One of the most important unique instruments to be designed for optometry during the past twenty years is the Intuitive Colorimeter™. Now used by over 600 community optometrists, hospital and university clinics worldwide, the Intuitive Colorimeter is able to prescribe the individual precision tint required to alleviate Visual Stress in reading and other neurological conditions.

Visual Stress (a condition related to light sensitivity) is an underlying cause of some people’s inability to read or read well when they often perceive visual distortions in the printed text. They may also develop headaches whilst attempting to read.

The Intuitive Colorimeter, distributed by Cerium Visual Technologies under license to the British Medical Research Council was designed by Professor Arnold Wilkins in the early nineties following substantial published research, at the British Medical Research Council.

The symptoms of the condition that can be treated by precision tinted lenses are often confused with those of dyslexia. The precision lenses do not treat dyslexia or any other specific learning problems. They do treat Visual Stress and the two conditions must be treated separately.
There is a propensity amongst the dyslexic population however, to also suffer from Visual Stress and where the conditions run concurrently the optimum tinted lenses can be beneficial in helping towards dealing with the more complex specific learning problems.

Thousands of UK schools use coloured overlays in the classroom to help poor readers. With the selection of the optimum coloured overlay both reading speeds and accuracy can improve, sometimes dramatically. The overlays are non-invasive, cheap to provide and durable and can be used continually. They cannot be used effectively however when copying from the board or from another book. In these instances, precision tinted lenses are more convenient.

The Wilkins Rate of Reading Test, created in the early nineties by Professor Arnold Wilkins and Manchester University School of Education’s Professor Peter Pumphrey, is used widely to determine the degree of improvement in reading speed and accuracy and before considering precision tinted lenses. The protocol within optometry for testing with overlays and prescribing precision tinted lenses from the Intuitive Colorimeter was validated by the College of Optometrists at the launch of the Colorimeter.

Claims by a New Zealand and US educationalists in the late nineteen eighties that coloured sheets of plastic and in some cases coloured lenses, helped reduce visual distortions, were met with scepticism on both sides of the Atlantic by vision and education professionals alike. Professor Arnold Wilkins noted press reports from individuals claiming that movement in printed text had been remedied using coloured overlays and lenses and cited symptoms that Wilkins recognised, from his previous researching photosensitive epilepsy in Canada, as being similar to those reported by visually induced epileptic sufferers.


In 1990, with British government and private funding, Professor Wilkins undertook a double blind study that lead to the design of the Intuitive Colorimeter. His published work confirmed an underlying photosensitive condition that could affect reading. His research also showed the need for a wide range of colours to achieve an optimum precision tint for many. The then British government’s chief Medical Office, for simplicity, chose to entitle the condition as Visual Stress. This is the term largely accepted to describe the condition.

The Intuitive Colorimeter instrument allows for swift selection of colour space particular to the needs of the individual. It also allows for fine tuning of hue and saturation until the optimum colour is arrived at. Presenting over 10,000 permutations of colour in strict scientific sequential order, the normal time required to arrive at the optimum colour in practice is usually 20 – 30 minutes, thereby ensuring patients are unlikely to tire before finalising their selection

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In 2011 professor Wilkins collaborated with Michigan State University in a study that induced migraine in a number of patients. Using a selection of control and other lenses to subjugate the migraine attacks, the research concluded that only the pre-selected precision lenses, chosen prior to the attacks from the Intuitive Colorimeter, were capable of subjugating the activity in the brain.

Precision tinted lenses are also used to help remedy some neurological conditions such as MS, Autism and closed head injury – following stroke or heart attack and including TBI (acquired traumatic brain injury).

Precision is possible with coloured lenses. Perhaps in consequence lenses are usually more effective than coloured overlays. Precision is not practical with coloured overlays. Nevertheless, overlays are suitable in assessing whether assessment for coloured lenses is likely to be useful.