Femtosecond laser lens surgery expands into sub-1 mm realm
Early experience with sub-1 mm cataract surgery performed using a currently available femtosecond laser platform (LenSx, Alcon Laboratories) demonstrates the feasibility of the procedure. It also provides additional data confirming the benefits of microincisional cataract surgery (MICS) for minimizing surgically induced astigmatism (SIA) and preserving the cornea's optical quality, said Professor Jorge L. Alió, MD, PhD, at the Refractive Surgery Subspecialty Day during the annual meeting of the International Society for Refractive Surgery/American Academy of Ophthalmology.
Prof. Alió presented what he described as the first report of sub-1 mm cataract surgery using a femtosecond laser to create the cornea incisions. The laser was also used to create the capsulotomy and for nuclear softening.
"This technique is about taking cataract surgery to the limits with femtosecond laser technology," said Prof. Alió, professor and chairman, Miguel Hernández University, Alicante, Spain, and medical director, VISSUM, Instituto Oftalmológico de Alicante, Spain. "Using the femtosecond laser, we can reproducibly create sub-1 mm incisions that are optimal in profile and size and achieve the goal of MICS, which is to maximize outcomes in cataract surgery."
"I developed the concept of MICS in 2004 based on the premise that minimizing the invasiveness of cataract surgery and using techniques to maintain corneal optical quality would improve the speed and level of visual recovery," said Prof. Alió, who has trademarked the term MICS.
After first gaining experience with the laser platform operating with Dr Zoltan Nagy, Budapest, Hungary, Prof. Alió began performing biaxial MICS with the femtosecond laser. The laser is used to create two sub-1 mm incisions, but because it can now only be programmed to create two incisions, the second 0.9 mm incision is made with a blade and later enlarged to 1.8 to 2 mm to allow implantation of a good quality IOL. One cataract incision is placed on the positive meridian and the other two are located 90° apart. Lens removal is done using 700 µm instruments (MicroSurgical Technology).
"The incisions are easy to open using a blunt spatula or Sinskey hook, and they are consistently self-sealing," he said. "After the capsulotomy is made with the laser, the capsular disc is completely detached from the remaining capsule and can be easily removed intraoperatively using a forceps, and softening of the lens with the laser allows the surgery to be done with minimal hydrodissection and reduced ultrasound energy."
Optical coherence tomography images documented the precision of the corneal incisions made with the femtosecond laser with respect to dimensions and architecture. Measurements recorded at 1 month postoperatively showed the widths were all within 0.1 mm of intended and the achieved incision angle was ±5.2° of target.
"Using the femtosecond laser, the surgeon can control the design of the incision and customize its geometry and position," he said. "The laser allows creation of incisions having a complex structure and located anywhere in the cornea, and what we target with the software is what we get. Our data from measurements of the incisions immediately after surgery and 1 month later demonstrate that incisions created with the femtosecond laser have excellent stability."
The positive optical consequences of the femtosecond laser-assisted sub-1 mm procedure were demonstrated through comparison of outcomes achieved in five eyes that underwent the femtoassisted sub-1 mm procedure and seven eyes operated on through a standard 2.75 mm incision (also created with the femtosecond laser). Results from wavefront aberrometry measurements taken preoperatively and at 1 month after surgery showed there were no significant changes in total RMS or RMS values for high- or loworder optical aberrations in the femtosecond laser group. The changes from baseline for each of the three endpoints were numerically greater in eyes that had the standard incision procedure relative to the sub-1 mm group, and the change in higherorder aberration in the standard surgery group was statistically significant.
SIA was also lower in eyes that had the femtosecond laser-assisted sub-1 mm surgery compared with the standard group, 0.88 ± 0.57 D versus 1.07 ± 0.55 D, Prof. Alió concluded.
Special contributorProfessor Jorge L. Alió, MD, PhD, is professor and chairman, Miguel Hernández University, Alicante, and medical director, VISSUM, Instituto Oftalmológico de Alicante, Spain. He may be reached by E-mail: firstname.lastname@example.org
Prof. Alió is a consultant to LenSx.