Eye Care

Coloured Overlays

Dyslexia and coloured lenses have become associated with each other in the public mind through TV, social media and some dyslexia charities who promote the association between dyslexia and visual stress. The reality is that the two are not strongly associated. Estimates vary but it is clear that the majority of dyslexics do not experience visual stress and there are many individuals with visual stress who read quite normally and are not considered to have dyslexia.

We should dissociate visual stress from dyslexia and consider it a separate, but comormid condition.

Visual stress refers to symptoms of discomfort and perceptual distortion that have a neurological origin. The symptoms are often thought of as a form of pattern glare elicited by black and white lines of text that simulate a grating pattern.  It is now well established that the use of appropriate coloured filters can alleviate the symptoms of visual stress and may improve performance in some types of visual task, notably reading speed.

Within the practice, we combine the Wilkins Rate of Reading test and the Institute of Optometry Coloured Overlay system. Using these tests, we find that an increase in reading speed of 15% is likely to indicate an improvement that exceeds any due to random variation. It should be noted that there is a known placebo effect, with some individuals finding initial improvement is not maintained through continued use of their overlay. Assessment of visual stress remains somewhat controversial in part due to the variety of testing procedures and also incomplete reviews of the literature.

At Christopher Nixon Optometrists our policy to carry out a full eye examination to rule out any optometric factors affecting reading before discussing and assessing for visual stress is considered best practice and we are always happy to discuss any symptoms that you or your child may be experiencing before assessment.