For more than 50 years corneal transplantation, or complete replacement of the cornea with the cornea of a donor, has been the standard of care for treatment of patients with reduced vision or blindness due to corneal disease. Success rates with cornea trans-plantation continue to be very good, but patients are plagued with long recovery times (6-24 months), and the frequent need for contact lenses or strong prescription glasses to fully rehabilitate their vision.
In addition, the large sutured incision required for cornea transplantation is prone to injury from trauma, due to reduced strength of the incision, and transplants can be complicated by transplant rejection.
In 1998 a Dutch Ophthalmologist, Gerrit Melles, described a technique for transplanting only the innermost layer of the cornea, the endothelium. This is the layer most responsible for maintaining the clarity of the cornea, or clear front surface of the eye. It is also the layer of the cornea most likely to fail as patients become older, especially if they have had prior eye surgery, or suffer from heredity dystrophies of the cornea, such as Fuchs’ dystrophy. The original idea of Melles has been refined and hi-tech precision instruments have been developed resulting in an improvement in his technique termed “DSEK”, or descemet’s stripping endothelial keratoplasty.
The first part of the DSEK procedure involves the removal of the diseased inner layer of the cornea, or endothelium and its underlying membrane. This is then replaced with the healthy inner layer of the cornea from a donor.
Prior to the procedure, a local anesthetic is injected to anesthetize and immobilize the eye so that no discomfort is felt. Two small incisions are then made in the eye. The incisions are small enough that they often do not require sutures, but allow the passage of microsurgical instruments which are gently used to strip off the diseased endothelium from the central portion of the patient’s cornea.
The donor endothelium is prepared with the aid of a sophisticated instrument called a microkeratome. This instrument precisely removes the inner layer of the donor cornea to produce the “donor button”. The donor button is gently folded and placed within the fluid-filled anterior chamber of the eye beneath the patient’s cornea.
After centering the donor button in the precise location, a delicate hook is used to secure the transplant, while sterile air is gently injected into the anterior chamber of the eye. This causes the donor button to unfold in the exact location where the diseased tissue has been removed.
When the anterior chamber has been completely filled, theair bubble serves to hold the graft in place until the natural functioning of the new endothelium resumes and the new tissue adheres to the patient’s cornea. This usually takes only 8-10 minutes.
After surgery, the patient lies flat for approximately 1 hour. At this point, the surgeon examines the patient with the microscope. If the new cornea is in place, a small amount of the air is removed and the patient is ready to go home. Patients are given antibiotic and anti- inflammatory eye drops and are seen in the office the next day. Discomfort with the procedure is usually mild, but activities are limited until it is certain that the transplant is healing normally, usually a few days.
The advantage of DSEK includes more rapid recovery, which is measured in weeks rather than months, and most patients are able to return to driving vision in 1 to 2 months. DSEK is also a shorter procedure for the patient, taking about half as long as the typical cornea transplant. Contact lenses and strong glasses are less likely to be necessary after DSEK because there are no sutures in the cornea. In the long run, DSEK may also be safer than cornea transplants since the greater strength of the small incision can make the cornea less vulnerable to traumatic injury. The risk of transplant rejection is also thought to be less, since much less tissue is transplanted.
In summary, DSEK is a new and exciting procedure which allows eye surgeons a new weapon in the fight against the vision threat posed by corneal disease. It gives patients a new and less invasive treatment option for some of the more common causes of visual disabilities related to corneal disease.