exposure to the sun is the development of skin cancer.