Photoadaptation of the skin during exposure to narrowband ultraviolet b radiation

Abstract

The aim of this study is to determine the rate at which UVB radiation takes effect in order to produce an effective regimen for treatment. Psoriasis, a chronic, proliferative, inflammatory disease that is under genetic and environmental control is the major condition where UVB radiation successfully reduces symptoms. The treatment regimen for at present involves exposure doses that are increased alogarithmically and is based upon previous broadband knowledge. No established protocol for TLOl UVB phototherapy exists. Patients were randomly chosen from Dryburn Hospital Phototherapy Department. Baseline minimal erythemal measurements were calculated (MED(_0)) and random measurements were taken during the course using a single TLOl lamp. Data was collected over a period of 1 year and the effects of photoadaptation were determined. Factors considered include the period of time in between treatments, the number of treatments already attended and cumulative doses. MED ratios were calculated and analysed to produce a skin adaptation model. The majority of patients were phototested 2-6 times during the treatment course, which lasted 6 weeks (mean). Results indicated that missing a treatment session was insignificant to the rate of tolerance. The model for tolerance was calculated to be: T(_n) = 1 + 3 [1 - exp (= 0.03n) ] n = tolerance following n treatments A revised protocol was established and a clinical trial implemented. Protocol results indicated that the new regimen significantly reduced cases of burning and significantly reduced the cumulative doses of radiation. Revised protocol patients (yellow group) received total doses of 12.7 J/cm(^2) (median) and the original regimen provided a total of 16.9 J/cm(^2) (median). There was no significance in the time length of the treatment protocols. The revised protocol is therefore significantly more suitable because it reduces chances of excessive erythema discomfort and by reducing the radiation exposure doses the regimen also reduces the risk of skin malignancies.