Why Reading Is About More Than Seeing Letters
Why can someone see perfectly well, yet still struggle to read? The answer lies in how the brain processes visual information and connects it with language.
Reading requires much more than recognising letters. Our eyes move rapidly across a page, while the brain must identify letters, establish their order, recognise familiar words and connect written information with sounds and meaning. These processes need to happen accurately and almost automatically for reading to become fluent.
For some people with dyslexia, differences in visual processing may contribute to the difficulties they experience. But dyslexia is not simply a problem with eyesight, and understanding it requires looking at several interacting systems.
How does the brain process what we see?
Our visual system uses three major pathways to process different kinds of information.
The magnocellular (M) pathway is particularly responsive to movement and rapid visual changes. It contributes to visual attention, spatial processing and the coordination of eye movements.
The parvocellular (P) pathway specialises in fine visual detail, helping us distinguish shapes, letters and visual patterns.
The koniocellular (K) pathway contributes to colour processing, particularly blue–yellow differences, and has connections with areas of the brain involved in movement and visual attention.
These pathways contribute to broader visual functions that help us recognise what something is, establish where it is and determine how to respond to it.
Reading depends on all these abilities. We must recognise individual letters, identify their positions within words and direct our eyes and attention accurately across lines of text.
Research by Stein and Walsh (1997) proposed that differences in magnocellular processing might contribute to reading difficulties in some people with dyslexia.
If a child or adult continues to struggle with reading, spelling or writing despite appropriate teaching and practice, a comprehensive assessment can help identify whether dyslexia or another specific learning difficulty is contributing. At INPSYGHT, assessment focuses on understanding the pattern of difficulties rather than assuming that everyone struggles for the same reason.
What does detecting movement have to do with reading?
One fascinating area of research concerns a region of the brain called V5/MT, which helps us detect visual movement.
Researchers can measure motion sensitivity using computer displays containing moving dots. Some dots move together, while others move randomly. Participants identify the direction of movement, allowing researchers to measure how accurately their brains detect visual motion.
In research I was involved in at Oxford, Talcott, Witton et al. (2000) found that children's visual motion sensitivity was associated with their orthographic reading skills—their developing knowledge of written words and letter patterns.
Interestingly, auditory processing was associated more strongly with phonological skills, which involve recognising and manipulating the sounds within words.
This distinction is important because reading involves both recognising familiar written words and decoding unfamiliar ones.
For example, a child might successfully sound out a new word but struggle to recognise familiar irregular words quickly. Another child might recognise many words by sight but have difficulty decoding unfamiliar words.
These different patterns are precisely why a dyslexia assessment should examine more than reading accuracy alone. Understanding decoding, reading fluency, spelling, phonological processing and broader cognitive abilities can help identify the support that will be most useful.
Why do some people say that words move on the page?
Some people with reading difficulties describe letters as blurring, shimmering, moving or appearing unstable. Others experience eyestrain, headaches or difficulty keeping their place while reading.
These symptoms are not experienced by everyone with dyslexia, and they do not establish a diagnosis. Visual symptoms may also require assessment by an appropriately qualified eye-care professional.
However, they were an important focus of research undertaken by myself, under the supervision of Professor John Stein, Dr Sue Fowler and colleagues at Oxford.
As one of the researchers in dyslexia research group at Oxford University, I worked alongside researchers including Professor Stein, Dr Fowler, Joel Talcott, Caroline Witton and Nicola Ray on investigations of visual processing and coloured filters.
Our research investigated whether differences in visual stability, eye coordination and motion processing could help explain some of the experiences reported by people with reading difficulties.
If reading is slow, effortful or uncomfortable, it is worth investigating the wider learning profile rather than assuming the problem is simply visual. An assessment at INPSYGHT can explore reading, spelling, written expression and related cognitive skills, while identifying when additional visual examination may be appropriate.
Can coloured lenses help with dyslexia?
Research into coloured filters developed partly from observations that some individuals experienced changes in visual comfort or stability when reading through different colours. But it turns out that they need to be very specific colours, related to the properties of these parts of the visual system:
Yellow filters were investigated for their potential effects on magnocellular processing, eye coordination and motion sensitivity. Ray, Fowler et al. (2005) reported improvements in several visual measures.
Blue filters were investigated in relation to different visual experiences, particularly the apparent movement or instability of print. The koniocellular pathway's involvement in blue–yellow processing and its connections with motion-sensitive regions such as V5/MT offer possible explanations for colour-related effects.
However, coloured lenses are not an established treatment for dyslexia. Systematic reviews have found insufficient reliable evidence that they consistently improve reading ability (Griffiths, Taylor et al., 2016).
Where someone experiences significant visual discomfort or apparent movement of print, appropriate visual assessment may be useful. But this is not a substitute for investigating the reading and learning difficulties themselves.
What does this mean for a dyslexia assessment?
Perhaps the most important finding from decades of research is that dyslexia does not look the same in everyone.
Some people struggle primarily with phonological decoding—working out unfamiliar words from their sounds. Others have difficulties with reading fluency, recognising familiar written words, spelling or written expression. Many experience a combination of difficulties.
Reading problems can also occur alongside differences in attention, working memory, processing speed or broader language abilities.
A comprehensive assessment therefore needs to go beyond asking whether someone has dyslexia.
At INPSYGHT, assessments of dyslexia and other specific learning difficulties can examine reading accuracy, decoding and fluency; spelling and written expression; phonological and orthographic processing; cognitive abilities; working memory; processing speed; and mathematics where relevant.
The aim is to understand why learning is difficult for this particular child, adolescent or adult, identify their strengths and provide practical recommendations for education, work and everyday life.
Dyslexia is not simply about seeing letters incorrectly. It is about how the brain learns to turn written symbols into meaningful language.
If you or your child are experiencing persistent difficulties with reading, writing, spelling or mathematics, a comprehensive assessment can provide clarity about the underlying difficulties and the support that may help.
References
Hendry, S. H. C., & Reid, R. C. (2000). The koniocellular pathway in primate vision. Annual Review of Neuroscience, 23, 127–153.
Stein, J., & Walsh, V. (1997). To see but not to read; the magnocellular theory of dyslexia. Trends in Neurosciences, 20, 147–152.
Talcott, J. B., Witton, C., et al. (2000). Dynamic sensory sensitivity and children's word decoding skills. Proceedings of the National Academy of Sciences, 97, 2952–2957.
Sincich, L. C., Park, K. F., et al. (2004). Bypassing V1: a direct geniculate input to area MT. Nature Neuroscience, 7, 1123–1128.
Ray, N. J., Fowler, S., et al. (2005). Yellow filters can improve magnocellular function: motion sensitivity, convergence, accommodation, and reading. Annals of the New York Academy of Sciences, 1039, 283–293.
Griffiths, P. G., Taylor, R. H., et al. (2016). The effect of coloured overlays and lenses on reading: a systematic review of the literature. Ophthalmic and Physiological Optics, 36, 519–544.
Stein, J. (2019). The current status of the magnocellular theory of developmental dyslexia. Neuropsychologia, 130, 66–77.