There is some debate about how specific the colour of tinted lenses and overlays must be to produce the optimum benefit.  Some have argued that some individuals are very specific in their choice of colour and a small deviation from this optimum colour results in a rapid loss of comfort and reading speed.  If this is the case, it would be necessary to tint lenses to a high level of precision.  Proprietary systems such as the Intuitive Colorimeter and Precision Tinting are based on this assumption.


Others argue that the evidence to support this high level of colour specificity is weak and have argued that:


    • The research literature in this area is at best, inconclusive
    • Individuals with such precise colour specificity are likely to require a different tint depending on the lighting (illuminant) that they were working under.
    • While such precise colour specificity could perhaps occur in a monochromatic (black and white) world, it is difficult to explain in a “multicoloured” world.  The precise wavelengths that enter the eye are a complex interaction between the wavelengths reflected from objects and those absorbed by the tinted lens.  This means that the colour appearance and contrast of coloured objects changes in a complex fashion when viewed through tinted lenses. It is difficult to understand how such precise colour specificity could be satisfied by a single tint under such conditions.
    • It is difficult to understand why if 9 overlay colours seems to be adequate (or 18 if used in combination), and yet thousands of colours are apparently required for tinted lenses.  
    • Anecdotal evidence from experienced practitioners suggests that the majority of those with Visual Stress syndrome can be satisfied from a much reduced palette of tints.


While the jury is still out on the precise number of colours required, trials have shown that at least 85% of individuals with Visual Stress are “satisfied” with one of the 24 ReadEZ colours.


ReadEZ tints have been designed to be approximately equally distributed in u’,v’ colour space under daylight.  This means that the perceived difference between the colour of the tints is approximately equal from one tint to the next. Each tint is carefully calibrated during the production process to ensure that the tints are within the prescribed tolerance.


By reducing the number of tints required, the costs are greatly reduced providing a solution for those who show a clear benefit of using colour but cannot afford bespoke tinted lenses. While the majority of those with Visual Stress can be satisfied from the choice of 24 ReadEZ tints, it is possible that a few individuals may require a small variation on the colours provided.