July 2019


Research Highlight
The straight scoop on zig-zag femtosecond keratoplasty

by Maxine Lipner EyeWorld Senior Contributing Writer

Because of the angled edge, there is a smoother
transition from donor to host tissue with zig-zag FLEK.
Source: Marjan Farid, MD


Recent study results1 indicate that a zig-zag cut configuration for femtosecond laser-enabled keratoplasty (FLEK) can offer quicker healing than the conventional approach, as well as good long-term refractive astigmatism outcomes, according to Marjan Farid, MD.
The study was spurred by the long history the University of California, Irvine has had with femtosecond laser keratoplasty. This resulted in a long-term cohort that may be the largest in the country, Dr. Farid said. With this data, investigators launched a study investigating long-term outcomes with the femtosecond laser, including cases of deep anterior lamellar (DALK) and full-thickness corneal transplants.

Studying zig-zag cuts

The 335 eyes investigated in the study underwent FLEK with a zig-zag cut configuration. This harked back to a 2009 study2 of Dr. Farid’s, in which femtosecond zig-zag incisions done in 49 eyes were compared to conventional PK in 17 eyes. Investigators found faster recovery in eyes that underwent zig-zag femtosecond keratoplasty, with the majority attaining 20/40 acuity at 1 month, and topographic astigmatism also tended to be lower, Dr. Farid reported.
Investigators in the earlier study theorized that the angled anterior edge of the zig-zag cut would have a smoother transition from donor to host tissue and a more natural fit. Faster wound healing was attributed to the increased surface area, which allowed surgeons to adjust and remove sutures sooner.
The natural hermetic seal between the donor and the host tissue resulted in less vertical and torsional misalignment of the tissue compared to a conventional straight-cut wound edge. “We think this is why the visual acuity recovers faster,” Dr. Farid said.
With evidence suggesting that femtosecond laser keratoplasty eyes fare better, investigators evaluated long-term patient outcomes. The recent study looked at how these patients have done in terms of visual acuity, refractive astigmatism, and topographic astigmatism. When compared to typical conventional outcomes, investigators found that results attained with the zig-zag approach were superior in the long term. After sutures were removed, mean uncorrected visual acuity with femtosecond laser keratoplasty was 20/138, while spectacle-corrected visual acuity was at a mean of 20/40, Dr. Farid reported, adding that manifest cylinder was 3.38 and topographical cylinder was 4.77.
“The majority have refractive astigmatism in lower ranges, so they can be treated with spectacles and are not necessarily committed to having to wear rigid contact lenses because of higher-order aberrations,” she said. “Patients continued to do well in terms of refractive astigmatism and vision even a decade out.”

Future possibilities

Dr. Farid hopes practitioners come away from the study with the understanding that a customized, zig-zag trephination pattern is better than standard trephination. Cost has kept this from becoming more widespread, but it is becoming less of a factor. Newer femtosecond laser platforms with incorporated OCT imaging can enhance cuts to also facilitate DALK without the creation of a big bubble. This should improve overall success rates with DALK as well.
Dr. Farid said she will continue research in this area in the hope of increasing femtosecond laser accessibility to all corneal surgeons and making it the standard of care.

About the doctor

Marjan Farid, MD
Professor of ophthalmology
Gavin Herbert Eye Institute
University of California, Irvine


1. Wade M, et al. Long-term results of femtosecond laser-enabled keratoplasty with zig-zag trephination. Cornea. 2019;38:42–49.
2. Farid M, et al. Comparison of penetrating keratoplasty performed with a femtosecond laser zig-zag incision versus conventional blade trephination. Ophthalmology. 2009;116:1638–43.

Financial interests

Farid: Allergan, BioTissue, Carl Zeiss Meditec, CorneaGen, EyePoint Pharmaceuticals, Kala Pharmaceuticals, Johnson & Johnson Vision, Shire

Contact information

Farid: mfarid@uci.edu

The straight scoop on zig-zag femtosecond keratoplasty The straight scoop on zig-zag femtosecond keratoplasty
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