Eyeworld

EW CATARACT 54 March 2016 ring edge into uniform contact with the anterior capsule. A train of tiny brief electrical pulses causes water molecules trapped between the ring edge and the microscopically stretched anterior capsule to vapor- ize. This phase transition creates an instantaneous mechanical splitting of the anterior capsule along the entire ring circumference, result- ing in a perfectly circular opening of a precise diameter. There is no cautery or burning of tissue, and all 360 degrees of the capsulotomy are created at the exact same instant. A small console placed on top of or integrated into the phaco machine creates the suction and generates the precision electrical pulses. The device was developed through testing in rabbit and hu- man cadaver eyes, and results of this testing were presented at the AAO meeting. Live rabbit studies done by Nick Mamalis, MD, and Liliana Werner, MD, at the Intermountain Ocular Research Center at the Mo- ran Eye Center, University of Utah showed no issues with inflammation or endothelial cell loss. In addition, thermocouple probe measurements confirmed that there is negligible temperature change within the an- terior chamber associated with PPC. "The tiny and momentary electrical impulses are on the order of just a few milliseconds," Dr. Chang said. "In addition, the surrounding sili- cone suction cup shields the rest of the eye from any heat or energy that might be momentarily generated." Based on clinical and SEM findings with the femtosecond laser, a major question with any new capsulotomy method is whether the resulting capsular edge resists tearing as well as a manual CCC. Extensive testing of the PPC edge tear strength was performed using paired human cadaver eyes to compare PPC with either femtosecond laser capsuloto- my or manual CCC. "We think that such comparisons should be made using paired eyes from the same hu- man donor," Dr. Chang said. "Com- parisons in animal eyes or using eyes from two different human donors are less valid." The results of these studies performed by Dr. Chang and Vance Thompson, MD's group in South Dakota revealed unexpected exciting results. "The PPC capsular edge was consistently stronger than either the The Zepto capsulotomy system consists of a disposable handpiece attached to a control console that provides power and suction for the capsulotomy (left). The handpiece terminates in a soft, clear silicone capsulotomy tip that houses a circular collapsible super elastic nitonol ring to perform the capsulotomy (right). Source (all): David F. Chang, MD An example of a Zepto capsulotomy in a human cadaver eye femtosecond laser or manual capsu- lotomies," Dr. Chang noted. "This was true in all 16 pairs of human cadaver eyes—half using femto and half using manual CCC in the fellow paired eye. "I think that most surgeons would welcome the option of an affordable disposable technology to automatically create a perfectly sized and circular capsulotomy that could be used in the usual surgi- cal sequence without interrupting our OR workflow," Dr. Chang said. "If the resulting capsulotomy was stronger and more tear resistant than a manual CCC, that would be a huge bonus." A clear central window in the silicone shell would permit patients to fixate on the microscope light filament. Additional advan- tages would be the ability to center the capsulotomy on the visual axis intraoperatively for a refractive IOL and the ability to use the device fol- lowing mechanical pupil expansion, he said. The company has received CE mark approval in Europe and has ap- plied for 510K approval in the U.S., Dr. Chang said. Clinical trials will be conducted shortly. EW Editors' note: Dr. Chang has financial interests with Mynosys and Abbott Medical Optics (Abbott Park, Ill.). Contact information Chang: dceye@earthlink.net New continued from page 52

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