Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptor cells in conscious vision connect light to movement. In higher organisms the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in molluscs, chordates and arthropods.
The simplest "eyes", such as those in microorganisms, do nothing but detect whether the surroundings are light or dark, which is sufficient for the entrainment of circadian rhythms. From more complex eyes, retinal photosensitive ganglion cells send signals along the retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian adjustment.
Other articles related to "eye, eyes":
... An eyelid is a thin fold of skin that covers and protects the eye ... The levator palpebrae superioris muscle retracts the eyelid to "open" the eye ... features a row of eyelashes which serve to heighten the protection of the eye from dust and foreign debris, as well as from perspiration ...
... At age nine, he injured his right eye while whittling a slingshot with a knife, permanently blinding him ... Haywood never had his damaged eye replaced with a glass eye when photographed, he would turn his head to show his left profile ...
... In addition to the Flying Eye Hospital, ORBIS operates permanent country offices with local partners in several countries ... multi-year projects focusing on the prevention and treatment of the regions’ most prevalent eye diseases ... their capacity to provide comprehensive, affordable and sustainable eye care services over the long term ...
... A version is an eye movement involving both eyes moving synchronously and symmetrically in the same direction ... up and left Laevodepression / gaze down and left Dextrocycloversion - top of the eye rotates to the right Laevocycloversion - top of the eye rotates to the left ...
... The pigment molecules used in the eye are various, but can be used to define the evolutionary distance between different groups, and can also be an aid in determining which ... The eyes of vertebrates usually contain cilliary cells with c-opsins, and (bilaterian) invertebrates have rhabdomeric cells in the eye with r-opsins ... ancestors used this pigment in vision, and that remnants survive in the eyes ...
Famous quotes containing the word eye:
“Bias and impartiality is in the eye of the beholder.”
—Lord Barnett (b. 1923)
“No direct hit to smash the shatter-proof
And lodge at last the quivering needle
Clean in the eye of one who stands transfixed
In fascination of her brightness.”
—Karl Shapiro (b. 1913)
“Like a wild stranger out of wizard-land
He dwelt a little with us, and withdrew;
Black and unblossomed were the ways he knew,
Dark was the glass through which his fire eye shined.”
—Edwin Arlington Robinson (18691935)