Visual reading problems & Coloured Filters

Visual Problems in Dyslexia- Wobbles

Recent research by the DRT and others has suggested that magnocellular (M-) neurones in the brain play an important role in reading and that M- deficits contribute powerfully to reading problems because the M- system is so crucial for directing visual and auditory attention and eye movements to letter and word features and sounds during reading. These nerve cells are called magnocells because of their noticeably large size; this equips them for rapid signalling, timing events and tracking changes. Anatomical, electrophysiological, psychophysical and brain imaging studies all concur that these nerve cells develop slightly abnormally in dyslexic brains.

The main aim of DRT research into visual and auditory weaknesses in poor readers is to develop treatments that will help them, and to prove by properly controlled trials that they work. We have shown that simple treatments such as viewing text through blue or yellow coloured filters, musical training or eating oily fish, really can help children to learn to read.

Then we aim to persuade Policy makers to make these treatments available to all those with reading problems. If we can do these things we should be able to save thousands of children from the loss of self confidence, shame and misery that reading failure so often brings in its train.


So it is really amazing that 4/5ths of all children actually do learn to read quite fluently, and perhaps it is not so surprising that 1/5th leave school unable to read properly. But this is not only a most potent cause of misery, but also an appalling waste which costs the country £2 billion per year in terms of additional teaching, truancy, school exclusion, unemployment, drug addiction and crime.


Prof John Stein, a medical tutor at Magdalen College Oxford, was introduced to children's reading problems by a very wise orthoptist, Sue Fowler. She had found that, like patients with cerebellar damage whom John had been researching for many years, many could not hold their eyes steady, so that letters seemed to wobble, move around and cross over each other. These wobbles represent a mild form of oscillopsia that is often seen in cerebellar patients. You can't visually identify letters and their order if they're moving around all the time (try reading when very drunk!).

In cerebellar patients he had shown that their unstable vision was due to damage to large nerve cells in the brain, known as visual magnocells, that are specialised for detecting movement. When these magnocells are not working properly the servo system that keeps your eyes fixed on a letter fails, and so the letters appear to move around. So with Sue he set up a clinic to investigate whether children's visual reading problems were due to the same cause. Sue & John were able to show that many dyslexics do indeed have impaired development of these magnocells (though not as seriously as in cerebellar disease), because the cells move into the wrong positions and make the wrong con-nections during the early development of the brain; this explains why many dyslexics' vision is so unstable. They found that in everybody the quality of their visual magnocellular function plays a very important role in how well they can acquire the visual skills required for reading. Even though letters don't move, the eyes do; so a person's sensitivity to moving visual stimuli predicts his skill at identifying the visual order of letters and the visual form of words - their 'orthography'.

Coloured Filters
Olive Meares in Australia was the first to suggest that children with visual reading difficulties may see print more easily through certain coloured filters. This was taken up commercially in the USA and UK. But these systems require that each child is individually prescribed a special colour; so the glasses tend to cost a lot! However since the visual magnocellular system is mainly influenced by just yellow and blue light, John & Sue argued that these are the only two colours that will really make much difference.

Skiers in a 'whiteout' know that yellow goggles can make things look brighter and more contrasty. This is because yellow enhances their visual magno-cellular input. Thus we've recently confirmed in a small double blind, randomised control, trial that in suitable children simple and cheap deep yellow filters can help them to improve their reading very significantly. We are carrying out a much larger trial now to try to convince the sceptics.


Alertness & Arousal

Melanopsin retinal ganglion cells and their projections (melanopsin RGCs)
Photosensitive pigments located in the retina translate light into electrical activity. Most photopigments are located in the retinal rods and cones, rather than in ganglion cells. But recently it was discovered that some retinal ganglion cells are themselves photosensitive, the melanopsin RGCs. The melanopsin responds most strongly to deep blue light (475 and 485 nm). These RGCs are spread diffusely forming a photoreceptive net that samples the whole retina. They project strongly to the 'biological clock', the suprachiasmatic nucleus (SCN) in the hypothalamus, which controls the body's diurnal rhythms. This retinohypothalamic tract (RHT) input synchronises this clock to seasonally changing day length to maintain the correct phase relationship between daylight and the biological rhythms of endocrine, physiological and cognitive activity.

The effects of blue on dyslexia

The effects of blue light on sleep

The effects of blue light on migraine

Light and Seasonal Affective Disorder

Fluorescent Lighting