532-nm Diode Laser for the Treatment of Facial Telangiectasia and Pigmented Lesions

Keywords:laser, treatment, medical,  Time:26-11-2015

As previously stated, the target for vascular lesions is oxyhemoglobin. The absorption peaks for oxyhemoglobin are approximately 418, 542, and 577 nm. The theory of selective photothermolysis spurred the development of flashlamp-pumped, pulsed-dye, and copper-vapor medical lasers. These lasers emit light between 577 and 585 nm. These wavelengths are selectively absorbed by oxyhemoglobin, thus destroying the ectatic vessel with minimal damage to the underlying tissue. This type of laser differs from previous lasers by emitting light in pulses rather than a continuous beam.7 In addition to the pulses, the time between each pulse allows thermal cooling of the target chromophore. If the pulse width is equal to or less than the thermal relaxation time (TRT) of the telangiectatic vessel (the time during which 50% of the incident heat has transferred out of the vessel to adjacent tissues), the resultant thermal damage will be confined to the vessel.10 Having a pulse duration that is shorter than the TRT of the treated vessel prevents the energy from dissipating too far beyond the targeted vessel. For vessels as small as 50–75 mm in diameter, the TRT is approximately 1 millisecond.10 Larger vessels, such as those found on the ala, have a much longer TRT. A vessel with a diameter of 300 mm has a TRT of approximately 42 milliseconds, about 10 times that of a vessel one third its size. Vessels with a diameter of 1000 mm (1 mm) have a TRT of about 500 milliseconds.10 The 585-nm flashlamp-pumped, pulsed-dye laser has become the gold standard by which other vascular surgical lasers are judged. The flashlamp-pumped, pulsed-dye laser has the significant drawback of posttreatment purpura, which is difficult to conceal and can persist for up to 14 days.


There is no installation cost, and operating costs are almost nonexistent. The energy-based control system delivers the specific treatment fluence in laser pulses between 10 and 25 milliseconds. The 532-nm wavelength is a green light and is obtained by a process known as frequency doubling (FD). Diodes are commonly used in many devices such as bar code readers and compact disc players. They are typically made of gallium arsenide (GaAs) and can be mixed with other elements to change their characteristics. A high-powered diode laser at 808 nm is used to optically pump a Nd:YAG crystal that produces 1064-nm light (Figure 2). This light is then focused onto a potassium titanyl phosphate (KTP) crystal to double its frequency and split the wavelength in half, producing a 532-nm wavelength. A red diodeaiming beam is added to target the 532-nm beam. The diode-pumped, frequency-doubled Nd:YAG laser is referred to as the DP FD Nd:YAG laser.All 3 lasers penetrate tissues to a similar depth and react with oxyhemoglobin essentially the same way. With similar absorption coefficients, there are in fact significant differences that are largely the effect of pulse durations (Figure 3). Pulsed-dye lasers produce pulse durations of 450 microseconds to 1.5 milliseconds. These pulse durations produce selective treatment of vascular lesions; however, the 585-nm flashlamp-pumped, pulsed-dye laser causes violent vaporization of blood within the vessel. The short pulses of 450 microseconds (0.45 milliseconds) heat the oxyhemoglobin so rapidly that it creates a steam bubble and bursts holes in the vessels. This destruction of the vessel, with resultant extravasation of red blood cells, gives rise to clinical purpura (Figure 4). The Krypton laser produces long pulse durations of 0.1 or 0.2 seconds, which are beyond the TRT of most facial vessels, allowing for thermal conduction into the surrounding tissue. These extended exposures do not cause purpura, but allow conduction loss from the target vessel to the surrounding tissue, increasing nonspecific injury.

