EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/129516
Update on the latest in refractive cataract techniques and technologies 11 Lenticular applications of the femtosecond laser in cataract surgery by Ronald Krueger, MD The precision of the femtosecond laser makes it an ideal choice for creating the capsulotomy and for lens fragmentation T he advent of femtosecond laser-assisted refractive cataract surgery has turned a surgery with typically stellar outcomes into one with potentially phenomenal outcomes. While we've seen incremental improvements in intraocular lens technologies over the recent years, it wasn't until the femtosecond laser's applications for cataract surgery started to be explored that we realized what opportunity there was to simplify our techniques while (potentially) improving safety and enhancing outcomes. Patients undergoing modern cataract surgery are no longer impressed with excellent results—they are demanding perfection. Using the femtosecond laser to create the capsulotomy and to perform lens fragmentation can help turn difficult cataract surgeries into simpler ones and can make even routine surgeries easier. That's not to say these devices are not without potential drawbacks. Surgeons using these lasers will have to justify the cost of acquisition and during the early implementation may have to factor in additional time for the surgery until they develop a system that works for their practice. It is my belief, however, that the potential advantages far outweigh any drawback. Laser capsulotomy As refractive surgeons can attest, lasers offer a precision that manual procedures cannot. This extends to the capsulotomy creation during cataract surgery, too. As with corneal laser vision correction, the capsulotomy is best centered over the visual axis, and achieving this accurate centration is a challenge with man- ual rhexis techniques. Warren Hill, MD, has shown in several studies that a consistently round and centered capsulotomy helps the implant remain in a more stable position.1,2 Manual capsulorhexis will never match the precision of a laser. Although it's possible to be good at making the capsulorhexis, variability in anterior segment anatomy and pathology among patients makes it impossible to achieve a similar precision to that of the laser. " Manual capsulorhexis will never match the precision of a laser. " In particular, dense hypermature cataracts, eyes with zonular weakness, or hyperopic eyes with small, shallow chambers pose unique challenges when creating a manual capsulorhexis that simply no longer exist when a femtosecond laser is used. For surgeons who use premium IOLs, a capsulorhexis that is too large or imperfectly circular can create issues with lens centration and stability. That can lead to the need for premium lens repositioning or explantation to alleviate any visual distortion. In my hands, the femtosecond laser is able to create a capsulotomy that will symmetrically overlap the lens' edge, enhancing the effective lens position in nearly all cases. Lens disassembly In my opinion, an advantage of femto-fragmentation of the lens nucleus is that it's simply easier to disassemble the lens for emulsification, especially in denser cataracts or complex situations where excessive manipulation may jeopardize our outcomes (such as zonular dehiscence, pseudoexfoliative glaucoma, posterior polar cataracts, etc.). The LENSAR laser system (LENSAR, Winter Park, Fla.) data on lens fragmentation shows less cumulative dispersed energy (CDE) with the laser compared to conventional phacoemulsification.3 Less CDE, in turn, results in less endothelial cell loss. Similar data suggest that reductions in CDE of up to 95% or more may be possible with grades 1 or 2 nuclear cataracts, such that only aspiration may be needed. With denser nuclei, CDE can be reduced by two-thirds in grade 3 nuclear sclerosis and by 27% in grades 4 or higher. Furthermore, the lens fragmentation can be performed on any programmed algorithm; some clinicians have advocated a "pie-shaped" fragment in cases of hard nuclei and a spherical-based fragment for softer cases. There has also been a trend toward faster visual recovery after femtosecond laser in cataract surgery compared to standard phaco.4 References 1. Hill WE. The importance of the capsulorhexis—does it really matter? Presented for LENSAR at: the Annual Meeting of the American Academy of Ophthalmology; October 16, 2010 :Chicago. 2. Hill WE. The component parts of IOL power calculations. Paper presented at: the 25th Asia-Pacific Academy of Ophthalmology and the 15th Congress of the Chinese Ophthalmological Society; September 19, 2010: Beijing. 3. Fishkind W, Naranjo-Tackman R, Villar-Kuri J. Alternative fragmentation patterns in femtosecond laser cataract surgery. Paper presented at: the ASCRS Symposium on Cataract, IOL and Refractive Surgery; April 12, 2010: Boston. 4. Edwards KH, Frey RW, Naranjo-Tackman R, et al. Clinical outcomes following laser cataract surgery. Invest Ophthalmol Vis Sci. 2010;51:5394. Dr. Krueger is professor of ophthalmology and medical director, Department of Refractive Surgery, Cleveland Clinic Cole Eye Institute, Ohio. He can be contacted at 216-444-8518. Ronald Krueger, MD " [There is] less cumulative dispersed energy with the femtosecond laser compared to conventional phacoemulsification, [which] results in less endothelial cell loss. "