cornea

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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 ?
The researchers found that while a complicated mix of multiple genes and alterations as well as environmental conditions all contribute to glaucoma, the most common risk factor among all is having a thin cornea.
Currently there is a desperate shortage of donated corneas in the UK, Europe, and the USA.
Women who receive cornea transplants are more likely to reject them if the donors are male, freelance writer Amber Dance reported in "A view to better cornea transplants" (SN: 9/3/16, p.
Muscat: Experts are putting in place plans to begin offering cornea transplant surgery in Oman.
The corneal thickness was measured in the same corneas before alkali injury (corneas of healthy eyes) and five and fifteen days after the injury (all experimental groups).
The aim of our study was to explore the efficacy and limitations of transplanting the decellularized corneal matrix derived from xenogeneic corneas.
In addition, eye banks in the US exported about 20,000 corneas to other countries in 2012, an increase of 7% over 2011.
Specular Microscopy: Assessment of endothelium can be done by Specular Microscope, Most of the eye banks use Konan Eye Bank Keratoanalyzer where in Corneas are examined through standard corneal storage media vials after Securing the viewing chamber or storage media vial on the holding device of the specular microscope.
Let alone the issue of scarce donor material, a sub-group of patients do not tolerate transplanted corneas, necessitating the employment of an alternative means of restoring eye sight.
Corneal Collagen Cross Linking is a technique that strengthens the chemical bonds in one's cornea by applying Vitamin B2 followed by treatment with UV Light.
STEM cells, the body's "building blocks", are taken from the cornea of a dead donor and grown in a lab for around two weeks.
Scientists at the Sahlgrenska Academy, University of Gothenburg, have taken the first steps toward replacing donated corneas with corneas cultivated from stem cells.