Cerebral Visual Impairment

In order for us to see well, the eyes and the brain need to work together. When light enters the eye, it is focused onto the retina at the back of the eye. The light sensitive cells in the retina convert the light into an electrical signal. These signals travel along the optic nerve, which connects the eye to the brain. The visual processing areas of the brain interpret what we see and guide our movements. This allows us to ‘see’ the world around us.

Cerebral visual impairment is a condition caused by damage to the parts of the brain that process vision. It is not due to any condition affecting the eyeball itself. The word cerebral refers to the affected area of the brain called the cerebrum. The cerebrum is the main part of the brain.

CVI is caused by damage to the parts of the brain which deal with vision.

In children, this damage most commonly occurs before, during or shortly after birth. However, this damage can happen at any age.

Common causes of CVI in babies and young children include:

• being born prematurely
• lack of oxygen or blood supply to the brain
• fluid build-up in the brain (hydrocephalus)
• infection
• injury to the head
• certain genetic conditions.

Causes in older children include:

• complications of heart or brain surgery
• lack of oxygen or blood supply to the brain (such as stroke)
• inflammation of the lining around the brain and spinal cord (meningitis)
• inflammation of the brain (encephalitis).

Causes in adults can include:

• traumatic brain injury
• infection
• stroke
• dementia.

When CVI develops in adults it is called acquired CVI. The symptoms related to acquired CVI may be different to those which develop in childhood. This information will focus on CVI that has occurred before, during or shortly after birth. Further information on acquired CVI can be found on the CVI Scotland’s website.

Children with CVI often have damage to other parts of the brain that can cause other disabilities or health conditions, including:

• developmental disabilities
• cerebral palsy (a brain disorder that causes movement problems)
• epilepsy (a brain disorder that causes seizures)
• hearing loss.

CVI affects how the brain makes sense of what the eyes see. People with CVI can have mild to severe challenges using their vision. Some people have good vision when measured on a letter or picture chart but find it hard to use their vision for everyday tasks. This happens because their brain finds it difficult to process visual information. Some people can also have reduced vision as part of their CVI. This means they will struggle to interpret what they see and have reduced vision.

CVI affects everyone differently and uniquely. It depends on the specific areas of the brain that are damaged.

Over half of the brain is used when processing information from the eyes to see the world around us. Vision uses a lot of brain power, so it can be quite an effort for some people with CVI to see. Someone with severe CVI may only be able to see very basic shapes and might get tired quickly when using their vision. When that happens, their brain may “switch off” their vision for a while.

There are emotional and environmental factors that can make a person with CVI see less well compared to when they are relaxed and in simple surroundings. Factors such as stress and anxiety, background noise, lots of detail, clutter or patterns on an object or in the surroundings, may make it harder for someone with CVI to see.

Someone with CVI might have difficulty with:

• seeing fast moving objects, such as vehicles or people
• seeing while moving, such as walking or moving in a wheelchair
• identifying objects below eye level, such as their feet or kerbs
• recognising a familiar face in a crowd
• adapting to changes in floor surfaces e.g. moving from   carpet to a hard floor
• finding their way around a new place
• finding the start of a line when reading
• finding items in a cluttered environment
• seeing and hearing at the same time, especially when there is a lot of background noise.

Visual field

The visual field is the full area that a person sees. It includes central vision as well as side (peripheral) vision. CVI may cause part of the visual field to be affected. Sometimes CVI will cause part of the lower visual field to be missing, or half of one side of the visual field to be missing (hemianopia).

Visual acuity

Visual acuity is a measurement of central vision and how well detail can be seen. It is measured by how well the letters on the letter chart can be read. CVI can cause difficulty in reading some of the letters on the chart, even when the eyes may be healthy.

Colour vision 

CVI can cause difficulty when trying to name colours, even when the eye can see the colour. It can also affect the ability to make out colours.

Contrast sensitivity 

Contrast sensitivity is a measure of how well an object can be distinguished from its background. For example, a black object on a white background is easier to see than a grey object on a white background. CVI can cause reduced contrast sensitivity, meaning it can be difficult to detect objects from their backgrounds, especially when they are similar in colour or shade. It is possible to have very good visual acuity but have poor contrast sensitivity.

