A NEW APPARATUS WITH HIGH RADIATION ENERGY BETWEEN 320-460 NM - PHYSICAL DESCRIPTION AND DERMATOLOGICAL APPLICATIONS

A new apparatus (UVASUN 5000) is presented presented with high radiation energy between 320-460 nm. The measurable energy below 320 nm was many orders of magnitude too low to produce erythema. The radiator was a specially developed source for high UV-A intensity, housing a quartz bulb with a mixture of Ar, Hg and metal-halides. At a skin-target distance of 0.2 m, the size of the irradiated area was 0.35 .times. 0.35 m and the measured mean UV-A intensity was about 1400 W/m2 (140 mW/cm2). The UV-A energy in the range of 320-400 nm was about 84% of the total radiation energy. Effects of very high doses of UV-A on human skin were studied. Following single UV-A applications the minimal tanning dose UV-A (MTD) and the immediate pigment darkening (IPD) dose of UV-A were established. The calculated IPD threshold time was 1.8 min at 0.2 m. Repeated exposure to this UV-A delivering system yielded long lasting dark brown skin pigmentation without clinical or histological signs of sunburn (UV-B) damage, epidermal hyperplasia or thickening of the stratum corneum. The instrument was successfully used for photopatch testing and reproduction of skin lesions of polymorphous light eruption. Minimal therapeutic value was seen in the phototherapy of vitiligo and inflammatory acne.