Femtosecond laser enables PKP, but not all eyes are candidates

San Francisco-Femtosecond laser-assisted penetrating keratoplasty (PKP) has potential advantages over conventional PKP performed with manual corneal trephination. The laser-assisted procedure has disadvantages, however, that should not be overlooked and that make appropriate patient selection, careful preoperative planning, and use of an incomplete incision pattern important, said Anthony Aldave, MD, associate professor of ophthalmology and director, cornea services, Jules Stein Eye Institute, UCLA David Geffen School of Medicine, Los Angeles.

"Femtosecond laser-assisted PKP offers greater wound strength and results in faster visual recovery and less astigmatism than conventional PKP," Dr. Aldave said. "However, the cost of the procedure is higher, there is a risk of wound rupture during patient transport from the refractive suite to the operating room, and there is a higher rate of endothelial cell loss when the donor is cut using the femtosecond laser compared with mechanical trephination."

To illustrate the results of the femtosecond laser-assisted procedure, he reviewed the experience at the Jules Stein Eye Institute, where 18 cases have been performed so far. Endothelial cell density data showed about an 8% loss after donor cutting, whereas about a 3% rate of loss was seen after manual trephination, Dr. Aldave said.

Ten eyes had achieved 3-month follow-up after femtosecond laser-assisted PKP, and refraction data were available for eight of those eyes. In six eyes, astigmatism was 4.5 D or less, and six eyes also experienced best spectacle-corrected visual acuity (BSCVA) of 20/30 or 20/40.

"Comparing groups of eyes that had conventional PKP versus PKP using a femtosecond laser-assisted, zig-zag technique, Roger Steinert, MD, found the femtosecond laser group had less astigmatism at all follow-up intervals from 1 to 12 months as well as an advantage for better BSCVA at 1 and 3 months, with no significant difference between groups thereafter," Dr. Aldave said.

Candidates for the femtosecond laser-assisted procedure are patients with stromal opacification or ectasia without comorbid ocular pathology, he said. Patients are considered marginal candidates if they have moderately dense midperipheral corneal opacity, a failed corneal transplant, or any factors that may predispose to suction loss during the femtosecond laser procedure, he added.

Eyes with a dense midperipheral corneal opacity, very thick (>1200 µm) or very thin (