Author(s): Dr Faisal R. Ali and Dr Firas Al-Niaimi, Consultant Dermatologists, Dermatological Surgery & Laser Unit, St John’s Institute of Dermatology, Guy’s and St Thomas’ NHS Foundation Trust, London, United Kingdom. DermNet NZ Editor in Chief: Adjunct A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy edited by Gus Mitchell. September 2018.
A picosecond laser is a laser device that uses very short pulse durations to target endogenous pigmentation and exogenous ink particles (tattoos). The medium varies accordingly to the wavelength being used: neodymium-doped yttrium aluminum garnet (Nd:YAG) crystal (532nm, 1064nm), Alexandrite crystal (755nm).
The main indication for use of a picosecond laser is tattoo removal . Depending on the wavelength, they are particularly useful for clearing blue and green pigments, which are difficult to eliminate using other lasers, and tattoos that are refractory to treatment with the traditional Q-switched lasers.
As with other laser devices, picosecond lasers are relatively contraindicated in patients with darker skin tones (Fitzpatrick skin types 4–6), who are more susceptible to side effects.
Picosecond lasers use pulse durations of less than one nanosecond, which causes predominantly photoacoustic damage (ie, mechanical reverberation) rather than photothermal destruction of pigment or ink particles. This results in effective clearance of abnormal pigment, whilst minimising photothermal damage to the surrounding tissue.
A picosecond laser selectively destroys the target pigment without damaging healthy, normal tissue. This allows rapid clearing of the abnormal pigmentation with minimal collateral damage to surrounding tissue.
Picosecond lasers used for tattoo removal require fewer treatments, cause fewer side effects, and result in reduced post-procedural downtime compared to nanosecond Q-switched lasers. They can clear some tattoos that are refractory to other forms of laser therapy and there is a reduced risk of causing scarring and hypopigmentation.
The additional cost and reduced availability of picosecond lasers compared to Q-switched lasers currently restricts their widespread use.
Picosecond laser treatment is mostly well tolerated. Potential side effects include pain, erythema, oedema, pinpoint bleeding, crusting, blistering, scarring, post-inflammatory hyperpigmentation and post-inflammatory hypopigmentation. Side effects are more severe if excessive fluences are used.
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