What A Retina Does
You already know that in order to see, light rays must be bent or “refracted” so that they can focus directly on our retina, the nerve layer that lines the back of the eye. From the retina, light is picked up by millions of photoreceptors called cones and rods that convert the light waves into useful information including color, shape and motion.
- More than one layer: One layer of the retina is brain tissue which begins coding visual information even before messages are sent via the optic nerve to the brain. Another layer is made up of blood vessels which need the oxygen from a good aerobic workout.
- Cones: You have about 6 million cones on your retina. Cones work in bright light and help you see color and fine detail. There are three different kinds, each sensitive to a different color: red, green and blue. Your brain mixes the messages from these cones to see all colors. Cones “turn off” in the dark, that’s why it’s hard to see color at night.
- Rods: You have about 95 million rods scattered across your retina. Rods “turn on” in the dark to help your eyes gather light. Rods can’t help you see color or detail which is why it’s hard to match your socks in the dark.