laser of hair removal

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Laser of hair removal. by: DR Neda Adibi Dermatologist. WHAT IS HIRSUTISM?. The growth of unwanted and terminal hairs in androgen dependent area in the females called hirsutism The etiology is either idiopathic or due to androgen excess. - PowerPoint PPT Presentation


  • by: DR Neda Adibi Dermatologist

  • The growth of unwanted and terminal hairs in androgen dependent area in the females called hirsutismThe etiology is either idiopathic or due to androgen excess

  • (1) The damage may result from direct photothermal destruction, whereby a light source emitting a wavelength in the absorption spectrum of the desired chromophore melanin (6001100 nm) results in selective heating of the hairshaft, follicular epithelium, and hair matrix..

  • The laser emits a gentle beam of light which is absorbed only by the hair follicle (leaving the skin unharmed). This light energy is transformed to heat which destroys the hair follicle permanently. Thats really all there is to it. This is called Selective Photothermolysis.

  • The laser emits a gentle beam of light which is absorbed only by the hair follicle (leaving the skin unharmed). This light energy is transformed to heat which destroys the hair follicle permanently. Thats really all there is to it. This is called Selective Photothermolysis.

  • Anagen follicles of terminal hair extend deeply into the subcutaneous fat, lying 27 mm below the skin surface.

  • The bulb of a telogen, or club, hair is unpigmented because of the cessation of melanin production during the catagen stage. In fact, the cessationof melanin production is the first sign of catagen. As anagen progresses, the bulb and papilla descend deeply into the dermis so that late anagen hairs may also be somewhat laser resistant to treatment. It would seem

  • , therefore, that it is in early anagen that hair follicles are most sensitive to laser induced injury. Since any injury, even a laser injury, may induce telogen, the timing of a second laser treatment after the first laser induced telogen formation, becomes critical. As the laser resistant terminal follicles now enter an anagen growth phase, after a first treatment, the second treatment may be more effective than the first. Conversely, a second treatment given too early, or too late, would be expected to have little effect.

  • Lin et al postulate that follicles treated in the telogen phase show only agrowth delay for weeks, whereas, when those follicles are treated in the anagen phase they may be susceptible to lethal damage, may have a growth delay, or may simply switch into telogen phase. This could partly explain the growthdynamics of the hair cycle. Repeated treatments could lead to a synchronization of the anagen phase by induction and/or shortening of the telogen phase,which could increase the effiveness of hair removal with

  • Another explanation might be that the follicle is not destroyed immediately, but shows a growth arrest after only one (shortened) anagen cycle. Some have questioned the assumption that effective laser hair removal is determined solely by treating hairs in the anagen cycle. These investigators suggest that melanin within a hair follicle may be more important than the actual time of treatment.

  • Permanence, defined as an absolute lack of hair in a treated area for the lifetime of the patient, may be an unrealistic goal. Dierickx et al. have suggested a more practical approach. They defined permanent hair loss as a significant reduction in the number of terminal hairs, after a given treatment, that is stable for a period longer than the complete growth cycle of hair follicles at any given body sit

  • Permanent hair reduction is dened by the FDA as stable decrease in the number of terminal hairs for a period longer than the complete hair cycle at a given site following a treatment regime, which may include multiple sessions.

  • 1.Laser induces catagen phase 2.One of the uncertainties in laser hair removal is the exact tissue target. it appears that complete destruction of hair follicle without regeneration potential may occur when both the germinative cells in the bulb and the stem cells in the bulge area are destroyed. As follicular stem cells appear to be very resilient to thermal damage, this may be dif cult to achieve

  • It should be noted that there is a general consensus that hair removal results will always be affected by chosen anatomic site. Most investigators note a better response on chest, face, legs, and axilla. Lesser responses appear to occur on the back, upper lip, and scalp. In addition, terminal hairs, and not vellus hairs respond to laser treatment. The ideal patient has realistic expectations, normal endocrine status, with thick dark hair and light skin tones .

