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Biomedical subjects

B L Diffey

Publications and source records attributed to B L Diffey.

At least 55 records · Page 3Linked to original sources
PubMed1992

The influence of pigmentation and illumination on the perception of erythema.

The visual assessment of erythema induced by ultraviolet radiation (UVR) involves a comparison of the irradiated site with surrounding nonirradiated skin. By viewing the skin through plastic filters of varying shades of brown to simulate different degrees of pigmentation and under either incandescent or fluorescent lighting, we were able to examine the influence of pigmentation and illumination on the perception of erythema. Illuminating the skin with either light source at the same illuminance did not affect the determination of the minimal erythema dose (MED). Likewise, the range of pigmentation that may occur in Caucasian skin had little or no effect on the perception of the MED compared with white, untanned skin. However, when the skin was viewed through dark brown filters that approximate the absorbance of Negro skin, erythema was only perceived at sites that had been irradiated with more than about twice the MED.

Erythema↗
PubMed1991

Sunscreen protection against UVB, UVA and blue light: an in vivo and in vitro comparison.

The photoprotection against UVB, UVA and blue light provided by a widely prescribed sunscreen (RoC 15+ A+B) was compared with two new products containing microfine titanium dioxide (Sun E45 lotion SPF 15 and Sun E45 cream SPF 25) [corrected]. Comparisons were made in vivo using photosensitive patients with either chronic actinic dermatitis or erythropoietic protoporphyria, and in vitro using a newly developed spectrophotometric assay. Good agreement was obtained between the in-vivo and in-vitro methods at each waveband. All products showed high protection against UVB radiation, but the products containing microfine titanium dioxide showed significantly higher protection against both UVA and blue light than RoC 15+ A+B. Products containing microfine titanium dioxide are likely to offer superior photoprotection in those patients who are abnormally sensitive to long wavelength ultraviolet radiation than products which are currently available on prescription.

Adult↗
PubMed1991

PUVA treatment of psoriasis in the United Kingdom.

Information concerning the operation of 134 PUVA units in 96 dermatology centres in the U.K. was collected by a postal questionnaire. The most common protocol was to give PUVA three times weekly in the treatment of psoriasis, and to choose the initial dose of UVA according to skin type. However, the initial UVA dose encompassed a range of five or more within each skin type.

Clinical Protocols↗
PubMed1991

The action spectrum between 320 and 400 nm for clearance of psoriasis by psoralen photochemotherapy.

We have compared the effectiveness of oral 8-methoxypsoralen photochemotherapy (PUVA) using ultraviolet fluorescent lamps with peak emission at either 325, 352 or 370 nm in the treatment of 24 patients with psoriasis. The forearms of each patient were treated three times weekly with two of the three lamps. The erythemal sensitivity of each patient was tested before the first treatment to ensure that equally erythemal doses of radiation were given from each of the lamps. A side-to-side comparison was used to assess response to treatment at weekly intervals for the 6 weeks of the trial. The lamp with peak emission at 325 nm was shown to be significantly superior to either of the other lamps in terms of response assessed at weekly intervals, and time to clearance of psoriasis. An action spectrum, constructed from the median doses required for clearance of psoriasis using each of the lamps, showed that the effectiveness of the radiation decreased exponentially with increasing wavelength throughout the UVA waveband, such that radiation at 320 nm was an order of magnitude more effective than at 360 nm. This suggests that lamps with peak emission around 325 nm will be more effective than those conventionally used in PUVA units with a peak emission at 352 nm. Lamps with peak emission around 325 nm are also highly effective in the treatment of psoriasis with phototherapy alone. Thus a single treatment unit containing these lamps could be used either for PUVA or ultraviolet phototherapy of psoriasis, avoiding duplication or irradiation equipment.

Adolescent↗
PubMed1991

The relationship between plasma psoralen concentration and psoralen-UVA erythema.

