What is Cortical Visual Impairment (CVI)?
Cortical visual impairment (CVI) is a brain-based visual impairment. The processing of visual information is impaired as a result of a neurological problem in the areas of the brain responsible for visual function. As many areas of the brain are responsible for visual function, some areas process movement, colours and even forms. This demonstrates the convoluted nature of visual impairment; each experience is unique – as one (or more) of these different areas of the brain may not be fully functioning. I will be exposing this visual impairment not with a scientific eye, but with an eye that will emphatically uncover the visual world of cortical visual impairment.
There are many characteristics in cortical visual impairment, so many of these will be stated and explained to hopefully develop a deeper understanding. Furthermore, suggested guidance will be on adaptations and sources for further support if you feel like a lot of these are familiar with your children or adults.
The experience may be unique or differ slightly, so some of these characteristics may be similar but not exact. However, that does not diminish the importance to adapt and access potential support. So here are how the symptoms may present.
The below images are taken from a CVI-SIM (virtual reality progress video) on the CVI Scotland website. The videos are the result of students’ work from the Department of Computer Studies of the University of St Andrews (2020/21 academic year) in partnership with the Department of Medicine.
Vision may be variable, someone with this condition may experience poorer vision when tired or ill. This could well be a common occurrence as eye fatigue is an inevitable experience throughout the day. However, another characteristic is sitting closer than 30cm to the television. This in conjunction with being able to see less when tired may cause an intensified experience.
Speaking as a visually impaired person I find that it’s never just one problem that the biggest issue, it’s the combination of multiple problems which amount to a more overall hindrance to the daily experience of living with a disability. Using the two characteristics stated before, sitting closer to the TV for anyone will cause a level of fatigue potentially due to the brightness of the TV. Combine this with a decreased sense of vision when tired, the two characteristics influence one another.
Adaptations maybe not so obvious, but they can be made. Unfortunately, the nature of some disabilities is that they will never go away, despite that fact it doesn’t mean it will disable the person from living a functional life. With the characteristic of sitting closer to the TV, the obvious answer would be sitting further away from the TV. However, someone with cortical visual impairment may react angrily when being distracted from a task, so a suggestion could have allowed them to sit close to the TV but enable a blue light mode on devices. That will minimise the potential tiredness which could cause further vision issues based on the characteristics.
With CVI, the experience is unique to the individual and every person should be treated as an individual, having adaptations that cater to those unique experiences.
In summary, it is the multiple attributes of CVI that influence one another to intensify the one seemingly copiable characteristic. Although this may be the case small adaptations and understanding go a long way to providing whoever is in need with the ability to function in the new normal.
Summary of Symptoms
- Specific preferences for certain colours/textures. It’s hard to pinpoint exactly what these preferences are, however, there would be a clear distinction for visual preferences based on how that item/object is presented.
- Specific need or preference for movements, some objects may be easier to see based on its movement.
- Delayed visual responses to objects/faces, there may be a sense of latency to look at an object/face and be able to recognise it.
- Struggling with visually complex situations. The visual world for a person with CVI should preferably be as simplistic as possible. This could be incorporated through solid colours and minimising a visually busy environment.
- Preference of visual fields. Someone with CVI may have different preferences on how they would like to interact visually with objects. Some people may prefer seeing objects in their peripheral vision rather than centrally.
- Difficulties with visual distance. Many people with CVI have difficulties seeing objects from a greater distance. This is reminiscent of short sightedness and having issues with depth perception.
With CVI the list of characteristics and symptoms could keep on going on, demonstrating the complexity of this visual impairment. Despite this, the ones listed above should reflect the majority of CVI characteristics.
Often with CVI, those who have one symptom generally present with a reduction in visual acuity. For some people CVI is not singular, but a pattern resulting in several CVI symptoms. These patterns are called CVI clusters, and relate to different parts of the brain affected. Further information about CVI clusters can be found here.
The 10 Characteristics of CVI
The Pediatric Cortical Visual Impairment Society (PCVIS) has published a really good article on the 10 characteristics of CVI. Pediatric Cortical Visual Impairment Society
Getting a Diagnosis
If you suspect your child, or adult with SMS, may have CVI you should seek advice from your doctor or optician who can refer you to a specialist ophthalmologist.
Living with Cortical Visual Impairment (CVI)
As mentioned above, cortical visual impairment is unique to the person. This video clip shows Lily, who is diagnosed with Smith-Magenis syndrome, and her challenge with processing depth perception and descending a staircase. Lily’s mum says:
Lily requires a lot of support coming down steps and has to ‘feel’ her way down, especially if the stairs are unfamiliar to her. Typically, there is a queue of people waiting at the top for her to reach the bottom and this can make it difficult in public spaces. It usually takes a very long time for Lily to reach the bottom and causes her a huge amount of anxiety.Leeann Stevenson, mum to Lily
Strategies and Tips to help someone with CVI
Even though many people with CVI learn to adapt to their disability, there are a few simple things that can be done to provide extra safety and support for that person. Patience, understanding, and, conscientiousness are vital to supporting the needs of someone with CVI. Making simple adaptations around the home, or workplace, to ensure the environment is made as safe and comfortable as possible will also help. Some ideas may include:
- Sensitive use of Illumination within the environment, i.e. ensuring the rooms are well lit to avoid dark areas. Also, avoiding any glaring or very bright lights that could cause distraction and/or discomfort.
- Ensure there is no clutter/debris on the floors and/or surfaces.
- Use of handrails on stairs, or in the shower/bath.
- Avoiding busy patterns on furnishings or home decor to minimise visual stimulation, particularly in areas where there are high levels of interaction.
- Avoid moving furniture or large objects around a room. Many people with CVI rely on memory.
- Try to plan visits to busy public places like supermarkets, or cinemas, when it is likely to be quieter. Many of the large supermarket and cinema chains have introduced ‘Autism Friendly’ times which are quieter and have reduced lighting to minimise visual stimulation.
Strategies for Interacting with a Child Who Has CVI (The University of Nevada, Reno)
What does my child with CVI see?
Perkins School for the Blind – What does my child with CVI see
Support for CVI
The CVI society
The CVI Society Website
Royal National Institute of Blind People (RNIB)
Supporting children with cerebral visual impairment
Sim-Sight (CVI Scotland)
Sight-Sim is a computing programme that lets you see how different things look like for people with reduced clarity of vision (visual acuity), with reduced contrast sensitivity or with both.
Sight-Sim was developed by a team of Scientists, Engineers, Computer Programmers and Ophthalmologists in Glasgow. It is a world-leading and award-winning software which has also inspired Peek Vision’s smart phone apps (see below). Click here for Sight-Sim Instructions
Peek Acuity (Mobile Simulator by Peek Vision)
As mentioned above, Peek Acuity is a mobile phone app that simulates visual acuity, and was inspired by Sight-Sim. Click here to find more about Peek Acuity.
Talks and Lectures by CVI Scotland
CVI Scotland have published a range of talks and lectures about CVI on their website.
Scientific Paper (published on the Wiley Online Library)
University of Nevada, Reno
There are some excellent resources and tips shared by the University of Nevada, Reno in their ‘Nevada Dual Sensory Impairment Project‘.
Disability Legislation around CVI
Document submitted by Professor Gordon Dutton to a Scottish Parliamentary enquiry on visual disability in children.
Access to Services and Support for Children with VI (NHS Scotland) – Visual Impairment Network for Children & Young People