Iris

Iris,

river: see Yeşil IrmakYeşil Irmak
, anc. Iris, river, c.260 mi (418 km) long, rising NE of Sivas, N Turkey. It flows NW, then NE, past Tokat and Amasya into the Black Sea near Samsun.
..... Click the link for more information. .

iris:

see eyeeye,
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
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Iris

(ī`rĭs), in Greek mythology, goddess of the rainbow; daughter of Electra and Thaumas. She was often represented as a messenger of Zeus and Hera.

iris,

common name for members of the genus Iris of the Iridaceae, a family of perennial herbs that includes the crocuses, freesias, and gladioli. The family is characterized by thickened stem organs (bulbs, corms, and rhizomes) and by linear or sword-shaped leaves—small and grasslike in the crocuses and blue-eyed grasses. It is widely distributed over the world except in the coldest regions and is most abundant in S Africa and in tropical America. Almost all of the family's 90-odd genera include commercially valuable ornamentals. The iris family is closely related to the lily and amaryllis families, differing from them in having three stamens rather than six. The cultivated irises (genus Iris), freesias (genus Freesia), and gladioli (genus Gladiolus) show a wide variety of colors in their large, usually perfumed blossoms; they are mostly hybrids of Old World species. The many species of wild iris are most common in temperate and subarctic regions of North America, where they are often called flags, or blue flags. The fleur-de-lis is thought to have been derived from the iris, and the flower of the Greek youth HyacinthHyacinth
or Hyacinthus
, in Greek mythology, beautiful youth loved by Apollo. He was killed accidentally by a discus thrown by the god. According to another legend, the wind god Zephyr, out of jealousy, blew the discus to kill Hyacinth.
..... Click the link for more information. may have been an iris. Orrisroot, a violet-scented flavoring used in dentifrices, perfumes, and other products, is prepared from the powdered rhizomes of several European species of iris. The freesias, native to S Africa, characteristically bear their blossoms on a horizontal extension of the stem. The crocuses (genus Crocus), which usually bear a single yellow, purple, or white blossom, are native to the Mediterranean area and to SW Asia. One species, saffronsaffron,
name for a fall-flowering plant (Crocus sativus) of the family Iridaceae (iris family) and also for a dye obtained therefrom. The plant is native to Asia Minor, where for centuries it has been cultivated for its aromatic orange-yellow stigmas (see pistil).
..... Click the link for more information. , is cultivated commercially for a yellow dye made from the pollen; the unrelated meadow saffron or autumn crocus and the wild crocus or pasqueflower belong to the lilylily,
common name for the Liliaceae, a plant family numbering several thousand species of as many as 300 genera, widely distributed over the earth and particularly abundant in warm temperate and tropical regions.
..... Click the link for more information. and buttercupbuttercup
or crowfoot,
common name for the Ranunculaceae, a family of chiefly annual or perennial herbs of cool regions of the Northern Hemisphere. Thought to be one of the most primitive families of dicotyledenous plants, the Ranunculaceae typically have a simple
..... Click the link for more information. families respectively. Other members of the family found in the United States are the blue-eyed grasses (genus Sisyrinchium) with small clusters of blue, white, or purplish flowers, ranging from Canada to Patagonia, and the celestial lily (genus Nemastylis) with pairs of blue flowers, ranging from the Kansas prairies to Tennessee and Texas. Irises are classified in the division MagnoliophytaMagnoliophyta
, division of the plant kingdom consisting of those organisms commonly called the flowering plants, or angiosperms. The angiosperms have leaves, stems, and roots, and vascular, or conducting, tissue (xylem and phloem).
..... Click the link for more information. , class Liliopsida, order Liliales, family Iridaceae.

Iris

(in electron and ion optics), an opening in a conducting plate; used to limit the cross section and vary the expansion (aperture) angle of a charged-particle beam. A round iris under a potential V and placed in an external electrical field is the simplest electrostatic lens. If E₁^ and E₂ are equal to the field intensity along different sides of the plate at a distance from the aperture, the focal length of such a lens is approximately f = 4ø/ (E₁ - E₂) where ø is the potential at the center of the iris. Depending on the sign of f, an iris may be a converging or diverging lens. Combinations of irises under different potentials are also electrostatic lenses.