In contrast, the 532-nm diode (DP FD Nd:YAG) laser delivers pulse durations from 1 to 100 milliseconds that provide selective photothermolysis without purpura. Typically used between 10 and 25 milliseconds, the 532-nm diode (DP FD Nd:YAG) laser uses moderate pulses targeting the abnormal vascular structures while sparing the normal capillaries, hence producing no purpura. The much longer pulse duration of 1–100 milliseconds seems to be well matched to the TRT of most facial vessels. It is this longer pulse of the 532nm diode (DP FD Nd:YAG) laser that spares gross vessel damage. Those with experience with the 532-nm diode (DP FD Nd:YAG) laser are familiar with the immediate disappearance of the ectatic vessel after laser-light exposure. Active or passive vasoconstriction cannot explain the total resolution or emptying of the vessel lumen. With the longer 532-nm diode (DP FD Nd:YAG) laser pulses, the blood is more gently heated and damages the endothelial cells, but it does not burst the vessel. There are theories that state that the laser energy creates a small steam bubble that expands along the axis of the vessel, clearing the lumen and pushing a column of hot blood along the vessel. As the vessel cools during its TRT, the vapor bubble condenses and collapses the vessel wall. Thermal coagulation of the blood, now ejected well beyond the actual exposure site, creates an intravascular plug, leaving an empty, thermally damaged lumen at and around the site of the laser exposure.  Patients reported a significantly greater degree of swelling, bruising, pain, and redness after the flashlamp-pumped, pulsed-dye laser. Hevia concluded that the 532-nm diode (DP FD Nd:YAG) laser appeared to be the optimal choice for the treatment of facial telangiectasia because of its effectiveness combined with patient comfort. This study was well constructed, but with a small sample size (N 5 15 patients). No permanent pathologic skin changes were noted.

Clinical Applications

Millions of people, especially those with Fitzpatrick skin-types 1 and 2, develop telangiectasias. The nasal ala and medial cheeks are the most commonly involved areas. Telangiectasias are permanently dilated cutaneous blood vessels visible to the naked eye and by definition do not exceed 1 mm in diameter. On the Spider telangiectasias consist of red radiating arms stretching from a central pulsating arteriole. Histologically, they represent dilated or ectatic vessels in the superficial papillary dermal plexus. Thin, wiry, and red telangiectasias extend from arterioles or from the arterial side of a capillary loop. Cordlike, blue vessels arise from venules or from the venous side of a capillary loop.16 Red capillary telangiectasias stretching from the capillary loop may also become blue with time as hydrostatic pressure and venous backflow increase.17 Telangiectasias occur in up to 48% of healthy children and 15% of normal adults. Telangiectasias of the lower extremities occur in 29– 41% of women and 6–15% of men.20 Telangiectasias derive from various factors.16 Some intrinsic factors include congenital causes, primary cutaneous disorders (eg, Rosacea), systemic disease (eg, collagen vascular disease), Cushing’s disease, metastatic carcinoma, pregnancy, venous incompetency, and inherited genetic disorders such as hereditary hemorrhagic telangiectasia. Some extrinsic factors can be drug induced by estrogens or chronic steroid use. Other extrinsic factors include actinic and radiation dermatitis, postsurgical rhinoplasty (wound closure under tension), radiotherapy, and trauma.

It should always be kept in mind that the presence of numerous telangiectasias can indicate dermatologic or systemic internal disease. The Iridex 532-nm diode (DP FD Nd:YAG) laser comes complete with a polarizing magnified headlight (Seymour Light XL-2000 Illumination System) that significantly enhances the contrast of the vascular lesions (Figure 5). By eliminating the glare and reflection, the surgeon has the illusion of seeing beneath the skin. This incorporates a retractable magnifying loop for improved visualization. In addition, the 532-nm diode (DP FD Nd:YAG) laser requires wavelength-specific eye protection for the patient and doctor. The patient wears opaque metal goggles, and the operator and assistants wear safety glasses that are able to absorb the laser wavelength. The laser is accompanied by 5 separate handpieces that deliver spot sizes of 200, 500, 700, 1000, and 1400 mm, respectively (Figure 1). The laser is used on various settings to treat vascular and pigmented lesions. Telangiectasias, cherry angiomas, spider angiomas, and smaller port-wine stains are vascular lesions readily and predictably treated with the 532-nm wavelength. A larger spot handpiece treats the same lesion with less energy density. Ideally, the spot size utilized should match the diameter of the vessels being treated.

The author’s experience has shown more pain perception by the patient with the larger spot sizes. A computerized scanning device is also available for the Diolite laser to treat larger areas or lesions, but the author has no experience with this device.

