This article explores cerebral visual impairment (CVI), a brain-based visual processing disorder in children, often resulting from birth trauma or acquired brain injuries.

CVI can vary in severity, impacting a child’s ability to communicate, navigate, perform daily activities, and affecting their future independence, employment opportunities, and overall quality of life.

As recognition and diagnosis improve, understanding the wide-ranging effects of CVI becomes increasingly critical for providing appropriate support and interventions both in clinical and legal areas.

CVI is a disorder of visual processing which is common in children with brain injuries, including those due to birth trauma or acquired injury; of which the cause of the visual difficulties lies within the brain and visual pathways, rather than being an abnormality of the eye itself. It is now recognised as the most frequent cause of visual impairment in children across high-income countries.

CVI results from damage to the visual cortex (in the occipital lobes) and visual pathways within the brain (including the optic chiasm, optic tracts, lateral geniculate bodies, and optic radiations) and is typically seen in children with abnormalities seen on brain MRI scan in these areas. (It is recognised however that milder forms of CVI can occur in the presence of a normal brain scan (Sakki et al 2021).)

The most common underlying cause of CVI is hypoxic ischaemic encephalopathy, although other causes include traumatic brain injury, prematurity, seizures, hydrocephalus, infections and genetic/metabolic conditions (Chang and Borchert 2020). CVI is frequently seen in association with cerebral palsy and intellectual impairment.

All this means that children with CVI can experience a range of difficulties – from mild challenges to severe impairments – with CVI having a spectrum of effects on visual function, from mild visual difficulties to profound visual impairment and blindness and can affect the ability of a child to communicate, navigate, perform activities of daily living, as well effecting future independence, employment and driving.

Thankfully, CVI is becoming more frequently diagnosed due to better prognosis of children with premature birth or brain injuries early in life and also better recognition and understanding of the condition.

There is wide variation in the effect of CVI on visual function, depending on the severity and site of the brain damage. Visual function can be affected in many ways in CVI, for example;

Visual Field Defects: These can vary from hemianopia (loss of half the visual field) to inferior field defects, making it challenging for children to navigate their environment without tripping over objects.

Difficulty with Complex Visual Scenes: They may struggle to interpret cluttered backgrounds and often prefer looking at objects at close range.

Recognition Issues: Many children have difficulty recognizing faces or objects, which can affect social interactions.

Impaired Depth and Motion Perception: This makes everyday activities, such as going down stairs or catching a moving ball, particularly challenging.

These visual difficulties significantly impact a child’s ability to communicate, perform daily tasks, and interact with others, affecting their long-term independence, learning, and future employment opportunities.

Visual processing has been divided into dorsal and ventral processing within the brain (RCOphth 2023).

Children with Ventral stream issues may have issues with visual memory such recognising people and objects, and route finding and orientation. They may mistake strangers for parents and become easily lost.

Dorsal stream issues result in impaired ability to see more than one object at a time and impaired movement perception and visually guided movement. Effected children may not be able to see a moving object such as a ball or car, and may be unable to reach for objects or navigate steps or kerbs.
Such challenges can make daily life more difficult, explaining why children with CVI often appear clumsy or inattentive.

CVI can be accompanied by other ocular issues. Parents or carers often report better visual function in one area of the visual field, or that the child does not see things in one part of their visual field.

Visual field defects in CVI are variable and include hemianopia (loss of half of the visual field), or inferior visual field defects or inferior visual field neglect (leading to a child missing things in their lower visual field, and tripping over things on the floor for example). Formal visual field testing is not usually reliable, in fully able children, until at least the age of 10 and visual field testing even to confrontation may be of limited benefit in children with learning difficulties and cerebral palsy.

It is also becoming increasingly recognised that CVI can occur in children with previous brain injury who have normal vision and only subtle functional issues. Some cases of CVI remain undiagnosed as clinicians and carers may not attribute the child’s functional issues to a visual processing disorder.

The associated issues include:

Squint is very common in children with CVI, particularly divergent squint (exotropia, when the eyes turn outwards). Esotropia (when the eyes turn inwards) and vertical deviations can also be seen. The population incidence of squint is 1-2% but the incidence is as high as 50% in children with cerebral palsy. Surgery can be considered for squint in children with CVI if there are cosmetic issues.

Nystagmus (a rapid involuntary to and fro movement of the eyes) can also occur in children with CVI. There is often co-existent refractive error and appropriate glasses should be prescribed, particularly during the period of visual development up to approximately age 7-8 years.

Amblyopia (when the vision in one eye is reduced compared to the fellow eye) can occur in children with CVI and treatment for amblyopia (patching or atropine penalisation of the better eye to promote visual development in the amblyopic eye) should be considered. Binocular function (the ability to use both eyes together to get 3-D vision, stereopsis) is often absent or reduced in CVI, particularly when there is a squint or amblyopia. Loss of binocular function can lead to clumsiness, lack of manual dexterity and lack of judgment of distance.

The eye itself is not the cause of the visual processing issue and so the ocular examination is usually normal. Children with CVI and severe brain injuries may however have optic atrophy, and it is recognised that CVI can also occur in the presence of co-existent ophthalmic pathology.

Children with early brain injuries, either through birth trauma or other causes such meningitis, seizures or complications of surgery, often have very poor visual behaviour immediately following the insult but may show some improvement for several months or years.

