LONDON: An “elegant weapon from a more civilised age,” announced Obi-Wan Kenobi, introducing the world to the light sabre. Ever since, millions of children have been waving plastic tubes at each other, wishing they could have the real thing. Meanwhile, hi-tech alternatives are replacing steel blades — but their wielders are surgeons rather than Jedi knights.

The best-known alternative to a blade is the laser beam. While not a magical solution, medical lasers are extremely useful. The key feature is that each type can usually only produce light of one wavelength or colour, and each wavelength has specific uses.

The most common surgical laser is the carbon dioxide type, producing a beam in the far infrared. This is absorbed by the water in human tissue, resulting in instant heating. A typical CO2 surgical laser has a power of about 20 watts and is focused on a spot 0.1mm in diameter. The energy level can be varied: high power is used for making incisions or destroying tumours, low power for stopping bleeding.

Eye surgery often involves an Excimer laser, which generates a beam of ultraviolet light that does not heat, but breaks down the bonds within protein molecules. Excess tissue is vaporised without damaging surrounding tissue. This is the laser behind the boom in photorefractive keratectomy, which has improved the eyesight of millions of patients.

Not all medical lasers are used for cutting. Q-switching allows a laser to produce a very short, powerful pulse to remove tattoos. The colour of the laser has to be matched with the pigment being removed; particles of the pigment absorb laser energy of the right colour so quickly that they “explode” into microscopic fragments that can be carried away by the body’s natural processes.

An older technology is electrosurgery, which goes back to Victorian times. In its earliest form, this was a substitute for heating instruments in a brazier. A platinum wire was heated by passing a current through it; when red-hot it could cut and cauterise wounds. However, a low-frequency alternating current could cause violent muscle contractions.

The most recent addition to the surgeon’s toolkit is the ultrasonic scalpel. This has a blade that vibrates at 55KHz. The vibration makes the blade into a high-speed version of an electric carving knife, and the ultrasonic vibration also causes protein to denature, causing coagulation and so sealing off blood vessels.—Dawn/The Guardian News Service.