A corneal transplant or penetrating keratoplasty (PKP)
involves replacing a diseased or scarred cornea with
a new one. When the cornea becomes cloudy, light cannot
penetrate the eye to reach the light-sensitive retina.
Poor vision or blindness may result. Corneal transplants
are very common in the United States with about 40,000
performed each year.
In corneal transplant surgery, the surgeon removes the
central portion of the cloudy cornea and replaces it
with a clear cornea, usually donated through an eye
bank. A trephine, an instrument like a cookie cutter,
is used to remove the cloudy cornea. The surgeon places
the new cornea in the opening and sews it with a very
fine thread. The thread stays in for months or even
years until the eye heals properly (removing the thread
is quite simple and can easily be done in an ophthalmologist's
office).
Following surgery, eye drops to help promote healing
will be needed for several months with certain drops
being required indefinitely to prevent rejection of
the donor cornea. After a 6-12 month period of recovery,
patients may be fitted with eyeglasses or contact lenses.
Alternatives to Corneal Transplants
PTK
For diseases that only affect the surface of the cornea,
phototherapeutic keratectomy (PTK) is one of the latest
advances in eye care for the treatment of corneal dystrophies,
corneal scars, and certain corneal infections.
Only a short time ago, people with these disorders would
most likely have needed a corneal transplant. By combining
the precision of the excimer laser with the control
of a computer, doctors can vaporize microscopically
thin layers of diseased corneal tissue and etch away
the surface irregularities associated with many corneal
dystrophies and scars. Surrounding healthy tissue is
spared. New tissue can then grow over the now-smooth
surface.
Recovery from the procedure takes a matter of days to
weeks, rather than months as with a transplant. The
return of vision can occur rapidly, especially if the
cause of the problem is confined to the top layer of
the cornea. Studies have shown close to an 85 % success
rate in corneal repair using PTK for well-selected patients.
The PTK procedure is especially useful for people with
inherited disorders, whose scars or other corneal opacities
limit vision by blocking the way images form on the
retina. PTK has been approved by the U.S. Food and Drug
Administration.
LKP
For diseases that affect the anterior portion of the
cornea but are not amenable to PTK, a partial thickness
cornea transplant or lamellar keratoplasty (LKP) can
be performed. This is the preferred technique for patients
with keratoconus, a progressive gradual thinning of
the cornea usually requiring a contact lens for best
vision.
Recovery from LKP is similar to PKP but long term drop
use to prevent rejection is often not necessary after
one year of recovery.
DSEK
Descemet’s stripping with endothelial keratoplasty
(DSEK) is sometimes called a partial cornea transplant
and can be used to treat corneal swelling after cataract
surgery or from Fuchs’ dystrophy (a familial dysfunction
of the back surface of the cornea). DSEK replaces only
the damaged cell layer instead of the entire thickness
of the cornea. In the procedure, the inner most layer
of the cornea (Descemet's membrane) is removed and replaced
with that of a donor. Due to the small incision, there
is limited need for sutures.
Recovery from DSEK is more rapid than convention corneal
transplant. Eye drops are necessary to prevent rejection
of the donor cornea. This has become the preferred technique
in patients due to improved safety, potentially less
rejection and more rapid visual recovery.
Modified from The National Eye Institute (NEI),
the Federal government's leading agency for vision research
For more information regarding corneal diseases and
surgery, contact:
National Eye Institute
2020 Vision Place
Bethesda, MD 20892
(301) 496-5248
