Femtosecond laser may supplant scalpel in traditional applications

Technologies enable surgeons to fragment cataractous lenses, create LASIK flaps, cut deep lamellar grafts and perform intrastromal ablation.

Ronald R. Krueger

The femtosecond laser promises a host of applications; for some surgeons, it may even supplant the conventional scalpel, a clinician said.

“As a precision intraocular cutting tool, the femtosecond laser offers a wide range of possibilities,” Ronald R. Krueger, MD, said at the joint meeting of the American Academy of Ophthalmology and Middle East Africa Council of Ophthalmology in Chicago. “It is going to revolutionize modern-day ophthalmic surgery: cataract, refractive, corneal, presbyopic, glaucoma, vitreoretinal. There are a host of possibilities with this technology.”

Dr. Krueger cited three mechanisms of tissue separation: cutting, cleaving and ablating.

“Cutting, of course, is a sharp dissection, cleaving is a blunt wedge dissection along a cleavage plane, and ablation a subtractive dissection,” he said. “We see these mechanisms in refractive surgery with microkeratomes because the typical, mechanical microkeratome is more cutting, the epikeratome is more cleaving and the femtolaser is more ablating.”

But the mechanism of tissue separation with femtosecond lasers is also influenced by the cavitation bubbles that form during pulse application.

“Basically, those lasers with higher pulse energy are likely using cleaving more than ablation in the actual separation of tissue, due to the larger cavitation bubbles and spacing between pulses, whereas those with lower pulse energy, closer spacing and a lot more laser pulses are probably using more of the ablation mechanism,” Dr. Krueger said. “Ultimately, the precision of femtosecond laser delivery leads us to question whether cutting is the way we continue to go in the future using blades. Or will we be shifting toward using ablation, and cleaving, in most of our types of ocular surgery?”

Intrastromal ablation, keratoplasty

Femtosecond lasers are used to perform various corneal procedures, such as creating LASIK flaps and assisting in the preparation of shaped corneal transplantation. Because the femtosecond laser beam is in the infrared wavelength of the light spectrum, it passes easily through transparent tissues and enables intrastromal delivery and ablation.

For example, the Visumax femtosecond laser (Carl Zeiss Meditec) not only creates flaps by the intrastromal delivery of laser pulses, but can also carve out a lenticule of tissue in procedures such as FLEx (femtosecond lenticule extraction) and ReLEx, a method that combines FLEx and SMILE (small-incision lenticule extraction).

“These procedures seek to replace the excimer laser in reshaping the cornea and need to be highly precise to achieve this goal. But these newer-generation femtosecond lasers are very precise, and our capabilities are increasing as we move forward,” Dr. Krueger said.

The intrastromal delivery and precise application of the femtosecond laser can also be used to change the biomechanical properties of the cornea in order to increase depth of focus in presbyopic eyes, Dr. Krueger said.

“This is true of the IntraCOR procedure, popularized by the Technolas Femtec laser,” he said.

Overall, corneal femtosecond lasers are being used to create zigzag and top-hat incisions for corneal transplantation surgery, create pockets to enhance the placement of intrastromal ring segments and perform corneal biopsies, all in a more elegant manner than conventional cutting with blades.

“In the future, I believe we’ll see a greater application of these intrasomal procedures come to play, primarily because femtosecond lasers allow us to get easier access to the tissue and with greater precision than a scalpel,” Dr. Krueger said.

Femtosecond cataract surgery

Ongoing studies are evaluating the use of femtosecond lasers to perform all stages of cataract surgery, such as corneal incisions, lens fragmentation and capsulotomies. Dr. Krueger noted that femtosecond lasers may even be used to restore the accommodative effect of the crystalline lens, prior to its development as a cataract.

Femtosecond lasers are currently being investigated to ablate dense lens nuclei, Dr. Krueger said.

“Going into a harder nucleus is possible,” he said. “You see more fracturing because the nuclei are harder, but it is still possible to fracture or fragment that lens into a composite of smaller lens pieces that can more easily be separated and removed with reduced cumulative dispersed phaco energy. Even the very dense lenses can be fragmented with this technology.”

Using a femtosecond laser not only fragments the cataractous lens to enable easier phacoemulsification, but it also precisely ablates the anterior capsule to safely and accurately create a well-centered and uniformly shaped capsulotomy, which can easily be removed from the eye, Dr. Krueger said.

In the future, femtosecond lasers may also be used to open the trabecular meshwork in treating glaucoma and to perform delicate retinal procedures that are less invasive than current vitrectomy methods. The same remarkable precision of the femtosecond laser can be used in performing intracellular surgery, and with that kind of precision, one can imagine that the femtosecond laser can be used in any kind of ophthalmic procedure, Dr. Krueger said. – by Matt Hasson

• Ronald R. Krueger, MD, can be reached at Cole Eye Institute, Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195; 216-444-8158; fax: 216-445-8475; e-mail: krueger@ccf.org.
• Disclosure: Dr. Krueger is a cofounder and investor in LensAR.