Laser Treatment of Pigmented Lesions for Asians

The term Asian refers to East Asians of the Pacific Rim who share not only a common heritage and skin type but also the same set of clinical skin problems. Pigmentation of the skin is often considered the number one esthetic skin concern in Asians. Asians idealize unblemished complexion of facial skin and are less tolerant to facial dyschromia than White. The problems of ephelides (freckles), nevi of Ota, and melasma are common and difficult to treat. This article reviews laser treatment of pigmented lesions in Asians.

The characteristics of the Asian skin, in general, can be described as having less wrinkles, more photoprotective effect with darker complexion than White, thicker dermal structure, and more superficial dyschromia and solar lentigines. The problems of ephelides (freckles), nevi of Ota, and melasma are common and difficult to treat.

Asian skin types have been categorized by either the Fitzpatrick grading system from grades II to IV or Fanous’ racial-based skin classification system that divides the globe into latitudinal zones in the temperate zones.

Problems faced in the treatment of the Asian skin are:

1.

Dissimilarities between Asian populations
2.

Definite anatomic traits
3.

Thicker dermal layer
4.

More sebaceous glands, and hence more rigorous response to exfoliation
5.

Pigmentary problems
6.

Prolonged erythema
7.

Postinflammatory hyperpigmentation/hypopigmentation.

The study by West and Alster states that an intensive preoperative regimen of tretinoin ± hydroquinone failed to suppress postoperative melanin production, melanocytic nevi/superficial melanocytes that have been curbed by topical agents are eventually removed by the peeling process, and deeper melanocytes remain undisturbed by the preoperative treatment. For this reason, there is no evidence to support that preoperative treatment of the Asian skin with tretinoin improves postinflammatory hyperpigmentation. Treatment of Asian skin pigmentation can be divided into nonablative and ablative treatments.

Nonablative therapy

The essence of nonablative treatment is not to affect the epidermis and target a specific chromophore in skin, for example, melanin pigments or red vascular lesions.

Common options available include:

1.

Q-switched (QS) lasers
2.

Intense pulsed light (IPL) therapy
3.

Photodynamic therapy.

QS laser permits a short burst of intense energy that leads to a temperature gradient between the target and the neighboring tissue. Local shockwaves emitted cause tissue fragmentation and melanosomal injury and are therefore an effective nonablative treatment.

Popular QS lasers for Asians are:

1.

QS neodymium:yttrium-aluminum-garnet (Nd:YAG)
2.

QS ruby laser
3.

QS alexandrite laser.

Drawbacks of the QS laser are the following:

1.

It is only good for isolated lesions.
2.

Most Asians have generalized uneven facial dyschromia.

Repeated treatment may result in variation of hyperpigmentation/hypopigmentation or mottled appearance.

IPL is designed for the treatment of pigmented spots, vascular lesions, and photorejuvenation of fine wrinkles. It addresses dyschromia effectively but requires more treatment sessions. IPL is a noncoherent broadband (500–1200 nm) light device with selective cutoff filters to block specific shorter wavelengths. Pulse varies from 0.5 to 25 ms, and fluency ranges from 3 to 90 J/cm ². IPL requires epidermal protection with a cooling gel. Ultraviolet (UV) photography may enhance the visibility of epidermal melanocytic hyperpigmentation.

Florescent pulsed light (FPL) emits a very broad spectrum: 300 to 1500 nm with the harmful UV spectrum blocked by filters. FPL transforms a substantial part of noneffective wavelengths into useful red light. The filtered wavelengths are then conducted to the target chromophores in the tissue using a sapphire crystal waveguide. The major parts of tissue structures experience a continuous pulse. The first third of the pulse with higher power heats up the target, and the remaining pulse with lower power maintains the temperature of the target tissue, thus minimizing the risk of side effects. The author’s personal experience favors FPL over IPL for its gentleness toward Asian skin. The term gentleness is used here in a generic sense in that FPL tends to cause less side effects and hyperpigmentation than IPL and is a gentler and safer modality of intense light treatment with a bigger margin of safety.

Photodynamic therapy can exert 2 effects on Asian skin. Its photographic effect resembles that of a sustained IPL treatment. It is also very effective in treating active acne vulgaris. The mechanism of action is based on the skin absorbing aminolevulinic acid (ALA) and converting into protoporphyrin, a natural photosensitizer. ALA occurs naturally in the body and is involved in heme synthesis. When exposed to visible light of high intensity, protoporphyrin generates singlet oxygen, which causes cell membrane damage of target cells.

Ablative therapy

Ablative treatment consists of:

1.

Chemical peel
2.

Dermabrasion
3.

Lasers.

Chemical peel in Asians classically done using trichloroacetic acid (15%–35%). There are many commercial preparations available. It is effective in rejuvenation of mild to moderate rhytidosis and superficial dyschromia. However, the problem of postinflammatory pigmentation in Asian skin requires rapport and understanding between physicians and patients. The once-popular phenol peel for White is unacceptable to Asians. Not only does it cause severe postinflammatory hyperpigmentation but the permanent hypopigmentation that it may cause could be devastating for the patients. Mild gradual daily exfoliation using tretinoin or other acids is more acceptable to Asians. This can be achieved by several commercially available formulae.

Dermabrasion is mechanical abrasion of skin using a rotatory brush or diamond burr. Apart from certain type of cystic acne scars in Asians, it is not a common tool for treatment of pigmentary problems in Asian skin because of its unpredictable results and the risk of permanent scarring or hypopigmentation.

Lasers are common tools for the treatment of pigmentary problems in Asian skin. The most common ablative lasers described in the literature are:

1.

CO ₂laser
2.

Erbium YAG laser
3.

Fractional erbium YAG laser in pixel mode
4.

Fractional CO ₂laser.

CO ₂laser used as an ablative exfoliator is too aggressive for Asians because of its prolonged recovery time and the risk of scarring and permanent hypopigmentation.

Erbium YAG laser is a very effective tool for the treatment of mild to moderate dyschromia with repeated exfoliation of epidermis/dermis. It is also very effective for selected areas of deeper tissue removal. Its minimal thermal effect makes it ideal for this purpose in Asian skin with effective healing and minimal scarring. Variation of focal length (spot size) and energy level (fluency) can be altered simultaneously for the removal of skin lesions such as keratosis, melanocytic nevi, and so forth, and general exfoliation of other facial skin. However, its longer recovery time than fractional lasers limits its use for superficial lesions or isolated tissue removal.

Fractional erbium YAG laser/CO ₂laser in pixel mode is the newest form of ablative laser treatment for pigmentary problems in Asian skin. The mechanism of action is based on its effect on epidermal/dermal photothermolysis and at the same time seeks to address the limitations of both ablative resurfacing and nonablative treatments. An array of microscopic thermal wounds (microscopic treatment zones) are induced into the skin to stimulate a therapeutic response deep in the dermis. There is some promise for treatment of melasma using this therapy.

Dr Zheng, a renowned dermatologist from Chengdu, China, uses the following treatment regimen for Asian dyschromia with fractional erbium YAG laser in pixel mode: