Vascular-specific laser systems target intravascular oxy- hemoglobin in order to effect destruction of varrous congenital and acquired vascular lesions Lasers and light sources that have been used to treat vascular lesions include the argon (488/514 nm), argon-pumped tunable dye IAPTD, 577 /585nm), potassium-titanyl-phosphate (KTP, 532 nm), krypton (568 nm), copper vapor/bromide [578 nm), pulsed dye laser (PDL, 585-595 nm), and neodymium; yttrium-aluminum-garnet [Nd:YAG, 532/1064 nm) lasers and the intense pulsed hght (IPL) s o u r c e ( 5 1 5 - 1 2 0 0 n m J .
The argon laser emits a continuous blue-green beam with wavelength peaks at 488 and 514 nm Although it
Complications in Laser and Light Surgery
Fig-7.12 Aggressive fractional resurfacing techniques can result in erosions due to the dense placement of microthermal treatment zones (A) Erosions can be managed with an open wound technique involving application of cool compresses and healing ointment several times daily until re-epithelialization is complete (B)
has been used in the past for a variety of vascular lesions, several histologic studies have shown that the tissue effect of the argon laser is due to nonspecific thermal injury resulting from exposure intervals exceeding the thermal relaxation time of the vessels. Consequently, the risk of scarring and dyspigmentation is increased and is the reason that the argon laser is no longer in common use
Quasi-continuous systems such as the APTD, krypton, copper vapor/bromide, and KTP lasers are CW lasers that can be mechanicaliy shuttered to deliver puises as short as 20 ns to treat facial telangiectasias However, their 'quasi-CW'
nature is often associated with higher risk of hypertrophic scarring and textural changes than ts seen rvith pulsed laser systems.
KTP lasers emit light at 532 nm and are used to treat a variety of vascular and pigmented lesions. As with the argon-pumped tunable dye laser, the KTP laser handpiece
Lasers and Lights Volume ll
is used in a quasi-continuous mode at varying repetition rates to trace individual blood vessels or a scanner can be employed to facilitate faster treatment of large skin areas.
Side effects are generally limited to linear crusting of skin overlying treated blood vessels, transient pigmentary changes, and mild fibrosis, which usually improve without any specific intervention (Fig. Z.r:). Postoperative hypoprg- mentation is a particular risk due to the 532-nm pigment- specific wavelength and so should be used cautiously in patients with recent sun exposure or in those with natu- rally darker skin tones. RoshanKetab 02l-66950639
The PDL was developed specifically for the treatment of cutaneous vascular lesions employing the principles of selective photothermoiysis. With its ability to target blood vessels with minimal risk of collateral thermal injury and subsequent scar formation, it has proved to be the safest vascular-specific laser available to date and is widely used to treat congenital and acquired vascular lesions in chil- dren and adults, including port-wine stains and heman- giomas. The most common side effect of traditional [0.45-1.5 ms) PDL treatment includes transient purpura and dyspigmentation (FiS. lr+). Vesiculation, crusting, textural change, and scarring are rarely seen. Isolated cases of hypertrophic and keloid scar development after PDL irradiation have been reported in patients concomitantly taking isotretinoin or with application of excessive energy densities and/or pulse overlapping. More recent pulsed dye lasers with longer wavelengths (590, 595, 600 nm) and pulse durations (up to 40 ms) retain their vascular- specificity, but produce little, if any, postoperative purpura.
The IPL source emits noncoherent lisht within the 515-1200nm portion of the electromagnetic spectrum and has been used successfully for a variety of vascular lesions Filters are used to eliminate shorter wavelengths, thereby concentrating light energy so that improved
dermal penetration is achieved. Lesions with smaller caliber vessels are best treated with low cutoff filters (515 or 550 nm), while iesions with larger vessels respond best to longer wavelengths (570 or 590nm). Because shorter wavelength light also interacts more readily with epidermal melanin, the lower cutoff filters should only be used for patients with fair skin phototypes. With longer pulse durations, the IPL source can slowly heat more deeply located vessels/ thus improving treatment efficacy and decreasing the risk of postoperative purpura and hyperpigmentation.
Although sclerotherapy remains the cornerstone of leg- vein treatment by most practitioners, it can be associated with side effects including ulceration, allergic reactions, and telangiectatic matting. As such, interest in the laser treatment of 1eg veins remains high Early attempts to treat leg veins with the argon, APTD, or CO2 lasers have been largely unsuccessful. Despite success in the treat- ment of facial telangiectasia, the KTP and PDL are less effective in the treatment of leg veins and are hindered by significant postoperative crusting and prolonged purpura, respectively.
Most recently, based upon a small but significant absorption peak of hemoglobin in the near-infrared portion of the electromagnetic spectrum, long-wavelength pulsed lasers have been used to treat moderately deep, larger caiiber spider and reticular veins. Since high fluences are often necessary to adequately damage the vessel, con- comitant cooling systems are used to limit unwanted col- lateral thermal injury The long-pulsed alexandrite laser has been shown to improve large caliber reticular verns;
however, patients are subject to transient pigmentary alteration due to the pigment-specificity of the 755 nm wavelength. Several clinical trials have demonstrated encouraging results with long-pulsed Nd : YAG (1064 nmJ laser treatment of lower-extremity small to medium-sized
Fig. 7.13 Transient hyperpigmentation is often observed along the course of leg veins treated with KTP or PDL lasers
Fig. 7.14 Shod-pulsed (0 45-1 5 ms) dye laser irradiation often results in purpura that persists for several days. The use of longer- pulse systems (up to 40 ms) minimizes the risk of this side ettect
veins. In addition, Nd:YAG lasers with extended pulse durations have been deveioped to treat leg veins up to 3 mm in diameter Side effects are usually minimal and include purpura/ vesiculation, superficial thrombosis, transient hyperpigmentation, and telangiectatic matting
PIGM ENT-SPECI FIC LAsER5
Melanin-specific, high-energy, Q-switched (QS) laser systems can successfully lighten or eradicate a variety of benign epidermal and dermal pigmented iesrons and tattoos with minimal risk of untoward effects. Eoidermal lesions (solar lentigines, ephelides, caf6-au-lait macules, and seborrheic keratoses), dermal and mixed epidermal/
dermal lesions (melanocytic nevi, blue nevi, nevi of Ota/lto, infraorbital hyperpigmentation, drug-induced hyperpigmentation, Becker's nevi, and nevus spilus), and amateur, professional, and traumatic tattoos have all been shown to be amenable to laser treatment. Utilizing Ander- son and Parrish's principles of selective photothermolysis, Q-switched laser systems replaced earlier CW lasers, due to their ability to induce thermal necrosis that remains largely confined to the melanosomes with limited coagula- tive necrosis of surrounding structures, thus decreasing the risk of untoward side effects
The continuous and quasi-CW laser systems that have been used for pigment and tattoo destruction include t h e 4 8 8 / 5 1 4 n m a r g o n , 5 l l n m c o p p e r v a p o r , 5 2 0 n m krypton, 532 nm KTP, and 10,600 nm CO2 lasers. These lasers typically emit light with pulse durations longer than the thermal relaxation time of a melanosome (l ms) and therefore may result in scarring or textural irregularities due to excessive thermal damage of surrounding tissue during laser irradiation Use of CW lasers is therefore generally reserved for removal of epidermal lesions srnce treatment of deeper, dermal lesions is often associated with significant tissue scarring. Treatment with a CW laser removes pigment by epidermal ablation and destruction of the epidermal-dermal junction. Potential postoperative sequelae include persistent erythema, pigmentary altera- tion, and skin texture irregularities.
The ruby laser with a wavelength of 694 nm is used in the treatment of epidermal and dermal pigment. This laser operates in a Q-switched mode, which produces high-energy light in nanosecond pulses An ultrashort tissue dwell time is ideal for treating melanocytic lesions and dermal pigment and minimizes the risk of unwanted collateral thermal damage However, during ruby laser treatment, side effects include tissue splatter, punctate bleeding, edema, pruritus/ vesiculation, and purpura.
Like all of the Q-switched pigment-specific lasers, the ruby produces an immediate ash-white epidermal tissue response on impact. Because normal epidermal melanin may also absorb ruby light, transient hypopigmentation may be seen in 25-500/o of patients (Fig. Z.tf). Postinflam- matory hyperpigmentation, hair whitening, and hair loss have also been observed in ruby laser-treated areas Skin crusting commonly develops locally after treatment and
Complications in Laser and Light Surgery
Fig. 7.15 Hypopigmentation may occur more readily in darker-skinned patients who receive pigmenfspecific laser treatment lt tends to resolve soontaneouslv over time
Fig. 7.16 Q-switched (QS) laser irradiation of iron or titanium oxide tattoo inks, commonly found in cosmetic tattoos, can lead to tattoo ink darkening. Surgical excision or CO2 laser ablation is often necessary to eliminate the darkened pigment
epidermal atrophy has been reported in as many as 500/o of patients following ruby irradiation; however, perma- nent textural changes or scarring occur in fewer than 50/o of patients.
