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DV Palanker, A Vankov, P Huie, MS Blumenkranz; A Plasma-Mediated Cutter for Anterior Segment Surgery . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1941.
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Purpose: Improved methods are needed for precise and rapid dissection of harder ocular tissues such as sclera and lens with minimal damage to the adjacent material. We present a new plasma-mediated cutting technique based upon extension of the Pulsed Electron Avalanche Knife (PEAKTM) technology, that allows for fast dissection and ablation of soft tissue in liquid medium. Methods: Trains of high voltage pulses with durations varying between 0.1 to 10 µs and amplitudes varying between 100 V and 5 kV are applied to microelectrodes of 50 to 100 µm in diameter exposed to the physiological medium to a length of up to 10 mm. Experiments have been performed on excised bovine and pig ocular tissues including cornea, sclera, lens and lens capsule. Results were analyzed using histology and scanning electron microscopy. Results: A train of pulses can form a quazi-steady jacket of ionized vapor (plasma) around the central wire. In various regimes the width of the plasma jacket varies between 3 to 100 µm with temperature of the central wire varying between 250 and 650 oC. Plasma causes fast evaporation of tissue resulting in formation of cuts as narrow as 70µm with the depth determined by the length of the microelectrode. Rapid fall-off of temperature occurs in water or in tissue outside of plasma layer so that the thermal damage zone in the adjacent tissue can be as small as 10 µm. Conclusion: This novel plasma knife with appropriate geometry of the microelectrodes can be applied to dissection of ocular tissues such as sclera, lens capsule, lens cortex and others. Potential applications include improved lens removal and controlled scleral dissection or thinning for glaucoma treatment.
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