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Eye

Eye

The eye is the organ of sight (vision) in humans and animals. The eye works by transforming light waves into visual images. Eighty percent of all information received by the human brain comes from the eyes. These organs are almost spherical in shape and are housed in the eye (orbital) sockets in the skull.

Sight begins when light waves enter the eye through the cornea (the transparent layer at the front of the eye), pass through the pupil (the

Words to Know

Aqueous humor: Clear liquid filling the small cavities between the cornea and the iris and between the iris and the lens.

Astigmatism: Vision disorder caused by an uneven curvature in the cornea (sometimes the lens), resulting in indistinct or slightly out-of-focus images.

Cataract: A clouding of the lens of the eye.

Choroid: Delicate membrane between the sclera and the retina.

Cones: Light-sensitive nerve cells of the retina that function chiefly in bright light and are sensitive to color.

Cornea: Protective lens covering the iris.

Farsightedness: Vision disorder caused by an eyeball that is too short or a lens that is too weak; objects far away are seen easily while those up close appear blurry.

Glaucoma: Serious vision disorder caused by a buildup of aqueous humor, resulting in pressure against the retina.

Iris: Colored portion around the pupil that regulates the amount of light entering the eye.

Lacrimal gland: Tear-producing gland that lies immediately above each eyeball at the outer corner of the eye socket.

Nearsightedness: Vision disorder caused by an eyeball that is too long or a lens that is too strong; objects up close are seen easily while those far away appear blurry.

Pupil: Adjustable opening in the center of the iris through which light enters the eye.

Retina: Photosensitive lining inside the eye.

Rods: Light-sensitive nerve cells of the retina that function chiefly in dim light.

Sclera: Tough, fibrous outer covering (the "white") of the eyeball.

Vitreous humor: Clear, gel-like substance inside the large cavity in back of the lens (the center of the eyeball).

opening in the center of the colored portion of the eye, called the iris), then through a clear lens behind the iris. The lens focuses light onto the retina, which functions like the film in a camera. Nerve cells in retinas, called rods and cones, convert light energy into electrical impulses. These impulses are then carried via the optic nerve to the brain where they are interpreted as images.

The human eyeball is about 0.9 inch (2.3 centimeters) in diameter and is not perfectly round, being slightly flattened in the front and back. The eye consists of three layers: the sclera (pronounced SKLIR-a), the choroid (pronounced KOR-oid), and the retina.

Sclera

The sclera, the outer fibrous layer, encases and protects the eyeball. The visible portion of the sclera is seen as the "white" of the eye. When that portion is irritated, the small blood vessels contained in the layer enlarge, producing a "bloodshot eye." In the center of the visible portion of the sclera is the cornea, which projects slightly forward. A delicate membrane, the conjunctiva, covers the cornea and visible portion of the sclera.

Choroid

The choroid is a thin membrane lying underneath the sclera. It is composed of a dense pigment and numerous blood vessels that nourish the internal tissues of the eye. At the front end of the choroid is the ciliary body. Running like a ring around the visible portion of the eye, the ciliary body connects the choroid with the iris. The ciliary body contains muscles that are connected by ligaments to the lens behind the iris. The iris is the visible portion of the choroid. It gives the eye its color, which varies depending on the amount of pigment present in the choroid. Dense pigment makes the iris brown, while little pigment makes the iris blue. If there is no pigment the iris is pink, as in the eye of a white rabbit. In bright light, muscles in the iris constrict the pupil, reducing the amount of light entering the eye. Conversely, the pupil dilates (enlarges) in dim light, increasing the amount of light entering. Extreme fear, head injuries, and certain drugs can also dilate the pupil.

Lens

The lens is a crystal-clear, flexible body that is biconvex (curving outward on both surfaces). The entire surface of the lens is smooth and shiny, contains no blood vessels, and is encased in an elastic membrane. The lens sits behind the iris and focuses light on the retina. In addition to holding the lens in place, the muscles of the ciliary body contract and relax, causing the lens to either fatten or become thin. As the shape of the lens changes, so does its focus.