Immediate and irreversible pigment darkening of cos- metic tattoos (particularly white, pink, and flesh-colored inks) has been reported after ruby laser irradiation, pre- sumably due to chemical reduction of the iron-containing tattoo pigment from ferric oxide to the ferrous oxide form (FiS. l.t6) rv\rhile continued ruby laser treatment may eventually fade the darkened pigment, results are not predictable and additional procedures such as surgical excision or CO2 laser ablation may be necessary for its effective elimination.
L a s e r s a n d L i g h t s V o L u m e l l
Fig, 7.17 Granulomatous allergic reactions and hypertrophic scarring can occur upon QS pigment-specific laser irradiation of tattoos due to liberation of antigenic intracellular ink particles Treatment with intralesional corticosteroids mav be reouired
Type IV cutaneous allergic reactions to laser tattoo removal have also been reported. It is hypothesized that laser treatment liberates intracellular pigment into the extracellular space where it becomes antigenic Both gen- eralized and localized urticarial, pruritic, and eczematous reactions may develop and can be treated with oral or mid-potency topical corticosteroids and oral antihista- mines. Rarely, a granulomatous allergic reaction can occur with subsequent hypertrophic scar formation {FiS. 1.til.
Intralesional steroid injections or occlusion/pressure therapy can be used to reduce the bulky nature of such lesions without further worsening of the inciting allergic reactron.
Like the ruby laser, the alexandrite laser also operates by a Q-switched mechanism and emits red light [755 nm) to effectively treat a variety of pigmented lesions and tattoos. Hypo- and hyperpigmentation have been reported following treatment with the alexandrite iaser. Upwards of 500/o of patients being treated for tattoos may expen- ence postoperative hypopigmentation for 3-6 months Skin lightening tends to occur more commonly in darker skin types and is also related to the total number of laser treatments, with an average of seven treatments necessary to induce significant hypopigmentation (Fig. 7.r8).
Punctate bleeding and tissue splatter may occur with the alexandrite laser especially at high fluences but is generally less common than that observed upon QS Nd:YAG laser irradiation. Older faded tattoos tend to show a milder tissue response in terms of bleeding and epidermal erosions. However, when tattoos (especially those of the distal lower extremitv) are treated with the alexandrite or any of the other QS i"r". systems, hemor- rhagic bullae may form. Rarely, scarring and tissue fibrosis can occur with the alexandrite laser as a result of poor wound management. Immediate irreversible pigment
Fig. 7.18 Hypopigmentation after QS pigment-specific laser treatment of tattoos is more often observed in patients with darker skin tones, after multiole lreatmenl sessions. and/or with the use of hioh treatment fluences
darkening of cosmetic, white, flesh-tone, and pink tattoos has been observed after laser treatment with any of the QS systems, including the alexandrite laser.
The QS Nd:YAG laser emits a wavelength of 1064 nm with a pulse duration as short as l0 ns. It has been used to effectively treat primarily dermal pigment such as blue and black tattoos, melanocytic nevi, and nevi of Ota and Ito. An immediate ash-white tissue response occurs at laser treatment sites with a subsequent wheal-and-flare reaction. Other significant side effects of QS Nd:YAG laser treatment include tissue splatter and bleeding, textural changes, hypo- and hyperpigmentation. Textural changes may occur in up to 8% of patients but are gener- ally transient and are only evident when patients are examined earlier than 4-weeks post treatment. Hypopig- mentation may also develop after several treatments.
Generalized cutaneous allergic reactions to tattoo laser removal have been reported with this laser as well as with the ruby and alexandrite lasers. As described with the QS systems above, immediate and irreversible ink darkening of white, flesh-tone, and pink cosmetic tattoos can also occur with QS Nd:YAG irradiation.
The frequency-doubled QS Nd:YAG laser is utilized for the treatment of epidermal pigment as well as red, orange, and yellow tattoos. By passing 1064-nm Nd:YAG light through a potassium diphosphate crystal, the fre- quency is doubled, producing a 532 nm wavelength. The resultant green light targets epidermal pigment due to its marked absorption by melanin. Complications experi- enced with this laser include transient erythema, which may persist for up to 6 weeks and appears to be fluence- dependent, purpura for up to I week, pigmentary altera- tion, textural changes, and blistering. Postinflammatory hyperpigmentation occurs in upwards of 80/o of patients and occurs more often in patients with darker skin tones
Pain and postoperative bleeding have been reported to be greater with the frequency-doubled Nd:YAG than with the ruby laser and is more common with the use of higher fluences.
