Cat's Sight

Opposite to what everybody thinks, cats can't see in the dark, but in penumbra it's sight is more acute than that of most humans. As they are night hunters this ability is very valuable for them. Almost all their eye characteristics are related with its instinct of hunting.

An extraordinary sight
To begin, the frontal disposition of the eyes on the cats head, with 120º of binocular sight and 80º of lateral sight; this makes a total of 280º. The ligaments of the eye permits the movement of the lenses for focusing objects at close distance, although in reality cats can't see very well at short distances, its best vision distance is of 2 to 6 meters.

The capacity of cats to see in the penumbra is due partly to the flexibility of the iris muscles, which is the membrane that opens and closes to show a bigger or smaller section of the pupil, depending on the conditions. In daylight, the iris closes until a real small part of the pupil is shown with the object of protecting the internal eye from the direct light without loosing the capacity of sight. At night, however, the muscles of the iris can open up to 12 mm, which permits the entrance of more light to the retina, situated in the posterior part of the eye, and by so increasing the quantity of information transmitted to the brain.

Seeing in the dark
Here is when the excellent characteristics of the cat's eyes become active. We are talking about the tapetum lucidum, a membrane situated on the surface of the retina that reflects the light inside the eye and whose action increases the sensibility of the retina and betters the image. Thos membrane is responsible for the bright reflection on the cats eyes when the lights of a car shines directly on them, effect that has been copied by the highway engineers for the reflecting signals on the road.

The tapetum lucidum is not exclusive of felines due that it is possible to find it in other nocturnal animals. But, though the cat's eye can pick up a great quantity of information in poor conditions of light, the data is not very concrete..

Although the nocturnal vision is blurred and lacks of details, it doesn't represent a problem for the cat, because what really is important is the movement of possible preys, something he detects easily thanks to the smell and hearing.