Blocked viens block eye sight

by Medindia Content Team on  July 27, 2001 at 11:02 AM Research News   - G J E 4
Blocked viens block eye sight
"Occlusions in the retinal vein could not only make you loose your sight but even your eye". The pressure due to blocked veins is so painful that the eye may have to be removed.

Researchers at the Stanford University California have devised a new instrument that uses a plasma to shoot tiny bullets of blockage-dissolving drugs into a clogged vein.

The tiny blood vessels that supply blood to the retina drain into a single vein. "If this central vein becomes blocked, you get a build up in blood pressure in all the smaller veins" says Forrester, an opthalmologist at the University of Aberdeen.

The pressure makes the small veins rupture and leak, flooding the inner cavity of the eye with blood because of the blockage, blood cant flow into the eye, so the cells in the retina die due to lack of oxygen. Once the retinal cells begin to loose life, they release growth factors to encourage new veins to grow - but they grow in the iris instead of the retina. These large veins that grow in the iris obscures vision and exert painful pressure on the eye.

To treat this condition Stanford researchers Palanker and Flecther have developed a needle-shaped probe that could shoot drugs right at the site of blockage and reopen the vein.

The hollow needle is 1.5 millimetres in diameter and tapers to a point just 50 micrometres across. Inside the needle, a fine wire electrode surronded by a metal sheath is filled in with electrically conductive solution containing a drug.

Palanker found that when 1,000 volts were applied between the electrode and metal sheath, an ultra hot plasma formed at the tip of the electrode producing a rapidly expanding vaporized bubble. By alternating the voltage the bubble could expand and collapse within a millionth of second.

Palanker and Flecther plan to mix a drug called tissue plasminogen activator into the saline solution within the probe. The tip of the probe could be brought near the vein and by shooting the drug into the vein it will dissolve the blockage.

Planker stated that the hole made by the bullet will heal quickly. He further stated that the probe has advantages over the other surgical needles as this probe does not damage the vulnerable vein. He now plans to test how good the plasma-powered bullets are at cutting tissue during microsurgery. As lasers tend to damage the surrounding tissues by creating bubbles in local body fluids, the pure saline jet might make even finer cuts without causing stress to the nearby tissue.

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