Excimer Lamp vs Excimer Laser in Dermatology

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Excimer 308nm light is a form of selective phototherapy that produces a wavelength of 308nm of ultraviolet B radiation using an excimer lamp or a laser device. The U.S. Food and Drug Administration (FDA) has approved the use of both excimer lamp and laser in dermatology. Although the excimer lamp and laser use the same wavelength, they are different devices with distinct radiation properties.

An excimer lamp and laser work on the same principle. The generation of photons produces ultraviolet light involving excited dimers. Both the devices use a complex of the noble gas xenon and halogen chloride gas known as exciplex. This complex dissociates to produce 308nm of UV-B light. This 308nm xenon-chloride wavelength is the most practical in treating various autoimmune skin conditions.

An excimer lamp is a hand-held portable device weighing 1 kilogram. It is easier to carry as compared to the heavier laser machine. This could allow selected phototherapy to become more accessible. The heavier weight and bigger size of the laser limits the accessibility.

The lamp produces spontaneous incoherent emissions due to the generation of photons in all directions. Thus, its power distribution is homogenous to the affected skin, treating each area equally and efficiently. In contrast, the laser produces stimulated coherent beam of light which results in a smaller treatment spot that does not treat all affected skin homogenously. This results in a red hot spot which can cause increased erythema of the skin.

The power density of an excimer lamp is 100mW/cm2 and that of the laser is approximately 150mW/cm2. Considering that the lamp is a small device, this power density is enough to treat various skin conditions making it very versatile.

The cost effectiveness appears more favourable for the lamp with no additional costs. On the other hand, the laser is expensive and it is used only in specialised dermatological centres.

More than 200 clinical studies have been published proving that the monochromatic 308nm excimer light is the most suitable wavelength to treat autoimmune skin conditions. These include vitiligo, psoriasis, alopecia areata, mycosis fungoides and atopic dermatitis. However, there are only a few studies showing a direct comparison of the excimer lamp to the laser.

One such randomized control study shows the comparison between the 308nm excimer lamp and laser in the treatment of non-segmental vitiligo. In this study, the two treatments showed similar results in terms of efficacy in treating vitiligo. It also showed that excimer lamp is a more affordable and easily accessible device for the treatment of vitiligo as compared to the laser.