Visual agnosias

Agnosia is a condition where a person has difficulty understanding information from one or more of the senses.

CVI can cause visual agnosia. Visual agnosia happens when the brain is damaged which makes it hard to recognise objects even though they can be seen. This can include difficulty recognising faces and facial expressions. It is not caused by memory problems or a lack of understanding.

Visual agnosias due to CVI affect how the brain processes what is seen. There are many different types. Here are some examples:

• Simultanagnosia: Difficulty seeing more than one or two objects at a time. This can mean only seeing the object being looked at and not being aware of surrounding objects (dorsal simultanagnosia). It can also mean seeing multiple objects but only recognising the one being looked at (ventral simultanagnosia).
• Dyskinetopsia: Difficulty seeing fast moving objects.
• Prosopagnosia: Difficulty recognising faces or familiar people.
• Agnostic Alexia: Difficulty recognising written words, despite being able to write and understand spoken words.

Optic ataxia

Optic ataxia causes difficulty in reaching out to accurately touch an object. This can lead to bumping into things or knocking things over.

Apraxia of gaze

Apraxia of gaze is when someone has difficulty moving their eyes to look at an object when asked to. It’s caused by simultanagnosia, which makes it hard to see multiple objects at the same time.

Dorsal stream dysfunction

When CVI is caused by damage to a part of the brain called the posterior parietal lobes, a type of vision problem called dorsal stream dysfunction may be present.

This can lead to different degrees of simultanagnosia, optic ataxia and apraxia of gaze, and different kinds of challenges such as:

• difficulty seeing more than one object at a time (simultanagnosia)
• difficulty reaching for an object (optic ataxia)
• difficulty with moving the eyes to look at an object (apraxia of gaze).

These challenges happen because the brain is having trouble processing where things are and how to respond to them. Each person with dorsal stream dysfunction can be affected in their own unique way. Often, people with this condition also have trouble seeing things in the lower part of their vision, but not always. The most severe form of dorsal stream dysfunction is called Balint Syndrome.

Light gazing

People with CVI might be drawn to stare towards a light source without meaning to. This isn’t something they can control, and it may even be uncomfortable for them.

Photophobia (light sensitivity)

Some people with CVI are sensitive to light. They may avoid light sources and tire quickly in bright conditions.

Movement

Some people with CVI see moving objects more easily, while others see objects better when they are stationary. This is because the brain processes information about moving and stationary objects separately.

Eye conditions

It is common for people with CVI to have eye conditions which may affect how well they can see.

Some signs of CVI can be hard to diagnose because they can also happen in other conditions. For example, if a person has difficulty recognising faces or understanding facial expressions, it might be caused by poor vision, autism spectrum disorder, prosopagnosia or a combination of these.

To truly understand how CVI is affecting someone, doctors and specialists need to do several tests and closely observe how the person sees and reacts to the world.

It can be difficult to understand what your child with CVI can see because CVI can cause a variety of visual symptoms. Some children can see more easily when they are surrounded by familiar objects. This is because their brain has had repeated opportunities to recognise the objects.

Observing a child with CVI is an important way to assess how it is affecting them. There are some key questions that can help you have a better understanding of the way CVI affects your child’s vision such as:

• At what distance do they respond to an object of interest?
• How does contrast sensitivity affect what they can see?
• At what distance, if at all, can they respond to faces and facial expressions?
• Do they prefer or respond better to particular colours? If unsure, try “warm” colours such as red, orange or yellow, as these often lead to a better response.
• How do they respond to large clear targets? This can be used to assess how big or small something needs to be for the child to see it.
• Which areas of the visual field do they respond in?
• How long does it take for them to respond?
• What detail can be seen and responded to?

There’s no single test to check for CVI. If you suspect that your child has vision problems, the first step is getting an eye examination. This is usually with an optometrist (optician). The optometrist can assess:

• visual acuity
• how well the eyes work together to give depth perception (binocular vision)
• visual field
• contrast sensitivity
• colour vision
• the health of the eyes.

