Green-light pulsed lasers

These lasers produce energy with pulses shorter than the thermal relaxation time of melanosomes. Examples of these lasers are the flashlamp-pumped pulsed dye and frequency-doubled Q-switched Nd:YAG lasers. The flashlamp-pumped pulsed dye laser produces a 510-nm wavelength and 300-nanosecond pulse of energy, whereas the frequency-doubled Q-switched Nd:YAG laser produces a 532-nm wavelength and a 5- to 10-nanosecond pulse of energy. Both lasers produce excellent results when used to treat epidermal pigmented lesions such as solar lentigines and ephelides. Because the green wavelength of these lasers is also well absorbed by oxyhemoglobin, purpura formation may occur following laser irradiation. The purpura resolves 1-2 weeks after treatment, with resolution or lightening of the clinical lesion 4-8 weeks after treatment. Purpura occasionally leads to postinflammatory hyperpigmentation.

Flashlamp-pumped pulsed dye laser treatment results in excellent clearing of epidermal pigmented lesions (eg, lentigines, ephelides, seborrheic keratoses, café au lait macules). In a study of 492 benign epidermal pigmented lesions in 65 patients, 50% of the treated lesions cleared completely after one treatment when treated at a fluence of 2-3.5 J/cm². Another 33% of the treated lesions were lightened considerably. Ninety percent of treated epidermal pigmented lesions can be cleared after 3 treatments.

Treatment results can be affected by anatomic location. Although up to 90% of hand and facial lentigines may be cleared, less favorable results are usually seen following treatment of trunk or leg epidermal pigmented lesions. A typical treatment response includes purpura lasting 5-7 days, followed by subsequent sloughing of the treated lesion at 7-14 days. The underlying new skin is pink for 2-3 days but fades to normal skin color with rare textural changes or scarring.

In another study, 25 patients with solar lentigines showed excellent laser-induced clearing after 1-2 treatments. Fourteen patients with café au lait macules showed complete clearing after 3-6 treatments. Two patients with nevus spilus and 2 patients with Becker nevi showed clearing with up to 6 treatments. As a general rule, this laser produces a variable response in epidermal pigmented lesions such as café au lait macules, Becker nevi, and epidermal melasma.

Epidermal postinflammatory hyperpigmentation also may respond. Dermal pigmented lesions predominantly show little to no response. Because some lesions show a variable clinical response, spot testing the treatment areas of the respective lesion may be prudent prior to engaging in a full treatment. Even when café au lait macules and Becker nevi show resolution after treatment, recurrences have been reported. Lesions may recur because of the impact of these lasers on melanosomes, with little effect on the pigment-producing melanocytes.

Careful sun protection may retard but will not prevent recurrence. Because melasma occurs secondary to a combination of genetic, sun-induced, and hormonal factors, successful laser treatment is the exception rather than the rule with the use of this laser.

The Q-switched Nd:YAG laser is a solid-state, high-fluence, short-pulsed (10-20 nanoseconds) laser that emits at a wavelength of 1064 nm. By placing doubling crystals in the laser beam's path, the wavelength is effectively halved to 532 nm. Epidermal lesions such as lentigines and café au lait macules can be lightened considerably by the frequency-doubled Q-switched Nd:YAG. In one study, 84% of lentigines in 17 patients lightened by at least 50% after several treatments at 2-5 J/cm². Postoperative purpura developed in all patients, and 25% of treated individuals showed transient hyperpigmentation. The degree of response to the laser at this wavelength is proportional to the amount of pigment chromophore present at the treatment site. When a high fluence is delivered through a small spot size, whitening of the skin is noted. This is then followed by pinpoint bleeding leading to a hemorrhagic crust, which falls off in 7-10 days.