The retina is located at the back of your eye. The retina is a thin tissue layer that contains millions of nerve cells. The nerve cells are sensitive to light. A main purpose of your eye is to focus light on the retina. The choroid is the lining underneath the retina. The choroid contains blood vessels that supply your retina with blood and oxygen to keep it healthy.
Cones and rods are specialized receptor cells in the retina. Cones are specialized for color vision and detailed vision, such as for reading or identifying distant objects. Cones work best with bright light. The greatest concentration of cones is found in the macula and fovea at the center of the retina. The macula is the center of visual attention. The fovea is the site of visual acuity or best visual sharpness. Rods are located throughout the rest of the retina.
Your eyes contain more rods than cones. Rods work best in low light. Rods perceive blacks, whites, and grays, but not colors. They detect general shapes. Rods are used for night vision and peripheral vision. High concentrations of rods at the outer portions of your retina act as motion detectors in your peripheral or side vision.
The receptor cells in the retina send nerve messages about what you see to the optic nerve. The optic nerve extends from the back of each eye and join together in the brain at the optic chiasm. From the optic chiasm, the nerve signals travel along two optic tracts in the brain and eventually to the occipital cortex, where you process and perceive vision.