Harry_DSC_0305 79Colorimetry is an enhanced examination developed to assess which precision tint is beneficial to people who suffer Visual Stress or Mears-Irlen Syndrome.  Unfortunately overlay assessment and colorimetry assessment are not available through the NHS or General Ophthalmic Services

What is Visual Stress?

Simply explained, Visual Stress (Meares-Irlen syndrome) is a sensitivity to visual patterns, particularly stripes.  In some individuals this condition can cause visual perceptual problems which interfere with reading. The symptoms can occur despite normal vision. One current scientific explanation is that the perceptual problems are due to a hyperactivation of the visual cortex of the brain, particularly in more anterior visual areas, which is reduced by precise individual colour.

Symptoms of Visual Stress

All or some of the following symptoms may be present

  • Movement of the printed text.
  • Blurring of print
  • Letters changing size or shape
  • Patterns in the print (sometimes described as rivers or worms)
  • Halos of colour surrounding letters or words
  • Tiring easily whilst reading
  • Headaches or visual discomfort
  • Red, sore, watery eyes


Signs of Visual Stress
  • Moving closer to or further away from the book or printed material
  • Moving book around on the desk
  • Fidgeting continuously while reading
  • Using finger as a marker on the page
  • Skipping  words or lines when reading
  • Frequently re-reading the same line
  • Rubbing eyes or blinking frequently when reading
  • Poor comprehension of content when reading
  • Frustration and low self-esteem


Frustration and low self esteem can occur in children who are underachieving due to visual stress. Early diagnosis of the problem is essential. The longer it takes to identify and remedy visual stress, the greater the loss of confidence that can result.

Is this Dyslexia?

‘Dyslexia’ is a term used to refer to reading problems that are not due to poor teaching. Dyslexia is often associated with spelling difficulty. Visual Stress is NOT the same as dyslexia but is more common in those who are dyslexic. People who fail to read because of visual stress are frequently mis-diagnosed as dyslexic. For this reason it is important that the existence of visual stress is identified at an early stage. Once the visual stress has been treated, the remaining problems are more easily dealt with. Visual stress can occur in non-dyslexic individuals. Symptoms may become more apparent when a intensive reading is necessary, as when studying for exams.

Visual Stress and Photosensitive Migraine

Migraine attacks have many triggers, including stress, particular foods and hormones. About 40% of migraine attacks may be visually-induced by flickering light, patterns or reading. These attacks may be helped by precision tinted lenses. Research in the US undertaken recently by a team of neuro-scientists, using brain imaging, has shown that a suppression of hyper-excitability in the visual cortex occurs in migraineurs when individually selected precision tinted lenses are worn. The lenses for the study were selected using the Intuitive Colorimeter. Symptoms of other neurological conditions such as Autism, MS, ME and Parkinson’s have been shown to reduce with the application of a precise colour.

A Solution

Visual Stress can be reduced by the use of coloured filters : an coloured overlay placed over text or coloured lenses worn in spectacles. The reduction occurs only when the colour is selected to suit the individual. The selection of lenses is best undertaken with the aid of the Intuitive Colorimeter. Coloured overlays are widely used by teachers in schools throughout the UK.  If an overlay proves useful it is likely that precision tinted lenses will also be beneficial. Lenses can be used for writing as well as reading.  They can also be worn to reduce glare. It is important to note that the most effective coloured overlay is unlikely have the same colour as the optimal precision lenses.

A full eye examination is necessary before prescribing precision tinted lenses. This procedure is best undertaken by an optometrist who also specialises in colorimetry examinations. Appropriately tinted lenses frequently result in reading that is more fluent and comfortable. Some lens wearers enjoy significant improvement in both reading rate and accuracy. The degree of improvement differs: some individuals experience improvements in reading age of one – two years within a few weeks of acquiring the lenses.  In others the lenses may offer greater comfort when reading, but the reading improvement may be less dramatic because of other reading difficulty.

How to discover if colour can help
1. Eye Examination

Every child who displays problems with reading should be referred to an optometrist for a full vision test.  It is recommended that the chosen practice should also specialise in using the Intuitive Colorimeter. If a refractive prescription is required (e.g. for long or short sight) then this can be incorporated in the coloured lenses.

2. Overlay Assessment

An assessment with overlays may already have been carried out in school. If the school does not use overlays an optometrist can also carry out this assessment. The optometrist may suggest the patient use an overlay and return within a few weeks, noting any improvements that result.  Alternatively, in cases where the benefit from an overlay is clear, the optometrist may suggest moving directly to testing with the Intuitive Colorimeter.

3. Colorimetry Assessment

If overlays are beneficial the optometrist may suggest Colorimetry as the next stage. This may result in the prescribing of spectacles with coloured lenses. The colour will be more specific to each individuals needs, much more precise than the overlay and very often a different colour to the overlay. Coloured lenses are also much more convenient than overlays for board and computer work.

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