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 µm for the range of voltages and pulses typically used during surgery. For comparison, damage radius for microsurgical scissors was 50 µm, and for diathermy, 400 to 850 µm. 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).