The plasma 8-methoxypsoralen (8-MOP) concentration was measured in 60 patients commencing psoralen photochemotherapy (PUVA). At the time of blood sampling each patient was phototested using a series of 10 exposures to UVA. The resulting erythema was measured objectively 72 h after irradiation and dose-response curves for psoralen-UVA erythema were constructed. Although the dose of 8-MOP was calculated according to body weight, patients receiving 30 mg of 8-MOP had a significantly lower mean plasma concentration than those receiving higher doses. There was no significant correlation between plasma 8-MOP concentration and minimal phototoxic dose, either estimated visually or calculated from the dose-response curves. However the slope of the dose-response curve showed significant correlation with plasma 8-MOP concentration. The variation between patients in the rate of increase of the erythemal response, but not the variation in threshold sensitivity, can be explained by difference in plasma psoralen concentration.

Adolescent↗
PubMed1990

Inhibition of photosensitivity in erythropoietic protoporphyria with terfenadine.

The effect of terfenadine on the response to irradiation with blue light was measured in seven patients with erythropoietic protoporphyria. Terfenadine caused significant inhibition of the immediate flare reaction, but did not alter the erythemal response localized to the irradiation sites. Treatment with beta-carotene had no effect on the flare and erythemal responses. However, the flare reaction was still inhibited by terfenadine during treatment with beta-carotene. These results show that histamine release is involved in the mechanism of porphyrin photosensitivity. H1 receptor antagonists may be of use in the treatment of patients with erythropoietic protoporphyria.

Adolescent↗
PubMed1990

Effect of topical solvents on ultraviolet B erythema.

The skin of subjects was pretreated with 3 solvents, normal saline, 95% ethanol and diethylether. No significant difference in erythemal sensitivity to UVB was demonstrated for any of the solvents.

Administration, Cutaneous↗
PubMed1990

Human exposure to ultraviolet radiation.

Although the sun remains the main source of ultraviolet radiation (UVR) exposure in humans, the advent of artificial UVR sources has increased the opportunity for both intentional and unintentional exposure. Intentional exposure is most often to tan the skin. People living in less sunny climates can now maintain a year-round tan by using sunbeds and solaria emitting principally UVA radiation. Another reason for intentional exposure to artificial UVR is treatment of skin diseases, notably psoriasis. Unintentional exposure is normally the result of occupation. Outdoor workers, such as farmers, receive three to four times the annual solar UV exposure of indoor workers. Workers in many industries, eg, photoprinting or hospital phototherapy departments, may be exposed to UVR from artificial sources. One group particularly at risk is electric arc welders, where inadvertent exposure is so common that the terms "arc eye" or "welders flash" are often used to describe photokeratitis. In addition to unavoidable exposure to natural UVR, the general public is exposed to low levels of UVR from sources such as fluorescent lamps used for indoor lighting and shops and restaurants where UVA lamps are often used in traps to attract flying insects.

Environmental Exposure↗
PubMed1990

Exposure to solar ultraviolet radiation in flight.

The ultraviolet radiation (UVR) exposure of airline pilots during flight was measured with ultraviolet-sensitive film badges. The badges were worn by flight crew on the epaulette nearest to the window of either a Boeing 737 or 767 during 18 different flights in 1989. The results showed in every case that the UVR exposure was negligible; a flight lasting several hours resulted in an exposure equivalent to no more than a minute or two outdoors. There is anecdotal evidence that pilots may be at increased risk of developing skin cancer compared with many other occupational groups. The suggestion that this is due to significant exposure to UVR, the main aetiological factor in skin cancer, on the flight deck cannot be sustained.

Aerospace Medicine↗
PubMed1990

Textiles and sun protection.

The spectral transmission of ultraviolet radiation was measured through natural textiles (cotton, wool, silk) and human-made textiles (acrylic, viscose, polyester). Each textile exhibited a characteristic spectral transmission curve, but the protection afforded by a given fabric depended more on the nature of the weave than on the particular type of textile.

Humans↗