Cornea transplant

Image:Cornea transplant800.jpg A cornea transplant, also known as a corneal graft or penetrating keratoplasty, is a surgical procedurewhere a damaged or diseased corneais replaced by donated corneal tissue which has been removed from a recently deceased individual having no known diseases which might affect the viability of the donated tissue. The cornea is the clear part of eyein front of the irisand pupil. The surgical procedure is performed by ophthalmologists, medical doctors who specialize in eyes, and are often done on an outpatient basis (The patient goes home following surgery).

Indications

Indications for corneal transplantation include the following:

• Optical - To improve visual acuity by replacing the opaque host tissue by clear healthy donor tissue. The most common indication in this category is pseudophakic bullous keratopathy, followed by keratoconus, corneal degenerationand dystrophy, as well as scarring due to keratitisand trauma.
• Tectonic/reconstructive - To preserve corneal anatomy and integrity in patients with stromal thinning and descemetoceles, or to reconstruct the anatomy of the eye, e.g. after corneal perforation.
• Therapeutic - To remove inflamed corneal tissue unresponsive to treatment by antibioticsor anti-virals.
• Cosmetic - To improve the appearance of patients with corneal scars that have given a whitish or opaque hue to the cornea. [1]

Pre-operative examination

In most instances, the patientwill meet with their ophthalmologist for an examination in the weeks or months preceding the surgery. During the exam, the ophthalmologist will examine the eye and diagnose the condition. The doctor will then discuss the condition with the patient, including the different treatment options available. The doctor will also discuss the risks and benefits of the various options. If the patient elects to proceed with the surgery, the doctor will have the patient sign an informed consentform. The doctor might also perform a physical examination and order lab tests, such as blood work, X-rays, or an EKG.

The surgery date and time will also be set, and the patient will be told where the surgery will take place.

Procedure

On the day of the surgery, the patient arrives to either a hospitalor an outpatient surgery center, where the procedure will be performed. The patient is given a brief physical examination by the surgical team and is taken to the operating room. In the OR, the patient lays down on an operating table and is either given general anesthesia, or local anesthesiaand a sedative.

With anesthesia induced, the surgical team prepares the eye to be operated on and drapes the face around the eye. An eyelid speculumis placed to keep the lids open, and some lubrication is placed on the eye to prevent drying. A metal ring is then stitched to the sclera, which will provide a base for a trephine.

A trephine is then placed over the cornea and is used by the surgeon to cut the host cornea. The trephine is then removed and the surgeon cuts a circular graft(a "button") from the donor cornea. Once this is done, the surgeon returns to the patient's eye and removes the host cornea.

The donor cornea is then brought into the surgical field and manuvered into place with forceps. Once in place, the surgeon will fasten the cornea to the eye with a running stitch (as used in the image above) or a multiple interrupted stiches. The surgeon finishes up by reforming the anterior chamberwith a sterile solution injected by a canula, then testing that it's watertight by placing a dye on the wound exterior.

With the metal ring removed and antibioticeyedropsplaced, the eye is patched, and the patient is taken to a recovery area while the effects of the anesthesia wear off. The patient typically goes home following this and sees the doctor the following day for the first post operative appointment.

Risks

As with any surgery, there are some possible risks. While the cornea itself doesn't have any blood vessels, there is still a potential for some blood loss, usually from suturing the metal ring to the sclera. Any blood loss is typically less than a teaspoon, or less than 2 cc.

There is also a risk of infection. Since the cornea has no blood vessels (it takes its nutrients from the aqueous humor) it takes longer to heal than would a cut on the skin. While the woundis healing, it is possible that it might become infected by various microorganisms. This risk is minimized by antibiotic prophylaxis(using antibiotic eyedrops, even when no infection exists).

Graft failure can occur at any time after the cornea has been transplanted, even years or decades later. The causes can vary, though it is usually due to new injury or illness. Treatment can be either medical or surgical, depending on the individual case.

Prognosis

When the primary purpose of a cornea transplant is to improve visual acuity, the prognosis is dependent upon whether the rest of the eye is healthy. If the rest of the eye is healthy, then it should be possible to recover normal vision.

History

The first cornea transplant was first performed in 1905, by Dr. Eduard Zirm, making it one of the first types of transplant surgery successfully performed.

Advances in microscopesenabled surgeons to get a better view of the surgical field, while advances in materials scienceenabled them to use suturesfiner than a human hair.

Instrumental in the success of cornea transplants were the establishment of eye banks. These are organizations located throughout the world to coordinate the distribution of donated corneas to surgeons, as well as providing eyes for research. Some eye banks also distribute other anatomical gifts.

See also

• Cornea
• Corneal graft rejection
• Eye

External links

• Eye Bank Association of America
• EyeMD link cornea transplant page
• Larry Wall's cornea transplant diary
• Merck Manual: Corneal transplantation

• Fuchs' Dystrophy Support Group

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Cornea+transplant Wikipedia article Cornea transplant.