CVI introduction video

Visual Processing- sensory processing- cortical visual impairment- cerebral visual impairment

CVI is a term to describe the visual difficulties caused by damage to the parts of the brain that process vision. CVI is an abbreviation for 'cerebral vision impairment'. In some literature, the term 'cortical vision impairment' is used to refer to the same visual difficulties. Some professionals prefer the term 'sensory processing' to refer to processing vision as well as sound, or simply 'visual processing' to refer to processing vision. To add to confusion, the abbreviation CVI is also used for 'certificate of vision impairment'. Terminology can be confusing and overwhelming. What is more constructive than dwelling on the terminology, is to focus on identifying and addressing the visual difficulties. Cirta Tooth offers specialist assessments to support you in that process.

Reading difficulties- Dyslexia- Alexia- Visual stress

Reading difficulties can be caused by different underlying problems:

In dyslexia, a person has difficulty identifying speech sounds and learning how these relate to letters and words, also known as phonological processing. It refers to a neurodevelopmental disorder, rather than an acquired reading difficulty.

However, before a diagnosis of dyslexia is made, one needs to rule out other possible causes for their reading difficulties, for example a hearing or a sight impairment.

Eye conditions can render it difficult to read when the print is too small or too pale for a person to see due to reduced vision or contrast sensitivity. Some eye conditions cause patchy vision, tunnel vision or loss of vision in the middle, which means that letters or words are missing. These issues affect reading speed and text navigation.

Difficulties with text navigation can also be caused by eye movement control issues and impaired depth perception. Letters may appear to jump, move or multiply (double vision).

Finally, text navigation can also be affected by a number of visual processing disorders. For example, a person who is only able to see things on one side, may have trouble seeing the next word or the beginning of the next line. A person who is unable to process vision when there is too much crowding of the text will find it difficult to navigate through the text and may also have difficulties copying texts from other sources into their jotter.

Word and symbol recognition can be another cause for problems with reading. If these issues develop after an acquired cerebral lesion later in life, the term alexia is commonly used to describe the inability to comprehend written or printed words or characters such as musical notes.

In a CVI assessment, the focus is on reading difficulties related to visual issues as described above. When the underlying visual difficulty is identified, appropriate strategies can be offered to support literacy development in a child with CVI. In adults, strategies can be taught to support everyday reading tasks.

The term ‘visual stress’ is particularly popular among optometrists who prescribe coloured overlays to improve reading performance.

Autism, ADHD, Neuro-diversity

Autsim, ADHD and neuro-diversity can often mask CVI. This is due to the overlap in typical behaviours in these conditions. For example, a child who is unable to recognise faces and facial expressions might avoid social situations and a child who struggles with clutter needs to line up their toys as a strategy for finding what they need and may not be able to find their friends when they are standing in a group.

This publication by Chokron et al. (2020) explains the inter-relationships between CVI, autism and intellectual disability very well: