Rods and cones, the two main photoreceptor cells, are vital to human sight -- converting visible electromagnetic radiation into information our brains can use. And it turns out, the biological technology has been around for more than 300 million years.

A team of international scientists, led by researchers at Japan's Kumamoto University, recently discovered and analyzed an ancient fossilized fish boasting a perfectly preserved eye. Inside the ancient eye, researchers found rods and cones.

"Rods and cones are not usually preserved, because these soft tissues are more fragile," lead study author Gengo Tanaka, a paleontologist at Kumamoto, told Live Science.

Rods and cones are sensitive to color and also help perceive fine detail and rapid changes. Rods are more sensitive to light than cones, but are not sensitive to color, and are responsible for peripheral and night vision.

The eye (and the fish that hosts it) was discovered in Kansas, but it is currently housed in the National Museum of Nature and Science in Tokyo. These ancient rods and cones helped a type of fish called Acanthodes bridgei, the last known common ancestor of modern jawed fishes -- both bony and cartilaginous species -- including barracudas and sharks.

The same photoreceptor cells and phototransduction capabilities that allow the human brain to recreate the visual world, also helped A. bridgei -- which grew no more than four inches in length -- navigate the shallows, locating prey and avoiding predators.

Because rods and cones are so delicate, scientific have had a difficult time painting an accurate picture of the evolution of eyesight. But the latest discovery suggests modern eyesight has been around for at least 520 million years, when A. bridgei first appeared on the fossil record.

The study was published this week in the journal Nature Communications.