Familiarity with the femtosecond laser

Take-Home

When learning the intricacies of femtosecond laser technology, the quirks and capabilities of the individual lasers must be mastered.

By Lynda Charters; Reviewed by William W. Culbertson, MD

Miami-No technology comes without glitches. Even the femtosecond laser, with its advanced capabilities, has the potential for complications.

William W. Culbertson, MD, shared his pearls about making the most out of femtosecond laser cataract procedures.

“The difficulties and complications that are most commonly associated with femtosecond [laser] cataract surgery are incomplete capsulotomies, anterior capsular radial tears, posterior capsule breaks (possibly from extension of radial anterior capsular tears), and inaccurate placement of the main and relaxing incisions,” said Dr. Culbertson, the Lou Higgins Professor of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami.

Learning curve

The learning curve that accompanies gaining familiarity with femtosecond laser instruments should include “easy” cases first (i.e., performing surgery on patients with larger pupils, patients who are cooperative, and avoiding patients who are anxious, claustrophobic, or undependable). Anatomic characteristics to be wary of during the learning curve are small palpebral fissures, deep-set eyes, prominent orbital rims, loose conjunctiva, small pupils, and corneal scars.

“These features can interfere with docking of the interface on the eye and/or block the laser beam,” Dr. Culbertson said.

When performing a femtosecond laser procedure, topical anesthetic is typically applied. Use of block anesthesia results in loss of the patient’s ability to centrate, and sedation can interfere with patient cooperation. However, in pediatric or special cases, general anesthesia can be used.

Stability of the patient’s head and the table are important. The head should be comfortably taped to the table and rotated toward the opposite side, away from the laser cone, to permit sufficient room for the laser cone to clear the patient’s nose.

Surgical planning and pearls

“For safety, we observe certain safety zones that can be programmed into the computer software,” Dr. Culbertson said.

These include the location of the treatment (500 µm from the pupillary margin); the anterior capsulotomy (300 to 500 µm anterior or posterior to the capsule); the nucleus (500 µm from the anterior and posterior capsules), and astigmatic keratotomy (75 to 100 µm for placing the relaxing incisions).

Planning the segmentation pattern is based on surgeon preference, and the softening pattern depends on the nuclear density.

“We are still trying to determine the best patterns to use,” he said. “[This year], we should know more about the spacing, type of energy, and patterns that will improve our treatments.”

The size and the position of the anterior capsulotomy can be programmed into the laser but they are pupil-dependent parameters.

Dr. Culbertson advised minimizing the time between laser treatment and surgery.

“In some patients, the pupil begins to decrease in size, particularly in patients who have [taken] tamsulosin [Flomax, Boehringer-Ingelheim]. From 15 to 30 minutes after laser application,” he said, “the pupil can become substantially smaller compared with at the time of laser treatment. These pupils generally can be dilated again with intraocular mydriatic drugs.”

During docking, Dr. Culbertson advises against use of a speculum and avoiding eye tilt, pseudo-suction on the conjunctiva, and external forces on the patient interface. Each commercially available femtosecond laser docks differently, and familiarity with the system being used is paramount.

During imaging, the cornea, iris, and capsules must be adequately visualized and measured to ensure the safety zones for treatment. Adequate imaging can aid compensation for eye or lens tilt.

When placing relaxing incisions, the proper depth, planned axis, and planned arc length must be ensured and registered with the laser. When creating cataract corneal incisions, the arcus, pannus, pterygium, and limbus must be avoided.

The capsulotomy site should avoid corneal folds. When considering the capsulotomy incision, Dr. Culbertson advised evaluating the bubble pattern for completeness and checking for defects at the edge of the capsule. He explained his preference for removing the capsule in a curvilinear maneuver to allow tearing through an attachment if present.

Avoiding hyperinflation of the capsule is important during hydrodissection. He recommended “burping out” the gas around the lens equator or through the center segmentation.

When removing the segmented nucleus, a divide-and-conquer technique using a chopper and/or a prechopper can be performed. Venturi fluidics keeps the softened and segmented nuclear fragments on the aspiration tip. If the nucleus is softened, aspiration primarily can be used.

The cortex at the capsulotomy edge can be hard to differentiate from the capsule and difficult to engage in the aspiration port. For cortical removal, care must be exercised during this segment of the procedure.

“You need to know the capabilities and quirks of your laser, review the images personally, and be careful [with] dissecting the capsular cap, hydrodissection, and cortical cleanup,” Dr. Culbertson concluded.

fyi

William W. Culbertson, MD

E: wculbertson@med.miami.edu

Dr. Culbertson is a consultant for Abbott Medical Optics, Alcon Laboratories, Bausch + Lomb, Carl Zeiss Meditec, and OptiMedica. This article is based on Dr. Culbertson’s presentation during Refractive Surgery 2012 at the annual meeting of the American Academy of Ophthalmology