Often the effect of CVI on a child’s visual function is not apparent until the child recovers and starts to return to activities and independence. Visual difficulties may become more apparent when the child gets older and attempts more challenging tasks.

The diagnosis of CVI is not well established, but the recent medical literature is attempting to provide clarity and improve understanding of this area.

It has been suggested that three criteria should be met for a diagnosis of CVI to be made (Pilling et al 2022) –

Known history of a pre or perinatal event causing brain injury and abnormality,

Observations from parents or caregivers about functional visual difficulties in everyday life,

Objective evidence of visual difficulties on clinical examination.

Medico-Legal Aspects of Paediatric Cerebral Visual Impairment.

Because CVI symptoms can be subtle and vary with fatigue or environment, questionnaires are often used to assess visual functioning and determine if symptoms of abnormal visual processing are present, pointing towards a diagnosis of CVI (Chang and Borcherht 2020). There are many questionnaires in the literature, and potential CVI screening questions include:

1. Does your child have variable visual function which is better when they are well rested or in a familiar environment?
2. Does your child have problems seeing things which are moving fast? (Do they have difficulty in seeing or catching a ball, and find it hard to judge speed and distance?)
3. Does your child have problems going down steps or stairs?
4. Does your child have problems picking something out in the distance?
5. Does your child have trouble picking out an object (T shirt/toy) from a cluttered pile of objects or struggle in busy environments?
6. Does your child have trouble copying simple shapes or words?
7. Does your child have difficulty recognising faces?

These questions can be invaluable in uncovering functional visual difficulties that might otherwise go unnoticed.

When reviewing patients, children who have normal visual acuity and no demonstrable visual field defect may need referral for psychometric testing by those with appropriate expertise (for example a neurodevelopmental paediatrician, Qualified teacher for Visual Impairment QTVI or an educational psychologist) to demonstrate verifiable visual dysfunction to help to confirm the diagnosis of CVI.

It is important to also highlight that a study classifying CVI into subgroups identified 3 groups; A1, A2 and B, with group A1 having normal visual acuity but apparent dorsal stream difficulty and group B having more severe visual impairment (Sakki et al 2021). It is often very difficult to quantify vision in children with CVI and co-existent learning difficulties, due to concentration and learning difficulties.

Currently, there’s no proven treatment to improve visual function in CVI directly. However, interventions focus on maximizing the child’s existing visual abilities through environmental modifications, such as reducing clutter, simplifying backgrounds and highlighting edges, altering the position of the visual target and presenting objects on the favoured side of vision.

Treatments such as vision stimulation training and electrical stimulation have poor quality evidence to support them and these are not in routine clinical use (Delay et al 2022). Use of technology such as eye gaze technology may be possible in some children with CVI but its use may be limited in others due to concentration, learning difficulties and consistency.

The most crucial area of support is the role of the sensory support team/specialist teacher for the visual impaired. They support children with CVI through school, providing appropriate educational material, and advice to teachers and parents.

Secondly, occupational therapy, adaptive technology experts and motility and orientation training may be helpful for some children with CVI.

From a medico-legal perspective, understanding CVI’s impact is crucial, especially in cases of personal injury or clinical negligence. The condition’s effects on a child’s independence, learning, and future employment must be thoroughly documented to ensure appropriate support and compensation.

In conclusion, CVI is a complex and evolving area of paediatric ophthalmology becoming increasingly recognised and understood as a significant cause of functional impairment in children. Increased awareness and understanding will lead to better support and outcomes for children affected by this challenging condition.

If you need further insights into CVI in a medico-legal context, feel free to reach out.

Dr. Jane Ashworth graduated from the University of Oxford in 1992 and began her career as an Ophthalmologist at Manchester Royal Eye Hospital (MREH) in 1993.

She earned a PhD from the University of Manchester in 1999 and completed Fellowships in paediatric ophthalmology at Manchester and in strabismus at Walton Hospital, Liverpool.

In January 2007, she joined the paediatric ophthalmology department at MREH as a consultant.

To request her CV or for any medico-legal matters she can be reached at janeashworth@inneg.co.uk

• Visual function subtyping in children with early-onset cerebral visual impairment. Sakki H, Bowman R, Sargent J, Kukadia R, Dale N.Dev Med Child Neurol. 2021 Mar;63(3):303-312.
• Advances in the evaluation and management of cortical/cerebral visual impairment in children. Chang MY, Borchert MS.Surv Ophthalmol. 2020 Nov-Dec;65(6):708-724.
• The Role of the eye clinic in Clinical Assessment, Investigation, Diagnosis and Initial Management of Paediatric Cerebral Visual Impairment. The Royal College of Ophthalmologists Concise Practice Points 2023.
• The Role of the Eye Clinic in Clinical assessment, investigation, diagnosis and initial management of cerebral visual impairment: a consensus practice guide. Pilling RF, Allen L, Bowman R, Ravenscroft J, Saunders KJ, Williams C.Eye (Lond). 2023 Jul;37(10):1958-1965.
• Interventions for children with cerebral visual impairment: A scoping review Ariana Delay 1 2, Melissa Rice 3 4, Elsie Bush 2, Karen Harpster Dev Med Child Neurol 2023 Apr;65(4):469-478.