What is Sight?
{{for|information on how the eye works|Eye}} [[File:Ventral-dorsal streams.svg|thumb|The ''dorsal stream'' ([[green]]) and ''ventral stream'' ([[purple]]) are shown.]] '''Sight''' (also called '''eyesight''' or '''vision''') is one of the [[Sensory system|senses]]. Having sight means to be able to '''see'''. Seeing gives [[animal]]s [[knowledge]] of the [[world]]. Some simple animals can only tell light from dark, but with vertebrates, the visual system is able to form [[image]]s. The ability to interpret [[visible light]] information reaching the [[eye]]s is called '''visual perception'''. Sight is the resulting [[perception]]. The components that are necessary for vision are known as the [[visual system]]. == Process == Light enters the animal's [[eye]]s, and a part of the eye called the [[Lens (eye)|lens]] sends information from the light to the back part of the eye called the [[retina]]. The retina is composed of light-sensitive cells which fire a signal down the [[optic nerve]] when light hits the cell. The optic nerve is a bundle of [[nerve fibre]]s from all over the retina. When the information from the light leaves the retina, it goes to the brain. It travels along the [[optic chiasma]] until it reaches the [[optic cortex]] at the rear of the brain. The information is then processed to find out the shapes and colours of objects. From that and from [[memory]], it can tell of what kind the object is. For example, it can somehow tell a [[tree]] from a [[house]]. The path on which this kind of information flows is called ''ventral stream''. The brain can also tell where objects are. For example, it can tell how far away an object is (this is called [[depth perception]]). This is needed when catching a ball. The path on which this kind of information flows is called ''dorsal stream''. == What is sense of sight == The major problem in visual perception is that what people see is not simply a translation of an image on the [[retina]]. For one thing, we see the world right side up, even though the image on