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
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These drones would help in transporting cornea tissues to transplant centres or where the patient waiting-list is long for surgeries.
He affirmed his commitment to the noble cause and hoped for the extension of the cooperation in similar fields to assure the availability of the cornea.
He said that there are around 200,000 people in Pakistan who are suffering from corneal blindness and these people can have a perfectly normal life if their damaged corneas are replaced with healthy ones.
Knowing that he will soon need a cornea transplant in his right eye, Declan is heartened by changing perceptions.
'The cornea has no blood supply, it is seldom subject to the rejections like other organ transplants,' he explained.
In Forth Valley over the past year, corneas were retrieved from around 15 patients.
'We wanted this material to allow the cells of the cornea to mesh with the adhesive and to regenerate over time to mimic something as close to the native cornea as possible.'
? photorefractive keratectomy (PRK) - where a small amount of the cornea's surface is removed, and a laser is used to remove tissue and change the shape of the cornea
Dr Arbelaez, a pioneer in Descemet's Membrane Endothelial Keratoplasty (DMEK) Corneal Transplant in Oman, a surgery only some cornea surgeons worldwide are trained on, is also recognized for his high experience in cornea disease, keratoconus management and refractive surgery.
The health authority said that in the last year, 3,504 people in England have had their sight restored through cornea transplants.
Newcastle University researchers have successfully produced artificial corneas using a low-cost 3D bio-printer and a gel formed from human corneal stromal cells, alginate and collagen.
The method consists of mixing stem cells from a healthy donor cornea with a gel derived from seaweed and collagen.