REFERENCE

Glaser, V. Osnovy elektronnoi optiki. Moscow, 1957. Sections 77 and 89. (Translated from German.)

Iris

a genus of plants of the family Iridaceae. They are perennial rhizomatous herbs with sword-shaped or linear leaves. The flowers are large, with a brightly colored corolliform perianth; the ovary is three-celled and inferior; and the fruit is a trihedral, many-seeded pod.

There are about 200 species, distributed throughout the northern hemisphere; in the USSR there are about 60 species. The iris species that form tubers and bulbs are often subdivided into the genera Junona, Xiphium, Iridodictum, and Gynandriris. Irises are widely used for ornament, especially varieties of the species I. kaempferi, I. hybrida, I. spuria, and I. iberica. They grow best in sunny places with well-drained soil. The orrisroot is obtained from the rootstocks of some irises, and a coarse fiber for making brushes is produced from the leaves of the species I. songarica.

REFERENCES

Rodionenko, G. I. Rod Iris. Moscow-Leningrad, 1961.
Rodionenko, G. I. Irisy. Moscow, 1961.

G. I. RODIONENKO

Iris

a part of the anterior portion of the eye in animals and man that is located between the vitreous and anterior chambers. The iris is a thin and movable diaphragm with a pupillary aperture in the center; light is regulated through the pupil and onto the retina by the contraction and dilation of the aperture.

The iris is composed of both retinal and uveal structures. The retinal, or posterior, surface consists of two pigmented epithelia. The posterior epithelium is covered by an internal restricting membrane and is a continuation of the retina and the ciliated epithelium. The anterior epithelium is a continuation of the pigmented epithelium of the retina and the ciliary body. The neuroepithelial muscles of the iris are the sphincter, which constricts the pupil, and the dilator, which widens the pupil. They are formed from the anterior epithelium. The sphincter is innervated by parasympathetic fibers of the oculomotor nerve and the dilator is innervated by sympathetic nerves.

The uveal, or mesodermal, surface of the iris is also called the anterior surface. It is a continuation of the vascular layer of the ciliary body and the vascular coat and is composed of exterior reticular and deep vascular layers. The uveal surface is covered with endothelium that extends from the cornea. At the level of the restricting membranes of the iris is the barrier that separates blood from the eye. The anterior surface of the iris is divided into a peripheral, or ciliary, zone, which contains both the reticular and vascular layers, and a pupillary zone, which is the lesser circle of the iris and contains the sphincter. The exterior layer of stroma atrophies in the pupillary zone.

The blood vessels of the iris originate in the vascular circulus major located along the margin of the peripheral zone and are positioned radially. In man, they anastamose into the arterial and venous arches of the vascular circulus minor, 1.5 mm from the pupil margin. No independent lymphatic system has been discovered in the iris. The stroma of the iris is composed of thin collagenic and elastic trabeculae. The predominate cells of the stroma are chromatophores, which determine eye color; man has only melanocytes, while birds, reptiles, and amphibians have iridophores and lipophores in addition to melanocytes. There are also fibroblasts and granular plasma cells in the stroma. The color and architectonic of the uveal part of the iris are determined by species and racial characters and change with age.

Inflammation of the iris (iritis) accompanies traumas and various infectious and metabolic diseases; as a rule, there is also inflammation of the ciliary body.

O. G. STROEVA

iris

[′ī·rəs] (anatomy) A pigmented diaphragm perforated centrally by an adjustable pupil which regulates the amount of light reaching the retina in vertebrate eyes. (botany) Any plant of the genus Iris, the type genus of the family Iridaceae, characterized by linear or sword-shaped leaves, erect stalks, and bright-colored flowers with the three inner perianth segments erect and the outer perianth segments drooping. (electromagnetism) A conducting plate mounted across a waveguide to introduce impedance; when only a single mode can be supported, an iris acts substantially as a shunt admittance and may be used for matching the waveguide impedance to that of a load. Also known as diaphragm; waveguide window. (optics) A circular mechanical device, whose diameter can be varied continuously, which controls the amount of light reaching the film of a camera. Also known as iris diaphragm.

