What is excimer 308-nm light treatment?
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 regarding 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 for the treatment of localised psoriasis and vitiligo. The disadvantages of narrowband UVB include irradiation of the whole body (even if the psoriasis is localised) 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:
- Healthy skin surrounding the affected areas is not exposed to radiation
- Different templates are used according to the area to be treated
- A higher dose of radiation can be delivered, with a reduced cumulative dose of irradiation
- In some cases, a shorter course of treatment is effective
- It can be used in areas difficult to reach with conventional phototherapy, such as ears and genitals
- It can be used in children, as it is a relatively friendly–looking piece of equipment.
What are the indications for excimer 308-nm light treatment?
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.
Some case reports document its use for localised severe atopic eczema, alopecia areata, cutaneous T-cell lymphoma, localised scleroderma, and granuloma annulare.
What are the side effects of excimer light treatment?
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:
- Painful erythema
- Koebnerisation (development of skin lesions due to trauma in case of a burn)
- Reactivation of herpes virus infection.
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.
What does the treatment involve?
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 seven weeks.
Some patients have long remission periods, while others may relapse within 3–6 months.