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Corneal surgery is any surgical operation performed on the outermost layer of the eye, called the cornea. The cornea is the transparent outermost part of the eye that helps focus and refract light. Damage to the cornea causes visual distortion or complete vision loss. Corneal surgery might consist of a corneal transplant, stromal rings to maintain proper corneal shape, or implantation of an artificial cornea. Osteo-odonto-keratoprosthesis, stem cell implantation, and biosynthetic corneas are among the more recent types of corneal surgery.
A healthy cornea is shaped with the center thinner than the periphery. The shape of the cornea is critical to its proper function; an improperly shaped cornea will bend light and distort vision. Corneal scarring obstructs light altogether, and the greater the degree of scarring, the darker and more blurry vision becomes. Excessive scarring might render corneal surgery unlikely because new tissue might not graft properly in this event.
In a corneal transplant, damaged corneal tissue is partially removed and replaced with donated healthy cornea with the expectation that the new tissue will graft with the old. The cornea receives its oxygen and nutrition from the air and from the aqueous humor of the eye respectively. There is no blood supply, which makes the possibility of rejection of a corneal transplant much less likely than in other types of transplants.
Another type of corneal surgery is the placement of stromal rings. Stromal rings are implanted in the inner layer, or stroma, of the cornea. The purpose is to force a misshapen cornea into a shape that admits light into the eye with little or no distortion. Research shows that the success rate of stromal rings is lower than that of corneal transplantation.
Artificial corneal implants are an alternative to traditional transplantation. An artificial cornea is a transparent device that is used instead of donated corneal tissue. This type of corneal surgery potentially eliminates the possibility of graft failure, and is much more expensive than corneal transplantation. It is usually performed when graft failure is highly likely or when traditional corneal transplantation has failed.
A rarely used procedure known as osteo-odonto-keratoprosthesis might be used to help patients with the most severe corneal damage. A thin layer of the patient’s tooth is grafted at the site of the corneal damage, and an artificial lens is placed in the tooth graft.
Other forms of corneal surgery include stem cell implantation and biosynthetic corneas. Stem cell implantation involves insertion of healthy corneal stem cells after removing the damaged cornea. These stem cells then differentiate into a healthy cornea. Experimental biosynthetic corneas are made of collagen grown into special types of cells and shaped into a cornea.
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