What is a corneal transplant?
A corneal transplant 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.
In corneal transplant surgery, the surgeon removes the central portion of the cloudy cornea and replaces it with a clear cornea, gifted by an organ donor and procured by 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 simple and painless and can easily be done in an ophthalmologist’s office). Following surgery, eye drops to help promote healing will be needed for several months.
Corneal transplants are very common in the United States; about 40,000 are performed each year. The chances of success of this operation have risen dramatically because of technological advances, such as less irritating sutures, or threads, which are often finer than a human hair; and the surgical microscope. Corneal transplantation has restored sight to many, who a generation ago would have been blinded permanently by corneal injury, infection, or inherited corneal disease or degeneration.
What is ultra-thin Endothelial Keratoplasty (DSEK)?
The back layers of the cornea are the endothelium and Descemet’s membrane. Endothelial cells pump fluid out of the cornea to keep it clear to maintain good vision. When these cells aren’t functioning, the cornea becomes swollen. This may be seen in conditions such as Fuchs dystrophy and after cataract surgery. If there isn’t significant scarring in the front of the cornea, ultra-thin DSEK can be performed to replace these cells to clear the cornea. This surgery involves removing the damaged endothelial cells and Descemet’s membrane and replacing it with partial thickness graft, only 0.08mm thick, including donor endothelium and Descemet’s membrane. This surgery is performed through a small incision, similar to the one used for cataract surgery, requiring that the graft be folded or rolled to get it into the eye. It is then held into position with an air bubble for a period of time, after which (most of the time) it adheres. Advantages include a small incision with few sutures, faster visual recovery than after a full-thickness corneal transplant, and minimal change in astigmatism or post-operative refraction. DSEK is performed using local or general anesthesia in the operating room.
Are there alternatives to a corneal transplant for outer layer corneal problems?
Phototherapeutic keratectomy (PTK) combines the precision of the excimer laser with the control of a computer. With this technology, doctors can vaporize microscopically thin layers of diseased corneal tissue and etch away the surface irregularities associated with many corneal dystrophies and scars. Surrounding areas suffer relatively little trauma. New tissue can then grow over the now-smooth surface. Recovery from the procedure takes a matter of days, rather than months as with a transplant.
The Excimer Laser
One of the technologies developed to treat corneal disease is the excimer laser. This device emits pulses of ultraviolet light–a laser beam–to etch away surface irregularities of corneal tissue. Because of the laser’s precision, damage to healthy, adjoining tissue is reduced or eliminated.
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.