Femtosecond laser-assisted cataract surgery seems to be a major step forward as a result of the added safety and precision that the laser confers, such as to the creation of the incision, relaxing incisions, capsulorhexis, and nuclear removal steps.
"We know that the femtosecond laser results in increased safety, reliability, and precision [with LASIK] in that flaps of predictable diameters, positions, and thicknesses can be created," said Dr. Culbertson, professor of ophthalmology and holder of the Lou Higgins Distinguished Chair in Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami. "We wanted to see if we could apply this technology to achieving more refinements of surgeries involving the lens, and to corneal incisions."
Dr. Culbertson and his colleagues conducted a study in the Dominican Republic that included 90 patients with grade 2 to 4 nuclear cataracts on the Lens Opacity Classification System III scale. Eight ophthalmologists participated in the study. All patients were followed for 3 months after surgery. A proprietary femtosecond laser system for cataract surgery (OptiMedica) was used for all procedures.
"From there, we can determine where the geometric center of the anterior lens capsule is and place the anterior capsulotomy concentric to that point," he added. "This should assist with centration of IOLs in the capsular bag and the pupil."
The femtosecond laser allows creation of cataract incisions with reverse geometry that are self-sealing, as well as limbal-relaxing incisions that have very accurate arc length, depth, angular position, and optic zone along the desired axis.
The technology also creates anterior capsulotomies that are perfectly shaped, sized, and positioned, according to Dr. Culbertson.
"We found that we have to cut a 4.6-mm capsulotomy to get a capsulotomy of 5 mm, because the opening expands," he said.
"The laser capsulotomies are quite round and perfectly sized with very little deviation from the intended size compared with the best manually created capsulotomies. For the anterior capsulotomy, the diameters were within 0.1 mm of the intended size. The capsulotomy openings measured intraoperatively and postoperatively were 0.4 mm larger than the resected capsules. The positions of the capsulotomy were within 0.1 mm of the intended location," he added.
Dr. Culbertson also highlighted the results of another study in which the capsulotomies were found to be an average of 50% stronger compared with manually created capsulorhexes. In addition, the edge of the capsulotomy was smooth and without any defects visible using electron microscopy.
Lens segmentation, softening
The femtosecond laser also can be used for lens segmentation and softening, he said.
"We can perform lens segmentation precisely down to 500 µm from the posterior capsule in hard nuclei," Dr. Culbertson said. "We actually can get pneumodissection by the gas bubbles that form posteriorly as we begin lasing posteriorly and bring the patterns anteriorly with four-quadrant segmentation and softening within each quadrant."
He explained how easily the quadrants can be separated by simply pushing them apart followed by aspiration of hard segments of cataractous lens nucleus with low phaco levels.
The study results for lens segmentation indicated that nuclei treated with the laser were separated easily into quadrants without chopping. The segmentation seemed to reach the desired depth of the nucleus. All the nuclei were aspirated using minimal phaco energy, Dr. Culbertson said.
William W. Culbertson, MDPhone: 305/326-6364
Dr. Culbertson is a consultant to OptiMedica. OptiMedica's femtosecond laser-assisted cataract surgery system is not for sale in the United States.