If the examination doesn’t find an eye condition to explain your child’s symptoms, it might mean the issue is with their brain. Your child will need to see an ophthalmologist (eye doctor) who’s familiar with CVI to get a diagnosis. Your child may also need to visit other specialists. These can be a paediatric neurologist or neuro-ophthalmologist (doctors specialising in conditions affecting the brain).

The doctor will examine your child and ask about their medical history. They may also order scans of your child’s brain. CVI can be difficult to diagnose so may take some time. The correct diagnosis is key to getting your child the help they need. If there are concerns about your child’s vision that can’t be explained by an eye condition or a need for glasses, ask your doctor if it could be CVI. This is especially important if your child has had a brain injury.

There are a number of qualified professionals that may be involved in the diagnosis and management of CVI.

Ophthalmologists–are medically trained doctors who have specialised in eye health. They diagnose, treat and monitor eye conditions with medication or surgery. They usually work in the hospital eye departments or clinics (often called ophthalmology departments).

Optometrists (often called opticians) are trained to examine eyes and check vision, prescribe glasses and contact lenses and detect eye conditions. If necessary, they can refer on to other health professionals.

Orthoptists are qualified to investigate and manage certain eye conditions which affect the way the two eyes work together, such as a strabismus (squint) or double vision. They usually work in hospital eye departments. They often provide eye screening for children at school.

Dispensing opticians are qualified to fit and supply spectacles. They are also qualified to give advice on suitable frames and lenses for your child’s spectacle prescription. Some dispensing opticians may also have additional qualifications to fit contact lenses and prescribe low vision aids.

Eye Care Liaison Officers (ECLOs) provide emotional and practical support to people who have a condition affecting their sight. They are trained to give support with emotional and practical challenges and supply information about all the local and national support services that might be of help.

Paediatricians are medically trained doctors specialising in managing medical conditions affecting infants, children and young people. A paediatric neurologist has expertise in how the brain works in very young children. A paediatrician usually works in a hospital or child development setting.

Qualified Teacher of Children and Young People with Vision Impairment (QTVI) is a qualified teacher who has additional qualifications and experience in working with children with a vision impairment. They are employed by the local council or authority’s Children’s Sensory Services, and work with children in different schools in the area. Each local council or authority should have at least one QTVI to work with children and parents, both at home and at school.

Occupational therapists aim to improve a person's ability to do everyday tasks when they have difficulty due to physical, mental or cognitive conditions. They look at all aspects of someone’s daily life in their home, school or workplace. They assess what activities are difficult and see if there is another way to do them. This may involve adapting environments, recommending assistive devices, or teaching new strategies for completing tasks.

Unfortunately, there is no treatment or cure for most types of CVI. However, visual rehabilitation can help people with CVI to use their vision better. For some people the visual symptoms caused by CVI can improve over time. This is especially true if their visual challenges are identified and managed effectively.

Early intervention, therapy, educational support and other special services can help babies and children with CVI develop and learn. If your child has CVI, working with their doctors to find the best plan for their care is important.

Glasses or contact lenses may be needed to correct any focusing errors (such as long or short sightedness). If glasses are needed, they help make vision clearer and more focused. This is especially important for children as the brain grows and develops.

Using large, widely spaced print and a ‘letterbox’ to see one word at a time can make reading easier. Removing distractions from the environment and other senses like hearing and touch, may also help.

Low vision aids can help make the most of the sight a person has by making things bigger, brighter and bolder. Using contrasting colours can also help to make some things stand out. An example of this could be making the edges of steps stand out using contrasting colours. You’ll be more comfortable if your environment causes you minimal glare. This can involve the lighting around you and the devices you’re using.

You can find out more in our Making the most of your sight booklet which you can find on our website or by calling our Helpline.

Glare shields may be helpful for light sensitivity. Our factsheet on light sensitivity gives more information on managing glare. You can find this on our website or by calling our Helpline.

Here are some tips to manage visual difficulties caused by CVI:

• Give extra time. Someone with CVI may take longer to process what they are seeing. It can also be tiring, so give regular breaks.
• Reduce clutter. Have separate storage for favourite items and always store in the same place.
• Reduce distraction. Patterns can make it difficult to see an object.
• Use contrasting colours. Black on white can make an object easier to see.
• Reduce noise. Background noise can be distracting, making it difficult to see and hear at the same time.
• Position objects where they find it easiest to see. Some children with CVI find it difficult to use their lower visual field.

