Femtosecond laser surgery still raising bar for cataract surgery outcomes

Take-home message: Femtosecond laser cataract surgery has demonstrated comparable safety, superior effectiveness, and greater efficiency compared with traditional phacoemulsification.

Reviewed by Mark Packer, MD, FACS, CPI

Boulder, CO-Cataract surgery technology has reached a high level of precision with superior levels of vision postoperatively. A decided surgeon learning curve, however, is attached to achieving these great outcomes, said Mark Packer, MD, FACS, CPI.

Patients presenting for cataract surgery-especially those in the baby boomer generation-are generally considered better educated and more demanding than their predecessors.

They want surgeons to provide them with postoperative vision that is as good at all distances as they had when they were in their youth. Technologies behind state-of-the-art femtosecond laser cataract surgeries are striving to meet those demands, and surgeons have to step up to the plate to optimize the patient experience, said Dr. Packer, president of Mark Packer MD Consulting Inc., Boulder, CO.

Safety

Safety

The safety outcomes with femtosecond laser cataract surgery show evidence of a learning curve, and are comparable or superior to standard phacoemulsification.

Dr. Packer cited a study (Roberts et al. Ophthalmology 2013;120:227-33) that showed the importance of mastering the learning curve associated with femtosecond laser cataract surgery.

In this study, investigators evaluated the outcomes and safety of femtosecond laser cataract surgery in 1,500 patients in one practice who had been divided into two groups based on surgeon experience (group 1 included the first 200 patients treated with femtosecond laser cataract surgery and group 2 included 1,300 patients who underwent the same surgery performed by the same surgeons).

After evaluating complication rates between the two groups, it was clear that surgeons improved with experience.

The respective complication rates between groups 1 and 2 are as follows: anterior capsular tears, 4% and 0.31%; posterior capsular tears, 3.5% and 0.31%; posterior lens dislocation, 2% and 0%; number of docking attempts/case, 1.5 and 1.06; incidence of postlaser pupillary constriction, 9.6% and 1.23%; and anterior capsular tags, 10.5% and1.61% (p < 0.001 for all comparisons).

When compared with traditional phacoemulsification, the complication rates associated with femtosecond laser cataract surgery are markedly lower, as demonstrated by Chen and colleagues (Int J Ophthalmol. 2015;8:201-203).

When investigators evaluated five surgeons who performed traditional phacoemulsification and laser-assisted cataract surgery, they found that overall complications rates were 5.8% and 1.8%, respectively.

However, another study found the integrity of the anterior capsulotomy may be compromised with femtosecond laser cataract surgery and that a learning curve may be responsible for part of the increased complication rate (femtosecond laser, 1.87% in 15 of 804 cases versus traditional phacoemulsification, 0.12% in 1 of 822 cases; p = 0.0002), Dr. Packer noted.

Safety (cont.)

Dr. Packer and colleagues undertook at laboratory study to determine the ideal femtosecond laser capsulotomy based on the capsular histology and biomechanics. Criteria for defining a capsulotomy as ideal were that the capsulotomy should prevent posterior capsular opacification (PCO), maintain the effective lens position, and optimize capsular strength.

Results indicated that ideal capsulotomy construction should completely overlap the IOL to prevent PCO, centration should be on the clinical approximation of the optical axis of the lens to ensure concentricity with the capsular equator, and the maximal capsular thickness should be at the capsulotomy edge to maintain integrity, according to Dr. Packer. The results were reported in the British Journal of Ophthalmology (2015;99:1137-1142).

A comparison of the effective phaco time between manual phacoemulsification and femtosecond laser cataract surgery showed that the mean phaco time was significantly lower in the femtosecond laser cataract surgery group compared with the manual phacoemulsification group (1.58 versus 4.17 seconds: p = 0.001) and the endothelial cell loss in the femtosecond laser cataract surgery group was also significantly (p = 0.02) lower (Mayer et al. Am J Ophthalmol. 2014;157:426-432).

The morphologic features of corneal incisions were found to be significantly improved in association with femtosecond laser cataract surgery with lower endothelial gaping, endothelial misalignment, Descemet’s membrane detachment, and posterior wound detachment than the clear corneal incisions that were created with a microkeratome.

In addition, the incisions were within 10% of the intended length, said Dr. Packer, citing a study by Grewal and Basti (J Cataract Refract Surg 2014; 40:521-530).

“The overall complication rates are comparable to standard phaco, anterior capsule tears are a learning curve issue, corneal Incisions are associated with improved morphology, and there is a significant reduction in the effective phaco time,” he said.

Effectiveness

Effectiveness

A recent comparison (Chee et al. Am J Ophthalmol. 2015;159:714-719.e2) of the uncorrected visual acuity levels after femtosecond laser cataract surgery and conventional phacoemulsification in eyes with a targeted spherical equivalent of ± 0.5 D showed that the former provided patients with significantly better results.

Thirty-eight percent of eyes versus 28.2%, respectively, achieved 20/20 or better vision 6 weeks postoperatively, and 68.9% and 56.4%, respectively, achieved 20/25 at the same time point (p = 0.02, and p = 0.00, respectively).

Efficiency

These results are likely due to the advanced imaging and guidance systems that are now available or will soon become available to surgeons, Dr. Packer summarized. These include:

• Verion Image Guided System (Alcon Laboratories)

• cOS 4 (Advanced Medical Optics) with its Steep Meridian Registration Technology (SMRT)

• Spectrus (Bausch + Lomb) with iris registration and guidance

• Streamline (LENSAR) with corneal analysis, registration, and guidance

The Verion reference unit can perform keratometry and pupillometry and provides a reference image. The advantage of the Verion system include toric IOL planning; the limitations are the solid interface and the ability to perform keratometry only (no posterior corneal surface measurement).

SMRT performs keratometry with a non-contact interface and iris registration.

In addition, surgeons can create toric alignment arcuate incisions.

Dr. Packer pointed out that the benefit is that SMRT measures the keratometry through the laser optics.

Limitations and advantages

The limitations are that it performs keratometry only, does not incorporate preoperative measurements in the plan, requires a separate interface for measurements under laser, and uses “marking” incisions for toric IOL alignment, not virtual guidance, he noted.

The LENSAR Laser System with Streamline is integrated wirelessly with the Cassini Corneal Shape Analyzer (iOptics) and has the following applications: iris registration, cataract density imaging, customized fragmentation patterns, and arcuate incision planning.

Advantages of the system are that it measures the topography and the posterior corneal surface, and provides a reference image; integrates arcuate incision planning based on the surgeon’s nomogram; and performs imaging, registration, and guidance through a liquid interface. Toric IOL guidance may be achieved with small reference marks constructed by the laser on the corneal surface.

Bausch + Lomb is currently developing a system (Spectrus) for image-guided surgery that will link preoperative topography to its femtosecond laser (Victus).

“Femtosecond laser cataract surgery is safe, and offers improved incision construction and reduced effective phaco time,” Dr. Packer said. “There is a learning curve attached to the capsulotomy. The technology is effective in that it provides a superior uncorrected distance visual acuity.”

He concluded that refractive cataract surgery has become significantly more efficient than previously because of image-guided surgery.

Mark Packer, MD, FACS, CPI

E: mark@markpackerconsulting.com

Dr. Packer is a consultant to and holds equity in numerous vision technology manufacturers.