Visual Processing Disorder and Dyslexia

Visual processing disorder refers to a reduced ability to make sense of visual information. This is different to problems involving sight or sharpness of vision. Instead, difficulties with visual processing affect how visual information is interpreted. A person with visual processing disorder may have difficulties discriminating foreground from background, forms, size, and position in space, despite having 20/20 vision. They may be unable to synthesise and analyse visually presented information accurately or fast enough. The eyes look and the brain sees.


Lateral Geniculate nuclei
Basis of Dyslexia

Dyslexia is a brain-based disorder that makes it difficult for people to read, write and spell. Dyslexia is associated with varying degrees of difficulty detecting fine movement from hues and phonetic (word sound) differentiation. For all sighted people, tiny eye-movements (called saccades) scan words when reading, but in a person with Dyslexia the brain makes the stream of pictures and words move around. This makes reading a challenge.

According to research by Prof. John Stein and his team at Oxford University, Dyslexia is due to dysfunction in a part of the brain called the lateral and ventral geniculate nuclei of the thalamus. People with dyslexia can be fussy eaters and/or have a relatively poor nutrient uptake, which affects the integrity of their brain structure. 


Treatment of Dyslexia

BNC has a two-part approach treating learning difficulties. Each approach is highly effective in improving the symptoms of dyslexia and other learning difficulties. When both approaches are used together, we see the best outcomes. Therefore, the follows treatments are recommended:

  • An individualised nutrient supplementation program is recommended to promote healthy brain cells and brain structures. John Stein's team and Alex Richardson at Oxford University have published several studies demonstrating that Omega 3 (from fish oils), along with the associated nutrients, can help treat Dyslexia and other learning disabilities.
  • Neurotherapy can reduce the excessive slow brainwave activity associated with learning difficulties through promoting connectivity between the brain structures essential for learning and the acquisition of knowledge. Through stimulating neuroplasticity in this way, we see improvements in brain function and attention.

Visual Motion Detection in Dyslexia

Nerve endings (rods and cones) at the back of the retina relay visual information to the lateral geniculate body of the Thalamus. These visual signals are processed by two types of cells:

  • Parvocellular pathways (small cell bodies) concerned mostly with colour hues and contrast.
  • Magnocellular pathways (large cell bodies) concerned mostly with movement detection.

Research indicates that in Dyslexia these cell bodies may not differentiate adequately. Consequently, people with Dyslexia have problems associated with an overlapping of these two pathways. There is growing evidence that issues with parvocellular and magnocellular pathways are responsible for visual motion detection and other learning difficulties.

  • The white page of a book (where the background contains all colours and hues) can overwhelm Parvocellular (P) cells and mistakenly activate Magnocellular (M) cells.
  • Words seem to move on the page.
  • A page of text appears as blocks of blurred black (text) with rivers of white in between.
  • The orientation of letters and text keeps changing e.g., "d and b" become difficult to differentiate. As a result, someone with dyslexia may reverse these letters.
  • A coloured visual filter (Irlen lenses) can help some people with dyslexia through reducing the overwhelming colour that leads to the scrambling of letter pathways.
  • People with Dyslexia can find it difficult to visually track text on a page, since this skill requires fine eye movements and very tight eye muscle control.
  • The cerebellum, a part of the brain that plans our movements a fraction of a second before we execute them, orchestrates fine motor control. Thus, people with dyslexia often suffer from dyspraxia (difficulties with fine and/or gross motor control (e.g., have an awkward gait).

Other Types of Visual Processing Disorders

Visual processing disorders, which are NOT related to the ability to see clearly, involve difficulties understanding visual information such as movement, spatial relationships, form, or direction.

Visual processing disorders, together with Central Auditory Processing Disorders, frequently result in dyslexia and can undermine academic performance.

There are other visual processing difficulties which cause learning difficulties that should be treated. If unaddressed, the child is likely to become bored at school and may refuse to complete their schoolwork (and homework). As a result, they risk falling behind the school curriculum.

1. Visual Closure

Difficulties in visual closure are often observed in school activities where the child is asked to identify, or complete, a drawing of a human face. It can become apparent in such tasks that a single missing facial feature (a nose, eye, mouth) makes the face unrecognisable to the child.

2. Visual-Spatial Relationships

The ability to perceive the location of objects in relationship to others is critical for reading, maths, and handwriting since these skills involve recognising and perceiving the direction between different symbols and telling the difference between similar shapes. Children who have difficulties with spatial relationships may appear unusually clumsy or accident prone, refuse to read, or have poor handwriting (dysgraphia).

3. Form Discrimination

Whether differentiating the shape of a circle from a square, or the letter b from d, the ability to perceive the shapes of objects and pictures is an important skill for developing children. There are few academic activities that do not require engagement in form discrimination. The most obvious classroom activity requiring this skill is reading. Learning the letters of the alphabet, syllables, and words is a challenge if it is a struggle to perceive their form.

4. Visual Discrimination

Visual discrimination allows us to discriminate similar objects from each other, tell where one ends and another begins, and recognise objects and symbols when only part of them can be seen (or they are fuzzy). People who have visual discrimination disorders tend to mix up letters or numbers and have difficulty reading or scanning pictures for information.

5. Visual Memory

Visual memory is a critical academic skill that allows us to recognise objects and remember letters, numbers, symbols, words, and pictures. In partial visual agnosia (visual access problems), what is learned on day 1, is ‘forgotten’ on day 2, but may be remembered again on day 3.

6. Visual Integration

Some people have difficulty perceiving or integrating the relationship between an object or symbol in its entirety, or in its component parts. Some children perceive only pieces of the object, while others are only able to see the whole. Children with a visual integration disorder have difficulties learning to read (dyslexia) and recognise symbols.

7. Visual Pursuit & Tracking

The ability to track moving objects, and the ability to keep a stable visual image when the head or eyes are in motion, is part of the ocular-vestibular system. People who have visual pursuit disorders have difficulty watching moving objects (e.g., on videos or computer programs), difficulty copying from a board, and difficulty reading.

Visual Processing Assessment

A Behavioural Optometrist working in conjunction with BNC carries out assessments for Visual Processing Disorder. It is important to identify the specific visual dysfunctions involved, so that they can be addressed using a combination of the most effective interventions.

Visual Processing Interventions

A successful intervention needs to be specific to the visual processing problem. Interventions must be designed for the unique individual based on standardised tests. Typically, interventions involve daily eye exercises, working with specific computer programs, Neurotherapy, physical games and activities, and academic adjustment plans. Our Behavioural Optometrist will make recommendations for optometric exercises and a BNC clinician may recommend nutritional supplementation and/or Neurotherapy. Neurotherapy is advised in instances where retraining the relevant brain associated with visual processing issues is the best course of action (identified through QEEG brain mapping).

Light through the eye
Light through the eye