Retina

The retina is the innermost layer of the eye. The retina is thin, delicate, sensory tissue composed of layers of light-sensitive nerve cells. The retina begins at the ciliary body (not at the front of the eye) and encircles the entire interior portion of the eye. Rods and cones, nerve cells of the retina, convert light first to chemical energy and then electrical energy. Rods function chiefly in dim light, allowing limited night vision: it

is with rods that we see the stars. Rods cannot detect color, but they are the first cells to detect movement. Cones function best in bright light and are sensitive to color. In each eye there are about 126 million rods and 6 million cones.

Fluids of the eye

Between the cornea and the iris and between the iris and the lens are two small cavities. These cavities are filled with a clear watery fluid known as aqueous humor. This fluid aids good vision by helping maintain eye shape, providing support for the internal structures, supplying nutrients to the lens and cornea, and disposing of the eyes' cellular waste.

The large cavity in back of the lens (the center of the eyeball) is filled with a clear gel-like substance called vitreous humor. Light passing through the lens on its way to the retina passes through the vitreous humor. The vitreous humor is 99 percent water and contains no cells. It helps to maintain the shape of the eye and support its internal components.

Other structures of the eye

Tears are produced by the lacrimal gland, which lies immediately above each eyeball at the outer corner of the eye socket. Tears flow through ducts from this gland to the area beneath the upper eyelid. Blinking spreads the tears across the cornea's outside surface, keeping it moist and clean. Tear fluid then either evaporates or drains from the inner corner of the eye into the nasal cavity.

Eyelashes, eyelids, and eyebrows all help to protect the eye from dust and dirt. Extending from the eye socket to the eyeball are six small muscles that contract and relax, allowing the eye to move in various directions.

Vision disorders

Farsightedness and nearsightedness are common vision disorders. They occur because of a defect in the shape of the eyeball or in the refractive power (ability to bend light rays) of the lens. In these cases, the image the eye perceives is distorted because the parallel rays of light that enter the eye do not fall perfectly on a tiny hollow (called the fovea) in the retina at the back of the eye. However, corrective eyeglasses can easily overcome these disorders.

With farsightedness, objects far away are seen easily while those up close appear blurry. The cause may be that the eyeball is too short or the lens is too weak.

With nearsightedness, objects up close are seen easily while those far away appear blurry. The cause may be that the eyeball is too long or the lens is too strong.

Astigmatism, another common vision disorder, can occur in combination with farsightedness or nearsightedness. Individuals with astigmatism see indistinct or slightly out-of-focus images. The condition is brought about by an uneven curvature in the cornea (sometimes the lens). As a result, some light rays entering the eye focus on the fovea while others focus in front or behind it. Like farsightedness and nearsightedness, astigmatism can be corrected with eyeglasses or contact lenses.

A cataract is the clouding of the lens, which alters the amount of light entering the eye. The most common cataracts are senile cataracts, a result of aging that occurs in almost all people over 65 years old. These cataracts grow slowly over months or years, cause no pain, usually affect both eyes, and gradually reduce vision. If not treated, they eventually cause blindness. Clear vision can be restored by a relatively simple surgical procedure in which the entire lens is removed and an artificial lens is implanted.

Glaucoma is a serious vision disorder caused by a buildup of aqueous humor, which is prevented for some reason from properly draining. The excessive amount of fluid causes pressure against the retina, affecting vision. Long-term diseases like diabetes or a malfunctioning thyroid gland can bring about glaucoma. If left untreated, glaucoma will result in permanent blindness. The condition can be controlled with drugs that either increase the outflow of aqueous humor or decrease its production.

[See also Radial keratotomy ]

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Eye

Eye

The human eye is an amazing instrument. It is the body's camera, capturing images of the world with striking clarity in a virtual instant. The eye and the typical camera share many of the same structural features. A camera needs an operator, a housing (box) to hold onto and to contain the working parts and film, an aperture to let the light in (preferably one that allows for different light conditions), a lens for focusing the image, and film for capturing the image. Then the film must be developed (or the digital images downloaded). The following description illustrates how the eye performs these same functions.

