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 ?
He said that under cornea transplant programme, damaged patients of cornea due to different diseases and accidents was transplanted.
A cornea transplant involves an operation to remove all or part of a damaged cornea, the clear outer layer at the front of the eye ball, and replace it with healthy donor tissue.
The disease is a degenerative disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than the more normal gradual curve.
A cornea transplant is often referred to as a keratoplasty, or a corneal graft.
The antioxidant mechanism located in the corneal epithelium is very important for the protection of the cornea against toxic environmental influences.
sup][5],[6],[7] Studies of corneal acellular matrice from allogeneic or xenogeneic resources serving as scaffolds for tissue engineering, [sup][8],[9] have indicated that the porcine corneal acellular matrix is a promising scaffold for bioengineered cornea due to good three dimension structure, biocompatibility, and mechanical function.
The cardinal signs of a corneal ulcer include discomfort, ocular discharge, redness of the white of the eye and the opacity of the cornea itself," says ophthalmologist Eric C.
There's also surgery for refractive errors, such as lasik (when the cornea is re-shaped by a laser).
The study of 663 participants found that at 10 years, the transplant success rates for corneas from donors aged 12 to 65 and aged 6 to 75 remained similar, at 77% and 71%.
Summary: TEHRAN (FNA)- Scientists at the University of Nottingham have discovered a previously undetected layer in the cornea, the clear window at the front of the human eye.
INTRODUCTION: Outcome of a corneal transplant surgery mainly depends on the functional reserve of the cornea being transplanted.
Thousands of people have lost their eyesight due to damages to the cornea, such as trauma, absent limbal stem cells or diseases.