Like many other night hunting animals, cats have a light-reflecting surface behind the retinas in their eyes, which increases their chance of seeing something move when the light is very dim. This is why cats’ eyes 'glow' in the beam of a headlight, like the cat’s-eye reflectors in the road.

 

 

 

 

 

To a predator, the immediate detection of movement is more important than colour. Both functions are provided primarily by two different types of light detector in the retina. These are called rod and cone receptors. The outer zone of the retina is made up of rod receptors which detect movement even in dim light. The inner zone contains many cone receptors which are used to detect detail and colour, but only work in bright light. The combination of rods and cones makes the eye efficient under all lighting conditions.