Why use coloured overlays

The perceptual distortions may occur quite independently of any refractive error, although they are often, but not always, associated with a mild binocular vision difficulty i.

In most cases the binocular difficulties do not appear to be the basis for the distortions. Does visual perceptual distortion occur in families, and if so, why? Many traits run in families and visual perceptual distortions are no exception. The genetic contribution is the subject of investigation. Does visual perceptual distortion cause writing to deteriorate? The visual perceptual distortions that people experience can affect all aspects of visual function, but they are more likely when the visual material has many similar contours letters.

Text is unlike natural scenes in that it is composed of many identical elements. These are at their most confusing in small closely spaced printed text, but they also occur in hand-written work. Do children need coloured overlays or coloured glasses permanently? It seems that children benefit most from colour if it is offered as soon as any reading difficulty is suspected, before the cycle of failure has begun.

Many 7 year-olds appear to use coloured overlays for a year or two and then discard them as unnecessary. This may be because the acquired familiarity with text makes the distortion less distracting. Can overlays or glasses harm the eyes? Just as some colours are reported as being beneficial, others are often reported to be uncomfortable. Individuals sometimes show a marked aversion to these uncomfortable colours. Provided the appropriate colour is chosen, it seems unlikely that overlays can have any detrimental effect.

The possible long-term effects of wearing coloured glasses are unknown at present. Should coloured glasses be worn all the time? In our view, children should be free to wear the glasses if they find it helpful to do so, but not encouraged to wear them if they would not otherwise do so. The response to colour is subjective and individual, and the wearer is the best person to judge whether there is any benefit.

Should children with binocular difficulties who are undergoing orthoptic eye exercises or other medical treatment continue to use overlays? In our opinion, overlays can be used regardless of any simultaneous eye exercises or medical treatment. However, visual perceptual distortions can sometimes be caused solely by binocular vision problems, so it is sensible to have these corrected first.

If the distortions remain then coloured filters need to be tried. How long should overlays be used before coloured glasses are considered? There are many factors involved. First, are the overlays obviously beneficial? If so, only a short trial period, say six weeks, is necessary, particularly if headaches have been reduced but not eliminated, and if untidy writing continues to be a problem.

Under these circumstances glasses may further reduce the headaches and may well improve the handwriting. If, on the other hand, the response to overlays is less marked, it seems sensible to see whether the child continues to use overlays without prompting for, say, a school term or longer, before considering coloured glasses.

Coloured glasses are more expensive than overlays, and it may be wise to wait before incurring the cost. Another factor to consider is the age of the child. It is often difficult to assess a child for coloured glasses below the age of 8.

Are coloured glasses necessary? Children who persist in using their overlay usually find coloured glasses more convenient to use. Classes can help with writing, whereas overlays cannot. The degree of precision in the choice of colour is critical for obtaining the best results, and the precision available with lenses is far greater than with overlays.

Perhaps for this reason glasses often give better results 4. Are glasses the same colour as overlays? It is essential to realise that the appropriate colour for use in glasses is not the same as that in overlays 5.

For example, a child may choose a yellow overlay and benefit from blue lenses. The colour of the lenses can only be assessed by optometrists or orthoptists who use the Intuitive Colorimeter 0, or by the use of a very large number of coloured trial lenses. Other methods of selecting coloured lenses may be less likely to select the optimal colour. Why are glasses a different colour from overlays? When you wear glasses everything you see is coloured, but you are often unaware of the coloration because you adapt to it and make allowances for it.

Example, the colour of light from a normal household light bulb is very yellow in comparison to daylight, but you are never aware of this. When you use an overlay only part of what you see is coloured and the eyes are adapted to white light. The way that the brain processes what you see in the two circumstances is very different.

What is the best method for combining overlays? The best method is that which most efficiently covers the largest number of possible colours. The Intuitive Overlays copyright used in - recent research 4 were scientifically developed so that similar colours can be combined two at a time in a simple yet thorough way 6. If these overlays are used and all suggested combinations are tried, a wide range of colours will have been efficiently and systematically sampled.

How reliable is the choice of overlay colour? When tested a second time, individuals may sometimes choose a different colour, but it is usually a similar colour.

The choice of colour may appear random, but it is not! What does one do if a child reports a large range of colours beneficial, but cannot make a consistent choice? Beneficial colours should be compared side by side. If the choice remains unreliable, then one of the chosen colours should be given a trial for a period of a week, followed by one of the other colours. Alternatively, the Wilkins Rate of Reading Test can be used.

Do children change their preferred colour? Children sometimes seem to change their preferred colour. The precise reason for this is not known.

Does it matter if the child still sees areas of white page around the overlay? Areas of white page may well affect the choice of colour. The conditions of the test should resemble those under which the overlay will be used. If you experience challenges with writing, math, depth perception, night driving, or the environment, colored filters worn as glasses will be your best treatment option.

