Eye

An eye is a <a href="/facts/Sensory_organ/n9kYQ3rf">sensory organ</a> that allows an <a href="/facts/Organism/j8JkL09u">organism</a> to perceive <a href="/facts/Visual_perception/g7Tfaq2l">visual</a> information. It detects <a href="/facts/Light/jeofpMn4">light</a> and converts it into electro-chemical impulses in <a href="/facts/Neurons/G7CyTVdH">neurons</a> (neurones). It is part of an organism's <a href="/facts/Visual_system/QVcuA27K">visual system</a>.
In higher organisms, the eye is a complex <a href="/facts/Optics/p0vq4S1T">optical</a> system that collects light from the surrounding environment, regulates its intensity through a <a href="/facts/Iris_(anatomy)/e774BXL8">diaphragm</a>, <a href="/facts/Focus_(optics)/QuRKfhg6">focuses</a> it through an adjustable assembly of <a href="/facts/Lens_(anatomy)/yWz7AdHV">lenses</a> to form an <a href="/facts/Image/hbjEdTXK">image</a>, converts this image into a set of electrical signals, and transmits these signals to the <a href="/facts/Brain/EKla9NkJ">brain</a> through neural pathways that connect the eye via the <a href="/facts/Optic_nerve/3AJDdVN5">optic nerve</a> to the <a href="/facts/Visual_cortex/qmF8F5Sb">visual cortex</a> and other areas of the brain.
Eyes with resolving power have come in ten fundamentally different forms, classified into <a href="/facts/Compound_eye/yoRE9HWY">compound eyes</a> and non-compound eyes. Compound eyes are made up of multiple small visual units, and are common on <a href="/facts/Insect/IgDNvnUL">insects</a> and <a href="/facts/Crustacean/PBobIVJP">crustaceans</a>. Non-compound eyes have a single lens and focus light onto the retina to form a single image. This type of eye is common in mammals, including humans.
The simplest eyes are pit eyes. They are eye-spots which may be set into a pit to reduce the angle of light that enters and affects the eye-spot, to allow the organism to deduce the angle of incoming light.
Eyes enable several photo response functions that are independent of vision. In an organism that has more complex eyes, retinal <a href="/facts/Photosensitive_ganglion_cell/7mLNDzSX">photosensitive ganglion cells</a> send signals along the <a href="/facts/Retinohypothalamic_tract/m2EtrdVn">retinohypothalamic tract</a> to the <a href="/facts/Suprachiasmatic_nucleus/SILs86zl">suprachiasmatic nuclei</a> to effect circadian adjustment and to the <a href="/facts/Pretectal_area/xwVXH4bU">pretectal area</a> to control the <a href="/facts/Pupillary_light_reflex/owbnYMTj">pupillary light reflex</a>.

Eye open-in-new

Eye