ARTICLE | LASERS AND LIGHTS | should treat patients with recent tans, although with
some of the newer machines and cooling mechanisms, this has improved.
Pulse duration, fluence and cooling The pulse durations of these devices have also varied greatly over the past 15 years. The first commercial laser hair removal system was a Q-switched 1064 nm Nd: YAG laser and used a carbon suspension which, when applied to the skin, penetrated the hair follicles. Once the carbon suspension had time to penetrate into the skin and into the hair follicles, the laser would use nanosecond
pulse
adverse events. Finally, larger spot sizes have evolved to ensure that the laser energy penetrates deep enough to effectively reach the specific target and achieve appropriate laser or IPL hair removal (Figure 3). Most of the lasers and light sources on the market in
Most of the
duration to create a photoacoustic reaction in the skin and damage the hair follicle. This nanosecond pulse duration proved only a temporary answer to laser hair removal and with this modality, most hair was removed on a temporary basis, with the majority growing back within a 3-month time period. The ruby laser systems at first used microsecond pulse durations, which then became millisecond pulse duration modes ® now the standard for lasers and light sources used to remove unwanted hair. Through the use of milliseconds, a photothermal effect on the target is achieved, and has shown to be effective in the long-term removal of unwanted hair. The fluence, or energy, delivered to the target is also a
lasers and light sources on the market in the US have FDA clearance for permanent hair reduction, which in itself is not equal to permanent hair removal.
very important feature to ensure that hair is removed, and that adverse events are kept to a minimum when performing this procedure. Since the advent of laser hair removal devices, sufficient energy has been delivered to successfully remove hair. However, with the need to achieve safer hair removal for all, and to all skin types, many advances have been developed which are commonly used in todayÕs systems (e.g. squaring of the pulse for IPL; using lower doses of energy, but maintaining that energy for the duration of the pulse as compared with starting with a high energy, which tails off over the pulse duration ® something commonly seen with early generation IPL). A number of laser systems have lowered the energy given with each pulse, but now use multiple pulses given in a motion technique. Still others are using vacuum apparatus to bring the target closer to the light source, allowing lower energies to be used. This ingenuity allows for safer laser hair removal, even on darker-skinned individuals. The second important factor in achieving successful laser hair removal on all patients is to have sufficient epidermal cooling. Manufacturers have responded to this need and have provided a variety of cooling mechanisms. These include the dynamic cooling devices or cryogen sprays, sapphire-based cool tips, coupling gels, and cold air external cooling. All of these varied cooling mechanisms protect the epidermis and allow the laser or pulsed light to successfully reach the target, while minimising epidermal injury and potential
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the US have FDA clearance for permanent hair reduction, which in itself is not equal to permanent hair removal. Unfortunately, these terms are intermixed regularly, and most patients, as well as many clinicians, assume that reduction equates to permanence. Lasers and pulsed light produce long-term hair removal; some achieve permanence with the procedure; and others achieve a reduction of hair with each successive treatment.
Lasers for hair removal Ruby lasers The first report of the successful use of lasers for the treatment of unwanted hair came from Grossman et al in 19967
. The
laser used was a normal mode ruby laser at 694 nm. Thirteen patients were enrolled into the clinical trial, all of whom had dark hair and light skin. The patients had one treatment performed at fluences of 20–60 J/cm2
and were evaluated at 1 and 3 months post-treatment. At these follow-up
visits it was noted that there was a hair growth delay; at 6-month follow-up, five of the 13 patients had complete hair regrowth and four had less than 50% regrowth. Skin biopsies showed selective thermal damage to pigmented hair follicles, vaporisation of hair shafts, patches of follicular epithelial necrosis, and some perifollicular injury. Transient pigmentary changes were also noted in all patients, but none had any scarring. Dierickx et al8
also followed some of the patients for Spot size
Figure 3 Factors of depth penetration, spot sizes
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