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 ?
There's also surgery for refractive errors, such as lasik (when the cornea is re-shaped by a laser).
Surgeons often seek the youngest corneal tissue available regardless of patient age but historically, some surgeons set extremely restricting upper age limits, NIH said, and pointed out that when the study began in 2000, many surgeons would not accept corneas from donors over 65.
From a clinical perspective, there are many diseases that affect the back of the cornea which clinicians across the world are already beginning to relate to the presence, absence or tear in this layer.
The recommendations, endorsed by the Health Ministry, Order of Physicians and hospital leaders, suggest beginning the reform process by improving local cornea donation.
Storsberg and his team from the Fraunhofer Institute for Applied Polymer research IAP in Potsdam, are attempting to improve the situation by developing an artificial cornea.
They then stitch the new tissue, with the stem cells attached, to the cornea.
During CXL, the surgeon puts riboflavin eye drops on the cornea every couple of minutes for about half an hour.
During a LASIK procedure, the surgeon creates a flap in the eye's cornea and then uses a laser to reshape it for good vision correction, explains ophthalmic surgeon Dr.
As her eye was severely damaged, a conventional cornea transplantation would almost certainly be rejected by the body and fail within two years of surgery.
The human cornea is a thin, transparent layer of collagen and cells that acts as a window in the eyeball.
This new method depends on activating the cornea to rebuild itself and change its topography.
According to the appeal, a large group of 14 patients from Gaza, who were invited to Ramallah for cornea transplants from Sunday to Wednesday this week (January 3-5, 2010), did not reach their destination.