CORNEAL TRANSPLANT (Penetrating keratoplasty)
Number performed:
Currently about 34,000 cornea transplants done per year in the U.S.
Background:
The cornea is the clear front window of the eye which focuses light onto
the retina. A damaged cornea can get swollen or scarred. As a result,
vision becomes blurry because the cornea scatters or distorts light. Damage
can be caused by hereditary corneal failure, scarring after other eye
surgery or infections, rejection after the first corneal transplant; or
a condition called keratoconus (meaning “cone shaped” due
to the thin and protruding cornea). This condition usually appears when
patients are in their late teens and can progress for a decade or even
two decades. One eye is usually affected more severely than the other.
After the patient’s ophthalmologist recommends corneal transplant, the patient’s name is put on a list at the local eye bank. Before a donor cornea is released for transplant, the eye bank tests the human donor for the viruses that cause hepatitis and AIDS and the cornea is checked for visual clarity.
The procedure was first explored in the early 1960s. The number of operations performed has increased dramatically in 40 years. For example, Tissue Banks International, which was founded 1962 collected 30 corneas in its first year. Today, it collects thousands.
Procedure:
Follow-up
After the operation, a shield is placed over the eye that has just received
the transplanted cornea. The patient can use eye drops and over-the-counter
pain medication to make the healing process more comfortable. Right after
the procedure, the donor button is swollen and even following healing
the button is usually thicker than the corneal bed in which it rests.
The time from surgery to the removal of the stitches is commonly 6 to
17 months.
Graft rejection reactions occur in 11% to 18% of the patients, and can occur anywhere from 1 month to 5 years after surgery. Persistent discomfort, light sensitivity, redness, or change in vision are all warning signs of rejection. The rejected cornea will cloud and vision will deteriorate. If signs of rejection occur, aggressive treatment with steroids is begun. Usually the reaction is overcome and the graft remains clear. Other treatable complications can include infection, bleeding, swelling, detachment of the retina, or glaucoma. Over 90% of the corneal grafts are successful with some studies reporting 97% to 99% success rates at 5 and 10 years. The rejection rate for bilateral grafts is higher than if only one eye is grafted. Corneal transplant surgery is the most successful type of all organ/tissue transplant surgeries.
The patient's eyeglass prescription may vary for a few months after surgery. Astigmatism is common following corneal replacement, and so most transplants require contacts lenses to correct distorted vision. However, it can be difficult to fit contacts after transplant because the edge of the new cornea can be slightly raised or tilted in comparison with the tissue around it. The irregularity of the cornea after transplant usually requires rigid instead of soft contacts. The lenses also must have good oxygen permeability should be used to minimize corneal swelling. Sometimes astigmatism can be lessened if the sutures are removed early. Alternatively, a relaxing incision may be done to decrease the astigmatism.
Alternatives:
Very careful contact lens fittings are necessary before recommending a
corneal transplant, especially if there is not significant corneal scarring
affecting vision.. One study found that 69% of keratoconics, most referred
for transplant, could be successfully fit with contact lenses if special
lens designs were used.
Links:
http://www.kellogg.umich.edu/patient/surg/cornealtransplant.html
http://www.opt.indiana.edu/lowther/html/keratoconus_transplant.htm
http://eyelaser-chicagoland.com/crntrans.htm
http://www.eyemdlink.com/EyeProcedure.asp?EyeProcedureID=65
http://www.milliman.com/health/publications/research_reports/hrr_07-2002.pdf
http://www.tbionline.org/annual-report/2003/report.htm
