cornea

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Related to corneal: corneal ectasia, Corneal topography, corneal opacity, Corneal neovascularization, Corneal erosion

cornea:

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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.

Cornea

 

the anterior transparent part of the outer tunic of the eye that is part of the eye’s light-refracting apparatus and protects the eye from injury and dust.

There are five layers in the cornea: the anterior epithelium, the anterior limiting membrane (Bowman’s membrane), the substantia propria (connective-tissue stroma), the posterior, or Descemet’s, membrane, and the endothelium of the anterior chamber. Corneal epithelium is multilayered—in man it is composed of eight to ten layers with a total thickness reaching 50 micrometers. It is lined with Bowman’s membrane, which is an acellular part of the postepithelial stroma consisting of a network of collagenous fibers that run in various directions parallel to the surface of the cornea.

A membrane without a distinct boundary becomes the substantia propria of the cornea. In man the substantia propria occupies as much as 90 percent of the entire thickness of the cornea. It is solidly packed with collagenous fibers that are produced by fibroblasts; the intercellular matter of this layer contains mucopolysaccharides, chondroitin sulfate, chondroitin, and keratosulfate. The transparency of the cornea depends on the degree of dehydration and orderliness of the molecules of the acellular portion of the cornea’s basic matter.

Descemet’s membrane lines the basic matter of the cornea and is tough and elastic; its posterior surface is covered by the single-layered endothelium of the anterior chamber of the eye.

There are no blood vessels in corneal tissues. In man the cornea is innervated by 70–80 radial nerve trunks that originate in the optical branch of the fifth pair of cranial nerves; the branching of the trunks penetrates the entire thickness of the cornea, except Descemet’s membrane and the endothelium.

The most common diseases of the cornea include traumas, blennorrhea, keratitis, and staphyloma.

O. G. STROEVA

cornea

[′kȯr·nē·ə]
(anatomy)
The transparent anterior portion of the outer coat of the vertebrate eye covering the iris and the pupil.
(invertebrate zoology)
The outer transparent portion of each ommatidium of a compound eye.

cornea

the convex transparent membrane that forms the anterior covering of the eyeball and is continuous with the sclera
References in periodicals archive ?
Endothelial cell density is a gauge of endothelial function, although it does not always correlate with corneal thickness.
Identify and understand important and diverse types of therapeutics under development for Corneal Ulcers
They sought to determine whether SIV infection leads to decreases in corneal nerve fiber density, and whether corneal nerve fiber density correlates with epidermal nerve fiber length counts, thereby setting the stage for follow-up investigation using corneal confocal microscopy.
Since the introduction of medical standards for corneal standards for corneal tissue in 1980, there has not been a reported case of infectious disease transmission via corneal transplantation.
This helps to highlight subtle corneal opacities, allows assessment of the pupil, and gives a clue as to the health of the posterior segment of the eye.
Obtained Samples of corneal ulcer in a direct smear, were positive in 23% and 77% negative, while Samples of cultured corneal ulcer were positive in 63% and 37% negative.
Visual impairment due to high-altitude corneal oedema in association with other factors has occasionally been reported, however.
With the initiation of a multi-organ transplantation programme in June 2007, corneas were available for patients in the capital city and enabled 55 patients between the ages of 3 to 63 to undergo corneal transplants, 60 per cent of whom were men.
Using a first-generation corneal confocal microscope, the ConfoScan P4 (Tomey Corp.
Still, cornea transplants from dead donors have thrived only when a recipient has a reserve of corneal stem cells, which reside where the cornea meets the white of the eye.
A CORNEAL ulcer is an open sore on the cornea and can result in the loss of sight if not treated quickly.
The approach was considered radical at the time for its recommendation that corneal topography - that is, the external shape of the cornea, which is the clear "window" at the front of the eye - be considered together with the patient's refraction in the surgical planning of refractive surgery.