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The Intuitive Colorimeter: a valuable optometric tool
Prof Bruce JW Evans | 17 May 2011
Optometrists have long been interested in helping people with reading difficulties. There is good evidence that several visual problems are particularly likely to be found in people with reading difficulties, including binocular visual anomalies, accommodative anomalies, and subtle deficits of sensory visual processing (e.g., a deficit of the magnocellular system). Many optometrists have specialised in this area and one of the most exciting developments has been in the use of coloured filters. There is now a growing awareness amongst the public that coloured filters have grown into an "evidence-based" intervention. Most importantly, research highlights the fact that coloured filters do not replace the conventional role of the optometrist in caring for children with reading difficulties. Children with reading difficulties still need to see optometrists who have specialised in vision and learning and those optometrists still need to carry out a thorough eye exam and detect and treat refractive, binocular vision, accommodative, and other optometric anomalies. But one of the conditions that they need to search for is visual stress (previously called Meares-Irlen Syndrome), the condition that is helped by coloured filters. This is now known to be a surprisingly common contributory factor to reading difficulties.
Colour is not new
It has been argued for many years that coloured glasses can make reading easier and the adjacent picture shows glasses used over 200 years ago to ease eyestrain when reading (British Optical Association Museum, UK). But claims in the 1980s went further and said that coloured filters can make a vast difference to some people with reading problems like dyslexia. An American psychologist, Helen Irlen, claimed that many poor readers experience eyestrain, headaches, and see text blurring and moving and that this can be helped by individually prescribed coloured glasses. She argued that different sufferers need different colours, and exactly the right colour has to be prescribed for each sufferer. Irlen's claims caused antagonism in some quarters and the situation was not helped by the fact that Irlen often operated outside the normal eyecare services so that the coloured lenses were not prescribed as part of a comprehensive package of eyecare.
This situation changed following an invention 15 years ago by a British scientist, Professor Arnold Wilkins, who was employed by the Medical Research Council (MRC), the leading government funded health research organisation in the UK. The MRC realised the potential and rapidly patented this invention, the Intuitive Colorimeter, which was licensed to Cerium Visual Technologies. There are now several hundred of these instruments in use in many different countries, including Australia. Worldwide, well over 100,000 children have been helped with this innovative new optometric instrument. The recently launched Mark 3 Intuitive Colorimeter is shown above.
The Intuitive Colorimeter
Research has shown that in visual stress the optimum colour needs to be defined with precision and the Intuitive Colorimeter makes this possible in a scientifically valid and time efficient way. The Intuitive Colorimeter comes with an associated set of Precision Lenses which allow the optimal colour found with the Intuitive Colorimeter to be prescribed in Precision Tinted spectacles or contact lenses.
An integrated approach
Since the earliest research with the Intuitive Colorimeter a decision was made that this should not be used outside of conventional eyecare services. Rather, the instrument is used by optometrists (and some orthoptists, ophthalmologists, and opticians) as part of the integrated package of eyecare that they offer to patients with reading difficulties.
The flow chart illustrates the published clinical system that is typically followed. It is recommended that children who struggle at school should be referred to an eyecare practitioner who has specialised in vision and learning. The practitioner will of course check for basic ocular problems (e.g., ocular health, refractive error). They will also check for any eye co-ordination difficulties (including binocular vision or accommodative anomalies) that need treating. Visual stress can be detected by screening with coloured overlays and coloured lenses are prescribed with the Intuitive Colorimeter. The Wilkins Rate of Reading Test can be used to quantify the benefit from coloured filters.
One of the most intriguing findings is that the colour needs to be precisely prescribed. For reasons to do with colour adaptation, a person's preferred overlay is usually different to the colour of their preferred lens (spectacle lenses should not be tinted to match the colour of a preferred overlay). Very recent research has been unravelling the mechanism behind such precision. Early claims that the magnocellular system is involved are no longer thought to be correct, but rather the mechanism is due to a hyperexcitability of the visual cortex. Studies suggest that some patients with migraine, visually precipitated epilepsy, or autism also can be helped by Precision Tinted Lenses.
Prof Bruce JW Evans BSc PhD FCOptom DipCLP DipOrth FAAO FBCLA
Director of Research, Institute of Optometry, London Visiting Professor, City University, London
Allen, P. M., Evans, B.J.W., Wilkins, A. J. (2010) Vision and Reading Difficulty, Ten Alps, London.
Evans, B.J.W. (2001) Dyslexia and Vision, Whurr, London.
Evans, B.J.W., Busby, A. , Jeanes, R, and Wilkins, A.J. (1995) Optometric correlates of Meares-Irlen Syndrome: a matched group study. Ophthal. Physiol. Optics. 15 481-487.
Evans, B.J.W., Drasdo, N., and Richards, I.L. (1996) Specific Learning Difficulties: the link with visual deficits. Ophthal. Physiol. Opt. 16 3-10.
Evans, B.J.W., Patel, R., Wilkins, A.J., Lightstone, A., Eperjesi, F., Speedwell, L., Duffy, J. (1999) A review of the management of 323 consecutive patients seen in a specific learning difficulties clinic. Ophthal. Physiol. Opt. 19 (6), 454-466.
Wilkins, A.J. (2002) Reading Through Colour, John Wiley and Sons, Chichester.
Wilkins, A.J., Evans, B.J.W., Brown, J., Busby, A., Wingfield, A.E., Jeanes, R., Bald, J. (1994) Double-masked placebo-controlled trial of precision spectral filters in children who use coloured overlays. Ophthal.Physiol.Opt. 14:365-370.
It has been argued for many years that coloured glasses can make reading easier