Hair removal through treatment with the long-pulse alexandrite laser is effective in meeting the expectations of the patients who desire permanent hair reduction. When compared with other techniques, this method is faster and provides greater patient comfort. For optimal results, we recommend that physicians provide extensive patient education and follow the treatment guidelines.
Principles of Laser Hair Removal:
Laser depilation has provided an alternative, clinically superiot means of permanent hair removal since Goldman et als first described ruby laser injury to pigmented hair follicles in 1963. The efficacy of this technique is altered and affected by several variables depending mainly on the laser light itself, and hair follicle and skin characteristics.
Laser hair removal is generally based on a physicalprocess called “selective photothermolysis,” which was first described by Anderson et al.6 This process is defined as the absorption of laser energy specifically by the hair follicle rather than by any other possible tat get on or within the skin surface. The “melanin contained by the hair follicle is the target“chromophore. ” / Both the physical and chemical effects created by the laser’s thermal energy accomplish the destruction of the target.
The hair follicle resides in the dermis of the skin andconsists of 3 distinct parts: the bulb, the isthmus, and the infundibulum. Melanocytes are located in the bulb and bulge of the hair follicle, which are approximately 4 mm below the skin surface. To effect hair removal, the laser energy must target the skin layer housing the bulb and bulge. This is achieved by altering the laser wavelength and spot size. Longer wavelengths penetrate more deeply in the dermis but are less absorbed by melanin. The larg er the spot size, the deeper the laser light penetrates.
The growth cycle of the hair follicle is another important factor affecting the results. A complete cycle consists of 3 phases? anagen, catagen, and telogen. The period in which the hair is most susceptible to laser light is the anagen, Or active growth phase.8,” The duration of the cyclevaries on different parts of the body; consequently, morethan one laser session is usually needed because follicles on different parts of the body are in different phases of growth.
Currently, lasers with a variety of wavelengths are used for hair removal, ranging from the 695-nm ruby laser at the short end to the 1064-nm Nd:YAG laser at the long end.10 While shorter wavelengths are ineffective in achieving the desired long-term hair removal, longer wavelengths are too close to the light absorption rates of oxyhemoglobin and melanin to be fully effective. The alexandrite laser, which is almost in the middle of this spectrum with its 75S-nm wavelength, represents an ideal choice.
The energy of the laser light is defined by the number of photons delivered to the target and is measured in joules (J). The power of laser a device defined by the amount of energy delivered over time and is measured in watts. Fluence is the energy applied on unit area (J/cm). Spot size is defined by the diameter of the laser beam; large spots allow deliverance of more effective fluences in the dermis 11 In order for laser treatments to be safe, the surround
ing tissue must be preserved while the laser energy destroys the hair follicle. This is achieved through application of the principle of thermal relaxation time (TRT).
This term refers to the cooling duration of the target; selective thermal damage is accomplished when the energy delivered is longer than the TRT of the adjacent Structures but shorter than the TRT of the hait follicle, so that the target is not allowed to cool and consequently the hair follicle is damaged.!1,12 While the TRT of epidermis had been measured as 3 ms, it takes almost 40 to 100 ms for the hair follicle to cool. In addition to this principle, cooling devices can be used on the skin. Such devices both protect the skin from possible thermal damage and reduce pain for the patient, thus enabling the operator to deliver more energy safely.
Frequently asked questions
How does an alexandrite laser work?
The wavelength of high energy light emitted by the laser is converted to heat energy and this damages the specific
target area. Thus alexandrite lasers work by a process of photothermolysis: this means using light (photo) to heat
(thermo) a selected area for destruction (lysis).
Alexandrite lasers cause very precise tissue destruction of the lesion and leave the tissue in the surrounding area
What is an alexandrite laser used for?/How many laser treatments can l expect?
The US Food and Drug Administration (FDA) has approved a range of alexandrite laser machines emitting infrared light (wavelength 755 nm) for various skin disorders. .
The following skin disorders can be treated with Alexandrite laser beams.
1. Vascular lesions
- Spider and thread veins in the face and legs, some vascular birthmarks (capillary vascular malformations).
- Light pulses target red pigment (haemoglobin).
2. Pigmented lesions
Age spots (solar lentigines), freckles, flat pigmented birthmarks (congenital melanocytic naevi), naevus of Ota and acquired dermal melanocytosis. Light pulses target melanin at variable depth on or in the skin.
3. Hair removal
Light pulses target the hair follicle causing the hair to fall out and minimising further growth. May be used for hair removal in any location including underarms, bikini line, face, neck, back, chest and legs. Generally ineffective for light coloured hair, but useful for treating dark hair in patients of Fitzpatrick types? and perhaps light-coloured type IV skin. The typical settings employed include pulse durations of 2 to 20 milliseconds and fluences of 10 to 40 J/cmZ. Extreme caution is recommended in tanned or darker skinned patients, as the laser can also destroy melanin, resulting in white patches of skin.
4. Tattoo removal
The use of Q-switched alexandrite lasers has improved the process of tattoo removal and today is considered the standard of care. Alexandrite laser treatment is used to remove black, blue and green pigment. The laser treatment involves the selective destruction of ink molecules that are then absorbed by macrophages and eliminated. The short pulse duration of 50 to 100 nanoseconds allows laser energy to be confined to the tattoo particle (approximately 0.1 micrometres) more effectively than a longer-pulsed laser. Sufficient energy must be delivered during each laser pulse to heat the pigment to fragmentation. Without enough energy in each pulse, there is no pigment fragmentation and no tattoo removal. Tattoos that have not been effectively removed by other treatments may respond well to laser therapy, providing prior treatment has not caused excessive scarring Or skin damage. Alexandrite lasers may also be used to improve wrinkles in photo-aged skin
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