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Corneal transplant, also known as penetrating keratoplasty (PK), is a surgical procedure performed in an outpatient setting under local or general anesthesia. Corneal transplant involves replacing the individual's diseased or scarred clear anterior one-third of the eyeball (cornea) with a piece of donor cornea (allograft).
The procedure may be necessary when an individual's cornea becomes cloudy, scarred or distorted, preventing light from reaching the interior posterior surface of the eye (retina) where focusing occurs. Inherited degenerative diseases, infections, ulcers, and physical trauma (i.e., burns, scratches, foreign objects such as metal chips or splinters, fireworks, chemicals, etc.) can all cause corneal damage.
Corneal transplants typically use human tissue from donor corneas screened for presence of disease, infections, or other abnormalities. In recently developed techniques, artificial corneas (keratoprosthesis) made of flexible plastic may be useful for individuals with considerable corneal scarring or who have unsuccessfully undergone previous traditional procedures.
Individuals with overly thin tissue in the cornea are at risk of keratoconus (an abnormal, cone-shaped cornea), distorted vision, and/or corneal rupture and may require a corneal transplant.
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Source: Medical Disability Advisor
| A corneal transplant is considered when the individual's eyesight significantly is diminished due to a diseased, scarred, swollen, or otherwise distorted cornea. Corneal transplant is generally performed when medication or other corrective measures to repair the cornea or improve eyesight have failed. When traditional corneal transplants involving human tissue have failed or are inappropriate, artificial corneas made of flexible plastic might be considered for transplant. In some less severe cases, corneal transplants have been delayed or rendered unnecessary with a newer procedure called phototherapeutic keratotomy (PTK). PTK involves use of a laser to remove (ablate) and smooth corneal tissue damaged by scarring, disease or infection.
Several conditions are treated with corneal transplant, including ocular herpes virus infections and corneal dystrophies, which include Fuch's dystrophy, keratoconus, lattice dystrophy, map-dot-fingerprint dystrophy, corneal ulcer, and iridocorneal endothelial syndrome. Corneal scarring may also result from trauma or injury, or it could be a complication of another surgical procedure. |
Source: Medical Disability Advisor
| Corneal transplant surgery is performed in an outpatient setting. Individuals may be given a sedative if they are anxious about the procedure. Shortly before the procedure, the surgeon or nursing staff will administer a local anesthetic to numb the eye and control eye movement. In some cases, general anesthesia may be needed. A cookie cutter type surgical instrument called a trephine is used with the aid of a surgical microscope to remove a circle of tissue about 8 mm in diameter from the center of the cornea. The tissue then will be replaced with a matching piece of tissue cut from the donor cornea, and stitched into the recipient's eye with fine, hair-like sutures. The stitches will remain in place until the wound heals properly (from 2 months to more than a year).
The individual generally experiences very little discomfort and is released the day of surgery. Eyedrop medication may be prescribed to prevent pupil dilation and cycloplegic infection, possibly for as long as several months. |
Source: Medical Disability Advisor
| Following corneal transplant, the individual's vision will be blurred, but likely will clear over time. It may take up to a year or longer for vision to return to normal. During the interim, glasses may be prescribed to help improve vision. Survival rates of the grafted cornea tend to decrease between 1 and 5 years. After 5 years, the new cornea survives in about 80% of individuals (Akpek). Visual outcomes depend largely on the underlying condition and presence of complications. Success rates for corneal transplant surgery vary depending on the underlying disease, but are generally high.
In most individuals, the allograft will heal completely. Rarely, individuals may experience a complication (rejection, severe infection) resulting in permanent damage. If the procedure was required as treatment for an underlying disease such as corneal dystrophy, that disease could recur and affect the new cornea. A second procedure may be required. |
Source: Medical Disability Advisor
| The primary risk associated with corneal transplantation is tissue rejection, which typically does not occur during the first 2 months, but is possible at any time after that. Signs of impending rejection are redness, sensitivity to light (photophobia), sudden change in vision, and increased eye pain. If these symptoms occur, prompt intervention is crucial to save the transplant. Treatment (usually with a corticosteroid such as cortisone eye drops) usually helps stabilize the cornea and reverse the rejection. Delayed treatment or a particularly severe rejection could cloud the cornea, necessitating another procedure. Recent research suggests that matching donor and recipient blood types may be more important for preventing rejection than matching their tissue types.
Due to the slow healing rate of the corneal wound, infection is another potential complication. Underlying conditions causing the need for a transplant might recur. Corneal transplant in extremely rare cases has been associated with transmission of a fatal brain disorder, Creutzfeldt-Jakob Disease (CJD), from an infected donor to recipients. Rarely, despite screening, other diseases can be transmitted from donor tissue to the recipient. |
Source: Medical Disability Advisor
| Vision should be evaluated when it is critical to the individual's work assignment. Because the cornea heals slowly, the individual may require an alternative assignment until vision returns to normal. Those who require the use of safety glasses may need to obtain a pair with a corrective prescription. Some individuals may be fitted with a therapeutic contact lens and will be more sensitive to eye irritants, fumes, and dust. Larger computer screens may be helpful as the individual's vision returns to normal if there is a decrease in visual acuity in the opposite eye. Eye drops (pupil dilators, antibiotics, steroids) will be needed for a prolonged period of time after surgery, and accommodations for frequent breaks may be required. Strenuous activities, lifting, and bending will be limited following surgery. |
Source: Medical Disability Advisor
| Akpek, EK, et al. "Long-Term Outcomes of Combined Penetrating Keratoplasty with Iris-Sutured Intraocular Lens Implantation." Ophthalmology 110 5 (2003): 1017-1022. MD Consult. Elsevier, Inc. 1 Oct. 2004 <http://home.mdconsult.com/das/journal/view/41257480-4/N/13348972?sid=276456956&source=MI>. |
Source: Medical Disability Advisor
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