Precision Tinted Lenses

Have you ever stopped to think about the evidence behind the treatments you offer your patients? How do you know that the treatment is right for them? 

This series, Using evidence in practice, sets out a summary of that evidence for you, so that you know that there is a solid foundation behind the recommendations you make. 

Professor Bruce Evans has written an explanation of the evidence behind the use of precision tinted lenses.

What you should know

Claims that individually prescibed coloured filters aid reading were well-publicised in the 1980s and remain controversial. 

A system using the “Intuitive Overlays” (IO), the “Intuitive Colorimeter”, and Cerium Precision Tinted Lenses was developed by Wilkins at the MRC Applied Psychology Unit, is fully described in the scientific literature, systematically and efficiently sample colour space, has been shown to have the properties required for an appropriate method and is used by eyecare professionals. This latter is important to ensure that symptoms due to optometric conditions are alleviated before colour is used.

The condition that is purportedly helped by colour filters has been given various names. Pattern related visual stress (PRVS) is used here. There is no evidence of a causal link between PRVS and dyslexia. It is, therefore, not appropriate for optometrists to claim that they can treat dyslexia. When they treat PRVS, they should advise that they are not treating reading difficulties but a visual condition that may co-occur with and, in some cases, contribute to reading difficulties.

PRVS is suspected when patients report symptoms of visual perceptual distortions, eye strain or headaches during reading. More research is needed on the diagnostic process, which at present typically requires prolonged sustained voluntary use of a coloured overlay. An additional criterion is to exclude patients with an optometric problem that may account for their symptoms.

An evaluation of studies showing the effectiveness of coloured overlays is set out in Table 1 in the main report. Table 2 in the paper evaluates all controlled trials using the intuitive colorimeter. There are limitations to the research. 

It would seem sensible for children who struggle at school to have an eye examination to exclude relevant visual problems. But, it is important to appreciate that any intervention can carry a cost to the patient and family in terms of expense, time and raised expectations. Where the evidence for the benefit is weak, it is important not to overstate the case for intervention as the parents and patients might be vulnerable to the suggestion that any intervention may help. Until larger trials are completed, a conservative clinical approach is to follow College guidance