Lasers emit a beam of light of a single wavelength, which can be selectively absorbed by a target of a certain colour, causing heating and subsequent lysis (Table 24.1). This target is known as a chromophore, from the Greek word for ‘bearing colour’. The duration of the laser pulse is also set to be selective for the size of the chromophore. Larger targets such as hair follicles take longer to heat up and are slower to cool than smaller targets such as melanosomes. Lysis of the chromophore leaves a residue of smaller particles which are subsequently phagocytosed by macrophages. This concept of selective photothermolysis underpins laser science.

Preoperative assessment

Laser treatment should be preceded by a full medical history and dermatological examination.

Laser centres should offer a preoperative consultation by a qualified practitioner who can diagnose and manage skin disease and counsel the patient regarding the most appropriate therapy for their condition. It should always be borne in mind that laser treatment may not represent the optimum management for a patient and that patients are not infrequently referred with the wrong diagnosis. Careful patient selection for laser treatment has been shown to be associated with fewer adverse events, more realistic patient expectations and higher levels of patient satisfaction. The process of patient selection and preparation and an understanding of the cutaneous biology of the lesions to be treated are as important as the laser treatment itself.

Patients should be provided with comprehensive written information relating to the laser treatment of their particular condition before obtaining informed consent. The consent form itself should detail possible complications of treatment (Table 24.2). Scarring may be more likely in certain areas such as the chest, shoulders and back. It is sensible to perform a small test patch using the desired settings before starting laser treatment or increasing the energy (fluence).

Patients should avoid direct sunlight and use a high factor sun block before laser treatment in order to minimise the amount of pigment in the skin and reduce the risk of complications.

Table 24.3 shows which type of cutaneous disorders may be amenable to treatment with which lasers.

Perioperative anaesthesia

Patients experience varying amounts of pain during laser treatment, and anaesthesia must be adjusted to the needs of the individual patient and the procedure being undertaken. Some lasers have cooling devices attached, which provide a degree of anaesthesia, and many patients will undergo treatment without additional pain relief. Topical local anaesthetics (EMLA®, Ametop®) may be applied under occlusion before treatment but for procedures such as resurfacing or extensive port wine stains local or regional anaesthesia will be required. General anaesthesia is reserved for treatment of young children and other special cases.

Postoperative care

All patients should be given a greasy emollient to be applied regularly to the treated area for 3 days following treatment. The aim is to maintain the barrier function of the skin where this might have been disrupted by collateral thermal injury of the epidermis. Any blistering implies significant thermal injury to the epidermis and lower fluences should be employed. Patients should also avoid excessive exposure to sunlight for at least 3 months following treatment. Resurfacing procedures require intensive post-operative care by both the laser operator and the patient or carer.

Laser safety

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