It's one of the most delicate operations imaginable: An eye surgeon excises a piece of membranous tissue next to a patient's retina that threatens to damage or obscure the light-sensitive cells. Such "vitreoretinal surgery" can save the vision of someone whose eyes have been damaged by diabetes or trauma, but conventional microblades and microscissors can tear fragile tissues, and attempts to use lasers haven't succeeded. Researchers at Stanford believe they've developed a better option-a needle-sized "plasma knife" that cuts via blasts of electricity.

The new knife, explains Stanford physicist Daniel Palanker, is a tiny electrode that delivers electrical pulses a few nanoseconds long to create "plasma streamers"-lightning-like discharges that slice through soft wet tissues. Since the process doesn't require traction, as cutting with blades does, the risk of tearing is reduced. The surgeon sets the cutting depth and speed by adjusting pulse strength and duration. Mark Blumenkranz, chair of the department of ophthalmology at Stanford University School of Medicine, is helping test the plasma knife on rabbits; the researchers hope to begin human trials by year's end. Eventually, Palanker says, the plasma device could be used not only in vitreoretinal surgery but also to treat conditions such as cataracts and glaucoma.