Spectral filtering of fluorescent lighting: effects upon reading and visual discomfort in slow readers

The visual-perception disorder scotopic sensitivity syndrome (SSS), also known as Meares-Irlen syndrome is a form of visual system hyperexcitability which reportedly affects between 5% and 12% of the general population and between a quarter and half of individuals with dyslexia. The condition affects reading, writing and visual-attention abilities. Symptoms of SSS are known to be particularly exacerbated by fluorescent lighting. We investigated the effects of filtering specific wavelengths of fluorescent lighting upon reading and visual comfort in a group of slow readers with symptoms of SSS, and in a group of proficient readers without such symptoms. Our findings contradict the generally accepted concepts that visual and attention problems in fluorescent lighting are primarily caused by the 100 Hz flicker frequency of fluorescent lighting and suggest that the dissimilarity in the spectral power distribution in fluorescent lighting compared to natural and incandescent lighting is a major causal factor. We also present data indicating that simple and inexpensive adaptations to fluorescent lighting can dramatically reduce visual and reading discomfort in individuals who are sensitive to the standard form of illumination utilised in contemporary working environments.