Date: May 01, 2016 Author: Cheryl Guttman Krader Source: wix.com (
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LOS ALTOS, CA ::
PRECISION PULSE CAPSULOTOMY
(PPC) performed using novel disposable intraocular nanopulse technology (Zepto, Mynosys) may be a step forward toward the ideal capsulotomy, accord¬ing to David F. Chang, MD.
"PPC is an exciting new method that like a fem-tosecond laser could quickly and reliably create a perfectly circular capsulotomy with a precise di-ameter," said Dr. Chang, private practice, Los Altos, CA, and clinical professor of ophthalmology, Uni¬versity of California, San Francisco. "However, PPC has advantages of being lower cost and able to be used without disruption of the conventional sur¬gical sequence.
"As another bonus, PPC also seems to create a capsulotomy with a stronger edge than capsuloto-
mies created with either the femtosecond laser or a manual technique," Dr. Chang said.
The technology consists of a control console and a disposable handpiece containing the capsulotomy tip. The tip is comprised of a 6-mm silicone suction cup and the cutting element--a 5-mm nitinol capsu-lotomy ring. Using just a small amount of vacuum, the suction cup apposes the anterior capsule to the cutting element and also shields surrounding tis¬sues from the energy delivery.
A retractable push rod extends to stretch the cap-sulotomy tip into an elongated shape so that it can enter through a sub-2.2-mm clear corneal incision.
"The nitinol used for the capsulotomy ring is a shape memory alloy, which means that it can be collapsed to allow insertion through a small cor-neal incision and then will rebound back from the deformation to its native circular shape and diam-eter," Dr. Chang explained.
( Continues on page 9 : Capsulotomy )
surgery
To make the capsulotomy, very low energy electrical impulses are delivered to the cutting ring. This causes a rapid and momentary in-crease of temperature, leading to vaporization of water molecules that are trapped between the cutting ring and the capsule. The result is instantaneous mechanical cleavage of the capsule membrane around the entire circum¬ference of the ring in about 4 ms.
"There is no heating of the tissue with this technique, and it is not cautery, which would cre¬ate a capsulotomy with a weaker edge," he said.
Once the capsulotomy is made, the suction is released, and the device is withdrawn from the eye along with the excised capsule disc.
PPC performance has been evaluated in sev¬eral studies. Results from a series of inves-tigations conducted by Dr. Chang with Nick Mamalis, MD, and Liliana Werner, MD, PhD, in human cadaver eyes and in vivo in rabbit eyes highlighted the safety and efficacy of the novel tool for creating round, complete capsu-lotomies [Ophthalmology. 2016;123:255-264].
Serial slit lamp examination in the animal eyes showed no differences comparing eyes that underwent PPC and fellow eyes in which cap-sulotomy was done using manual continuous
curvilinear capsulorhexis (CCC) with respect to corneal edema, anterior chamber inflamma¬tion, capsular fibrosis, or capsule opacification.
"We also used a thermocouple to measure temperature change at the iris and corneal en-dothelium during the PPC and found negligible increases in both duration and magnitude," Dr. Chang said.
The capsulotomies created with the nano-pulse technology were found to be perfectly circular and free of tags. Intraoperative Miyake-Apple videos obtained during a study using paired human cadaver eyes showed minimal zonular movement during the procedure that was no different than that occurring during manual CCC. Imaging of human cadaver cap-sulotomies with scanning electron microscopy showed the capsule edges had the same smooth appearance of those created by manual CCC.
In collaboration with Vance M. Thompson, MD, John P. Berdahl, MD, and Joel M. Solano, MD, a comparative study in paired human ca¬daver eyes evaluated rim strength of capsuloto-mies created using the PPC technology, a fem-tosecond laser, or manual CCC [Ophthalmology. 2016;123:265-274]. The PPC capsulotomies were consistently the most resistant to tearing when capsulotomy edge retractors attached to force transducers were used to stretch the edge.
"The finding that the PPC capsulotomy edge was significantly stronger was intriguing," Dr. Chang said. ■
