Precision and safety of the pulsed electron avalanche knife in vitreoretinal surgery

Department of Ophthalmology , Stanford University, Palo Alto, California, United States
Archives of Ophthalmology (Impact Factor: 4.4). 07/2003; 121(6):871-7. DOI: 10.1001/archopht.121.6.871
Source: PubMed


We have developed a new surgical instrument, called the pulsed electron avalanche knife (PEAK; Carl Zeiss Meditec, Jena, Germany), for precise, "cold," and tractionless dissection of tissue in liquid media.
To evaluate the 3-dimensional damage zone induced by the PEAK compared with 2 other standard intraocular surgical instruments, diathermy and retinal scissors.
Damage zone and minimum safe distance were measured in vitro on chick chorioallantoic membrane and in vivo on rabbit retina with the use of propidium iodide staining.
The PEAK produced a paracentral zone of cellular structure disruption surrounding a crater and a peripheral zone of structurally intact but abnormally permeable cells. The instrument induced a damage radius that varied from 55 to 300 micro m for the range of voltages and pulses typically used during surgery. For comparison, damage radius for microsurgical scissors was 50 micro m, and for diathermy, 400 to 850 micro m. The PEAK also damaged tissue up to 1.4 mm away by the creation of water flow that formed at the tip of convex probes during collapse of a cavitation bubble. Concave probes, which prevent formation of the water jet, eliminated this effect.
The PEAK operated well within accept-able safety limits and may greatly facilitate both posterior segment surgeries (eg, membrane dissection and sheathotomy) and anterior segment procedures (eg, capsulotomy, nonpenetrating trabeculectomy, and iridectomy).

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Available from: Daniel Palanker, Sep 30, 2015
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    • "In pulsed ablation, tissue can also be damaged by mechanical effects of the rapidly expanding and collapsing cavitation bubbles [8], [9]. When the pulse duration is much shorter than the lifetime of the vapor bubble, the process of vaporization is explosive , leading to the formation of large and rapidly expanding vapor cavities. "
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    ABSTRACT: Electrosurgery, one of the most-often used surgical tools, Is a robust but somewhat crude technology that has changed surprisingly little since its invention almost a century ago. Continuous radiofrequency is still used for tissue cutting, with thermal damage extending to hundreds of micrometers. In contrast, lasers developed 70 years later, have been constantly perfected, and the laser-tissue interactions explored in great detail, which has allowed tissue ablation with cellular precision in many laser applications. We discuss mechanisms of tissue damage by electric field, and demonstrate that electrosurgery with properly optimized waveforms and microelectrodes can rival many advanced lasers. Pulsed electric waveforms with burst durations ranging from 10 to 100 mus applied via insulated planar electrodes with 12 mum wide exposed edges produced plasma-mediated dissection of tissues with the collateral damage zone ranging from 2 to 10 mum. Length of the electrodes can vary from micrometers to centimeters and all types of soft tissues - from membranes to cartilage and skin could be dissected in liquid medium and in a dry field. This technology may allow for major improvements in outcomes of the current surgical procedures and development of much more refined surgical techniques.
    IEEE Transactions on Biomedical Engineering 03/2008; 55(2-55):838 - 841. DOI:10.1109/TBME.2007.914539 · 2.35 Impact Factor
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    ABSTRACT: Cavitation bubbles accompany explosive vaporization of water following pulsed energy deposition in liquid media. Bubbles collapsing at the tip of a surgical endoprobe produce a powerful and damaging water jet propagating forward in the axial direction of the probe. We studied interaction of such jet with tissue using fast flash photography and modeled the flow dynamics using a two-dimensional Rayleigh-type hydrodynamic simulation. Maximal velocity of the jet generated at pulse energies of up to 1 mJ was about 80 m/s. The jet can produce tissue damage at a distance exceeding the radius of the cavitation bubble by a factor of 4. We demonstrate that formation of this flow and associated tissue damage can be prevented by application of the concave endoprobes that slow down the propagation of the back boundary of the bubble. Similar effect can be achieved by positioning an obstacle to the flow, such as a ring behind the tip. © 2003 American Institute of Physics.
    Journal of Applied Physics 08/2003; 94(4). DOI:10.1063/1.1593803 · 2.18 Impact Factor
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    ABSTRACT: To evaluate the advantages, disadvantages, safety, and surgical applicability of the pulsed electron avalanche knife (PEAK-fc), a new electrosurgical knife for "cold" and tractionless cutting, in vitreoretinal surgery. PEAK-fc is equipped with an integrated fiberoptic that makes bimanual procedures in intraocular surgery possible. A prospective consecutive trial of 18 eyes in 18 patients who underwent vitreoretinal surgery for proliferative diabetic retinopathy, proliferative vitreoretinopathy, subretinal macular hemorrhage, or macular pucker was performed. The following specific maneuvers were performed with PEAK-fc: transection of epiretinal membranes, retinotomies, retinal vessel coagulation, and posterior membranectomy. Detached and attached retina could be dissected successfully in eight cases. Intraoperatively, incision edges were sharply demarcated, showing no visible collateral damage. Deeper layers than the neurosensory retina were not affected. With the bimanual approach, epiretinal avascular and vascular membranes could be removed in 10 cases. Hemorrhages occurring during transection of vascularized membranes could be stopped immediately using the coagulation mode of PEAK-fc. Posterior capsule fibrosis was successfully excised in one patient. No complications were observed. PEAK-fc offers precise and tractionless tissue cutting during ocular surgery. Using different waveform parameters, the same device performs cold cutting and/or "hot" coagulation, thus improving the precision, safety, and ergonomics of vitreoretinal surgery.
    Retina 10/2005; 25(7):889-96. DOI:10.1097/00006982-200510000-00012 · 3.24 Impact Factor
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