Colour Overlays


Visual stress  – Are colour overlays the only answer?

Many children and adults suffer from visual discomfort when reading, which can affect fluency, concentration and can cause rapid fatigue. This is generally seen as a ‘movement’ (shimmering) of the print on the page causing headaches and eyestrain.  This phenomenon is termed ‘Visual Stress’ and is found to exist in dyslexia, photosensitive migraine, photosensitive epilepsy, autism and ADHD.  It typically affects 20% of the population, with 5% of the cases being severe.

For children in particular it is very important to diagnose ‘Visual Stress’ problems early, since their inability to read causes frustration, loss of self-esteem and poor performance at school in these crucial formative years.

The Use of Colour

It is thought that this discomfort when looking at the print is due to a hyperexcitability of the neurones in the anterior visual cortex (the part of the brain that processes vision), but these neurones are also colour sensitive – so by placing a very specific colour in front of that individual’s eye, this pattern of excitation can be changed. In other words the colour will help to slow and calm these cells, therefore quieting the pattern and reducing the visual stress.  This whole discovery on colour started in the 1980’s and early 1990’s by Olive Mears (New Zealand). Helen Irlen (USA) and Prof. Arnold Wilkins (UK).

An assessment using spectral overlays (coloured transparent acetate sheets) are used. These coloured sheets are used as a screening test only to give an indication if colour will be beneficial to this person. (Their accuracy falls down as the person’s eyes are adapted to the surrounding illumination and colour of the room, as opposed to being adapted to a precise colour of a lens held up to the eye – this will nearly always give a different colour of spectacle tint prescribed relative to the chosen overlay).

If colour apparently helps the individual, we move on to the Intuitive Colorimeter. This is an instrument which allows text to be viewed under different coloured light scenarios.  The hue (colour), saturation (how deeply coloured) and brightness can all be altered by tiny increments until a precise shade is found which helps the individual by minimising or eliminating their symptoms.

Trial coloured lenses are then used to match the chosen colour and ‘Rate of Reading’ tests carried out to confirm findings. Coloured spectacles, either with or without a prescription lens can then be ordered.