EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/220233
32 EW CATARACT November 2013 Cataract removal on the laser's edge by Maxine Lipner EyeWorld Senior Contributing Writer Targeting zero effective phacoemulsification time B eing able to extract a cataract with zero effective phacoemulsification time is a real possibility these days, with the right equipment. Recent study results indicate that with the aid of femtosecond laser pretreatment, optimized lens fragmentation algorithms and phacoemulsification tip adjustment, this was attained in 30% of cases, with investigators reaching this mark in many more patients subsequently, according to Brendan Vote, MD, Launceston Eye Institute, who conducted the trial along with Robin Abell, MD, research fellow, Tasmanian Eye Institute, Australia. The study, published in the May issue of Ophthalmology, grew out of the realization that the lack of guidelines for optimal laser fragmentation methods and intraoperative techniques meant that the full potential of this femtosecond technology had not yet been realized, Dr. Vote explained. "From very early on we were recognizing that grade 1 and 2 cataracts could be easily aspirated without the need for phacoemulsification, and hence we looked at ways of making it possible to use little phacoemulsification on even harder cataracts and for the optimal settings and techniques to facilitate that." Minimizing phacoemulsification There can be myriad benefits to keeping phacoemulsification time to a minimum, he pointed out. "Phacoemulsification energy is known to contribute to corneal edema and endothelial cell loss after cataract surgery," Dr. Vote said, adding that the reduction in effective phacoemulsification time and subsequent decrease in phacoemulsification energy has the potential to lessen endothelial cell loss, particularly in patients with pre-existing corneal endothelial cell dysfunction. This, he explained, will also result in early visual recovery and clearer corneas postoperatively, which can translate into increased patient satisfaction. "We also found the reduction in effective phacoemulsification time led to less postoperative inflammation, seen as a reduction in anterior chamber flare and macular edema," he said. Investigators found a significant reduction in effective phacoemulsification time (EPT) using the optimized grid pattern on the right. Included in the prospective study of 200 eyes were all of the patients from the Launceston Eye Institute who underwent femtosecond laser cataract surgery there between April and July 2012. These patients were compared with a concurrent group undergoing conventional phacoemulsification. In the femtosecond group the laser was used to segment the cataract prior to phacoemulsification. "There are multiple methods of segmentations available to the surgeon using predefined templates," Dr. Vote said. "These are a matter of preference, but the most basic pattern is a square grid pattern that segments the cataract into quadrants and softens each quadrant." increased treatment time and gas bubble formation," he said. In addition to optimizing the grid pattern, investigators used a larger phacoemulsification tip for the procedure. "We upgraded from a 21-gauge to a 20-gauge phacoemulsification probe tip," Dr. Vote said. "This allowed the larger pieces of cataract to be aspirated more easily." Despite the need for a slightly larger 2.7 mm main incision, the effect on surgically induced astigmatism was minimal, he added. Investigators determined that all patients in the study pretreated by the femtosecond laser had a com- plete capsulotomy. Dr. Vote reported that they also found a significant 84% reduction in effective phacoemulsification time over manual cases. Effective phacoemulsification time was reduced by 29% by using optimized lens fragmentation algorithms and by 73% when using a larger phaco tip. "This overall equated to a 96.2% reduction in effective phacoemulsification time between the control cases and the optimized femtosecond pretreatment group," he said. In his view, perhaps most significant, however, is the 30% incidence of zero effective phacoemulsification time. "This was associated with a Optimizing pretreatment To reduce the need for phacoemulsification, investigators optimized the femtosecond laser pretreatment. This was done by adjusting the segmentation-softening template, Dr. Vote explained. "We found the best method was a central cross, dividing the cataract into quadrants, with a softening grid pattern beginning 200 microns from the central cross in all quadrants," he said. "Each grid square was 400 microns." Investigators found that this allowed for easy chopping into quadrants. Then each rectangular grid piece of the softened quadrants could be easily aspirated without the need for phacoemulsification. "Smaller grid patterns carried a tradeoff with Upgrading from a 21-gauge to a 20-gauge phacoemulsification probe tip allowed the larger pieces of cataract to be aspirated more easily. Source (all): Brendan Vote, MD