Penetration depth of ultraviolet, visible light and infrared radiation in biological tissue has not previously been adequately measured. Risk assessment of typical intense pulsed light and laser intensities, spectral characteristics and the subsequent chemical, physiological and psychological effects of such outputs on vital organs as consequence of inappropriate output use are examined. This technical note focuses on wavelength, illumination geometry and skin tone and their effect on the energy density (fluence) distribution within tissue. Monte Carlo modelling is one of the most widely used stochastic methods for the modelling of light transport in turbid biological media such as human skin. Using custom Monte Carlo simulation software of a multi-layered skin model, fluence distributions are produced for various non-ionising radiation combinations. Fluence distributions were analysed using Matlab mathematical software. Penetration depth increases with increasing wavelength with a maximum penetration depth of 5378 μm calculated. The calculations show that a 10-mm beam width produces a fluence level at target depths of 1–3 mm equal to 73–88% (depending on depth) of the fluence level at the same depths produced by an infinitely wide beam of equal incident fluence. Meaning little additional penetration is achieved with larger spot sizes. Fluence distribution within tissue and thus the treatment efficacy depends upon the illumination geometry and wavelength. To optimise therapeutic techniques, light-tissue interactions must be thoroughly understood and can be greatly supported by the use of mathematical modelling techniques.

The treatment of acne vulgaris poses a challenge to the dermatologist, and the disease causes emotional anxiety for the patient. The treatment of acne vulgaris may be well-suited to home-use applications, where sufferers may be too embarrassed to seek medical treatment. This randomized controlled study is designed to quantify the effectiveness of using a blue light device in a therapy combined with proprietary creams, in the investigation of a self-treatment regimen. A total of 41 adults with mild-to-moderate facial inflammatory acne were recruited. The subjects were randomly assigned to combination blue light therapy (n = 26) or control (n = 15). Photography was used for qualitative assessment of lesion counts, at weeks 1, 2, 4, 8, and 12. All subjects in the treatment cohort achieved a reduction in their inflammatory lesion counts after 12 weeks. The mean inflammatory lesion counts reduced by 50.02% in the treatment cohort, and increased by 2.45% in the control cohort. The reduction in inflammatory lesions was typically observable at week-3, and maximal between weeks 8 and 12. The treatment is free of pain and side-effects. The blue light device offers a valuable alternative to antibiotics and potentially irritating topical treatments. Blue light phototherapy, using a narrow-band LED light source, appears to be a safe and effective additional therapy for mild to moderate acne.

This study, of 18 popular devices in regular daily use in England and Wales, provides example methods for measuring key IPL device parameters and highlights the need for regular measurement of at least those five key parameters measured in this study. These methods can help service technicians to check performance and eliminate device malfunction.

In the past 5 years since their US introduction, there has been a rapid proliferation of light-based hair removal devices intended for home-use. In the last 2 years in Europe, sales already run into many tens of thousands of units with well-known multi-national companies entering the market. These guidelines provide a definition of light-based home-use technology, to inform healthcare professionals about home-use light-based technology and encourage manufacturers wishing to sell in Europe to adopt 'best practice'. The review presents the current status on standards and regulation issues and considers home-use safety issues, encompassing human, device and electrical safety, given risks to the eyes and skin from optical radiation both to the consumer and persons in the vicinity.Proposed technical measurement methodology is considered with focus on recognized critical parameters for the safe use of light-based hair removal technology including recording the technical performance and safety claims of a range of home-use hair removal devices. The literature review emphasizes potential adverse incidents and safety aspects of treating cosmetic conditions, such as unwanted hair growth. Although some regulations exist, they differ from region to region and there is a specific need for international common principles and guidelines relating to the manufacture, marketing and use of intense pulsed light and laser devices, including manufacturing standards for home-use products intended, amongst others, for cosmetic hair removal and photo-rejuvenation procedures. In these guidelines, the European Society for Laser Dermatology (ESLD) provides a professional view of what 'best practice' may imply for manufacturers and consumers alike.