Although most surgeons do not use any type of anesthesia, this is not necessarily in the best interest of the patient. The author feels that the treatment pain is similar to a BOTOX injection, and most patients can tolerate the smaller spot sizes with no anesthetic; however, some patients react poorly or are uncomfortable during treatment. Single laser pulses are activated by tapping the footswitch intermittently, causing a minor, slightly delayed pain, which the author describes to the patient as a rubber band snap. Holding down the foot switch will cause a continuous but adjustable repeat rate. Slower repetition rates (4–7 Hz) usually result in less discomfort. Using the 15 Hz repeat provides faster treatment, but it is also considerably more uncomfortable for the patient. The use of a thin layer of refrigerated, water-based gel, such as aloe vera, will provide a thermal sink for the skin, will result in greater comfort, and will reduce the risks of epidermal injury.

When treating very sensitive areas such as the nasal alae, upper lip, or periorbital areas, the author frequently utilizes local anesthetic blocks. An infraorbital nerve block is used by injecting 1–2 mL of 2% lidocaine 1:100000 epinephrine at the infraorbital foramina (Figure 6). This block can be performed transcutaneously or intraorally. Transcutaneous injection is performed in the midline of the pupil approximately 5–7 mm below the inferior orbital rim. Intraorally, the needle is placed through the vestibular mucosa between the cuspid and first bicuspid about 20 mm above the tooth crowns.

The energy density is chosen by the lowest density needed to attain the disappearance of the vessels. Most frequently, the author uses the 700-mm handpiece with a setting of 3 W and 24 J/cm2. Most surgeons begin with a repeat rate of 4 Hz and increase this according to the patient’s comfort. The handpiece is moved quickly because the induced flushing will obscure smaller telangiectasias. This is important to communicate with the patient as the ensuing erythemia can lead them to think they are treated to resolution only to find that their vessels reappear several hours or days later. The basic treatment technique is simple. The laser spot is used to trace individual vessels to an end point of disappearance (Figure 7). The laser traces the individual vessels and causes them to collapse, which is the clinical endpoint. Some vessels may require several passes, and the skin should be allowed to cool between passes. A moderate energy density such as 16 J/cm2 is initially used, increasing the energy density until vessel collapse is observed. Excessive thermal energy can cause linear hypopigmentation, hyperpigmentation, and possibly atrophic scarring.26 Arborized telangiectasias are treated by starting at the branching and working toward the center, which is painted with several pulses. Cherry angiomas, or round punctate lesions, are treated with multiple pulses at the center of the lesion (Figure 8). Matted ectatic vessels or port-wine stains are better treated with a larger spot size and lower fluence (Figure 9). This treatment usually requires some form of anesthesia. A computerized scanning device is also available for large areas or lesions. The 532-nm diode (DP FD Nd:YAG) laser will cause immediate erythema and edema that usually only lasts a few hours (Figure 10). Prolonged treatments become difficult as the erythema obstructs smaller vessels. For these reasons, multiple short sessions are often used. Whereas most vessels can be adequately treated with a single session, some vessels are recalcitrant or recurrent and can require additional sessions. Because the epidermal integrity is not violated, no specific postoperative treatment is necessary, and makeup can be worn immediately. If excessive thermal energy is induced, crusting or ulceration can appear and is treated with a triple antibiotic ointment for several days. Cool compresses are used for edema and discomfort; analgesics have not been necessary.

Treatment of Pigmented Lesions The absorption spectrum of melanin includes the ultraviolet, visible, and near-infrared portions of the electromagnetic spectrum. Because of this, virtually every wavelength along the spectrum can theoretically be used to target melanin.

Discussion

Multiple 532-nm lasers are available for the treatment of telangiectasias and pigmented lesions. The Iridex Diolite 532 (DP FD Nd:YAG) laser is an extremely portable solid-state laser that enables transportation between offices or treatment rooms. The small handpieces are very flexible and are well suited for the precision tracing of individual telangiectasias. The 532-nm wavelength has been shown in multiple studies to be effective for the treatment of facial telangiectasia, minor vascular lesions, and some pigmented lesions.6,11–13 The portability, affordability, ease of use, and efficacy of the 532-nm diode laser makes it well suited for office-based cosmetic surgery practice.