Impact of Long Wavelength UVA and Visible Light on Melanocompetent Skin

1. Background:

• A great deal is known about the impact of UVB and short wavelength UVA on pigmentation. Most sunscreens only protect against UVB and portions of UVA. However, it is not clear if other components of the spectrum of sunlight, not currently protected by sunscreens, are capable of eliciting pigmentation. Very little is known about the impact of long wavelength UVA and visible light on the time course to pigmentation, the quality of pigmentation and durations of this change in pigment if any. This has implications on the use of sunscreens to inhibit pigment production and the treatment of conditions that are aggravated by sun exposure such as melasma.
• The impact of visible light (400-700 nm) on melanogenesis was studied by Porges et al in 1988 . The threshold dose for IPD with visible light was between 40 and 80 J/cm2, while the threshold dose for "persistent" pigmentation was greater than or equal to 80 J/cm2 (1).

2. Study objective:

-To determine the impact of long wavelength UVA and visible light on immediate and delayed pigment production of melanocompetent individuals. 3. Study design:

• Patient to serve as their own control. Patient must be melanocompetent (skin phototypes IV to VI) with no history of vitiligo, melasma or photosensitivity. The symmetric back or forearm will be used as a control of the irradiated area. Two phototherapy delivery system will be developed for the study: 1) A targeted visible light phototherapy device, 2) A targeted long wavelength UVA device.
• Pigmentation will be assessed by visual exam, fluorescent and reflectance spectroscopy at 6 timepoints: immediately after irradiation, 30 minutes after exposure, 1 hour after exposure, 1 day after exposure, 1 week after exposure and 2 weeks after exposure.