Bencini et al. were the first to evaluate hair removal efficacy with a long-pulsed millisecond Nd: YAG laser [28]. Such a system theoretically combines the pigmentation safety of a near-infrared laser with the photothermal benefits of millisecond pulsed technology. They studied 208 subjects who were treated during an 11-month period at multiple different areas. The vast majority (203 subjects) were Fitzpatrick skin phenotypes II-IV, while five were Fitzpatrick skin phenotype V. Hair colors were divided as follows: 124 subjects having dark hair, 2 with white hair, 78 with blond hair, and 4 with red hair.
The authors used a 3 or 4 mm spot size and fluences between 23 and 56 J/cm2. In general, lower fluences were utilized for darker or finer hair and higher fluences for lighter or thicker hair. A single treatment resulted in a 20-40% hair loss of the treated area, lasting over 24 weeks. Higher fluences, however, also caused more discomfort. This led the subjects to often choose comfort over greater efficacy in their treatments.
In a similar study, a millisecond Nd: YAG laser was evaluated using 15-30 msec pulse durations and fluences of 50-60 J/cm2 (S. Kilmer, personal communication). Twenty five subjects with 100 treatment sites were evaluated. Skin phenotypes I-V were evaluated; anatomic sites included the face, arms, legs, axilla, bikini line, and back. Response was assessed three months after a single treatment. The median hair count reduction three months after a single treatment was 32% for treatment parameters of 60 J/cm2 and 30 msec; 24% for the treatment parameters of 50 J/cm2 and 15 msec.
Tanzi and Alster used an Nd:YAG laser in 36 patients with types I-VI skin [29]. They performed three laser treatments at 4-6 week intervals using fluences of 30-60 J/cm2. The pulse durations used were varied based on Fitzpatrick skin type and were as follows: 10 msec for skin types I-II; 20 msec for skin types III-IV; 30 msec for skin types V-VI. Hair counts were taken at one, three, and six months after treatment. Peak hair removal was
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Figure 5.2 Unwanted hair before laser hair removal (left); four months after one Nd:YAG laser hair removal session (right). |
seen one month after the final treatment with mean hair reduction of 58-62% seen on facial sites, and mean hair reduction of 66-69% seen on nonfacial sites. At six months, a 41-46% mean reduction was seen on facial sites; a 48-53% reduction was noted on nonfacial sites. This study confirmed that Nd:YAG lasers are safe even in the darkest of skin phenotypes.
Levy et al. treated 29 patients with a 4 msec 1064 nm Nd: YAG laser at fluences of 56-70 J/cm2 and then evaluated for hair loss at three, six, and nine months after treatment [30]. They reported an average reduction at nine months of 46%. Finally, Raff et al. studied two different long-pulsed Nd:YAG laser systems on 42 patients with various pulse lengths, fluences, and spot sizes[31]. The average hair reduction, 12 months after the last treatment, was 48% with the Lyra XP® and between 30-35% with the Smartepil II®. They concluded that larger spot size and longer pulse duration improve efficacy.