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Colour Vision Assessment

Discover how colour can alleviate visual discomfort and help with dyslexia.

Visual stress is a term used to describe visual discomfort and perceptual distortions in the printed text, suffered by many people who struggle to read. The condition is estimated to be present in about 40 % of poor readers and in 20 % of the general population in varying degrees.


Coloured overlays can improve reading speed and accuracy. They can enable longer periods of reading free of discomfort. When they do, it is an indication that the individual may benefit from Precision Tinted Lenses. The lenses are prescribed using specialist equipment called a Colorimeter.


The following symptoms indicate you may be suffering from visual stress:

  • Tired when reading

  • Letters changing size or shape

  • Halos of colour surrounding letters of words

  • Red, sore, watery eyes

  • Blurring of print

  • Patterns on print

  • Tiring easily when reading ​ 

Is Colorimetry the right solution?

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Eye Examination


Every child who shows signs of visual difficulty when reading should be referred for a full sight test. 

If symptoms of eye strain and/or visual stress are not helped by glasses or spectacle correction, then the next assessment of coloured overlays should be carried out to see if the visual stress can be alleviated with the help of colour. If the coloured overlays work, then an assessment with the Colorimeter would be the next stage to find what colour of spectacle lens would help.

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Overlay Assessment


An optometrist can carry out an overlay assessment if this has not already been done in school. The optometrist may suggest that the patient uses an overlay when reading and then return within a few weeks, noting any improvements.

Alternatively, in cases where the benefit from an overlay is clear, the optometrist may suggest moving directly to testing with an Intuitive Colorimeter. 

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Colorimetry Assessment


The Colorimetry Assessment may result in special glasses with coloured lenses being prescribed to the patient. The colour will be more specific to each individual's needs. This is 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 computer work. 

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