Has Femtosecond Keratoplasty Come of Age?

Ophthalmology has come a long way over the years, and “Femtosecond Keratoplasty, Coming of Age?” highlighted how this journey appears most evident in the evolutionary advances in laser technology within the discipline. Professor Jod Mehta’s medal lecture at EuCornea 2025 claimed inspiration from his personal journey as much as ophthalmology’s. Expressing his appreciation for the work of Donna Strickland, the Canadian optical physicist known for her work developing the chirped pulse amplification technique for lasers, he provided a comprehensive overview of the benefits of femtosecond lasers.

Femtosecond lasers work by emitting ultrashort pulses of light with durations measured in femtoseconds (10^-¹⁵ s), the second shortest measurable unit of time currently known to science, which allows them to generate an extreme amount of power with relatively little energy expended.

These lasers cut tissue through photodisruption, involving plasma and shock wave formation to create a non-thermal ablation known as laser-induced optical breakdown (LIOB), during which plasma is generated by the laser pulse that expands to displace surrounding tissue.

“Femtosecond technology has been around since 2003, with first-generation devices like the AMO IntraLase 15/30 kHz proving effective. However, they were slow and prone to breaking down,” Prof Mehta said. “In 2007, technicians would regularly be flown into Singapore from Germany to fix them.”

The third-generation devices represent a significant improvement, Prof Mehta said. The AMO IntraLase 60 kHz, Alcon Wavelight FS200, and others are more powerful and can perform extra functions previously unavailable, such as keratoplasty.

The benefits of femtosecond lasers in keratoplasty are obvious according to Prof Mehta, especially when compared with manual keratoplasty. He said the manual approach involves mechanical straight trephination, which can cause potential misalignment due to divergent recipient cut angles, something femtosecond lasers can avoid.

“With femtosecond, you also have the advantage of a faster healing time and better wound strength thanks to the increased surgical wound area, plus resistance to leaking,” he said. “The technique also provides for earlier visual rehabilitation due to quicker suture removal and less postoperative astigmatism.”

Lasers and mushrooms rolled into one

The femtosecond laser’s journey towards its coming of age didn’t finish with the third generation, however. Prof Mehta said two innovations have allowed it to complete this process: liquid interface and intraoperative-guided tunnel creation (iOCT) combined with deep anterior lamellar keratoplasty (DALK).

“Liquid interface keratoplasty enables real-time intraoperative adjustment of trephination to tackle difficult posterior stromal scar cases. This causes less endothelial cell damage to the recipient, with a lower intraocular pressure rise and no corneal distortion,” Prof Mehta said.

“iOCT-guided mushroom tunnel DALK offers the advantage of tunnel creation with an optimal morphological and topographical profile, which provides improved safety and efficacy as a result.”

Prof Mehta pointed to several studies to verify their effectiveness, including one involving a 17-year-old girl with full-thickness corneal perforation related to paediatric keratitis. She was first treated with DALK in 2017 but withdrew from treatment until returning in 2020 with corneal scarring.¹

“I took off the first DALK and repeated it again, and after doing the intraoperative-guided, femto[second laser]-assisted DMEK, the scar was removed from the inside of the eye. She’s now 22 and we never had to do a full-thickness penetrating graft for her. She had smaller endothelial cell replacement and best-corrected visual acuity (BCVA) of 6/9,” Prof Mehta said.

Regarding the iOCT mushroom tunnelling technique, Prof Mehta described a case study involving one patient with granular corneal dystrophy. He carried out a mushroom configuration graft on one eye, having previously opted for a conventional straight DALK procedure for the other several years earlier.

On the ‘mushroom eye,’ visual acuity reached +2.50/-1.75 x 90 6/6, whereas the eye treated more conventionally achieved +2.50/-6.50 x 74 6/6. However, Prof Mehta noted what was particularly important was that he was able to achieve these results within four months in the ‘mushroom eye,’ but it took “the best part of a year and a half” to achieve the results he recorded for the first eye treated with conventional DALK.

“Femtosecond laser-assisted mushroom DALK tunnel has the refractive advantage of large keratoplasty,” he said. “The larger anterior surface reduces the chance of perforations in suturing, and the mushroom configuration provides a mechanical advantage that supports better wound healing.”

Prof Mehta delivered the 2025 EuCornea Medal Lecture in Prague.

Jod Mehta MBBS, FRCOphth, FRCS(Ed), FAMS, PhD is a senior consultant at the Singapore Eye Centre. jodmehta@gmail.com

1. Lim J, Abusayf MM, Liu YC, Mehta JS. Bioengineering (Basel), 2024 Nov 25; 11(12): 1192.