Image-guided femtosecond laser creates precise, predictable capsulotomies

Circularity was approximately three times more precise in laser cases than in manual cases, maximizing IOL positioning and refractive outcomes.

Femtosecond laser-created capsulotomy proved more accurate and reproducible than capsulotomy performed via the conventional manual approach, a study found.

Investigators used the Catalys Precision Laser System (OptiMedica), which includes a guidance package with long-range spectral-domain optical coherence tomography and near-infrared video imaging.

“The most significant finding was the precision, accuracy and reproducibility of the capsulotomy,” Neil J. Friedman, MD, the corresponding author, said. “It was perfectly sized, shaped and positioned, and that can clearly be seen in the data. This is analogous to femtosecond lasers for cutting corneal flaps for LASIK surgery. It offers exquisite control. It’s very accurate and precise.”

The femtosecond laser method maximized IOL positioning, Dr. Friedman said.

“In general, the advantage of the capsulotomy is keeping the IOL in a better position. With this technology, we can have a more accurate and precise opening in the anterior capsule. That’s helpful for maintaining the IOL in the proper position, and that should result in better refractive outcomes,” he said.

The Catalys system is awaiting 510(k) clearance from the U.S. Food and Drug Administration. It received a CE mark in the European Union in September.

Study results were published in the Journal of Cataract and Refractive Surgery.

Patients and procedures

The prospective study included 39 patients who underwent femtosecond laser capsulotomy in one eye. A control group comprised 24 of those patients who also underwent manual capsulotomy in the fellow eye. All procedures were performed at one center in the Dominican Republic.

Two other study arms involved capsulotomies performed ex vivo in porcine and human cadaveric eyes.

In the in vivo human eye study, all patients had grade 1 to 4 nuclear sclerotic cataracts according to the Lens Opacities Classification System III (LOCS III), ETDRS corrected distance visual acuity worse than 20/30, pupillary dilation of at least 7 mm and axial length of 22 mm to 26 mm. Mean patient age was 70 years (range: 55 years to 80 years).

After laser capsulotomy, patients underwent phacoemulsification and implantation of an AcrySof IQ SN60WF IOL (Alcon).

Capsule discs were excised, rinsed in saline solution, stained with 0.5% trypan blue and mounted on glass slides. They underwent histology, digital light microscopy and scanning electron microscopy.

Patients underwent a dilated eye examination at 1 week and 1 month postoperatively. Digital photographs of the anterior segment were obtained at the slit lamp; digital images were used to calculate capsulotomy size and centration. Images were scaled to the known diameter of the IOL optic.

“Once we removed the capsule at the time of surgery, we measured the anterior capsular opening,” Dr. Friedman said. “Subsequently at the slit lamp, we took photos and measured the capsulotomy to determine the size, shape and centration. The shape was compared to a perfect circle. There was a statistically significant difference between manual vs. laser-created capsulotomies.”

Outcomes and observations

Study results showed that deviation from the intended diameter of the resected disc was 29 µm in the laser capsulotomy eyes and 337 µm for the manual capsulotomy eyes. Target diameter was 4.6 mm in the laser group and 5 mm in the manual capsulotomy group.

Mean deviation from circularity was 6% in the laser capsulotomy eyes and 20% in the manual capsulotomy eyes.

Centration of laser capsulotomies was within 77 µm of intended centration in dilated pupils.

Capsulotomies were complete in all cases; no radial nicks or tears were identified.

“The main advantage of having a perfect capsulotomy is to hold the IOL in the position that’s assumed by our IOL calculation formulas, the effective lens position,” Dr. Friedman said. “That will maintain the IOL in its proper position. If it’s too large, the IOL can actually move forward, and that can cause a myopic shift in the target refraction. Similarly, if it partially overlaps one side and not the other as the capsule shrinks and contracts, it can also torque the lens and induce some astigmatism as well.”

Although not reported in the study, lens fragmentation and segmentation with the Catalys system enabled surgeons to use less total phacoemulsification energy.

“Less time in the eye and less manual manipulation in the eye translate into safer surgery because there’s less irrigating fluid going through the eye, less phaco energy being dissipated in the eye and less potential for instrument-induced trauma,” Dr. Friedman said. – by Matt Hasson

Reference:

• Friedman NJ, Palanker DV, Schuele G, et al. Femtosecond laser capsulotomy. J Cataract Refract Surg. 2011;37(7):1189-1198.

• Neil J. Friedman, MD, can be reached at Mid-Peninsula Ophthalmology Medical Group, 900 Welch Road, Suite 402, Palo Alto, CA 94304; email: njfmd@pol.net.
• Disclosure: Dr. Friedman is a consultant and member of the medical advisory board for OptiMedica.