114 TECHNOLOGY / LED
discrete LEDs tested could be classified into risk group 1 if the 500 Lux criterion of the IEC 62471 standard is applied. ANSES caused a major concern by stating the intense blue-white light was a “toxic stress” on the retina, with a severe dazzling risk and that young people in particular are sensitive to this risk as their eyes are still developing and the lens is not capable of filtering out the light wavelengths. This issue didn’t however state that other artificial light sources cause a similar hazard and thus one could argue that objectivity was not prevalent in the report. Indeed, one lighting industry association, CELMA, mentions that blue light exposure is important to human beings. Blue light with a peak around 460-480nm regulates the biological clock, alertness and metabolic processes. In natural conditions, outdoor daylight fulfils this function. Yet, people spend most of the day indoors (offices etc.) and are often lacking the necessary blue light exposure. Blue and cool white light sources can be used to create lighting conditions such that people will receive their daily portion of blue light to keep their physiology in tune with the natural day-night rhythm. Due to the highly flexible application possibilities, LED based light sources are particularly well suited for that purpose. A further study undertaken in 2010 by Health Canada measuring the amount of UV radiation given off by Halogen, Incandescent and CFL lamps revealed that at a distance of 30cm from a 60W incandescent bulb (see AG60 in Figure 5), UVR damage to unprotected skin or eyes may result if the bulb is repeatedly used for longer than 3.4 hr/day. Several single envelope CFL products required less time to achieve the recommended daily amount and the Halogen lamp required more than six hours of continuous exposure.
Effects of Light – Epilepsy
Five percent of the total world population has single seizures, and the annual incidence is 50 in 100.000 (WHO 2001). About five in 100 of epileptic people have photosensitive epilepsy. Photosensitive epilepsy is a form of epilepsy in which seizures are triggered by visual stimuli that form patterns in time or space, such as flashing lights, bold, regular patterns, or regular moving patterns.
The visual trigger for a seizure is generally cyclic, forming a regular pattern in time or space. Flashing or flickering lights or rapidly changing or alternating images are an example of patterns in time that can trigger seizures.
Figure 3: Estimating the blue light hazard of lighting fixtures.
Figure 4: Comparison of light sources against the blue light hazard.
While photosensitivity of epileptics has scientifically been proven there are few studies which determine if the flicker frequency range > 120 Hz causes seizures. All artificial lighting systems suffer from flicker however the frequency of the flicker will depend on the technology. For example incandescent lamps would have a frequency similar to that of the mains frequency however high frequency ballasts are now used on fluorescent tubes which have switching frequencies in the 20-90kHz range.
Effects of Light – Migraine Migraine can be defined as an intense pulsing or throbbing pain in one area of the head. It is often accompanied by extreme sensitivity to light and sound, nausea, and vomiting. Migraine is three times more common in women than in men. It is estimated that 14% of the adults in Europe have migraine (Stovner et al. 2006). According to self-reported information, certain visual patterns can reliably trigger a migraine attack, such as high contrast striped patterns or flickering lights. Fluorescent lamps can cause eye-strain and
headache (Wilkins et al. 1991). Patients with migraine show somewhat lowered flicker fusion thresholds during migraine- free periods. In addition, photophobia, which is an abnormal perceptual sensitivity to light experienced by most patients with headache during and also between attacks, is documented in many studies.
Effects of Light – Irlen-Meares Irlen-Meares manifests itself primarily as a difficulty with reading and spelling which may be improved by use of coloured lens or overlays. Self-reporting suggests that fluorescence lighting in contrast to incandescent light aggravate the symptoms of dyslexia. Probably the main problems are caused by UV radiation and blue light, emitted by cool white tubes.
Effects of Light – Autism/Aspergers Syndrome
Autism is a neuro-developmental disorder characterized by deficiencies in social interactions and communication skills, as well as repetitive and stereotyped patterns of behaviour. Recent epidemiological data show that autism is a frequent disorder,
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