Closed-sky PK technique offers short learning curve, reduces intraoperative risks and stress

The closed-system technique helps to eliminate iris prolapse, vitreous loss and choroidal hemorrhage.

Thomas John

Corneal transplantation has undergone a major paradigm shift from a full-thickness penetrating keratoplasty procedure to sutureless corneal transplantation — namely, Descemet’s stripping automated endothelial keratoplasty, which has eliminated the need for a full-thickness corneal wound. However, there may be instances when a corneal surgeon may elect to perform PK. Additionally, surgeons who have not embraced DSAEK may still be performing PK.

A PK procedure has several potential disadvantages compared to DSAEK, including:

• It permanently weakens the patient’s cornea.
• Corneal sutures can break, can induce neovascularization and are subject to secondary infection.
• PK induces corneal astigmatism due to the full-thickness corneal wound and suturing of the donor cornea.
• As an open-sky procedure, PK can result in iris prolapse, iris-lens diaphragm extruding through the corneal opening due to positive pressure, vitreous loss, expulsive choroidal hemorrhage with loss of intraocular contents and loss of the eye, all of which can result intraoperatively.

The conversion of a PK procedure from an open-sky to a closed-system technique can augment its safety. However, in any variant of corneal replacement surgery, it is important to evaluate the corneal endothelial cell status by endothelial cell counts over both short and long periods of time to determine the overall safety of the procedure.

In this surgical maneuver column, Dr. Lavery describes his new closed PK surgical technique. Although this procedure can be useful, fully evaluating it requires monitoring the transplanted endothelial cells over an extended period.

– Thomas John, MD
OSN Surgical Maneuvers Editor

A novel full-thickness corneal transplantation technique minimizes intraoperative complications and involves a short learning curve, according to the surgeon who invented it.

The closed-sky penetrating keratoplasty technique greatly increases the safety profile of corneal transplantation for full-thickness procedures, Kevin T. Lavery, MD, said.

“I, for one, cannot imagine going back to an open-sky PK for most of my grafts,” Dr. Lavery told Ocular Surgery News. “The doctors I have shared this with have all been very receptive to the technique and you can see the light bulb go on in their eyes once they see the technique and its advantages.”

The technique helps to eliminate intraoperative risks associated with PK, such as iris prolapse, lens prolapse or lens expulsion, vitreous loss, choroidal formation and expulsive choroidal hemorrhage. It is an ideal technique for phakic patients, according to Dr. Lavery.

PK by way of the open-sky technique may result in complications.

A closed-sky technique improves safety of corneal transplantation. Images: Lavery KT

“It is especially useful for keratoconus patients in which the surgeon may be choosing to undersize the donor graft,” he said. “It is also nice for patients with large necks or breathing problems. … The learning curve should be minimal in that it does not require special instrumentation or learning new maneuvers.”

Closed removal of recipient cornea

The closed-sky PK technique involves a partial-thickness 360· trephination of the host cornea. After the anterior chamber is entered through the base of the trephination, corneal scissors are used to cut one quadrant, or 3 clock hours, of tissue. A suture is immediately placed in this quadrant of the recipient cornea. This process is repeated sequentially until each quadrant has been cut with scissors and closed with a suture.

“The only technical point is to make sure that the cut is contiguous; otherwise there may be a bridge of tissue that still needs to be lysed,” Dr. Lavery said.

Next, an ophthalmic viscosurgical device is placed on the corneal surface, and the donor button is laid over the recipient cornea. The donor tissue is then affixed with four cardinal sutures. The four original oblique sutures are cut, and the recipient cornea is grasped and removed.

“Once the patient’s cornea is removed, the surgeon is left with the donor in place with four cardinal sutures,” Dr. Lavery said. “At that point, they can proceed with their preferred surgical technique and suture pattern.”

The closed-sky technique takes about 5 minutes longer to perform than a standard PK.

“However, at no time during the surgery is the eye fully open, so if there was an interruption such as finding a suture, there is no harm,” Dr. Lavery said. The technique may also eliminate the need for a scleral fixation ring.

“A formal study evaluating endothelial cell loss data would be helpful, but I have not experienced any graft failures, and my take on it is that since there is no folding of the tissue, the cell loss should certainly be less then DSAEK and comparable to a standard PK,” Dr. Lavery said.

One downside is that the closed-sky technique is less convenient than other methods for combined procedures, such as PK with pupilloplasty, posterior chamber IOL suspension and IOL exchange, he said. – by Matt Hasson

• Kevin T. Lavery, MD, can be reached at TLC Eyecare and Laser Centers, 1116 W. Ganson St., Jackson, MI 49202; fax: 517-782-5166; e-mail: lasikdoc@aol.com.