Eye

Eye

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.

Read more about EyeOverview, Evolution, Types of Eye, Relationship To Life Requirements, Visual Acuity, Perception of Colors, Rods and Cones, Pigmentation

Other articles related to "eye, eyes":

Eye - Pigmentation
... 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 are ... The eyes of vertebrates usually contain cilliary cells with c-opsins, and (bilaterian) invertebrates have rhabdomeric cells in the eye with r-opsins ... this pigment in vision, and that remnants survive in the eyes ...
Orbis International - Country Programs
... In addition to the Flying Eye Hospital, ORBIS operates permanent country offices with local partners in several countries ... projects focusing on the prevention and treatment of the regions’ most prevalent eye diseases ... to provide comprehensive, affordable and sustainable eye care services over the long term ...
Bill Haywood - Biography - Early Life
... 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 ...
Version (eye)
... A version is an eye movement involving both eyes moving synchronously and symmetrically in the same direction ... left Laevodepression / gaze down and left Dextrocycloversion - top of the eye rotates to the right Laevocycloversion - top of the eye rotates to the left ...
Eyelid
... 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 ... The human eyelid features a row of eyelashes which serve to heighten the protection of the eye from dust and foreign debris, as well as from perspiration ...

Famous quotes containing the word eye:

    There is all the difference in the world between the criminal’s avoiding the public eye and the civil disobedient’s taking the law into his own hands in open defiance. This distinction between an open violation of the law, performed in public, and a clandestine one is so glaringly obvious that it can be neglected only by prejudice or ill will.
    Hannah Arendt (1906–1975)

    To speak truly, few adult persons can see nature. Most persons do not see the sun. At least they have a very superficial seeing. The sun illuminates only the eye of the man, but shines into the eye and the heart of the child.
    Ralph Waldo Emerson (1803–1882)

    The eye of man hath not heard, the ear of man hath not seen, man’s hand is not able to taste, his tongue to conceive, nor his heart to report what my dream was!
    William Shakespeare (1564–1616)