excimer laser & Light
When a patient's psoriasis involves smaller, more localized areas or involves discrete plaques, targeted UV therapy is a good, effective option for treatment, as Targeted UV therapy results in less toxicity, fewer treatments, and a lower cumulative UV dose when compared with whole-body phototherapy. An example of a targeted phototherapy through localized delivery of Narrowband UVB can be performed using the308 nm excimer laser, utilizing a xenon-chloride (XeCl) medium.
The excimer laser uses a combination of an inert gas and a reactive gas to create an excited dimer, or excimer, which gives rise to laser light in the ultraviolet range.
The possible explanations for the superior efficacy of the excimer laser over traditional UVB therapy for psoriasis may be due to a higher intensity UV light to plaques, which is more effective in clearing psoriasis.
Excimer laser is mostly useful in localized lesions involving less than 10% of body surface area, in non-exposed sites (scalp, ears, axillae, groin, intergluteal cleft), in resistant sites (elbows and knees, lower legs and ankles, chronic lesions induced by trauma known as koebner lesions, palms with thin lesions), and in situations in which more accurate dosimetry is important. Excimer (308nm) laser reduces the risk of photo-aging and carcinogenesis associated with wide and long term exposure in UVB therapy.
More recently, 308-nm monochromatic excimer lamps (MEL) have become available. Monochromatic excimer light delivery system emits light at 308 nm by using xenon and chlorine gases. They seem to be as effective as non-targeted narrow-band UVB and 308 nm excimer laser therapy. Advantages of MEL over the excimer laser include the ability to treat larger areas with potentially lower operating costs.
Side-effects (pigmentation, crusting, blistering, erythema) are less than that of excimer laser.