Laser-induced injury of the skin: validation of a computer model to predict thresholds.

The exposure and emission limits of ICNIRP, IEC 60825-1 and ANSI Z136.1 to protect the skin are based on a limited number of studies. To broaden the database, a computer model was developed to predict injury thresholds in the wavelength range from 400 nm to 20 µm and was validated by comparison with all applicable experimental threshold data (ED) in the wavelength range from 488 nm to 10.

Laser-induced corneal injury: validation of a computer model to predict thresholds.

The exposure and emission limits of ICNIRP, IEC 60825-1 and ANSI Z136.1 to protect the cornea are based on a limited number of studies. To broaden the database, a computer model was developed to predict injury thresholds in the wavelength range from 1050 nm to 10.

Temperature-controlled in vivo ocular exposure to 1090-nm radiation suggests that near-infrared radiation cataract is thermally induced.

The damage mechanism for near-infrared radiation (IRR) induced cataract is unclear. Both a photochemical and a thermal mechanism were suggested. The current paper aims to elucidate a photochemical effect based on investigation of irradiance-exposure time reciprocity.

Ocular temperature elevation induced by threshold in vivo exposure to 1090-nm infrared radiation and associated heat diffusion.

An in vivo exposure to 197  W/cm 2 1090-nm infrared radiation (IRR) requires a minimum 8 s for cataract induction. The present study aims to determine the ocular temperature evolution and the associated heat flow at the same exposure conditions. Two groups of 12 rats were unilaterally exposed within the dilated pupil with a close to collimated beam between lens and retina.

1090 nm infrared radiation at close to threshold dose induces cataract with a time delay.

Purpose: To investigate whether infrared radiation (IRR)-induced cataract is instant or is associated with a time delay between the exposure and the onset of lens light scattering after an exposure to just above threshold dose.

Methods: Six-weeks-old albino Sprague-Dawley female rats were unilaterally exposed to 197 W/cm2 IRR at 1090 nm within the dilated pupil. In the first experiment, the animals were exposed with four exposure times of 5, 8, 13 and 20 second, respectively.

Review of thresholds and recommendations for revised exposure limits for laser and optical radiation for thermally induced retinal injury.

Exposure limits (ELs) for laser and optical broadband radiation that are derived to protect the retina from adverse thermally-induced effects vary as a function of wavelength, exposure duration, and retinal irradiance diameter (spot size) expressed as the angular subtense α. A review of ex vivo injury threshold data shows that, in the ns regime, the microcavitation-induced damage mechanism results in retinal injury thresholds below thermal denaturation-induced thresholds. This appears to be the reason that the injury thresholds for retinal spot sizes of about 80 μm (α = 6 mrad) and pulse durations of about 5 ns in the green wavelength range are very close to current ELs, calling for a reduction of the EL in the ns regime.

Medium-dose is more effective than low-dose ultraviolet A1 phototherapy for localized scleroderma as shown by 20-MHz ultrasound assessment.

Background: Recent studies suggest that ultraviolet (UV) A1 phototherapy is an effective treatment for localized scleroderma (LS); however, the optimum UVA1 dose remains to be determined.

Objective: We sought to compare the immediate and long-term efficacy of low- versus medium-dose UVA1 phototherapy for plaque-type LS.

Methods: Three comparable plaques in 16 patients were treated with 20 J/cm2 UVA1, 70 J/cm2 UVA1, or no irradiation.

Ex vivo and computer model study on retinal thermal laser-induced damage in the visible wavelength range.

Excised bovine eyes are used as models for threshold determination of 532-nm laser-induced thermal damage of the retina in the pulse duration regime of 100 micros to 2 s for varying laser spot size diameters. The thresholds as determined by fluorescence viability staining compare well with the prediction of an extended Thompson-Gerstman computer model. Both models compare well with published Rhesus monkey threshold data.

Outdoor workers' acceptance of personal protective measures against solar ultraviolet radiation.

The acceptance and usability of personal protection against solar UV radiation was evaluated in a field study with a group of tinsmiths in Austria. The personal protective measures (PPM) tested involved four categories: shirts, headwear, sunglasses and topically applied sunscreens; at least six different products per category were tested. Recommendations for the "ideal" shirt, headwear, pair of sunglasses and topical sunscreen are given based on data from questionnaires, i.

Variation of laser-induced retinal injury thresholds with retinal irradiated area: 0.1-s duration, 514-nm exposures.

The retinal injury threshold dose for laser exposure varies as a function of the irradiated area on the retina. Zuclich reported thresholds for laser-induced retinal injury from 532 nm, nanosecond-duration laser exposures that varied as the square of the diameter of the irradiated area on the retina. We report data for 0.

Nutritional and lifestyle correlates of the cancer-protective hormone melatonin.

Context: Despite growing support for melatonin as a promising agent for cancer treatment and possibly cancer prevention, few studies have elucidated factors that influence endogenous melatonin. This overview summarizes dietary and lifestyle factors that have been shown to affect circulating melatonin levels.

Biological Mechanisms: To date, many animal studies and in vitro experiments have illustrated that melatonin possesses oncostatic activity.

Parameters influencing the accuracy and practical applicability of UV indicator cards.

In order to evaluate the potential hazard for the skin and the eye presented by solar ultraviolet radiation, and to take appropriate precautions, it is necessary to characterise the biological effective irradiance or dose. Recently, inexpensive UV indicator cards became available that in principle would provide an attractive means to roughly indicate the local level of erythemal solar UV irradiance. We have characterised the properties of a number of different types of UV indicator cards.

Short- and long-wave UV light (UVB and UVA) induce similar mutations in human skin cells.

While the mutagenic and carcinogenic properties of longwave UV light (UVA) are well established, mechanisms of UVA mutagenesis remain a matter of debate. To elucidate the mechanisms of mutation formation with UVA in human skin, we determined the spectra of UVA- and UVB-induced mutations in primary human fibroblasts. As with UVB, we found the majority of mutations to be C-to-T transitions also with UVA.

Light at night and cancer risk.

Environmental lighting powerfully suppresses the physiologic release of melatonin, which typically peaks in the middle of the night. This decreased melatonin production has been hypothesized to increase the risk of cancer. Evidence from experimental studies supports a link between melatonin and tumor growth.

What is the meaning of threshold in laser injury experiments? Implications for human exposure limits.

The derivations of human exposure limits for laser radiation rely heavily upon experimental ocular injury studies. The limits are derived by committees of ophthalmic experts through a review of all available threshold data and an understanding of mechanisms of laser/tissue interaction. A major point of discussion in this derivation process relates to the level of uncertainty of the threshold of injury.