iris

of Tennessee. [Flower Symbolism: Golenpaul, 642]See: Flower, State

Iris

messenger of the gods. [Gk. Myth.: Kravitz, 130; Gk. Lit.: Iliad]See: Messenger

iris

emblem of the trinity in da Vinci’s “Madonna of the Rocks.” [Plant Symbolism: Embolden, 26]See: Trinity

iris

1. the coloured muscular diaphragm that surrounds and controls the size of the pupil 2. any plant of the iridaceous genus Iris, having brightly coloured flowers composed of three petals and three drooping sepals 3. a form of quartz that reflects light polychromatically from internal fractures

IRIS

(body)Institute for Research in Information and Scholarshipof Brown University (Providence RI).

Iris

(2)An object-oriented DBMS.

IRIS

(1) See IRIS printer and iris recognition.

(2) The name of Silicon Graphics's first terminals and workstations. The name was later used for SGI's high-availability server software (IRIS FailSafe).

(3) (Infrastructure for Resilient Internet Systems) See DHT.

Iris

(dreams)An iris is a spring flower that symbolizes several very positive and uplifting conditions. In Japan, it is believed that the iris has the power to purify the body and protect the household from disease and evil. Iris is also a God in Greek mythology. She is a messenger who represents the link between heaven and earth and between gods and men. This is a very interesting and specific dream symbol. In order to figure out what it means to you personally, consider your current needs. Do you have a need for purification and safety or are you looking for inspiration?

iris

eye

[i] the organ of vision" >vision; see also Plates. In the embryo the eye develops as a direct extension of the brain, and thus is a very delicate organ. To protect the eye the bones of the skull are shaped so that an orbital cavity protects the dorsal aspect of each eyeball. In addition, the conjunctival sac covers the front of the eyeball and lines the upper and lower eyelids. Tears from the lacrimal duct constantly wash the eye to remove foreign objects, and the lids and eyelashes help protect the front of the eye.Structure. The eyeball has three coats. The cornea is the clear transparent layer on the front of the eyeball; it is a continuation of the sclera (the white of the eye), the tough outer coat that helps protect the delicate mechanism of the eye. The choroid" >choroid is the middle layer and contains blood vessels. The third layer, the retina" >retina, contains rods and cones, which are specialized cells that are sensitive to light. Behind the cornea and in front of the lens is the iris, the circular pigmented band around the pupil. The iris works much like the diaphragm in a camera, widening or narrowing the pupil to adjust to different light conditions.Function. (See also vision" >vision.) The refraction or bending of light rays so that they focus on the retina and can thus be transmitted to the optic nerve is accomplished by three structures: the aqueous humor, a watery substance between the cornea and lens; the lens, a crystalline structure just behind the iris; and the vitreous humor, a jelly-like substance filling the space between the lens and the retina. Unlike the lens of a camera, the lens of the eye focuses by a process called accommodation. This means that when the eye sees something in the distance, muscles pull the lens, stretching it until it is thin and almost flat, so that the light rays are only slightly bent as they pass through it. When the object is close, the muscles relax and the elastic lens becomes thicker, bending the light rays and focusing them on the retina.
Because the eye must function under many different circumstances, there are two types of nerve cells in the retina, with different shapes: the cones" >cones and the rods" >rods. They cover the full range of adaptation to light, the cones being sensitive in bright light, and the rods in dim light. The cones are responsible for color vision. There are three types of cones, each containing a substance that reacts to light of a different color, one set for red, one for green, and one for violet. These are the primary colors in light, which, when mixed together, give white. White light stimulates all three sets of color cells; any other color stimulates one or two.
The optic nerve, which transmits the nerve impulses from the retina to the visual center of the brain, contains nerve fibers from the many nerve cells in the retina. The small spot where it leaves the retina does not have any light-sensitive cells, and is called the blind spot.
The eyes are situated in the front of the head in such a way that human beings have stereoscopic vision, the ability to judge distances. Because the eyes are set apart, each eye sees farther around an object on its own side than does the other. The brain superimposes the two slightly different images and judges distances from the composite image.Disorders of the Eye. If the eyeball is too short or too long, the lens focuses the image not on the retina but behind or in front of it. The former condition is called hyperopia" >hyperopia (or farsightedness) and the latter myopia" >myopia (or nearsightedness). An irregularity in the curvature of the cornea or lens can cause the impaired vision of astigmatism. strabismus (or squint or crossed eyes) is usually caused by weakness in muscles that control movement of the eyeball. conjunctivitis is an inflammation of the membrane that covers the front of the eyeball and lines the eyelids. When small pieces of the retina become detached from the underlying layers, the result is a detachment" >retinal detachment; surgery may be necessary to prevent blindness. presbyopia (usually taking the form of hyperopia) occurs in older persons and develops as the lens loses its elasticity with the passing years. Correction is easily made with properly prescribed eyeglasses.
Foreign bodies in the eyes are common occurrences. Protective eyewear should be worn by individuals at risk. Cinders, grit, or other foreign bodies are best removed by lifting the eyelid by the lashes. The foreign body will usually remain on the surface of the lid, and can easily be removed. Particles embedded in the eyeball must be removed by a qualified health care professional.
Eyestrain is fatigue of the eyes caused by improper use, uncorrected defects in the vision, or an eye disorder. Symptoms may include aching or pains in the eyes, or a hot, scratchy feeling in the eyelids. Headache, blurring or dimness of vision, and sometimes dizziness or nausea may also occur.

