En-bloc PK with KLAL a novel approach for severe limbal stem cell deficiency

Take-home message: Simultaneous en-bloc central penetrating keratoplasty and peripheral lamellar keratoplasty with annular keratolimbal allograft transplantation provides patients with severe limbal stem cell deficiency the benefit of rapid visual recovery.

By Cheryl Guttman Krader; Reviewed by Farid Karimian, MD

Tehran, Iran-En-bloc penetrating keratoplasty (PK) with annular keratolimbal allograft (KLAL) transplantation is a promising technique for the management of eyes with total limbal stem cell deficiency needing corneal transplantation, said Farid Karimian, MD.

“Compared with a staged approach where 360° KLAL is performed as a first step followed 3 to 6 months later by central PK, en-bloc PK combined with KLAL offers patients the opportunity for faster visual recovery and should have less risk for rejection since it does not require three donors,” said Dr. Karimian, professor of ophthalmology, Shahid Beheshti University of Medical Sciences, and director, cornea and anterior segment surgery service, Labbafinejad Medical Center, Tehran, Iran.

In addition, because corneal-KLAL ring suturing is not needed, the procedure time is shorter than simultaneous 360° KLAL with central PK, and risks of interface leakage and wound apposition problems are reduced, he noted.

“So far in these challenging eyes, the combined procedure has been associated with acceptable safety and functional outcomes after short- and medium-term follow-up,” Dr. Dr. Karimian said. “Now, more experience in a larger number of eyes and with longer follow-up is needed.”

Case series

To date, Dr. Karimian has performed en-bloc PK with annular PK in 14 eyes that had total limbal stem cell deficiency. The underlying causes for the ocular surface damage were severe chemical burns in 10 eyes and mustard gas exposure in 4 eyes.

Preoperative best-corrected visual acuity (BCVA) in the 14 eyes ranged from light perception to hand motion. All patients had clinical evidence of limbal stem cell deficiency based on presence of corneal opacification, and the diagnosis was confirmed by impression cytology in 10 eyes.

No significant intraoperative complications were encountered in the series. After surgery, patients were started on treatment with tacrolimus 2 mg/day and mycophenolate mofetil 1 gm/day, and the immunosuppressive medications are tapered over a period of 18 to 24 months.

Available follow-up for the 14 patients was between 6 and 32 months. At last visit, BCVA ranged from count fingers to 20/40, and 11 eyes had BCVA better than 20/200.

“The vision improves immediately after the operation, but it may take a few months to be stabilized,” Dr. Karimian said.

There have been 3 cases of limbal stem cell rejection, but all could be controlled medically. Endothelial graft rejection occurred in 4 eyes. Other postoperative complications included corneal epithelial defect, hyphema, and hyptony that occurred in 2 eyes.

Surgery details

The surgery-which is performed under general anesthesia and takes an average of 2 to 3 hours-begins with 360° of limbal peritomy and release and resection of fibrotic tissues. After hemostasis of episcleral vessels, a circumferential scleral flap (one-third thickness) is formed 2 mm from the limbus using a crescent knife. The dissection is extended over the patient’s cornea, resecting all scarred and opacified anterior lamellae. To reduce the risk of future rejection, the central cornea (which will be full-thickness), is trephined with a 7.5-mm trephine.

Donor limbal stem cells are harvested with underlying partial thickness sclera, and central full-thickness cornea from the whole globe is provided by the Central Eye Bank of Iran. The donor cornea trephination is performed from the endothelial side and made 0.5 mm smaller than the recipient cornea ring.

Finally, a scleral flap (wing) is sutured to the recipient scleral bed and donor limbal conjunctiva to the recipient surrounding conjunctiva.

Farid Karimian, MD

E: karimianf@orcir.org

This article was adapted from Dr. Karimian’s presentation during the 2015 meeting of the American Society of Cataract and Refractive Surgery. Dr. Karimian has no financial or proprietary interests to disclose.