Abstract Dyslexia is more than just difficulty with translat-ing letters into sounds. Many dyslexics have problems with clearly seeing letters and their order. These difficulties may be caused by abnormal development of their visual “magnocellular”(M) nerve cells; these mediate the ability to rapidly identify letters and their order because they control visual guidance of attention and of eye fixations. Evidence for M cell impairment has been demonstrated at all levels of the visual system: in the retina, in the lateral geniculate nucleus, in the primary visual cortex and throughout the dorsal visuomotor“where”pathway forward from the visual cortex to the posterior parietal and prefrontal cortices. This abnor-mality destabilises visual perception; hence, its severity in individuals correlates with their reading deficit. Treatments that facilitateM function, such as viewing text through yellow or blue filters, can greatly increase reading progress in chil-dren with visual reading problems. M weakness may be caused by genetic vulnerability, which can disturb orderly migration of cortical neurones during development or possibly reduce uptake of omega-3 fatty acids, which are usually obtained from fish oils in the diet. For example, M cell membranes require replenishment of the omega-3 docosahexaenoic acid to maintain their rapid responses. Hence, supplementing some dyslexics’ diets with DHA can greatly improve their M function and their reading. KeywordsVisual dyslexia. Magnocellular neurons. Dorsal visuomotor pathway.Visual attention. Coloured filters. Omega-3s. Genetic basis