Anatomic features of the eye. From Ignatavicius and Workman, 2002.artificial eye a glass or plastic prosthesis inserted in the eye socket to replace the eyeball; most are designed to be worn day and night. When patients become debilitated and unable to care for such a prosthesis, they must depend on members of the health care team to give proper care according to the chosen preferred routine.
Cleaning of a prosthetic eye is similar in principle to care of dentures; both are handled with care to avoid damage and are cleansed according to good hygienic principles. The prosthesis is removed while the patient is lying down so that it falls into the hand and is not likely to be dropped and broken. It is removed by depressing the lower eyelid, allowing the prosthesis to slide out and down. Mild soap and water are most often used for cleansing the prosthesis. Alcohol or other chemicals can damage prostheses made of plastic. If it is not replaced in the socket immediately after cleansing, it is stored in water or contact lens soaking solution. Insertion of the prosthesis is done by lifting the upper eyelid with the thumb or forefinger and placing its notched edge toward the nose. It is placed as far as possible under the upper lid and then the lower lid is depressed to allow it to slip into place. The process can be made easier by first moistening the prosthesis with water. If it is necessary to wipe the eye area of a patient wearing a prosthesis, one should gently wipe toward the nose in order not to dislodge the prosthesis.cross eye esotropia.dry eye keratoconjunctivitis sicca.pink eye popular term for acute contagious conjunctivitis.raccoon e's ecchymotic areas surrounding both eyes, suggestive of a basilar skull fracture.wall eye exotropia.

i·ris

, pl.

ir·i·des

(ī'ris, ir'i-dēz), [TA] The anterior division of the vascular tunic of the eye, a diaphragm, perforated in the center (the pupil), attached peripherally to the scleral spur; it is composed of stroma and a double layer of pigmented retinal epithelium from which are derived the sphincter and dilator muscles of the pupil. Synonym(s): orris [G. rainbow, the iris of the eye]

iris

(ī′rĭs)n. pl. irises or irides (ī′rĭ-dēz′, ĭr′ĭ-) 1. The pigmented, round, contractile membrane of the eye, suspended between the cornea and lens and perforated by the pupil. It regulates the amount of light entering the eye.2. Any of numerous widely cultivated plants of the genus Iris, having narrow sword-shaped leaves and showy, variously colored flowers.3. A rainbow or rainbowlike display of colors.4. An iris diaphragm.

iris

Fringe medicine
An essence which, in the pseudoscience of flower essence therapy, is believed to provide artisitic vision radiance and perspective.

i·ris

, pl. irides (īris, iri-dēz) [TA] The anterior division of the vascular tunic of the eye, a diaphragm, perforated in the center (the pupil), attached peripherally to the scleral spur; it is composed of stroma and a double layer of pigmented retinal epithelium from which are derived the sphincter and dilator muscles of the pupil. [G. rainbow, the iris of the eye]

iris

The coloured diaphragm of the eye forming the rear wall of the front, water-filled, chamber and lying immediately in front of the CRYSTALLINE LENS. The iris has a central opening, the pupil. It contains circular muscle fibres to constrict the pupil and radial fibres to enlarge (dilate) it.

iris

the pigmented part of the vertebrate eye. It consists of a thin sheet of tissue, attached at its outer edge to the CILIARY BODY, which has radiating muscles which can increase the size of the central pupil and a central ring of muscle around the pupil which, on contraction, causes a decrease in its size. The iris thus regulates the amount of light entering the eye. See ALBINISM for photophobia.