Anatomy of the Eye

The eye consists mainly of three layers, or tunics. The bulk of the outermost layer (fibrous tunic) is the white of the eye, or sclera. Like a camera's housing, the sclera is the eye's skeleton, giving structure to the eye and protecting the internal components; it also provides an attachment site for the eye muscles that position the eye under the control of the brain. In the very front of the eye, where the light must pass through, the fibrous tunic is a transparent structure called the cornea. The cornea is responsible for approximately 70 percent of the focusing power of the eye; without a cornea, vision would be impossible. (One can, however, see without a lens, just not very keenly.) Because it must be transparent, there are no blood vessels in the cornea. The tissue must get all of its oxygen and nutrients by diffusion; the cornea actually "breathes" across its surface (hence "gas-permeable" contact lenses can be worn for longer periods than "hard contacts").

The middle layer (vascular tunic) mostly provides for internal maintenance functions, as well as for aperture and fine focusing control. In the posterior two-thirds, the vascular tunic consists of the choroid, a layer of nutritive and supporting tissue. Toward the front, it forms the ciliary body and the iris.

The ciliary body contains the smooth muscles that pull on suspensory ligaments attached to the lens, changing its shape and thus adjusting its focusing power. (Sometimes the proteins that make up the lens become cloudy, a condition called a cataract.) The ciliary body also secretes aqueous humor, the watery fluid that fills the space between the cornea and lens (anterior cavity). This fluid provides a sort of circulatory system for the front of the eye. When excess fluid accumulation causes excess intraocular pressure, the vision-threatening condition known as glaucoma occurs.

The iris, the colored portion of the eye surrounding the dark opening (pupil), sits in front of the lens. The iris is made of two sets of smooth muscle that contract to produce pupil dilation or constriction; this brainstem reflex controls the intensity of the light reaching the innermost sensory layer, the retina.

The retina makes up the inner layer, or neural tunic, and occupies only the posterior two-thirds of the eye. The retina consists of several layers of cells, including the rods and cones, the sensory cells that respond to light. The tips of the rods and cones are embedded in a pigmented layer of cells on the very back of the retina. The pigment helps prevent light from scattering in the back of the eye. (Some nocturnal animals have a reflective layer instead of pigment, called the tapetum lucidum, which increases their sensitivity to low light and makes their eyes "shine" when a bright light strikes them.) When light strikes a rod or cone cell, it passes the signal to a bipolar cell, which passes it on to the ganglion cells, which perform the first level of information processing. The axons of the ganglion cells also form the "cables" that make up the optic nerve, carrying visual information to the brain. (There are no rods and cones where the optic nerve leaves the eye; this is called the "blind spot.") The retina is pressed flat against the inner wall of the eye by a thick, gel-like substance called vitreous humor, which fills the space behind the lens (posterior cavity).

Accessory Structures

There are accessory structures associated with the eye. The eye is protected by being located in the orbit of the skull. Eyelashes help prevent foreign matter from reaching the sensitive surface. The eyelids help protect the exposed anterior part of the eye. The eyelids have glands that produce lubricating secretions . Infection of the glands at the base of the eyelash produces a painful localized swelling called a sty. A thin membrane called the conjunctiva lines the inside of both eyelids and covers the exposed eye surface (except the cornea); when this membrane gets irritated, blood vessels beneath it become dilated, resulting in a condition called conjunctivitis ("pinkeye").

Tear (lacrimal) glands located on the upper lateral (outside) region of the eye provide secretions (tears) that lubricate the surface, remove debris, help prevent bacterial infection, and deliver oxygen and nutrients to the conjunctiva; blinking of the eyelids provides a wiping action across the surface that keeps the eye "polished" and distributes the tears. These tears then drain into the tear ducts in the lower inner corner of the eye, draining into the nasal cavity. Another gland, the lacrimal caruncle (the pinkish blob in the inner corner), produces thick secretions that sometimes accumulate during sleep (the "sand" from the "sandman").