It’s completely natural to be upset when you or your child have been diagnosed with a condition affecting sight, and it’s normal to find yourself worrying about the future and how you or your child will manage.

It can sometimes be helpful to talk over these feelings with someone outside of your circle of friends or family. Sometimes it can help to talk about your feelings. At RNIB, we can help with our Counselling and Wellbeing service. Your general practitioner (GP) or social worker can also refer you for counselling, if you feel this may be helpful.

Parent Pathways First Steps is a free and informal RNIB service for parents and carers whose child has recently been diagnosed with vision impairment, or who want to find out more about different support that is available.

The Eye Care Liaison Officer (ECLO) 

Your eye clinic may have a sight loss advisor working alongside the doctors and nursing staff. This advisor may be known as either the Eye Care Liaison Officer (ECLO), the Vision Support Officer or the Early Intervention Support Officer. They are on hand within your hospital to provide you with further practical and emotional support about your eye health. To find out if your hospital eye clinic has an ECLO, you can call our Helpline.

The low vision assessment

A low vision assessment might be appropriate if you are struggling with detailed visual tasks. You can ask your ophthalmologist, optometrist or GP about low vision aids and whether having a low vision assessment is appropriate for you. During this assessment with an optometrist, you’ll be able to discuss the use of magnifiers and aids to help you to see things more clearly.

Education

It’s important for teachers to know what a student with CVI needs in school, college or university. Teachers should also recognise that a student’s needs might be variable. This could be at different times of the day and in different situations. Therefore, the student’s access to learning materials may need to be tailored for them. Their learning environment, such as the lighting, can be adapted to meet their needs. There is educational support available within RNIB. Our Education and Children's service can provide advice and information about education for young people up to the age of 25. You can get in touch with this team by contacting [email protected] or calling our Helpline.

Employment

You may be worried about finding work or staying in your job. Our employment advisors can provide specialist support and advice about employment for people with sight loss. You can contact this team via our Helpline.

Assistive technology 

There is also technology available that can help with low vision. Many smartphones and tablets are already equipped with built-in software that can be helpful. This can enable people with low vision to access information. There are also specific apps and low vision devices that may help too. Computer software programmes are available. Our Digital Skills advisors would be happy to chat to you about the assistive technology that is available. You can get in touch with this team by calling our Helpline.

Certification and registration 

If you or your child has vision loss, then you may want to ask your ophthalmologist whether you or your child is eligible to register as sight impaired (partially sighted) or severely sight impaired (blind). Registration can act as your passport to expert help and sometimes to financial concessions. Even if you aren’t registered, a lot of this support is still available to you.

If you have questions about anything you’ve read in this factsheet, please get in touch. Whether you know someone who has just been diagnosed with CVI or have been living with it for a while, at RNIB, we are here to help and support you at every step.

If you need someone who understands sight loss, call our Helpline on 0303 123 9999, say “Alexa, call RNIB Helpline” to an Alexa-enabled device, or email [email protected]. Our opening hours are weekdays from 9am – 6pm.

SeeAbility support people who have learning disabilities or autism, who may also have sight loss.

Tel: 01372 755 000

Email: [email protected]

Web: seeability.org

CVI Scotland are devoted to helping people understand cerebral visual impairment.

Web: cviscotland.org

CVI Society aim to raise awareness of CVI as well as offering advice and support to those affected by CVI.

Web: cvisociety.org.uk

Ulster University - Cerebral Visual Impairment Assessment information

VICTA is an organisation aiming to empower children and adults who are blind or partially sighted.

Tel: 01908 240 831

Email: [email protected]

Web: victa.org.uk

Look is an organisation supporting visually impaired young people to thrive

Web: look-uk.org

Tel: 07464 351 958

Email: [email protected]

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This factsheet has been written by the RNIB Eye Health Information service. Our factsheets have been produced with the assistance of patient and carer input and up-to-date reliable sources of evidence. The accuracy of medical information has been checked by medical specialists. If you would like a list of references for any of our fact sheets, please contact us at [email protected].

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