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A new laser application (IntraLase-Enabled Keratoplasty [IEK], IntraLase Corp.) used with a femtosecond laser (IntraLase, IntraLase Corp.) to cut donor and host incisions is considered a significant advance in transplantation surgery. Initial experience using the laser to cut zig-zag incisions indicates the procedure has several advantages and is associated with favorable refractive and visual outcomes
"We believe [the new laser application] represents the first major advance in full-thickness corneal transplantation since the 1970s, when the operating microscope and 10-0 nylon sutures were introduced, and that it has the potential to become the gold standard for quality surgery. First, however, we will be further evaluating this procedure against Descemet's stripping endothelial keratoplasty and Descemet's stripping automated endothelial keratoplasty (DSAEK) in comparative studies that will include assessments of endothelial cell survival and visual acuity," said Dr. Steinert, professor of ophthalmology, University of California, Irvine.
He began his talk by noting that the subject may seem a little "off-topic" for a refractive surgery meeting. Nevertheless, he pointed out that it had relevance not only because many refractive surgeons have cornea subspecialty training but also recognizing that the vast majority of transplantations are performed for optical reasons.
The new femtosecond laser application is expected to provide several benefits that translate into better stromal wound healing and less induced astigmatism. By providing better initial incision integrity, it could limit the need for excessive suture tightness that could cause optical distortion. In addition, by providing greater surface area in the incision, it is expected to lead to improved wound healing and allow earlier suture removal. Cutting with a zig-zag pattern, which is the technique Dr. Steinert has been using, enables excellent tissue alignment between host and donor along with a watertight seal, he said. Therefore, the procedure also eliminates the need for excess suture tension and minimizes induced astigmatism.
"The femtosecond laser can be used to cut many different incisional patterns. Our experience shows the zig-zag configuration has great promise for being biomechanically stable and secure," Dr. Steinert said.
More than 50 eyes have undergone PKP with the new laser application. Dr. Steinert reported results for 30 eyes of 27 patients, all of whom were operated on with the same technique using the zig-zag pattern. The procedure involved creation of a 0.5-mm wide lamellar ring cut at 300-μm depth from the anterior surface. The anterior and posterior side cuts were made with a zig-zag configuration at a 45° angle after applanation was released. Fixation of the graft was performed using a 24 bite, 10-0 nylon running suture closure.
Dr. Steinert noted that the first-generation software used in those procedures did not feature radial alignment marks. That upgrade is coming and is expected to provide better rotational alignment.
As of the end of October, available follow-up was at least 1 month in all eyes and ranged up to 12 months. Topography results based on 26 eyes evaluated at 3 months showed the mean Sim K was 2.6 D.
"There were a few outliers, but mean astigmatism has been maintained below 3.0 D through follow-up to 1 year," he said.