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Suture-free DLEK preserves corneal surface topography and ensures faster wound healing

Mark A. Terry MD

DEEP lamellar endothelial keratoplasty (DLEK) eliminates corneal surface incisions and results in faster wound healing, smoother topography and a more stable eye by using an air bubble to re-attach the tissues after corneal transplants, Mark A. Terry MD told a session of Cornea 2002.

“We sometimes define ‘success’ after corneal transplantation as an eye with 20/20 vision after the operation. This may be the case, but the complications which may occur at later stages, such as globe rupture after minor trauma, may render this ‘success’ a long-term failure,” he explained.

Dr Terry pointed out that postoperative surface irregularities after PK can be avoided by transplanting only the posterior cornea and that complications related to sutures can be avoided by using a corneal suture-free procedure.

Deep lamellar endothelial keratoplasty (DLEK) is a technique used to replace the entire corneal endothelium through a limbal scleral tunnel incision. It avoids using any corneal surface incisions or sutures and preserves the corneal surface from limbus to limbus.
The adhesion of tissues is initially caused by the physical hydrophilic attraction of the wet posterior graft tissue to the wet recipient stromal tissue, created by an air bubble in the anterior chamber. After some minutes the air bubble is removed and it is the biological endothelial pump mechanisms that maintain the adhesion.

The main advantage of this technique is the preservation of the normal corneal topography. In addition, wound healing is faster and stronger and suture-related problems such as induced astigmatism, unpredictable corneal power, infections, ulcerations and suture-induced visualisation with subsequent graft rejection are all avoided.

On the down side, this procedure is relatively difficult to perform and it is a challenge for the surgeons to consistently obtain an optically pure interface.
Dr Terry presented a summary of the basic surgical steps. The 9.0 mm scleral incision is performed with a guarded diamond knife set at a depth of 0.35 mm, parallel to the limbus and 1.0 mm to 2.0 mm peripheral to it.
Healon is then injected through a stab incision at the 10 o’clock position into the anterior chamber to maintain adequate pressure. A mid to deep corneal pocket is formed from limbus to limbus. The surgeons use the specialised Devers dissectors, switching from straight to curved as necessary.

Healon is released from the anterior chamber through the stab incision. Trephination of the posterior disc of the recipient is done with a specialised intralameller 8.0 mm Terry Trephine until the anterior chamber has been found.
The posterior disc trephination is completed with the specialised intracorneal Cindy scissors and the disc is removed. The Healon is completely aspirated from the anterior chamber and the interface, and replaced with a balanced salt solution (BSS).
“This is extremely important because leaving Healon here can prevent adhesion of your donor disc later,” he warned.

The donor cornea-scleral tissue is placed onto an artificial anterior chamber where the donor posterior button is prepared. The chamber is a specialised device that allows a donor cornea-scleral cap of tissue to be anatomically positioned just as it would be in a whole eye. This allows the surgeon the latitude to use eye bank corneas rather than whole eyes. Either an automated microkeratome or manual resection can be performed to remove the anterior donor stroma and isolate the posterior donor tissue.
The donor tissue is then mounted on a punch block and the same size (8.0 mm) donor trephine is used to punch out the posterior donor disc.

The disc is placed (endothelial side down) onto a specialised Ousley insertion spatula previously coated with Healon. You need to make absolutely sure that a layer of Healon is protecting your endothelial layer, he stressed.
After filling the anterior chamber of the recipient with air, the donor disc is placed into the pocket, into the anterior chamber and then lifted anteriorly into the posterior stromal recipient bed.

The surgeon needs to hold it in position for three or four seconds and then gently slide the spatula out of the eye, leaving the disc in place, he explained.
Air is immediately injected into the anterior chamber to secure the graft. The donor disc position can then be gently adjusted and any air in the interface is removed.
The scleral wound is then closed using five or six 10-O nylon sutures.

The air in the anterior chamber is completely removed. By this time the biological response is taking over and the tissue will stay attached. Finally, the conjunctiva is also closed and a collagen shield with antibiotics and steroids is placed on the eye. The eye is patched and the patch removed the next day.
Dr Terry and his research associate, Paula Ousley, now have patients who were operated on with this technique three years ago and are now doing very well. In their first 40 patients the average change in astigmatism is less than 1.0 D and central corneal power does not change at all.

The average vision at one year is 20/50. He added that despite good initial results, several factors are needed to be taken into account when assessing these results.
“First, the average age of the patients treated with this procedure is quite advanced. It was 78 years in my initial 40 patients series. The number of non-related eye pathologies that reduce vision are considerable. Second, there is a learning curve and results will improve with time as the surgeon becomes more skilled in the procedure,” he said.

His results represent a 100% follow-up. No patients dropped out because of infection, ruptured globes or other complications present in more traditional techniques, he stressed. Dr Terry founded and leads the Endothelial Keratoplasty Group, which consists of 35 US sites and 15 international ones, to scientifically investigate and advance DLEK surgery.