The organ of sight. The word "eye" come from the Teutonic "auge." The eye has a number of components. These include the cornea, iris, pupil, lens, retina, macula, optic nerve and vitreous. The cornea is the clear front window of the eye that transmits and focuses light into the eye. The iris is the colored part of the eye that helps regulate the amount of light that enters the eye. The pupil is the dark aperture in the iris that determines how much light is let into the eye. The lens is the transparent structure inside the eye that focuses light rays onto the retina. The retina is the nerve layer that lines the back of the eye, senses light and creates impulses that travel through the optic nerve to the brain. The macula is a small area in the retina that contains special light-sensitive cells and allows us to see fine details clearly. The optic nerve is the nerve that connects the eye to the brain and carries the impulses formed by the retina to the visual cortex of the brain. The vitreous humor is a clear, jelly-like substance that fills the middle of the eye.
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1. The organ of vision that consists of the eyeball and the optic nerve; SYN: oculus [TA]. 2. The area of the e., including lids and other accessory organs of the e.; the contents of the orbit (common). [A.S. eage]
- amaurotic cat e. a yellow reflex from the pupil in cases of retinoblastoma or pseudoglioma.
- aphakic e. the e. from which the lens is absent.
- artificial e. a curved disk of opaque glass or plastic, containing an imitation iris and pupil in the center, inserted beneath the eyelids and supported by the orbital contents after evisceration or enucleation; it may be ready-made (stock) or custom-made.
- black e. ecchymosis of the lids and their surroundings.
- blear e. blepharitis accompanied by a viscid discharge that tends to cause the lid edges to cling together. SYN: lippitude, lippitudo.
- bleary e. sore, runny, watery e. with an associated lackluster appearance and, by extension, dimness of vision.
- compound e. the e. of arthropods, most highly developed in insects and crustaceans; the e. consists of a group of functionally related visual elements (ommatidia) whose corneal surfaces collectively form a segment of a sphere.
- crossed eyes SYN: strabismus.
- dark-adapted e. an e. that has been in darkness or semidarkness and has undergone regeneration of rhodopsin (visual purple), which renders it more sensitive to reduced illumination. SYN: scotopic e..
- dominant e. the e. that is customarily used for monocular tasks. SYN: master e..
- epiphysial e. SYN: pineal e..
- exciting e. the injured e. in sympathetic ophthalmia.
- fixing e. the e., in cases of strabismus, that is directed toward the object of regard.
- hare's e. SYN: lagophthalmia.
- light-adapted e. an e. that has been exposed to light, with bleaching of rhodopsin (visual purple) and insensitivity to low illumination. SYN: photopic e..
- Listing reduced e. a representation that simplifies calculations of retinal imagery : radius of anterior refracting surface, 5.1 mm; total length, 20 mm; distance of nodal point to retina, 15 mm.
- master e. SYN: dominant e..
- parietal e. SYN: pineal e..
- phakic e. an e. containing the natural lens.
- photopic e. SYN: light-adapted e..
- pineal e. a non–image-forming, photoreceptive e. in or near the median line in certain crustacea and lower vertebrates; homologue of pineal gland in higher forms. SYN: epiphysial e., parietal e..
- raccoon eyes bilateral ecchymosis in the periorbital region; suggests a basilar skull fracture and may also be seen in neuroblastoma. SYN: bilateral medial orbital ecchymoses.
- reduced e. a simplified design of the ocular optical system, represented as having a single refracting surface and a uniform index of refraction; a model based on this concept is used in retinoscopy and ophthalmoscopy.
- schematic e. the representation of the optical system of an ideal normal e. in which are listed the curvatures and indices of refraction of the refracting elements and their intervening distances.
- scotopic e. SYN: dark-adapted e..
- shipyard e. SYN: epidemic keratoconjunctivitis virus.
- squinting e. the e., in cases of strabismus, that is not directed toward the object of regard.
- sympathizing e. the uninjured e. in sympathetic ophthalmia that becomes involved later in the disease process.
- watery e. 1. SYN: epiphora. 2. excessive lacrimation.
- web e. SYN: pterygium (1).

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eye n
1) an organ of sight esp a nearly spherical hollow organ that is lined with a sensitive retina, is lodged in a bony orbit in the skull, is the vertebrate organ of sight, and is normally paired
2) all the visible structures within and surrounding the orbit and including eyelids, eyelashes, and eyebrows
3) the faculty of seeing with eyes
eye·less 'ī-ləs adj
eye·like -.līk adj

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the organ of sight: a three-layered roughly spherical structure specialized for receiving and responding to light. The outer fibrous coat consists of the sclera and the transparent cornea; the middle vascular layer comprises the choroid, ciliary body, and iris; and the inner sensory layer is the retina.
Light enters the eye through the cornea, which refracts the light through the aqueous humour onto the lens. By adjustment of the shape of the lens (see accommodation) light is focused through the vitreous humour onto the retina. In the retina light-sensitive cells (see cone, rod) send nerve impulses to the brain via the optic nerve. The arrangement of the two eyes at the front of the head provides binocular vision. Each eye is contained in an orbit, and movement of the eye within the orbit is controlled by extrinsic eye muscles.

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(i) [L. oculus; Gr. ophthalmos] the organ of vision; called also oculus [TA]. In shape the eyeball (bulbus oculi [TA]) is a large sphere, with the segment of a smaller sphere, the cornea, in front. It is composed of three coats: the external tough fibrous layer, consisting of the white sclera over most of the eyeball and the cornea on the anterior surface; the middle vascular layer or uvea, consisting of the choroid, the ciliary body, and the iris; and the inner layer, which is neural and sensory and consists primarily of the retina. Within the three layers are the refracting media: the aqueous humor, the crystalline lens, and the vitreous humor. The lens is a double convex transparent body between the vitreous and aqueous humors; its convexity is altered by the ciliary muscle during accommodation. Posteriorly, fibers of the optic nerve enter the ganglionic layer and receive sensations from the visual cells of the retina (the retinal rods and retinal cones). The arteries of the eye are the short ciliary, the long ciliary, the anterior ciliary, and the central artery of the retina. The nerves are the optic and the long and short ciliary nerves. See Plate 15.


Medical dictionary. 2011.


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