Iris (plural, irides)

The circular pigmented membrane behind the cornea of the eye that gives the eye its color. The iris surrounds a central opening called the pupil.Mentioned in: Eye Cancer, Eye Examination, Glaucoma, Hyperopia, Radial Keratotomy, Retinal Vein Occlusion, Trabeculectomy, Uveitis, Vitiligo

iris

The anterior part of the vascular tunic of the eye, which is situated in front of the crystalline lens and behind the cornea. It has the shape of a circular membrane with a perforation in the centre (the pupil) and is attached peripherally to the ciliary body. The iris forms a curtain dividing the space between the cornea and the lens into the anterior and posterior chambers of the eye. The anterior surface of the iris is divided into two portions: the largest peripheral ciliary zone and the inner pupillary zone. The two zones are separated by a zigzag line, the collarette. The iris consists of four layers which are, starting in the front: (1) the layer of fibrocytes and melanocytes; (2) the stroma in which are embedded the following structures: (a) the sphincter pupillae muscle which constricts the pupil and is supplied mainly by parasympathetic fibres via the third cranial nerve, (b) the vessels which form the bulk of the iris, and (c) the pigment cells; (3) the posterior membrane consisting of plain muscle fibres which constitute the dilator muscle which is supplied mainly by sympathetic motor fibres, via the long ciliary nerves; (4) the posterior epithelium which is highly pigmented.Sensory fibres from the iris are contained in the nasociliary branch of the ophthalmic nerve. The blood supply is provided by the ciliary arteries. The colour of the iris is blue in babies belonging to the white races and changes colour after a few months of life as pigment is deposited in the anterior limiting layer and the stroma. Iris colour is inherited; brown as a dominant trait and blue as a recessive trait. Iris patterns are unique for each individual and can be used as a type of identification. The function of the iris and pupil is to regulate the amount of light admitted into the eye, to optimize the depth of focus and to mitigate ocular aberrations.See cell, clump; corectopia; Fig. C 13; Fuchs, crypts of; heterochromia; inheritance; iridectomy; iridodialysis; iridology; iritis; melanin; membrane, pupillary; polycoria; reflex, pupil light.

Table I6 Differential diagnosis* between acute conjunctivitis, acute iritis and angle-closure glaucoma
	acute conjunctivitis	acute iritis (anterior uveitis)	angle-closure glaucoma
signs
injection	conjunctival	ciliary	conjunctival and ciliary
pupil	normal	contracted	semi-dilated and fixed
intraocular pressure	normal	normal or low, occasionally increased	high
cornea	normal	KP	Oedematous
anterior chamber	normal depth	normal depth, aqueous flare	shallow
iris	normal	faded	faded
view of fundus	clear	misty	almost invisible
symptoms
pain	irritation	moderate to servere	very severe and radiating
photophobia	slight	marked	slight
lacrimation	watery, purulent or mucopurulent	watery	watery
vision	normal	slightly reduced	much reduced, haloes
onset	gradual	rapid	sudden
systemic complications	none	malaise or fever	nausea and vomiting
*This is a guide, as individual cases vary according to the cause and severity of the disease.

" >

Fig. C13 Coloboma of the iris

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Iris (plural, irides)

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Synonyms for iris

noun plants with sword-shaped leaves and erect stalks bearing bright-colored flowers composed of three petals and three drooping sepals

Synonyms

Related Words

noun muscular diaphragm that controls the size of the pupil which in turn controls the amount of light that enters the eye

Related Words

noun diaphragm consisting of thin overlapping plates that can be adjusted to change the diameter of a central opening

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