The word "laser" is an acronym standing for "light amplification by stimulated emission of radiation." A laser is a beam of light energy that has very special properties. The most important quality is that all the light waves in a laser beam are emitted in exactly the same rhythm. In addition, all the light waves are of the same wavelength. These two qualities when taken together mean that laser light is much more powerful than ordinary light. Lasers have numerous applications in manufacturing industries, in the military field and in communications systems, but in this article we will focus on the medical uses of lasers.

Lasers have been widely used in surgery for more than thirty years and this use is increasing with the new implementation of keyhole surgery techniques. In keyhole surgery, instead of making an incision or making large incisions, surgeons use lasers to perform operations which are far less invasive than they used to be and this is made possible by the fact that surgeons can use laser beams as very accurate scalpels. The beam can be focused on a spot one-fiftieth the size of a human hair; yet its intensity is enough to kill cancer cells or drill through the most delicate bones. The greatest advances in laser surgery, however, have been achieved in the treatment of eye problems.

More than thirty years ago, eye surgeons realized that they could use a laser beam to seal individually the microscopic blood vessels in the retina; the beam is so fine that only the target is heated. Laser light passes through the cornea and is concentrated inside the eye. This means that it is no longer necessary to cut the eyeball to make an  opening — an extremely dangerous procedure which left many patients permanently blind in the past. Laser surgery is instrumental in the treatment of many eye diseases including glaucoma and cataracts. Lasers can also be used to treat the ocular complications caused by diabetes.

Diabetes causes specific changes in the blood vessels in the eyes. Blood vessel walls become weak and develop a tendency to leak. This means that fluid escapes from the blood vessels and passes into the layers of the retina. The retinal distension in turn causes significant loss of vision. The laser can seal the leaking blood vessels and so prevent further swelling of the retina. Lasers can help, too, in a later stage of diabetes. In this stage, blood vessels close and blood circulation is lost. New but abnormal blood vessels begin to grow and can cause further damage to the eyes. Special laser treatment can shrink the abnormal vessels and so allow circulation to occur and vision to remain only slightly impaired.

Eye surgery is by no means the only type of surgery to benefit from the introduction of lasers; some cancer patients can now benefit from a course of laser treatment. To ensure that cancer treatment is effective, the diseased cells must be killed while their healthy neighbours must be left unharmed. Where the cancer can be directly  and accurately attacked, laser treatment is indeed effective. Cancer of the cervix and certain skin cancers — if presented in their early stages— have been widely and successfully treated. These types of cancer are relatively easy to reach. For cancers that are less accessible, there is a valuable technique in which the patient is injected with a chemical that then attaches itself preferentially to cancer cells. When the laser strikes the chemical, it releases a form of oxygen that kills the diseased cells.

In addition to eradicating diseased tissue, the laser beam can also remove bone, and so it is invaluable in ear surgery. The sounds we hear are carried from the eardrum to the nerves of the ear by a delicate set of pivoting bones in the middle ear. These small, connecting bones sometimes stick together, causing either complete or partial deafness. Now, surgeons are able to use laser beams to loosen the bones without touching any of the surrounding tissue. The accuracy of the laser can be increased by sending the beam along fibres of glass far finer than a human hair. These optical fibres carry the beam around corners and direct it precisely at a tiny area. Very little of the beam spills from the glass, so there is virtually no risk of damaging healthy cells. This technique is particularly useful in ear surgery.

Serious threats to the quality of life are not the only phenomena which can be tackled by lasers. Cosmetic surgery also makes wide use of lasers. For example, birthmarks, a mass of blood vessels on the surface of the skin, can be removed by laser. Being red, birthmarks absorb the laser beam very efficiently. The beam is diffused to avoid scarring and seals the blood vessels, so that the mark becomes much less conspicuous. The normal cells of the skin’s surface, which do not absorb much of the laser beam, act in the healing process and help to conceal the mark. This simple procedure can transform the lives of people who previously had to accept their birthmarks or cover them as best they could by  cosmetic means.

In spite of the great benefits of lasers, it is necessary to end this article on a note of caution. The risks of laser surgery are less than those of conventional surgery, but a great deal depends on the skills of individual surgeons. Compared with training in conventional techniques, the learning curve for training to use lasers in operations 80 is a long and steep one; this means that surgeons learn the special techniques involved slowly and over a long period of time. Extensive —and expensive — training is vital, as is a calm temperament and very steady hands. Severe, permanent damage to soft tissue can result from laser procedures which are not administered correctly.