Surgical lasers

Surgical lasers (generally used to treat lesions such as seborrheic keratosis, warts, syringomas, trichoepithelioma, verrucous nevi, xanthelasma, and rhinophyma) can also offer an important support to the treatment of hyperpigmentation by inducing tissue ablation with partially-selective thermal damage and a moderate risk of scarring and dyschromia. The Er:YAG laser emits light with a 2940 nm wavelength, which is highly absorbed by water and penetrates much less than CO2 lasers, thus ablating the skin with only minimal thermal damage5.

Fractional photothermolysis is a relatively new concept in laser therapy in which multiple microscopic zones of thermal damage are created, leaving the majority of the skin intact. The fractional laser emission takes place by means of dots (DOT therapy) that generate micro-areas of ablative and thermal damage (microthermal zones; MTZ) alternated with healthy tissue. In the treated micro-areas, controlled heat release produces immediate tissue shrinkage and stimulates neocollagenesis. The areas of healthy tissue between the treated areas ensure rapid tissue repair and a drastic reduction in recovery time and post-treatment erythema. This exclusive emission system makes it possible to control tissue damage while simultaneously maximising efficacy, with repair of the damaged areas within 1 day and the disappearance of postoperative erythema usually within 3–4 days6–8.

Q-switched lasers

The τr of melanosomes ranges between 50 ns and 500 ns with a broad melanin absorption spectrum. Q-switched lasers (Nd:YAG, ruby, and alexandrite) deliver pulses lasting nanoseconds; therefore, they selectively target melanosomes with minimal thermal diffusion.

Q-switched ruby

The QS ruby laser, with a wavelength of 694 nm, is more selective for melanin than the QS Nd:YAG laser (1064 nm). Theoretically, therefore, it is expected to be more effective than QS Nd:YAG, but the role of the ruby laser is controversial, with studies showing conflicting results. In particular, one disadvantage is that a deeply pigmented epidermis can impede light penetration to the dermis and unwanted epidermal injury may result in dyspigmentation. In general, the QS ruby laser is not recommended for the treatment of hyperpigmentation disorders in darker-skinned patients (Fitzpatrick types IV–VI)9–10.

Figure 1 Pigmented blotches on the right side of the face

Figure 1 Pigmented blotches on the right side of the face

Q-switched Nd:YAG

The 532 nm QS Nd:YAG is well absorbed by melanin and being a longer wavelength, causes minimal damage to the epidermis and is not absorbed by haemoglobin. The deeper skin penetration also allows the physician to target the dermal melanin. The low-dose QS Nd:YAG laser induces sub-lethal injury to melanosomes, causing fragmentation and rupturing of the melanin granules into cytoplasm. This effect is highly selective for melanosomes as the wavelength is well absorbed by the melanin in other structures (Figures 1–3). The QS Nd:YAG, with its longer wavelength, is the safest type of laser for treating darker skinned patients11–12.

Q-switched alexandrite

Figure 2 Typical erythema immediately after a session of Q-switched Nd:YAG laser (Duolite QS; DEKA Laser, Florence, Italy)

Figure 2 Typical erythema immediately after a session of Q-switched Nd:YAG laser (Duolite QS; DEKA Laser, Florence, Italy)

The longer 755 nm wavelength of the QS alexandrite laser allows for deeper penetration into the skin. Unlike others in the Q-switched range, the alexandrite laser can be used in short pulse (5 ms) emissions (Figure 5). This type of laser enables selective damage of the pigmentation; however, there is a higher risk of dyschromia, rather than scarring or post-treatment hyperpigmentation. A number of studies suggest that a possible combination of low-energy QS alexandrite and QS Nd:YAG may also be effective in treating hyperpigmentation, especially that of the ‘light brown’ variety13–14.

Intense pulsed light

IPL is a non-laser light source that emits light in the range of 515 nm (red/yellow) to 1200 nm (infrared). The advantage of IPL is the versatility of the parameters. The wavelength, fluence, number, duration, and delay of pulses can be adapted to each patient in order to effectively target the chromophores. It can therefore be used to treat a variety of conditions, including vascular lesions, melanocytic lesions, and for hair reduction15.

Figure 3 The disappearance of the pigmented lesions

Figure 3 The disappearance of the pigmented lesions

In the authors’ experience, the use of IPL enables ablation of very superficial pigmented lesions with partially selective thermal damage and a low incidence of scarring, but with a high risk of discolouration (Figures 4–5). The laser settings play an important role in the treatment. Initially, 500–550 nm filters can be used for epidermal lesions, while higher wavelength filters can be used to target deeper melanin; for example, in patients with dermal/mixed melasma. The fluence can be adapted to suit the treatment sites, therefore, a higher fluence can be used for cheeks and zygoma, while the areas surrounding the eyes and neck require lower fluences. Higher fluences are useful for deeper lesions, but can cause PIH in darker-skinned patients. Single pulses are effective in heating the pigment, but double or triple pulses should be used as they reduce thermal damage, allowing the epidermis to cool while the target stays warm16–18.