Posterior lamellar keratoplasty can manage corneal endothelial disorders

Patients undergoing posterior lamellar keratoplasty may have less postop astigmatism and faster visual recovery than patients undergoing penetrating keratoplasty.

ROTTERDAM, Netherlands — Posterior lamellar keratoplasty through a sclerocorneal pocket incision is a feasible surgical approach to manage corneal endothelial disorders, according to a recent study.

“Compared with penetrating keratoplasty, posterior lamellar keratoplasty may have the advantages of less postoperative astigmatism and faster visual recovery, less risk of late wound dehiscence and elimination of all corneal suture-related complications,” said Gerrit R.J. Melles, MD, PhD, who practices at the Netherlands Institute for Innovative Ocular Surgery (NIIOC) here.

To determine whether posterior lamellar keratoplasty through a sclerocorneal pocket incision is an effective surgical approach to manage corneal endothelial disorders, Dr. Melles and his colleagues retrospectively reviewed seven eyes. In each eye, a deep stromal pocket was made across the cornea through a 9-mm superior scleral incision. “A 7- or 7.5-mm diameter posterior lamellar disc was excised and replaced by a same size donor posterior disc, without suture fixation. The scleral incision was sutured,” he explained.

Uneventful surgeries

---Posterior lamellar keratoplasty through a self-sealing, 5-mm scleral tunnel incision is seen at 1 week postop. Arrows point to the posterior donor disc.

Of the seven eyes, six underwent uneventful surgeries. One eye experienced a perforation of the recipient’s peripheral stromal bed during lamellar pocket dissection. At that point, the procedure was converted to a penetrating keratoplasty.

“In eyes that had a posterior lamellar keratoplasty, all posterior transplants remained in situ throughout the postoperative period, with complete apposition of the donor-to-recipient tissues at the stromal interface. All transplants cleared with a normal, transient degree of inflammation, and biomicroscopy showed minimal interface scarring and a normal healing response at the posterior stromal wound edges,” Dr. Melles said.

Postoperative best spectacle-corrected visual acuity ranged from 20/80 to 20/20. Two eyes had pre-existing maculopathies. The average astigmatic error was 1.54 D, average pachymetry was 0.49 mm and average endothelial cell density was 2,520 cells/mm².

A previous animal study evaluated a technique for posterior lamellar keratoplasty in which the anterior cornea was left intact and a posterior lamellar disc was transplanted through a scleral incision and a deep stromal pocket.

This study in humans used the same technique with minor changes. “Instead of the 6-mm diameter posterior lamellar transplant used in the preceding animal study, the patients had a 7- or 7.5-mm diameter transplant,” Dr. Melles said. “Instead of using a keratotomy knife to obtain the appropriate stromal dissection depth, the anterior chamber was filled with air to visualize the posterior corneal surface, so that the depth of dissection relative to the corneal thickness could be monitored optically. Furthermore, a stromal pocket was dissected at 80% instead of 50% corneal depth. With deeper dissections, the excision of posterior corneal tissue is easier, less interface scarring may be induced and a thicker portion of the anterior stroma is unaffected, so that postoperative astigmatism may be further minimized.”

Suture fixation not needed

According to Dr. Melles, all posterior transplants cleared and maintained their positions without suture fixation. “Although the anterior chamber was completely filled with air at the end of the surgery, an air bubble may not be necessary to fixate the posterior transplant,” he said.

In one patient who was made aphakic during the keratoplasty procedure, the air bubble in the anterior chamber escaped through the pupil into the vitreous cavity during the first hour after surgery, and the transplant did not loosen or dislocate. “We therefore speculate that the stickiness of the stromal tissue at the donor-to-host interface, the suction force of the donor endothelium, fibrin deposition throughout the wound area in the early healing phase and stromal repair in later phases keep the posterior transplant in position,” Dr. Melles said.

Except for the two patients with pre-existing maculopathies, the patients achieved good spectacle-corrected visual acuity by 6 months postop. All patients had relatively low with-the-rule astigmatism.

Removing the sutures from the scleral incision at 3 months postop may reduce suture-induced astigmatism. “However, because the astigmatic error could be easily corrected with spectacles in all patients, scleral suture removal was not performed,” he said.

All patients had a normal healing response after surgery, without evidence of excessive scarring at the posterior stromal wound edges or at the donor-to-host stromal interface. Retrocorneal membrane formation did not occur.

Complications

Three patients suffered intra- or postoperative complications. One patient experienced elevated intraocular pressure after surgery. Because the pressure could no longer be controlled by pressure-lowering medication, a trabeculectomy was performed 1 month after the keratoplasty procedure. Another patient had continuous vitreous pressure during surgery, so that the anterior chamber could not be maintained. A third patient had a microperforation that occurred during the dissection of the stromal pocket. Because of this, the posterior lamellar keratoplasty procedure was converted to a penetrating keratoplasty.

Technique improved

In the past months, according to Dr. Melles, the technique has been further improved. Instead of using a 9 mm superior scleral incision that must be sutured at the end of surgery, a self-sealing 5 mm scleral tunnel incision was used to transplant an 8.5 mm diameter donor posterior corneal disc. Five surgeries using this technique have been performed so far Although the series is small and the follow-up is short, advantages of the technique may be that a useful visual acuity is reached within the first month, postoperative astigmatism is minimal and the surgical procedure itself has been simplified.

In early 2001, said Dr. Melles, a surgical “hands-on-skill” instruction course will be organized by the NIIOC and the Dutch Ophthalmic Research Center, the company that manufactures the instruments for the procedure. More information on the course can be found at the Web site www.niioc.nl. (Editor’s Note: This course is not listed at the website as of 12/12.)

For Your Information:

• Gerrit R.J. Melles, MD, PhD, can be reached at the Netherlands Institute for Innovative Ocular Surgery, H.A. Maaskantstraat 31, 3071 MJ Rotterdam, The Netherlands; e-mail melles@niioc.nl. Dr. Melles has a direct financial interest in the products mentioned in this article. He is a paid consultant for the Dutch Ophthalmic Research Center.

Reference:

• Melles GRJ, Lander F, van Dooren BTH, Pels E, Beekhuis WH. Preliminary clincal results of posterior lamellar keratoplasty through a sclerocorneal pocket incision. Ophthalmology. 2000;107:1850-1856.