  • There are differences in the anagen:telogen ratio depending on the area that is treated. For example the axillae and bikini areas have a higher anagen: telogen ratio than the legs, arms, and chest. Therefore, it has been suggested that these areas would respond better to laser hair removal with more noticeable difference .in hair density

  • It is now widely accepted that almost any laser can induce temporary hair loss.Fluences as low as 5 J/cm 2 can induce this effect. The effect tends to last 13 months.The mechanism of action appears to be an induction of catagen and telogen.Permanent hair reduction, occurring at higher fluences is seen in 80% of individuals and is fluence dependent. Thus, the greater the delivered fluence, all else being equal, the better are the expected results.

  • Dark hair with ample amounts of eumelanin can be effectively treated by multiple devices, provided that appropriate fluence and spot size are used. Under these conditions, the average long term hair loss per treatment is about 20-30% based on studies performed with ruby lasers.Multiple treatment sessions are usually required to achieve the maximal level of hair reduction.In individuals with blonde, red, gray, or white hair, it is unlikely that laser treatment will produce the same degree of longlasting hair removal. However, such patients may be willing to undergo treatments spaced about 2-4 months apart as necessary to maintain temporary hair loss.

  • While treatment can be safely performed with a shorter wavelength device (e.g. ruby laser) in fair skinned patients, it is preferable to use longer wavelength devices in darker skinned patients.

  • The first laser hair removal system employed was the normal-mode ruby laser, but the pulse duration of 0.3 ms was not efficacious longer pulse durations of 0.7-0.8 ms subsequently increased its usefulness. When the pulse duration of the ruby laser was lengthened to 3 ms, permanent hair removal was demonstrated however, there was a significant risk of dyspigmentation. In general, use of the ruby laser for hair removal is limited to patients with skin types I-III, since absorption of694 nm light by epidermal melanin results in a higher risk of compli-cations (e.g. blistering, pigmentary changes) in individuals with darklypigmented skin.

  • BOLOGNIA:Multiple studies have demonstrated effective hair removal with thelong-pulsed alexandrite laser at fluences of 10-40 J/cm2 and pulse durations of 2-20 ms. At fluences of 20-40 Jlcm2, several investigators have reported hair reductions of 70-80% after multiple (at least 3-5) treatments. Use of the long-pulsed alexandrite in patientswith darkly pigmented skin has been reported, but side effects such asblistering and pigmentary alteration can occure in general, this laser isbest suited for hair removal in patients with skin types I-III.

  • Red hair contains pheomelanin, which absorbs poorly at any wave-length, but especially beyond 800 nm. Therefore, shorter wave-lengths, such as those of ruby or alexandrite lasers are needed in these patients.

  • In cases of low contrast between skin tone and hair color, such as darkly pigmented individuals or light hair in fair individuals, a signicant portion of emitted light is absorbed by the epidermal melanin. This occurs because epidermal melanin absorbs energy not only from direct exposure, but also from backscattering. As wavelengths of light increase, a greater ratio of dermal-to-epidermal deposition of energy results in greater safety in such individuals.

  • Diod:Both 800 and 810 nm wavelengths are absorbed by melanin to a slightly lesser degree compared to the alexandrite laser. Absorption is also approximately 30% less than that of the 694 nm wavelength. Decreased absorption by epidermal melanin permits safe treatment in patients with skin types I to IV .

  • Although the rates of melanin absorption by diod laser is lower than the ruby and alexandrate, the rates of hair reduction with the diode laser are similar to those observed with the alexandrite laser, likely due to deeper penetration into the dermis . Treatment with the diode laser can be somewhat more painful, however, at least partly due to greater volumetric heating of tissue. If necessary, pain can be partially alleviated by reducing the frequency of delivered pulses.

  • A diode laser was safely used in several patients undergoing isotretinoin therapy without increase in adverse effect or longterm sequela,the