Laser and Light-Based Devices

5.2.1 Alexandrite Laser (Fig. 5.1)

A multitude of lasers and light sources have been shown to be effective for laser hair removal. The first effective light-based systems were 694 nm ruby lasers. Although highly effective for the removal of pigmented hairs on light-skinned individuals, such systems are now rarely used. Today most light-based hair removal is undertaken with 755 nm alexan­drite, 800 or 810 nm diode, and 1064 nm Nd:YAG lasers as well as a variety of nonlaser intense pulsed light devices.

Finkel et al. were among the first group to evaluate the efficacy of the alexandrite laser in removing unwanted hair [9]. They treated 126 patients with an alexandrite laser over a 15-month period. All subjects were treated with a 2 msec pulse duration with fluences between 20-40 J/cm2 (average of 25 J/cm2) using a 7 mm spot size. Cooling of the epider­mis was accomplished with a topical cooling gel. The total number of treatments varied between three and five sessions and treatments were spaced between 1 and 2.5 months. The average hair count taken before a second treatment was 65% of the hair, as compared to the numbers present at baseline. However, the numbers varied in different anatomic locations. As would be expected, there was progressive improvement with each laser hair removal session. The average amount of hair present three months after the final treatment was

markedly less than that seen after the first session. An average of only 12% of hair persisted at the final analysis (88% reduction). The best responding area was the sideburns (95% hair reduction) and the poorest responding area was the abdomen (75% hair reduction).

Narukar et al. evaluated both a 20 and a 5 msec pulse duration alexandrite laser in skin phenotypes IV-V [10]. All individuals were treated with fluences less than 20 J/cm2. In this study, better results were obtained with the 20 msec pulse duration. Thus, longer pulse duration laser hair removal systems may be more beneficial, and clearly safer, in darker – complexioned individuals.

Nanni et al. also evaluated the hair removal efficacy of different alexandrite laser pulse durations [11]. In their 36 subjects study, they examined hair removal efficacy of a 5, 10, or 20 msec duration pulsed alexandrite laser. The mean fluence used was 18 J/cm2. An average of 66% hair reduction was recorded at the one-month follow-up, 27% average hair reduc­tion was observed at the three-month follow-up, and only a 4% hair decrease remained at the six-month follow-up visit. No significant differences were seen in hair regrowth rates between the different pulse durations. The authors noted that after the one treatment uti­lized in this study, there was on an average, no significant reduction in hair growth by the six-month follow-up. The authors concurred that multiple sessions of treatment are required for optimal results.

Jackson et al. reported similar findings in eight hair removal patients treated with Fitzpatrick skin phenotypes III-IV [12]. They used a 5 and 20 msec alexandrite laser and fluences between 14-20 J/cm2. Both pulse durations led to equal hair removal efficacy. The same authors then evaluated the effect of a 20 msec versus a 40 msec alexandrite laser in a similar patient population. Fifteen subjects were treated with fluences varying between 12-17 J/cm2 . Although clinical response was similar, greater posttreatment pigmentary changes were observed in the 20 msec group compared to the 40 msec group. In addition, the authors noted greater pain when the longer pulse duration system was used.

Rogers et al. evaluated alexandrite laser hair removal in 15 subjects [13]. All were Fitz­patrick skin phenotypes I-III with blond or brown hair. They utilized a fluence of 22 J/cm2 delivered in 20 msec pulse durations. The authors found that 80% of treated individuals had post-laser erythema, which lasted on average for 2-3 days; 47% showed perifollicular ery­thema which lasted on average for 90 hours. At two months, 55% of the hair was absent. However, at three months only 19% of the hair was absent. These findings might have been improved if only darker hair had been treated.

Touma and Rohrer evaluated a 3 msec alexandrite laser, used in conjunction with -30°C cryogen spray cooling [14]. They evaluated 21 subjects, 12-15 months after one treatment with average fluences of 33 J/cm2. The presumed permanent hair reduction was noted to be 30% at this period. Furthermore, the authors noted a 29% reduction in the width of the remaining hair.

Avram et al. also evaluated the same 3 msec alexandrite laser, used in conjunction with a 30°C cryogen spray cooling [15]. Using a variety of fluences, he noted a 40-60% hair reduction after three treatments performed at 4-8 week intervals. It was interesting to note that 15% of treated individuals showed 80% hair reduction after three treatments and 15% of treated individuals showed less than 30% hair reduction after three treatments. This sug­gests that results can vary from individual to individual and from one anatomic region to the next. The findings are also consistent with anecdotal reports suggesting that there are rare individuals who, for unknown reasons, may not respond to laser hair removal.

Goldberg et al. compared the effect of pulse duration and multiple treatments on alexan­drite laser hair removal efficacy in Fitzpatrick skin type I—III patients [16]. Fourteen sub­jects (3 men and 11 women) between the ages of 19 and 51 years were studied. All subjects had black or brown terminal hair. A pulse duration of 2 msec, and a repetition rate of 5 pulses per second was compared with an alexandrite laser with a pulse duration of10 msec and a repetition rate of 3 pulses per second. An energy fluence of 25 J/cm2 and a spot size of 7 mm were constant in both groups. Consecutive treatment and evaluations occurred at two to three month intervals for a total of three treatment visits. Six months after the last treatment, the average percentage of hair reduction was 33.1% for the 2 msec pulse dura­tion and 33.9% for the l0 msec pulse duration alexandrite laser. These were statistically equivalent. It is worth noting that there was a slightly greater, albeit statistically insignifi­cant, loss of thicker hair (such as those seen on the back of men) with the 10 msec alexan­drite laser.

In 2001, Eremia at al. reported their results of a cryogen-cooled 3 msec alexandrite laser in 89 patients who received a minimum of three treatment sessions 4-6 weeks apart [17]. Fluences of 30-50 J/cm2 were used. They noted a mean hair reduction of 74% with best results in patients with Fitzpatrick skin types I-IV [16]. Similarly, Lloyd using a 20 msec alexandrite laser achieved a 78% clearance one year after laser hair treatment [18].