However, colored overlays are an important first step in determining whether the Irlen Method can work for you and provide your first experience with relief. Our Irlen Colored Overlays are now available in three different forms to best fit your daily needs:.

Our digital overlay provides you with the flexibility to select and adjust your color for maximum comfort, and overlays your device no matter what app or function you are using. Performance is rarely abnormal on these tests, however. Benefits are common in children whose binocular vision is quite normal. There remains the possibility that colour may be affecting accommodation focussing of the eyes. Evans et al b studied children who benefited from coloured glasses and noted that the beneficial colour was not such as to reduce any residual refractive error.

Simmers et al measured changes in focussing and found them normal. However, when steady focus had to be maintained they found abnormal fluctuations.

These fluctuations were reduced by the prescribed coloured lenses, but also by grey lenses of similar density. These findings are preliminary, but important in that they reliably demonstrate for the first time a physiological abnormality in these children. The abnormality may be a correlate of visual stress, rather than a component of a causal mechanism for the benefits of coloured glasses. Lightstone et al noted that the colour optimal for use in lenses was not the same as that optimal in overlays, which suggests that any focussing mechanism is unlikely to be a sufficient explanation.

As yet, no retinal deficit has been demonstrated in individuals who benefit from overlays. Deficits of colour vision on clinical tests are no more prevalent than would be expected on the basis of age and gender Evans et al , a.

There are no obvious optometric or orthoptic deficits on clinical testing Scott et al , in preparation. Livingstone et al and Lovegrove et al have demonstrated that individuals with dyslexia have an impairment of visual function that affects the visibility of changes in the visual world magnocellular deficit The impairment has been widely proposed as providing a basis for the benefits from colour partly on the basis of the suppression of the activity of the magnocellular cells in the presence of red light, first noted by Wiesel and Hubel in and subsequently widely confirmed.

This hypothesis is unable to explain the large individual differences in optimal therapeutic colours demonstrated in these studies and under double-masked conditions by Wilkins et al in Wilkins has proposed an alternative speculative explanation which draws together aspects of visual stress in epilepsy, migraine and discomfort when reading.

The children who benefit from coloured filters are twice as likely to have migraine in the family as those who show no benefit Maclachlan et al Individuals with migraine are thought to have a hyperexcitable visual cortex Aurora and Welch, and this may explain their susceptibility to photophobia, given that the visual stimuli that provoke photophobia are very similar to those that trigger seizures in patients with photosensitive epilepsy Wilkins et al Gratings that can provoke photosensitive seizures interfere with normal perception Chronicle and Wilkins, , particularly in individuals with migraine Chronicle et al , ; Chronicle and Wilkins, Depending upon its layout, text can resemble a pattern of stripes with epileptogenic characteristics, and when it does it can provoke distortions similar to those provoked by such stripes Wilkins and Nimmo -Smith, ; Wilkins, Changing the colour of a visual stimulus must inevitably alter the distribution of normal neuronal activity within the visual cortex.

Zeki a ,b has measured the spectral sensitivity functions of neurons in visual areas V3 and V5, areas that code for space and movement. The functions show large differences between neurons, particularly in the short wavelength end of the visible spectrum.

Similar differences are likely to exist for neurons in other visual areas. Perhaps comfortable colours reduce strong excitation in hyperexcitable regions, reducing an inappropriate spread of excitation. Such an explanation is admittedly speculative, but does have the advantage of the predicting the benefits of coloured lenses recently observed in migraine and photosensitive epilepsy Wilkins et al.

Aurora , S. Brain excitability in migraine: evidence from transcranial magnetic stimulation studies. Jun 11 3 Bouldoukian , J. Chronicle E. Colour and visual discomfort in migraineurs. Lancet, , Chronicle, E. Gratings that induce distortions mask superimposed targets. Perception, 25 , Thresholds for detection of a target against a background grating suggest visual dysfunction in migraine with aura but not migraine without aura.

Cephalagia , 15 , Evans, B. Busby, A. A preliminary investigation into the aetiology of Meares-Irlen syndrome.

Ophthalmic and Physiological Optics, 16 4 , Optometric characteristics of children with reading difficulties who report a benefit from coloured filters. In: C. Dickinson, I. Murray, and D. London ; Taylor and Francis, pp. Jeanes , R. Prolonged use of coloured overlays for classroom reading. British Journal of Psychology, 88 , Lehmkule , S.

Neurological basis of visual processes in reading. Willows, R. Corcos ed. Livingstone, M. Physiological and anatomical evidence for a magnocellular defect in developmental dyslexia. Lovegrove , W. A theoretical and experimental case for a residual deficit in specific reading disability. Cognitive Neuropsychology , 3 , Lightstone , A. Both coloured overlays and coloured lenses can improve reading fluency, but their optimal chromaticities differ.

Ophthalmic and Physiological Optics, 91 4 , Maclachlan, A. Yale, S.