Older lasers used for skin surgeries were the continuous wave lasers like the carbon dioxide and argon lasers. These were used extensively to treat birthmarks like hemangiomas. Though the birthmarks were lightened, the side effect of scar formation was unacceptably high with these lasers. The new lasers which have been introduced during the last two decades are comparatively safe and much more effective compared to the older versions.
The lasers differ according to the medium used in each laser. The characteristics of wavelength, pulse durations and the absorption by different chromophores within the skin determine the uses and clinical applications of different types of lasers in dermatology.
Types of Medical Lasers
According to the medium present in the laser to produce the excited photons, following are the main types of medical lasers available:
- Gas Lasers: Carbon dioxide, Argon, Copper vapor etc. These are the first lasers which emit a constant beam of light for longer durations of exposure.
- Solid State Lasers: Ruby, Nd:YAG, Er:YAG, KTP, Alexandrite etc. These emit interrupted emissions of constant laser energy.
- Liquid Lasers: Dye lasers. Pulsed dye lasers emit high energy laser lights with very short pulse durations and longer intervals between each pulse.
- Diode Lasers: Diode lasers have several wavelengths and are suitable for soft tissue procedures.
Uses of Laser in Dermatology
- CO2 Lasers: The laser light from these lasers are absorbed by water in the skin, hence, used for skin resurfacing, removal of benign skin tumors like warts, xanthelasma, mucous cysts, cherry angiomas, leukoplakia and for surgical cutting.
- Nd:YAG Lasers: The active medium is Neodymium in yttrium-aluminum-garnet and the wavelength is 1064 nm. NdYAG lasers have slight absorption in melanin and hemoglobin and are used for laser hair removal, laser vein treatments, laser photo rejuvenation, laser acne treatments and in laser skin surgeries.
- Q Switched NdYAG Lasers have strong absorption in dark tattoo inks, hence used in laser tattoo removal.
- Er: YAG Lasers have a wavelength of 2940nm and the active medium is Erbium in yttrium-aluminum-garnet. It is absorbed by water in the skin and is used for skin resurfacing, laser photo-rejuvenation and for removal of skin growths.
- Ruby lasers have a wavelength of 694 nm and contain Chromium ions in aluminum oxide as the medium. Ruby laser light has very strong absorption in melanin and black and dark blue ink pigments. These are especially useful in tattoo removal. Laser hair removal and removal of pigmented (dark) skin lesions.
- KTP or Potassium Titanyl Phosphate Laser with 532 nm wavelength is a frequency doubled NdYAG laser with absorption by hemoglobin and melanin and used to remove vascular and pigmented skin lesions.
- Alexandrite Lasers: 755 nm, Q switched mode laser, used to remove blue, black and green tattoos and epidermal and dermal pigmentations as in melasma.
- Diode Lasers: With different wavelengths. The absorbing chromophores are melanin and hemoglobin in the skin. Diode lasers are used for laser hair removal, dilated vein treatments, and laser photo-rejuvenation.
- Dye Lasers contain organic compounds in solution (often rhodamine) as the active medium and have wavelength activity between 400 to 800 nm. The target chromophores are hemoglobin and melanin pigment. Dye lasers are useful in treating vascular lesions and for non-ablative skin rejuvenation.
- Excimer Laser containing compounds of xenon, krypton and argon target proteins and water and have wavelengths between 190-350 nm. Excimer lasers are useful in the treatment of psoriasis and vitiligo.
- Fractional Lasers are the latest lasers which produce microscopic treatment zones and target specific depths in the dermis. These are especially useful for the treatment of acne scars, wrinkles, sun damaged skin, melasma etc. Wavelength is in the range of 1550 nm, and the target chromophore is water within the tissue.
It is important to know which laser will suite your skin type and for your particular cosmetic issue. The effects of laser energy on different structures of the skin depend upon the wavelength, the power density and the temperature characteristics of the laser. It is also important to know how lasers work in dermatology before opting for the most suitable one.
Reference
- Eubanks SW. Lasers in Dermatology. In Dermatology Secrets. 1996: 332-340, Eds. JE Fitzpatrick & JL Aeling; Hanley & Belfus, Inc.
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