Most vertebrate animals have eyes that are essentially the same as the human eye. Among invertebrates, there is a wide variety of eyes. Some have simple eyespots that do not form images, detecting only the presence of light. Others, like the cephalopod mollusks (octopus, squid), have a camera eye very similar to that of vertebrates. Perhaps the most unusual eye is the compound eye found in arthropods such as insects and crustaceans. These eyes actually consist of hundreds of individual eye units, called ommatidia (up to thirty thousand in dragonflies). Each ommatidium has its own lens and set of receptor and supporting cells; each forms its own tiny picture of only a small part of the visual field. The insect's brain thus receives a mosaic of hundreds of individual images that it uses to make a somewhat "grainy" composite image of the entire visual field.

see also Vision

Harold J. Grau

Bibliography

Eden, John. The Physician's Guide to Cataracts, Glaucoma, and Other Eye Problems. Yonkers, NY: Consumer Reports Books, 1992.

Tucker, Lael. The Eye: Window to the World. Washington, DC: U.S. News Books, 1981.

Ward, Brian R. The Eye and Seeing. New York: Franklin Watts, 1981.

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eye

eye, organ of vision and light perception. In humans the eye is of the camera type, with an iris diaphragm and variable focusing, or accommodation. Other types of eye are the simple eye, found in many invertebrates, and the compound eye, found in insects and many other arthropods. In an alternate pathway to the one that transmits visual images, the eye perceives sunlight. This information stimulates the hypothalamus, which passes the information on to the pineal gland. The pineal gland then regulates its production of the sleep-inducing chemical, melatonin, essentially setting the body's circadian clock (see biorhythm).

The Human Eye

Anatomy and Function

The human eye is a spheroid structure that rests in a bony cavity (socket, or orbit) on the frontal surface of the skull. The thick wall of the eyeball contains three covering layers: the sclera, the choroid, and the retina. The sclera is the outermost layer of eye tissue; part of it is visible as the "white" of the eye. In the center of the visible sclera and projecting slightly, in the manner of a crystal raised above the surface of a watch, is the cornea, a transparent membrane that acts as the window of the eye. A delicate membrane, the conjunctiva, covers the visible portion of the sclera.

Underneath the sclera is the second layer of tissue, the choroid, composed of a dense pigment and blood vessels that nourish the tissues. Near the center of the visible portion of the eye, the choroid layer forms the ciliary body, which contains the muscles used to change the shape of the lens (that is, to focus). The ciliary body in turn merges with the iris, a diaphragm that regulates the size of the pupil. The iris is the area of the eye where the pigmentation of the choroid layer, usually brown or blue, is visible because it is not covered by the sclera. The pupil is the round opening in the center of the iris; it is dilated and contracted by muscular action of the iris, thus regulating the amount of light that enters the eye. Behind the iris is the lens, a transparent, elastic, but solid ellipsoid body that focuses the light on the retina, the third and innermost layer of tissue.

The retina is a network of nerve cells, notably the rods and cones, and nerve fibers that fan out over the choroid from the optic nerve as it enters the rear of the eyeball from the brain. Unlike the two outer layers of the eye, the retina does not extend to the front of the eyeball. Between the cornea and iris and between the iris and lens are small spaces filled with aqueous humor, a thin, watery fluid. The large spheroid space in back of the lens (the center of the eyeball) is filled with vitreous humor, a jellylike substance.

Accessory structures of the eye are the lacrimal gland and its ducts in the upper lid, which bathe the eye with tears, keeping the cornea moist, clean, and brilliant, and drainage ducts that carry the excess moisture to the interior of the nose. The eye is protected from dust and dirt by the eyelashes, eyelid, and eyebrows. Six muscles extend from the eyesocket to the eyeball, enabling it to move in various directions.

Eye Disorders

In addition to errors of refraction (astigmatism, farsightedness, and nearsightedness), the human eye is subject to various types of injury, infection, and changes due to systemic disease. Strabismus is a condition in which the eye turns in or out because of an imbalance in the eye musculature. A cornea damaged by accident or illness can sometimes be corrected by excimer laser or surgically replaced with a healthy one from a deceased person. Experimental retinal implants, consisting of electrode arrays that receive visual data from an external camera, have been used to partially restore sight to persons with damaged retinas, enabling some recognition of shapes, light and dark areas, and motion. Eyes that are used in various ways for surgical repairs are supplied by eye banks. People can arrange to have their eyes donated to such organizations after their death.

