The right tool: Lesion type determines which laser, light device is best choice

September 1, 2009

Hyperpigmented lesions come in many varieties. Etiologies vary from sun exposure to trauma to inflammation, and even idiopathic origins.

Key Points

With the plethora of etiologies also comes an abundance of possible therapies. Topical therapies targeting different steps in the process of pigmentation production are effective, but they usually do not produce complete resolution.

Patients frequently present to the office asking for laser therapy, thinking this is the curative answer.

Remember, the absorption spectrum of melanin shows a decreasing absorption from 335 nm to near infrared. Melanin shows its highest affinity for light at shorter wavelengths. All lasers or light devices with emitted wavelengths in this range will have some absorption by melanin.

Narrowing parameters

Hyperpigmentation is a broad descriptive term, offering us little information about etiology or pathophysiology of the lesion. Dividing this expansive category into primary versus secondary helps with treatment decision-making and predicting outcome.

Moreover, hyperpigmentation can stem from epidermal, dermal or a combination of these locations. Discrete lesions, such as lentigines, ephelides (primarily epidermal lesions) and nevus of Ito or Ota and decorative tattoos (primarily dermal lesions), show the most favorable response to laser and light-based therapies.

Postinflammatory hyperpigmentation would be the main component of the secondary hyperpigmentations. Melasma can also be considered in this category, as it generally behaves similarly to postinflammatory hyperpigmentation after laser treatments, showing the most unpredictable response to laser and light-based therapies.

Primary pigmented lesions are generally easier to treat than secondary lesions. For localized lesions on the trunk and face, the Q-switched lasers are very successful at removing pigmentation. These include Q-switched ruby (694 nm), Q-switched alexandrite (755 nm) and Q-switched Nd:YAG (both 1,064 nm and 532 nm). For darker skin types, choose the longer-wavelength Q-switched lasers, as their emissions have less absorption by melanin and hence less competition/absorption from normally pigmented skin.

Q-switched lasers

All Q-switched lasers have extremely short pulse widths (nanosecond), resulting in some inflammation. This inflammation, if long-lasting, can result in postinflammatory pigment alteration (PIPA). This risk is higher in patients with darker skin types.

However, in areas of slower healing (such as the lower legs), PIPA can occur even on the lightest skin types. It typically resolves, but it may take months to do so.

In general, Q-switched lasers are safe, reliable and easy to use for solar lentigines. In a comparison study, the frequency-doubled (532 nm) Q-switched Nd:YAG was found to be the most successful laser treatment for solar lentigines of the hands. It also had the least side effects (Todd et al. Arch Derm. 2000).

The spot sizes on these Q-switched lasers are adjustable and can be used to literally trace out the lesion, allowing for precise treatment of localized areas. Long-pulsed 532 nm, 694 nm, 755 nm and 800 nm lasers can also be used to treat pigmented lesions, but the results are less impressive and require more treatments.

However, because of the extended pulse duration, the photoacoustic effects that often lead to purpura and greater risk of PIPA are less prominent using extended-pulse durations. The most impressive results are seen with the long-pulsed 755 nm lasers.

IPL vs. LPDL

For lentigines, intense pulsed light (IPL) devices are easy to use and successful at removing pigmented lesions. They can also cause PIPA, if used at high fluences or short pulse-width settings on darker skin types, though this generally resolves in most cases.

For IPL of pigmented lesions, it is best to do multiple sessions beginning with low fluence/longer pulse-width settings to see how the patient tolerates the treatment.

If the lesion has any textural component suggestive of a flat seborrheic keratosis, then the Q-switched lasers are a more effective laser choice. In many cases, these seborrheic keratoses are best treated with chemical or liquid nitrogen destruction.

The long-pulsed dye laser (LPDL) has also been examined for the treatment of solar lentigines and photoaging. The LPDL (595 nm) is outfitted with a compression handpiece that helps flatten the skin and vessels, allowing for better pigment absorption. It also has no cooling, to avoid protection of the epidermis.

This device has been shown to be as effective for pigmented lesions as IPLs in split-face trials. (Jorgensen et al. Lasers Surg Med. July 2008), (Galeakas et al. Derm Surg. May 2008).

Both Jorgensen and Galeakas also showed that the LPDL was better than IPL for treatment of vascular lesions.

Amount of time to treat with the LPDL was longer than with IPL. These results will all depend on which IPL and IPL settings you use. All IPLs are slightly different in their peak wavelengths, pulse types and pulse widths.

The compression LPDL was also compared to the Q-switched ruby and was found to be more effective and was associated with fewer complications (Kono et al. Lasers Surg Med. 2006).