PHOTOEPII*ATION
Systems currently approved by the FDA for the reduction of hair include the long-pulsed [LP) ruby [694 nm), LP alexandrite (755 nm), LP diode [800 nmJ, QS and LP Nd:YAG (1064nm) lasers, and IPL (515-1200nm) sources. These systems are used most often for hair removal because they can target melanin in the hair shaft and follicle and penetrate to the appropriate dermal depth to effect selective follicular destruction.
Although the goal of laser-assisted hair removal is per- manent follicular damage, there also is a risk of epidermal injury during the hair removal process. Any melanin- containing structure, such as a melanocyte, keratinocyte, or nevus/ also may sustain thermal injury when irradiated by red and infrared light. Although hair shafts are often darker in color than the surrounding skin, partial absorp- tion of applied laser energy may occur by epidermal chromophores. Methods to protect the epidermis during laser-assisted hair removal have included contact cooling tips, cryogen sprays, and topical application of cooling gel.
Epidermal cooling serves to reduce the amount of super- ficial thermal injury sustained upon laser impact
Despite all efforts to protect the epidermis from injury, photoepilation may result in clinically significant adverse reactions. Complications after photoepilation are influ- enced by skin type, body location, seasonal variations, and patient history of recent sun exposure. The extremities tend to suffer the most side effects and sun-orotected areas, such as the axillary and inguinal regions, iuffer the least. Side effects of laser-assisted hair removal using LP lasers are usually minor and transient. The most common adverse reactions include pain during treatment, transient erythema, and perifollicular edema; however, vesicle formation, pigmentary alteration, and scarring have also been documented (Figs 7.ry and 7.zo) Most of the latter complications have occurred in individuals who are either tanned or have darker skin phototypes (SPT IV-VD after the use of a LP ruby, LP alexandrite, LP diode, or IPL source. Because the 1064-nm wavelength is less effi- ciently absorbed by endogenous melanin, significantly fewer incidences of blistering, crusting and dyspigmenta- tion occur after treatment of oatients with darker or tanned skin.
Paradoxical hair growh is a rare side effect of photo- epilation occurring in selected patient populations and body areas. Hair induction occurs predominantly on the face and neck of women of Mediterranean ancestry with darker skin phototypes. The border of the treated area and the immediately adjacent untreated skin are most commonly affected. The phenomenon is observed more often when low (sub-threshold) fluences are delivered to
Complications in Laser and Light Surgery
Fig. 7.19 Patients with tanned skin or with intrinsically darker skin tones are prone to hypopigmentation after long-pulsed (LP) pigment- specific hair removal treatment. The use of a LP Nd:YAG laser reduces the risk of this side effect
Fig. 7.2O Transient hyperpigmentation after laser-assisted hair removal is also more common in patients with darker skin. The use of high fluences and/or inadvertent sun exposure increases the likelihood of ils occurrence
a susceptible patient, triggering hair induction rather than follicular destruction. Although laser-induced paradoxical hair growth responds well to subsequent LP laser treat- ments at moderate-to-high fluences, all female patients undergoing laser-assisted hair removal shouid be clearly informed of the possibility of hair induction.
SUMMARY
Modern lasers and hght-based sources that were devel- oped based on the theory of selective photothermolysis are capable of destroying specific tissue targets while
L a s e r s a n d L i g h t s V o L u m e l l
minimizing the risk of scarring and pigmentary changes.
This is accomplished through the use of a wavelength and pulse duration that is best absorbed by a specific chromo- phore such as melanin or hemoglobin However, not all lasers and light-sources adhere to this principle. CW lasers are least selective and tend to produce unwanted tissue damage and scarring through heat conduction to normal skin. Quasi-CW lasers limit excessive thermal destruction by delivery of a series of brief iaser pulses, but still pose a higher risk of nonspecific tissue damage and thermal injury. The pulsed and QS systems adhere most closely to the principles of selective photothermolysis and result in the most selective destruction with the lowest risk of scarring and excess thermal diffusion Certainly, any laser system potentially can result in scarring and tissue damage when used incorrectly; therefore, adequate operator edu- cation and ski1l are essential. Side effects and complica- tions that occur as a conseouence of laser treatment can be significantly reduced if diagnosed and treated in an expeditious manner.
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