Eyes in Other Animals

The camera type of eye, which forms excellent images, is found in all vertebrates, in cephalopods (such as the squid and octopus), and in some spiders. In each of those groups the camera type of eye evolved independently. In some species, e.g., kestrels, the eye can perceive ultraviolet light, an aid to tracking prey.

Simple eyes, or ocelli, are found in a great variety of invertebrate animals, including flatworms, annelid worms (such as the earthworm), mollusks, crustaceans, and insects. An ocellus has a layer of photosensitive cells that can set up impulses in nerve fibers; the more advanced types also have a rigid lens for concentrating light on this layer. Simple eyes can perceive light and dark, enabling the animal to perceive the location and movement of objects. They form no image, or a very poor one.

The compound eye is found in a large number of arthropods, including various species of insects, crustaceans, centipedes, and millipedes. A compound eye consists of from 12 to over 1,000 tubular units, called ommatidia, each with a rigid lens and photosensitive cells; each omnatidium is surrounded by pigment cells and receives only the light from its own lens. The lenses fit together on the surface of the eye, forming the large, many-faceted structure that can be seen, for example, in the fly. Each ommatidium supplies a small piece of the image perceived by the animal. The compound eye creates a poor image and cannot perceive small or distant objects; however, it is superior to the camera eye in its ability to discriminate brief flashes of light and movement, and in some insects (e.g., bees) it can detect the polarization of light. Because arthropods are so numerous, the compound eye is the commonest type of animal eye.

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eye

eye / ī/ • n. 1. each of a pair of globular organs in the head through which people and vertebrate animals see, the visible part typically appearing almond-shaped in animals with eyelids. ∎  the corresponding visual or light-detecting organ of many invertebrate animals. ∎  used to refer to someone's power of vision and in descriptions of the manner or direction of someone's gaze: his sharp eyes had missed nothing. ∎  used to refer to someone's opinion or attitude toward something: in the eyes of his younger colleagues, Mr. Arnett was an eccentric. 2. a thing resembling an eye in appearance, shape, or relative position, in particular: ∎  the small hole in a needle through which the thread is passed. ∎  Naut. a loop at the end of a rope, esp. one at the top end of a shroud or stay. ∎  a rounded eyelike marking on an animal, such as those on the tail of a peacock; an eyespot. ∎  a round, dark spot on a potato from which a new shoot can grow. ∎  a center cut of meat: eye of round. ∎  the center of a flower, esp. when distinctively colored. ∎  the calm region at the center of a storm or hurricane. • v. (eye·ing or ey·ing) [tr.] look at or watch closely or with interest: Rose eyed him warily. PHRASES: all eyes used to convey that a particular person or thing is currently the focus of public interest or attention: all eyes are on the hot spots of eastern Europe. be all eyes be watching eagerly and attentively. close (or shut) one's eyes to refuse to notice or acknowledge something unwelcome or unpleasant: he couldn't close his eyes to the truth—he had cancer. give someone the eye inf. look at someone in a way that clearly indicates one's sexual interest in them: this blonde was giving me the eye. have (or keep) one's eye on keep under careful observation. ∎  hope or plan to acquire: the county sheriff has his eye on retirement. have (or with) an eye to have (or having) as one's objective: with an eye to transatlantic business, he made a deal in New York. ∎  consider (or be considering) prudently; look (or be looking) ahead to: the charity must have an eye to the future. (only) have eyes for be (exclusively) interested in or attracted to: he has eyes for no one but you. keep an eye (or a sharp eye) on keep under careful observation: dealers are keeping an eye on the currency markets. keep one's eyes open be on the alert; watch carefully or vigilantly for something: visitors should keep their eyes peeled for lions. lay (or set or clap) eyes on inf. see: Harry has not laid eyes on Alice for twenty years. make eyes at someone look at someone in a way that indicates one's sexual interest. open someone's eyes enlighten someone about certain realities; cause someone to realize or discover something: the letter finally opened my eyes to the truth. see eye to eye have similar views or attitudes to something; be in full agreement: Mr. Trumble and I do not always see eye to eye. with one eye on giving some but not all one's attention to: I sat with one eye on the clock, waiting for my turn.DERIVATIVES: eyed / īd/ adj. [in comb.] a brown-eyed girl. eye·less adj.

