Hagfish fossils reveal stepwise eye simplification before near-total vision loss‎

Many animals, including humans, rely on their eyes to detect changes in their surroundings. The eyes of vertebrates, animals with a backbone or a similar supporting structure, contain a transparent structure (i.e., the lens) that focuses incoming light onto a layer of light-sensitive cells, known as the retina. Cells in the retina then convert light into signals that are sent to the brain.