Laser resurfacing is the most reliable method for smoothing facial wrinkles. During resurfacing, skin tissue is ablated layer by layer. A healing period always follows resurfacing, during which superficial skin layers grow back to replace the layers that were removed. The major landmark of healing is re-epithelialization.
In 1998, an alternative laser treatment designed to improve facial wrinkles without ablating the epidermis was introduced. This method, called CoolTouch, uses a special Nd:YAG laser with a wavelength of 1320 nm. This long wavelength penetrates deep into the dermis and is relatively invisible to the epidermis. The energy passes through the epidermis and its effect is confined to the dermis, where it is absorbed by water, thus generating heat. The small amount of heat generated in the dermis appears to produce a minor injury, which in turn may stimulate the fibroblast cells to produce new collagen. Clinical studies in which skin biopsies were examined have revealed the synthesis of new collagen as a result of CoolTouch treatment and visible improvement in facial wrinkles.
The main advantage of CoolTouch treatment is the avoidance of an obvious healing process and thus no down time for treated patients. Disadvantages include the need for multiple treatments, variable results experienced by different patients, and rather modest improvement in wrinkles. The degree of improvement is generally significantly less than that achieved by laser resurfacing.
A similar non-ablative laser treatment is performed with the Q-switched Nd:YAG laser operating at 1064 nm. This wavelength also has a negligible effect on the epidermis and affects primarily the dermis. When used at higher fluences (above those used to treat tattoos), these treatments may result in purpura but will not significantly affect the epidermis. Similar to results from CoolTouch treatments, modest improvement in facial wrinkles usually occurs after a series of treatments with the Q-switched Nd:YAG laser.
Two additional non-ablative resurfacing modalities are the pulsed dye laser and an intense pulsed light (IPL) source. The same pulsed dye laser as that used for treating vascular lesions (see chapter 4), as well as a newer version that has a longer pulse duration, have been used for this purpose. Although the short wavelength of the pulsed dye laser does not penetrate very deeply into the dermis, physicians have noticed serendipitous improvement of both fine wrinkles and skin texture in patients who have received multiple treatments for facial telangiectases. The wavelength of light produced by the pulsed dye laser is well absorbed by both hemoglobin and melanin. Improvement in skin texture is thought to be the result of nonspecific heating of water in the superficial dermis, secondary to heating of the primary pigmented tissue. A slight injury is produced, stimulating fibroblasts in the dermis to produce more collagen.
The IPL source is not a laser; it is a flashlamp that produces noncoherent light over a broad spectrum of visible and infrared wavelengths. Filters are used to eliminate part of the output spectrum. Response of the skin to this intense light is similar in many respects to its response to laser energy of similar wavelength, power, and pulse duration. The most common IPL source is the Photoderm, which is generally used to treat vascular and pigmented lesions using wavelengths in the 500—800 nm range. When used on the face, subtle improvement in skin texture and fine wrinkles has been noted, similar to that observed following non-ablative laser treatment. Filters can also be used that allow delivery of infrared wavelengths up to 1200 nm. This infrared energy has less effect on pigmented targets and will produce greater heating of water, resulting in increased collagen synthesis and improved skin texture.
Recently, additional lasers have been developed for non-ablative skin texture improvement. These include a diode laser operating at 1450 nm ("Smoothbeam") and an erbium:glass laser operating at 1540 nm. Both of these wavelengths are absorbed mainly by water and can improve skin texture, but have little effect on excess melanin or hemoglobin pigments.
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