Rods are one of the two kinds of light sensing cell in the retina at the back of the eye. Rods do not sense colour, only shades of grey. They function best in low light conditions and are very sensitive to movements. They are found in greater numbers to the edge of the eye, including perpipheral vision, but stilll at a lower density than central vision (the fovea), which is very densely populated with colour-sensing cones.
Also known as: rods
Used in glossary entries: cones in the eye, retina