BBC Wednesday, 25 April, 2001, 23:40 GMT 00:40 UK

'Plasma bullets' could save sight

Vein blockages can cause eyesight damage Researchers are pioneering the use of super-heated gas to fire blockage-clearing drugs into the eye.

Veins in the retina of the eye can become blocked, endangering sight and causing pressure that can become so painful the whole eye has to be removed.

But a report in the New Scientist magazine says researchers from Stanford University in California have found a new way of treating blocked eye veins or "occlusions".

They have tested an instrument which uses super-heated gas, or plasma, to fire tiny bullets of blockage-dissolving drugs into a vein.

Occlusions in veins are one of the most common problems in the retina.

The tiny vessels that supply blood to the retina drain into a single vein, which if blocked causes excess pressure on other, smaller veins.

Extra pressure can cause smaller veins to rupture and leak, flooding the inner cavity of the eye with blood.

Needle-shaped probe

The blockage in the eye kills retina cells and causes misplaced veins to grow in the iris, damaging vision and causing painful pressure.

Stanford researchers Daniel Palanker and Dan Fletcher have created a needle-shaped probe which could re-open veins by accurately "firing" blockage-dissolving drugs.

The hollow needle is 1.5 millimetres in diameter, tapering to a point just 50 micrometres across, and contains a fine wire electrode surrounded by a metal sheath, bathed in salt solution containing a drug.

Dr Palanker discovered a 1,000 volt current created an ultra-hot plasma at the tip, producing a vapour bubble which could expand and collapse within a millionth of a second.

He said: "Each time the bubble expands, it ejects a pulse of saline [salt solution].

Mistakes avoided

"If you can get the tip of the probe near the blocked vein, you could shoot the drug into the vein, where it will dissolve the blockage."

Dr Palanker maintained the hole made by the bullet will heal quickly and that the probe has advantages over surgical needles.

He said: "These veins are very thin. If your hand is trembling slightly, you'll end up causing far more damage."

The researchers say the new instrument will not touch the vulnerable vein, greatly reducing the potential impact of mistakes.

"There's no new treatment for this at the moment, so any new ideas are good news," says John Forrester, an opthalmologist at the University of Aberdeen.

Dr Palanker will next test the potential of the plasma bullets to be used in cutting tissue during microsurgery.

-- Anonymous, April 25, 2001