The development and use of light and lasers for medical and cosmetic procedures has increased exponentially over the past decade. This review article focuses on the incidence of reported cases of skin cancer post laser or IPL treatment. The existing evidence base of over 25 years of laser and IPL use to date has not raised any concerns regarding its long-term safety with only a few anecdotal cases of melanoma post treatment over two decades of use; therefore, there is no evidence to suggest that there is a credible cancer risk. Although laser and IPL technology has not been known to cause skin cancer, this does not mean that laser and IPL therapies are without long-term risks. Light therapies and lasers to treat existing lesions and CO2 laser resurfacing can be a preventative measure against BCC and SCC tumour formation by removing photo-damaged keratinocytes and encouraged re-epithelisation from stem cells located deeper in the epidermis. A review of the relevant literature has been performed to address the issue of long-term IPL safety, focussing on DNA damage, oxidative stress induction and the impact of adverse events.

The domestic market for home-use hair removal devices is rapidly expanding and there are numerous intense pulsed light (IPL) products now available globally to consumers. Technological challenges for the design of such devices include the need to be cost-effective in mass production, easy to use without training, and most importantly, clinically effective while being eye-safe. However inexpensively these light-based systems are produced, they are designed to cause biological damage to follicular structures, so precautions to prevent both ocular and epidermal damage must be considered. At present, there are no dedicated international standards for IPL devices. This review directly compares three leading domestic IPL hair removal devices: iPulse Personal (CyDen, UK), Silk'n/SensEpil (Home Skinovations, Israel), and SatinLux/Lumea (Philips, Netherlands) for fluence, emitted wavelength spectrum, time-resolved footprint, and spatial distribution of energy. Although each device has a primary mechanical or electrical safety feature to ensure occlusion of the output aperture on the skin to prevent accidental eye exposure, the ocular hazard of each device has been measured to IEC TR 60825-9 standard using an Ocean Optics HR2000+ photo spectrometer for both potential corneal and retinal damage. Using established measurement methods, this review has shown that the measured output parameters were significantly different for the three systems. Using equipment traceable to national standards, one device was judged at its two highest settings to be hazardous for naked eye viewing. This investigation also reports on the significantly different pulse durations of the devices measured and considers the potential impact on safety and efficacy in the light of the theory of selective photothermolysis. Although these devices offer low-cost personal convenience of treatment in the privacy of the home, ocular safety may be inadequate in the event of primary safety mechanism failure.

Background and Objectives: High quality IPLs can offer simple, safe and effective treatments for long-term hair removal, removal of benign vascular and pigmented skin abnormalities, skin rejuvenation and acne treatments. Significant differences in clinical outcome have been recorded among different free-discharge and constant current IPLs despite identical settings. We investigated the differences in optical output of 19 IPLs in normal clinical use in the UK to evaluate spectral output, energy density values and pulse structure and propose a correlation between light-tissue interaction and spectral output as measured by time-resolved photo-spectrometry. Study Design/Materials and Methods: Using a fast spectrometer, generating 1,000 full spectral scans per second, time resolved spectral data of IPL outputs was captured with a resolution of 0.035 nm. IPL spectral outputs were calculated and graphically modelled using MathCAD TM software for comparison. Results: Several IPLs, which professed matching of pulse durations to the thermal relaxation times of specific follicular or vascular targets were shown to have effective pulse durations that were vastly shorter than those claimed. Some IPLs claiming 'square pulse' characteristics failed to show constant spectral output across the duration of the pulse or sub-pulses. Conclusions: This study provides a suitable method to determine accurately key parameters of the emitted light pulses from IPLs and confirms the direct correlation between the electrical discharge current profile and the output energy profile. The differences measured between first generation free discharge systems and modern square pulse systems may have important clinical consequences in terms of different light-tissue interactions and hence clinical efficacy and safety. IPL manufacturers should provide time-resolved spectroscopy graphs to users. Lasers Surg. Med. 40:83-92, 2008.

There is an urgent need for early ratification of the draft international IEC 60601-1 intense light standard, which will encompass manufacturing standards for both professional and home-use hair removal devices.