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eye

eye all my eye and Betty Martin nonsense; said in a letter of 1781 to be ‘a sea phrase’, although the identity of Betty Martin is unexplained.
eye-catcher in 18th-century landscape design, an architectural feature such as a sham ruin or a monument, intended to draw the eye in a particular direction.
an eye for an eye and a tooth for a tooth used to refer to the belief that retaliation in kind is the appropriate way to deal with an offence or crime, with biblical allusion to Exodus 21:23–4.
the eye of a master does more work than both his hands employees work harder when the person who is in charge is present; saying recorded from the mid 18th century.
eye of a needle the type of a minute gap through which it is difficult to pass; mainly with echoes of Jesus's saying, ‘it is easier for a camel to go through the eye of a needle, than for a rich man to enter into the kingdom of heaven’ (Matthew 19:24).
eye of the storm the calm region at the centre of a storm, often used figuratively.
an eye to the main chance consideration for one's own interests; main chance literally, in the game of hazard, a number (5, 6, 7, or 8) called by a player before throwing the dice.
what the eye doesn't see, the heart doesn't grieve over now sometimes used with the implication that information is being withheld to prevent difficulties. The saying is recorded in English from the mid 16th century, but an earlier Latin usage is found in the sermons of St Bernard of Clairvaux (1090–1153), ‘vulgo dicitur: Quod non videt oculus cor non dolet [it is commonly said: what the eye sees not, the heart does not grieve at].’ (Compare where ignorance is bliss, 'tis folly to be wise.)

See also apple of one's eye, a beam in one's eye, beauty is in the eye of the beholder, keep an eagle eye on, eyes, the naked eye, turn a Nelson eye, please your eye and plague your heart.

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eye

eye Organ of vision. It converts light energy to nerve impulses that are transmitted to the visual centre of the brain. Most of the mass of a human eye lies in a bony protective socket, called the orbital cavity, which also contains muscles and other tissues to hold and move the eye. The eyeball is spherical and composed of three layers: the sclera (white of the eye), which contains the transparent cornea; the choroid, which connects with the iris, pupil and lens, and contains blood vessels to provide nutrients and oxygen; and the retina, which contains rods and cones for converting the image into nerve impulses. The aqueous humour (a watery liquid between the cornea and iris) and the vitreous humour (a jelly-like substance behind the lens) both help to maintain the shape of the eye. The medical branch of ophthalmology is concerned with eye diseases, and optometry with corrective spectacles and contact lenses. See also sight

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eye

eye The organ of sight. The most primitive eyes are the eyespots of some unicellular organisms. More advanced eyes are the ocelli and compound eyes of arthropods (e.g. insects). The cephalopod molluscs (e.g. the octopus and squid) and vertebrates possess the most highly developed eyes (see illustration). These normally occur in pairs, are nearly spherical, and filled with fluid. Light is refracted by the cornea through the pupil in the iris and onto the lens, which focuses images onto the retina. These images are received by light-sensitive cells in the retina (see cone; rod), which transmit impulses to the brain via the optic nerve.

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eye

eye OE. ēaġe, Angl. ēġe = OFris. āge, OS. ōga (Du. oog), OHG. ouga (G. auge), ON. auga, Goth. augō :- Gmc. *auʒan-, rel. ult. to IE. *oq- on which are based many synon. forms, e.g. Skr. (Vedic) ákşi, Lith. akìs. OSl. (Russ.) óko, Gr. ósse (:- *ókje) the two eyes, ómma (:- *opma). ophthalmós eye, óps face, L. oculus eye, -ōx in atrōx, ATROCIOUS, ferōx FEROCIOUS.

