Femtosecond laser provides precision, accuracy in cataract surgery

ByEric D. Donnenfeld, MD

Eric D. Donnenfeld, MD
Eric D. Donnenfeld

There can be little doubt that traditional cataract surgery techniques have allowed surgeons to achieve a significant amount of success to the benefit of millions of patients. Cataract surgery, as it is currently performed with manual cutting tools and ultrasound energy, is arguably the most effective surgical technique in all of medicine. However, as the ophthalmic marketplace introduces newer techniques and technologies, such as the femtosecond laser, our ability to achieve even better results is realized.

The femtosecond laser will allow us to perform operations with lower energy ultrasound applied to the eye, to improve the precision, and to reproduce those results time after time. Ultimately, the goal of laser refractive cataract surgery is to improve every procedure every time, using technology to make the surgeon a better surgeon.

Femtosecond lasers

Femtosecond lasers were first introduced in ophthalmology for creating more precise LASIK flaps. The technology has since been incorporated into corneal transplantation and corneal tunnels, and is being evaluated for intrastromal operations and for creating limbal relaxing incisions. Now, the femtosecond laser can also be used in cataract surgery.

Although highly safe and effective, manual cataract surgery has certain inherent limitations. Notably, because the corneal incision is made with a handheld blade, it is difficult to create a two-plane incision, much less a three-plane incision. The slightest imperfection in creating the incision may yield a resulting wound architecture that spurs a visually significant astigmatic error. Additionally, the manual capsulorrhexis is performed with a blunt needle or forceps, leading to irregular shapes and possibly decentered lens positioning.

“These advances are important for surgeons to improve precision and accuracy in performing corneal incisions, to create the capsulorrhexis, and to fragment the lens.”
— Eric D. Donnenfeld, MD

As a result of these inherent limitations, the effective lens position of any IOL implant can be compromised. Moreover, excessive ultrasound technology used to fragment and aspirate the lens may transfer energy to the corneal endothelium and/or posterior capsule. Complications do occasionally occur: dropped nuclei, phaco burns, corneal edema, and endothelial cell loss.^1,2

Femtosecond lasers can aid the surgeon in creating the corneal incision, in creating the capsulorrhexis, and in fragmenting the lens. The technology is applicable to all cataract surgery, but it may be particularly important with advanced technology lenses. For one, the patient who elects for an out-of-pocket expense expects a premium experience. In addition, the ability of these lenses to perform optimally depends more on precision and accuracy than standard cases.

Image-guided femtosecond laser refractive cataract surgery

The femtosecond laser platform by Alcon, the LenSx laser, incorporates optical coherence tomography (OCT) to scan the entire anterior segment, including the cornea, lens, capsule, and iris. This image is projected onto a video microscope, allowing the surgeon to select the appropriate corneal incisions, capsulorrehexis, and lens disruption (which takes about a minute to perform).

These advances are important for surgeons to improve precision and accuracy in performing corneal incisions, to create the capsulorrhexis, and to fragment the lens.

1. Corneal incisions

Manual incisions may create astigmatic errors that disrupt the quality of postoperative vision. With femtosecond lasers, on the other hand, we are able to create smaller and more predictable incisions. The laser, guided by OCT, cuts to a repeatable depth, resulting in reproducible wound architecture and more favorable healing.

Figure 1: In a study performed by Nagy and colleagues, 100% of IOLs implanted after image-guided femtosecond laser refractive cataract surgery achieved accuracy within 0.25 mm. (Absolute difference between Attempted and Achieved.)

Adapted from data published in: Nagy Z, Takacs A, Filkorn T, Sarayba M. Initial clinical evaluation of an intraocular femtosecond laser in cataract surgery. J Refract Surg. 2009;25(12):1053-1060.

2. Refractive capsulotomy

Any IOL implant relies on precise centration, which, in turn, depends on a perfectly cut capsulorrhexis. Femtosecond laser can create an exactly sized, perfectly centered capsulorrhexis. Currently, imprecisely sized capsulotomies are thought to be a leading cause of unpredictable lens position.

In a study performed by Nagy and colleagues, 100% of IOLs implanted after image-guided femtosecond laser refractive cataract surgery achieved accuracy within 0.25 mm (Figure 1).³ By comparison, just 10% of lenses implanted after manual cataract surgery achieved the same degree of accuracy.

3. Lens fragmentation

Femtosecond laser cataract surgery is able to chop the lens more quickly than manual techniques (Figure 2). Average phaco power and effective phaco time may be reduced.³

Because there is less phaco energy required during the procedure, there is less potential for phaco burn, inflammation, and endothelial cell loss.

Figure 2: Femtosecond laser cataract surgery is able to chop the lens more quickly than manual techniques. Average phaco power and effective phaco time may be reduced.

Reprinted with permission from: Nagy Z, Takacs A, Filkorn T, Sarayba M. Initial clinical evaluation of an intraocular femtosecond laser in cataract surgery. J Refract Surg. 2009;25(12):1053-1060. doi: 10.3928/1081597X-20091117-04.

Conclusion

A new category has emerged in cataract surgery that helps patients meet their goals for refractive cataract surgery. Image-guided femtosecond laser refractive cataract surgery provides unique precision for corneal incisions and capsulotomies. For these reasons, it will be an important part of cataract surgery in the near future.

References:

Pereira AC, Porfírio F, Freitas LL, Belfort R. Ultrasound energy and endothelial cell loss with stop-and-chop and nuclear preslice phacoemulsification. J Cat Refract Surg. 2006;32(10):1661-1666.
Park JH, Lee SM, Know JW, et al. Ultrasound energy in phacoemulsification: a comparative analysis of phaco-chop and stop-and-chop techniques according to the degree of nuclear density. Ophthalmic Surg Lasers Imaging. 2010;41(2):236-241.
Nagy Z, Takacs A, Filkorn T, Sarayba M. Initial clinical evaluation of an intraocular femtosecond laser in cataract surgery. J Refract Surg. 2009;25(12):1053-1060.

Dr. Donnenfeld is Clinical Professor of Ophthalmology at New York University Medical Center, is a Trustee at Dartmouth Medical School, and practices at Ophthalmic Consultants of Long Island in New York. He is also a member of the Ocular Surgery News editorial board.