LASER (SURGICAL)

Typical Number in Hospital: 2

Cost Bands: 6

References: 4,9

A focused beam of laser light may be used for cutting and coagulating tissue with great precision without the probe needing to touch the tissue. Laser light can be focused to achieve great intensity (e.g. 10 kW/cm2) on to very tiny points.

Perhaps the best known application is the photocoagulation of points on the retina of the eye using the argon laser. The light beam may be directed through the cornea on to the retina using the natural focusing system of the eye under the full view of the surgeon. Bleeding points on the retina can be coagulated and re-attachment of the retina can be achieved. The area of the coagulation can be as small as 10 [u]m in diameter and the short time of application allows very little spread of the heat to the surrounding tissue. Garnet crystal lasers (Nb:YAG) are also used.

The carbon dioxide laser is now finding application in surgery and this produces light in the infrared region. Unfortunately these wavelengths cannot be conveyed through optic fibres and so must be reflected through the manipulating arm by a series of mirrors and lenses which are opaque to visible light (germanium lenses are often used). Laser light is normally absorbed and converted into heat in the first millimetre or so of tissue and so their application is for the cutting or coagulation of surface lesions without damage to deeper structures. Since the light will be absorbed in any surface water or exudate, a gas jet or flushing system is often employed to clear any liquid away.