Endokeratoplasty is a promising alternative to PKP for diseased endothelium

A microkeratome and artificial anterior chamber are required.

PITTSBURGH - Endokeratoplasty, in which only the posterior part of the recipient cornea is transplanted, represents a promising alternative to conventional penetrating keratoplasty in patients with diseased corneal endothelium.

"There is the potential for a much quicker healing period with endokeratoplasty," said Robert C. Arffa, MD, director of the cornea division at Allegheny General Hospital here. "All sutures can be removed at 3 months after surgery, while most corneal transplants typically require a full year with sutures."

Dr. Arffa said it is too early to assess whether outcomes will be better with endokeratoplasty compared to penetrating keratoplasty (PKP), but he doubts there will be much difference. "We think there will be less astigmatism. With PKP, visual rehabilitation is often hampered by high-degree astigmatism," he said.

Endokeratoplasty (also referred to as posterior lamellar keratoplasty) is a slightly more difficult surgical procedure than conventional PKP.

"It requires both a microkeratome and an artificial anterior chamber," Dr. Arffa said. "The donor cornea has already been removed from the globe; therefore, you need to use an artificial anterior chamber to hold the donor cornea for the microkeratome because you use only the posterior half of that cornea."

The artificial anterior chamber is manufactured by Moria.

Four patients

---The Moria One microkeratome is used in combination with an artificial chamber to produce corneal lamellae. A ring tightens the corneoscleral rim onto the artificial chamber. The pressure is increased in the chamber up to at least 85 mm Hg.

Dr. Arffa has treated four patients with the novel approach since October, all of whom had strictly endothelial complications. "These patients have endothelial decompensation, but normal anterior stroma. This probably represents about one-third of all corneal transplant patients," he said. In contrast, PKP is suitable for a wider range of patients.

Dr. Arffa was co-author of a seven-patient study of endokeratoplasty published last fall in Ophthalmology. All surgeries for that study were performed by Massimo Busin, MD, of the University of Ferrara in Italy. "All corneas became clear, and the surface re-epithelialized within 4 weeks after surgery," said Dr. Arffa, an adjunct associate professor of ophthalmology at the Medical College of Pennsylvania here. Regular astigmatism of less than 4 D was recorded in all cases as early as 4 weeks following surgery.

Epithelial interface ingrowth with extensive melting of the corneal flap was observed in one patient 3 months postoperatively. "This was managed by removal of the flap and resuturing of the donor button," Dr. Arffa said.

All initial surgeries included the creation of a 9.5-mm corneal flap and substitution of an underlying 6.5-mm button of deep stroma and endothelium with a 7-mm donor button.

"Dr. Busin sutured the flap back into position using a 10-0 running nylon suture," Dr. Arffa said. In the three most recently operated patients, an anterior lamella 160 µm in thickness was removed from the donor button before transplantation. "In these cases, the donor corneoscleral rim was placed in the Moria artificial anterior chamber, and an anterior lamella was removed with a microkeratome. The corneoscleral ring was then inverted on a Kaufman trephine block, and a 7-mm button was obtained by trephination."

The procedure has undergone refinement over time. This has led to simplification of the technique, including the elimination of all deep sutures. Surprisingly, the donor button adheres to the overlying flap without suturing it to the recipient bed, Dr. Arffa said. This accelerates resolution of postop corneal edema, which was slow in most cases performed with the original technique, he said.

As early as 1 month after surgery, useful uncorrected vision of at least 20/400 was recorded in all seven patients. Best corrected visual acuity ranged between 20/100 and 20/40.

All patients had all sutures safely removed by the end of the fourth postoperative month. "The deep location of the donor button might also lessen the risk of immunization of the host against the graft, which would lower the chances of an immune reaction," Dr. Arffa said.

Anterior cornea treatment

---The Moria One microkeratome is used without a stop to create an anterior lamella. Multiple heads allow for various lamellar thicknesses.

Dr. Arffa, a clinical assistant professor of ophthalmology at the University of Pittsburgh, said other practitioners worldwide are using the Moria One microkeratome and Moria artificial anterior chamber to develop other graft techniques.

"Anterior lamellar keratoplasty (LK) involves removing the anterior portion and leaving the posterior portion intact, which is just the opposite of endokeratoplasty," Dr. Arffa said. LK is extraocular surgery that preserves the endothelial cell layer with no endothelial rejection. "This technique allows for quick healing as well," he said.

In the past, LK required a donor whole globe, leading to possible technical difficulties and problems associated with the manual dissection (irregular donor lenticule, irregular bed, irregular interface, inadvertent perforation). Dr. Arffa has performed only one LK to date. "The surgery went very well and the initial results are very good," he said.

Although LK has been around for quite some time, it was not embraced because it is technically difficult and patients often developed haze between the two corneal layers (the new outer portion and old inner portion).

"This in turn limited the vision a patient could achieve after surgery, but the procedure is much easier today by using the microkeratome and the artificial anterior chamber. The haze also appears to be much less," Dr. Arffa said. "I encourage practitioners who are currently using penetrating keratoplasty to explore endokeratoplasty and LK."

For Your Information:

• Robert C. Arffa, MD, can be reached at Allegheny General Hospital, 420 E. North Ave., Pittsburgh, PA 15212; (412) 359-6300; fax: (412) 359-6768; e-mail: arffa@adelphia.net. Dr. Arffa has no direct financial interest in the products mentioned in this article.

• For more information on Moria Complete ALTK System including the One microkeratome and the artificial anterior chamber, contact Moria USA, 4030 Skyron Dr., Unit G, Doylestown, PA 18901; (800) 441-1314; fax: (215) 230-7670; e-mail: moriausa@moriausa.com.

Reference:

• Busin M, Arffa RC, Sebastiani A. Endokeratoplasty as an alternative to penetrating keratoplasty for the surgical treatment of diseased endothelium. Ophthalmology. 2000;107:2077-2082.