Comps. eye-ball XVI. eyebrow XVI. repl. (dial.) eyebree (OE. ēagbrǣw). eyelash XVIII. eyelid, eyesight, eyesore XII. eyetooth, eyewitness XVI.

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"eye." The Concise Oxford Dictionary of English Etymology. . Retrieved July 23, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/eye-2

eye

eye An organ, sensitive to light, that is developed in many animals. In its simplest form, it consists of a light receptor (ocellus) capable of distinguishing light from shade. In Arthropoda there are compound eyes, each consisting of many separate receptors (ommaidia) each of which contains light-sensitive cells. In Cephalopoda and vertebrates each eye is a single organ, possessing an iris which controls the size of aperture (pupil) through which light passes to a lens, which in turn focuses the light on to a retina.

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"eye." A Dictionary of Zoology. . Encyclopedia.com. 23 Jul. 2017 <http://www.encyclopedia.com>.

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"eye." A Dictionary of Zoology. . Retrieved July 23, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/eye

eye

eye (I) n. the organ of sight: a three-layered roughly spherical structure specialized for receiving and responding to light (see illustration). Light enters the eye through the cornea, which refracts it through the aqueous humour onto the lens. By accommodation light is focused through the vitreous humour onto the retina. Here light-sensitive cells (see cone, rod) send nerve impulses to the brain via the optic nerve.

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"eye." A Dictionary of Nursing. . Encyclopedia.com. 23 Jul. 2017 <http://www.encyclopedia.com>.

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"eye." A Dictionary of Nursing. . Retrieved July 23, 2017 from Encyclopedia.com: http://www.encyclopedia.com/caregiving/dictionaries-thesauruses-pictures-and-press-releases/eye

eye

eye.
1. Oculus, or any circular element placed in the centre of something, e.g. a bull's-eye circular window in the middle of the tympanum of a pediment.

2. Circular or nearly circular central part of a volute, as in an Ionic capital.

3. Very small, more or less triangular, light in Gothic tracery.

4. Circular base or rim of a cupola, i.e. the circle from which the domed part springs.

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"eye." A Dictionary of Architecture and Landscape Architecture. . Encyclopedia.com. 23 Jul. 2017 <http://www.encyclopedia.com>.

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"eye." A Dictionary of Architecture and Landscape Architecture. . Retrieved July 23, 2017 from Encyclopedia.com: http://www.encyclopedia.com/education/dictionaries-thesauruses-pictures-and-press-releases/eye

Eye

Eye: see EVIL EYE.

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"Eye." The Concise Oxford Dictionary of World Religions. . Encyclopedia.com. 23 Jul. 2017 <http://www.encyclopedia.com>.

"Eye." The Concise Oxford Dictionary of World Religions. . Encyclopedia.com. (July 23, 2017). http://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/eye

"Eye." The Concise Oxford Dictionary of World Religions. . Retrieved July 23, 2017 from Encyclopedia.com: http://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/eye

eye

eyeally, Altai, apply, assai, awry, ay, aye, Baha'i, belie, bi, Bligh, buy, by, bye, bye-bye, chi, Chiangmai, Ciskei, comply, cry, Cy, Dai, defy, deny, Di, die, do-or-die, dry, Dubai, dye, espy, eye, fie, fly, forbye, fry, Frye, goodbye (US goodby), guy, hereby, hi, hie, high, I, imply, I-spy, July, kai, lie, lye, Mackay, misapply, my, nearby, nigh, Nye, outfly, passer-by, phi, pi, pie, ply, pry, psi, Qinghai, rai, rely, rocaille, rye, scry, serai, shanghai, shy, sigh, sky, Skye, sky-high, sly, spin-dry, spry, spy, sty, Sukhotai, supply, Tai, Thai, thereby, thigh, thy, tie, Transkei, try, tumble-dry, underlie, Versailles, Vi, vie, whereby, why, wry, Wye, xi, Xingtai, Yantai

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"eye." Oxford Dictionary of Rhymes. . Encyclopedia.com. 23 Jul. 2017 <http://www.encyclopedia.com>.

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"eye." Oxford Dictionary of Rhymes. . Retrieved July 23, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/eye-0