Femtosecond laser-assisted cataract surgery promising but still evolving

The procedure offers precision but also presents new challenges.

Uday Devgan

Cataract surgery is one of the most rapidly evolving procedures in medicine, with modern techniques being far superior to older procedures. Our patients now benefit from a minimally traumatic surgery, taking just minutes, and they can achieve excellent vision almost immediately. But even with the great cataract procedure we have today, I am confident that our technique, instrumentation and lens implants will continue to evolve. Using the femtosecond laser to refine cataract surgery may represent the beginning of this next era.

Femtosecond lasers were initially used to cut corneal tissue, for LASIK flaps and corneal transplantation, and then adapted to cataract surgery. I have just begun to enlist the assistance of a femtosecond laser for some of my cataract surgery patients, and I think this new technology, although expensive, holds promise.

Potential benefits

The femtosecond laser can be used to do many parts of cataract surgery, including the capsulorrhexis, corneal incisions and even division of the lens nucleus (Figure 1). The laser energy can be delivered very precisely as long as the machine has an optical coherence tomography image and experienced surgeon input as a guide. The current use of the femtosecond laser in cataract surgery is to replace a manual part of our existing phacoemulsification procedure with a machine in the hopes of improving precision and, therefore, results.

Figure 1. The femtosecond laser treatment for cataract surgery is shown in this plastic polymer. The blue outline shows the temporal main incision and the paracentesis a few clock hours away. The green arrow points to the capsulorrhexis and the yellow arrows show the arcuate incisions for astigmatism management. The red arrows show the complex delivery pattern for nucleus division, with a cruciate pattern for dividing the lens nucleus into quadrants and a central cylindrical component to soften and debulk the apex of each quadrant to facilitate removal. The inset photo shows the depth of the incisions, with the capsulorrhexis (green) being quite shallow compared to the nucleus division (red). Images: Devgan U

As with the patterns created using a femtosecond laser for corneal transplantation, complex corneal incisions with intricate geometry can be created easily with the laser. This includes the main phaco incision and paracentesis, as well as arcuate incisions for treating astigmatism. Having very precisely controlled incisions can help to provide a more accurate postoperative refractive state with regard to astigmatism.

To help hone our spherical refractive outcomes, some surgeons have suggested that a laser-created capsulorrhexis may provide a more predictable effective lens position for the IOL. While I agree that having a round, symmetric capsulorrhexis with the anterior lens capsule overlapping the edge of the optic is important for accurate postoperative IOL position, it remains to be seen if a machine-made capsulorrhexis performs significantly better optically than one made by an experienced surgeon.

There are many techniques that have been described to disassemble the lens nucleus, from divide-and-conquer to phaco chop. Some studies have shown that the phaco chop maneuver allows the use of less phaco energy and provides better outcomes, but there is a learning curve that has deterred some surgeons from using it. With the femtosecond laser, the nucleus can be divided very easily into quadrants or other fragments within seconds. To further facilitate surgery, the laser that I am currently using allows for additional energy delivery into the central core of the nucleus in the form of cylinders. This additional treatment softens and debulks the apex of each quadrant so that the phaco probe can get a good purchase and more easily aspirate these lens pieces.

Corneal arcuate incisions for the treatment of astigmatism can be challenging to perform manually because precise depth, position and arc length are the primary determinants of their effect. With the femtosecond laser, the specific corneal pachymetry for each eye can be measured and then a preset depth can be specified along with arc length and position. These incisions can even be performed in semi-attached segments, with the surgeon able to titrate the astigmatic relaxing effect in the postoperative period by selectively opening along the arc length.

Limitations and challenges

Even experienced cataract surgeons will need to learn to dock the eye to the laser, interpret the anatomic images, adjust the laser parameters and safely deliver the energy. New machines also have complications that are specific to the technology. For example, with the ultrasonic phacoemulsification we learned to prevent corneal wound burns and fluidic surges, complications that were unique to phacoemulsification and not present in manual extra-capsular surgery. The same certainly applies to femtosecond lasers.

One of the side effects of femtosecond laser use in the eye is the creation of gas bubbles within the tissue — in this case, presenting as large bubbles in the anterior chamber, smaller bubbles around the capsulorrhexis edge, and larger gas pockets in and around the lens nucleus (Figure 2). This gas can help to perform a pneumo-dissection of the lens from the capsule, but it may also contribute to increased pressure and capsular block syndrome, leading to posterior capsule rupture and a dislocated lens nucleus.

Figure 2. Intraoperative view of femtosecond laser incisions in cataract surgery. Note the presence of small gas bubbles under the anterior lens capsule and the larger, yellow-appearing gas pockets in and around the lens nucleus.

If the laser is misaligned by even a fraction of a millimeter, the energy delivery can be misdirected with unexpected results, such as a partially completed capsulorrhexis. Even with a perfectly cut capsulorrhexis, there can be additional surgical challenges. When the laser cuts the capsulorrhexis, it also neatly cuts the anterior cortical layer of the cataract. During our normal cortex removal with the irrigation and aspiration probe, we grab strands of anterior cortex in order to completely clean the capsular bag. However, because the anterior cortex is cut with the femtosecond laser, these strands are no longer present and we must resort to alternate techniques.

In the most difficult surgeries, such as in patients with dense, white cataracts and small pupils, the femtosecond laser may not be as useful. The capsulorrhexis cannot be created if the iris is blocking the anterior lens capsule, and the laser energy to divide the lens nucleus may not adequately penetrate a truly opaque lens.

Further evolution of technology

Performing a capsulorrhexis and learning phaco chop are often challenging for the novice ophthalmic surgeon, and having laser precision for these parts of the procedure could help a beginning surgeon achieve better results. For routine cases, the femtosecond laser could make a good surgeon even better. For the highly experienced cataract surgeon, the benefits of these new lasers in their current iteration may be less pronounced.

Femtosecond laser assisted cataract surgery is still in its infancy, and the future will likely bring faster, less traumatic and more accurate platforms. Lasers are just another instrument, like a blade or forceps, and these instruments will further evolve in the future. A decade or two from now, I am sure that I will be doing an entirely different cataract surgical procedure with technologies that have not yet been invented. But rest assured that surgery will always require a surgeon, because surgical judgment simply cannot be programmed into a laser or any other machine.

Reference:

• Roberts TV, Sutton G, Lawless MA, Jindal-Bali S, Hodge C. Capsular block syndrome associated with femtosecond laser-assisted cataract surgery. J Cataract Refract Surg. 2011;37(11):2068-2070.

• Uday Devgan, MD, FACS, is in private practice at Devgan Eye Surgery in Los Angeles and Beverly Hills. He can be reached at 11600 Wilshire Blvd., Suite 200, Los Angeles, CA 90025; 800-337-1969; email: devgan@gmail.com; website: www.DevganEye.com.
• Disclosure: No products or companies are mentioned that would require financial disclosure.