Femtosecond lens fragmentation may reduce phaco energy and tip movement

Optical coherence tomography enabled surgeons to create safety zones around the iris and capsulotomy to boost accuracy and reduce risk, surgeon says.

William W. Culbertson

ORLANDO, Fla. — Femtosecond laser-assisted lens fragmentation significantly reduced the amount of phacoemulsification energy and phaco tip movement needed to remove the lens, according to a study presented here.

“We know that [femtosecond lasers] can already make incisions in the cornea to help with astigmatic control and also to help us with better-sealing cataract incisions,” William W. Culbertson, MD, said at the American Academy of Ophthalmology meeting. “We know we can make better and more accurate capsulotomies. But it can also help us with segmentation and softening of the lens, which can enable phacoemulsification to be accomplished more efficiently.”

Optical coherence tomography and lens segmentation software built into the Catalys femtosecond laser platform (OptiMedica) enabled surgeons to perform safe and precise capsulotomies and lens fragmentation, Dr. Culbertson said.

Patients and methods

The prospective randomized trial conducted in the Dominican Republic included 39 eyes that underwent femtosecond laser capsulotomy and lens fragmentation and a control group of 29 eyes that underwent manual capsulotomy and fragmentation.

All eyes underwent phacoemulsification and IOL implantation. Phacoemulsification was performed with the Infiniti platform (Alcon).

The OCT and mapping software were used to delineate 500-µm anterior and posterior capsule safety zones and a 0.5-mm safety zone around the periphery of the iris to enable treatment under the capsulotomy.

“We can automatically construct these 500-µm capsule safety zones both anteriorly and posteriorly so that we can extend the incisions down to within 500 µm in all cases from the posterior capsule,” Dr. Culbertson said. “The pupil had to be 1 mm in diameter larger to provide a safety zone for the capsulotomy treatment. The pupil would have to be 5.6 mm to achieve a 4.6-mm capsulotomy.”

Mean fragmentation depth was 4.3 mm.

The Lens Opacities Classification System was used to gauge nuclear cataract density. Cataracts were matched for color and density.

“We assigned a single nuclear grade using the higher of the nuclear opalescence and nuclear color grades and called that the type of cataract that it was,” Dr. Culbertson said.

Surgeons recorded cumulative dissipated energy (CDE) and active phaco steps, or phaco tip movement with power on.

Results and findings

Study results showed that femtosecond laser lens fragmentation required 17 CDE units, and the manual procedure required 9.4 CDE units. The 45% reduction in CDE was statistically significant (P = .005). In laser cases, CDE was reduced 47% in grade 1 to 3 cataracts and 45% in grade 4 cataracts.

Overall, CDE was reduced 38% for higher-grade cataracts and 65% for lower-grade cataracts, Dr. Culbertson said.

In addition, laser lens fragmentation reduced active phaco steps by 45%. Femtosecond laser-treated eyes required a mean six active phaco steps, and manually treated eyes required 11 steps.

“We almost cut the active phaco steps in half. This not only required less energy with the laser but we actually required fewer maneuvers, as well,” Dr. Culbertson said.

He noted the importance of segmenting the lens into quadrants to ensure safe, thorough removal.

“If you try to amputate it in a circular fashion, where you cut it off halfway across, you might be able to remove an anterior lamella of the quadrant, but the posterior lamella would be more difficult to get out and make it less safe,” Dr. Culbertson said. “We’re trying to make this surgery safer. But I think as we all experiment with these different patterns, we’ll find some that we haven’t even conceived of yet that will facilitate the procedure.”

Eccentric or elliptical movement of the phaco tip is not necessary, Dr. Culbertson said. – by Matt Hasson

• William W. Culbertson, MD, can be reached at Bascom Palmer Eye Institute, P.O. Box 016880, Miami, FL 33101-6880; 305-326-6364; email: w.culbertson@miami.edu.
• Disclosure: Dr. Culbertson has financial relationships with Abbott Medical Optics, Alcon, Carl Zeiss Meditec, Hoya Surgical Optics and OptiMedica.