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Light & Irlen Syndrome

The Relationship Between Light and Irlen Syndrome

White light (including sunlight) contains all of the colours of the rainbow. These colours form what we know as the VISIBLE SPECTRUM of light. Our brain “sees” (perceives) light as waves of energy and each colour has a different energy from the others. When light strikes a solid surface, it is reflected, much like the waves in the ocean are reflected when they strike the rocks. A white surface reflects all of the light that strikes it, but coloured surfaces absorb some colours and reflect the rest.

The diagrams below show the visible spectrum of light as it appears to us in the rainbow and also how each colour travels through the air. Our brain learns to recognize the colours by the amount of energy that they contain. The diagram shows that the Violet colour has the highest energy and the Red has the lowest energy.

Note that the Dark Red wavelengths have lower energy than the Indigo. This is shown by the different wavelengths of each colour. Light travels through air in waves of energy and the diagram shows us that there are ten Violet wave peaks but only six Dark Red wave peaks in the same space. This means that the Violet colour has more energy than the Dark Red.

People who have Irlen Syndrome are sensitive to particular wavelengths of light (colours) and these interfere with how their brain processes visual information.

Light & Irlen Syndrome - Dyslexia & Irlen Syndrome - Irlen Diagnostic Clinic
Light & Irlen Syndrome - Dyslexia & Irlen Syndrome - Irlen Diagnostic Clinic

In the diagrams below, a box is used to demonstrate how the colours of the rainbow can interfere with how people with Irlen Syndrome perceive what they are looking at. Remember that light is reflected whenever it hits a solid surface.


When we look at a white surface, all of the colours of the rainbow (the visible spectrum) are mixed up in the white light that we see and all of the colours are reflected into our eyes. Our eyes send messages to our brain and our brain processes (“works out”) what we are looking at. In this diagram, there is no interference from the colours so this person can see the box clearly. This is how it would appear to a person without Irlen Syndrome.

Light & Irlen Syndrome - Irlen Syndrome

Messages to our brain are processed correctly and we “see” a box


For people with Irlen Syndrome, some of the colours of the rainbow cause problems with the messages that their eyes send to their brain. This interferes with how their brain processes the visual information being

Light & Irlen Syndrome - Irlen Syndrome

The message to the brain are not working properly so the box does not look like a box.


If we block those colours of the rainbow that cause problems with the messages, the messages can function normally again, and the brain can process the information correctly. In the example below, a red coloured overlay has been used over the box and this is preventing the Blue and the Indigo colours from being transmitted to the eyes, and this allows the messages to work properly.

Light & Irlen Syndrome - Irlen Syndrome

Blue and Indigo colours have been removed before they leave the box

The messages to the brain are working properly so the box looks like a box.



In the next diagram, Irlen Spectral Filters are used to “filter out” those wavelengths of light instead of an overlay. In this case, all colours are reflected from the box, but the lenses refract (bend) those particular colours and prevent them from entering the eyes.

Light & Irlen Syndrome - Irlen Syndrome

The messages to the brain are working properly so the box looks like a box.
The Blue and Indigo colours are not removed until they reach the Irlen filters. They are then prevented from entering the eyes.


White surfaces reflect all of the wavelengths of light (the spectrum of colours) and for people with Irlen Syndrome, some of these wavelengths of light interfere with the way in which their brain can process  the visual signals that come from the eyes. Even without Irlen lenses or overlays, it is possible to make it easier for people to read and write if we use coloured paper instead of white. For example, Blue paper absorbs all colours other than Blue, and so it is only the blue wavelength of light that is reflected into the eyes. So, if the person is sensitive to colours other than blue, blue paper will help them to see the words more clearly, write the words more clearly and enable them to concentrate on their work more efficiently. The same applies to all other colours. Some people have difficulty reading on Blue paper, but many people can read better on blue paper. That is where the specificity of the colours comes in. Everyone who has Irlen is sensitive to particular colours or combinations of colours, so the selection of the best overlay and Irlen lenses for them results in the specific colour or combinations of colours that works best for them alone. 

Many students find it much easier to do their work on coloured paper instead of white paper. In order to help them, we have coloured exercise books printed up especially for those students who find it easier to concentrate on coloured paper. These exercise books are provided as 8mm lines, 12mm lines, 5mm grid, 10mm grid, and handwriting lines.