Author: Vanessa Ngan, Staff Writer, 2006. Updated by Dr Carolina Cordoba-Rincon, Dermatology Registrar; Dr Monisha Gupta, Dermatologist, Sydney Australia, October 2016.
Excimer 308-nm light is a form of targeted phototherapy that delivers a specific wavelength (308 nm) of ultraviolet B (UVB) radiation using an excimer laser or an excimer lamp. Both have shown similar results in terms of efficacy, but have technical differences.
Excimer light treatment is a development of whole body narrowband UVB. Narrowband UVB delivers energy at a wavelength between 311–312 nm and is effective in the treatment of localised psoriasis and localised vitiligo. The disadvantages of narrowband UVB include irradiation of the whole body (even if the psoriasis is limited to certain areas of the body) and the need for a high number of treatments (usually between 15 and 40 sessions).
The UV ray generated by the excimer light is delivered via a hand–held wand that focuses on the lesion. Compared with narrowband UVB, its advantages are:
Excimer laser therapy is an option for the treatment of localised vitiligo and moderately severe localised psoriasis and unresponsive to topical treatments. It is often combined with topical therapies to enhance response, for instance topical calcineurin inhibitors and topical steroids.
Further controlled studies are needed to compare excimer light therapy with topical treatments and other laser treatments in these conditions. Studies are also to determine the short and long term effectiveness and safety, establish optimal dosage regimens, and define appropriate patient selection criteria.
In most cases excimer light is tolerated well. The aim of treatment is to deliver a dose that induces visible redness in the psoriatic lesion (supra-erythematous dose) but that does not induce a blister or second-degree burn. It causes blisters on treated areas if the dose is too high.
Other side effects include:
Long term exposure to ultraviolet radiation ultimately causes skin ageing and skin cancer. Although the risk from excimer light therapy is unknown, research to date suggests it is less risky than narrowband UVB, as it doesn’t expose the whole body to UV radiation.
To date, there are no widely accepted disease-specific protocols for excimer light treatment.
Patients attend 1–3 times weekly. The amount of UV delivered is carefully calculated and monitored taking into account the skin type, age, skin condition, site and response to treatment.
The duration of treatment is shorter than for whole body phototherapy. Some response may be noted as early as 6–8 treatments and complete response may take 20–30 sessions. The average length of treatment is about 7 weeks.
Some patients have long remission periods, while others may relapse within 3–6 months.
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