September is CVI awareness month
Image of a brain
September is CVI awareness month, and if ever there was a condition that needs more awareness it’s CVI….
Have you heard of CVI?
For most people, the answer to this question is likely ‘no’, and this is rather surprising, given that it is the most common cause of vision impairment among children in developed countries. So what actually is it? CVI stands for Cerebral Visual Impairment and people with CVI have difficulty processing vision due to brain-based differences.
Who does it affect?
Anybody who has any form of difference to their brain is at risk of CVI, this includes people with brain damage, malformation, or under-development. The conditions most strongly associated with CVI include (but not limited to):
Cerebral palsy
Down Syndrome
Ex-prematurity
Global Developmental Delay
Traumatic brain injury
Hydrocephalus
Chromosomal disorders
Are the eyes affected at all?
Some people with CVI have co-existing ocular (eye-based) vision impairment, but in many people, the eyes are totally normal. This can make it challenging to obtain a diagnosis, since traditional eye exams are geared towards assessing eye health and vision function.
So what does it look like?
Well, another reason it can be challenging to obtain a diagnosis is that, as is the case with many neurological conditions, the presentations can vary widely. People with CVI can have difficulties with any or all of the following:
Visual field restrictions: this means that the area the person can view at any one time is reduced, when compared to typical levels. A lot of people with CVI struggle to see things in their lower field, and this makes it very difficult to get around, because you cannot easily see a flight of steps, or decipher whether a line on the ground is just a change in floor coverage (such as carpet to tiles) or actually a step. Some people cannot easily access their vision on one side, meaning they may frequently miss things on one side; they may regularly collide with door frames, be startled when people approach them from a particular side, only eat food from one side of their plate, or appear not to engage with their AAC communication system if it is positioned on the side where their vision is less reliable.
Motion perception: for some with CVI, processing information that is moving can be challenging. These people might not be able to discern if a car is moving towards them, or parked, they might struggle to catch a ball, or they might find it very difficult to navigate safely through an environment, particularly when it is unfamiliar to them.
Processing lots of things: this is a condition called ‘Simultagnosia’. When there is a lot to process visually, the area the person can actually process at any one time constricts to a much smaller area. Someone with simultagnosia will see individual parts of the visual scene, but will have difficulties grasping the overall scene and fitting together all the parts.
Complexity and viewing things at a distance: For many with CVI, if there is a lot to visually process, it becomes difficult to extract the required information. The person might have difficulties finding a particular item of clothing from in a pile, or a favourite toy from a toy box, or finding the stapler from the stationary drawer.
Dual sensory processing: For some, it can be difficult to process input from more than one sense at a time. The person might struggle to look and listen at the same time; imagine how difficult that is when you are sitting in a classroom with the teacher talking through a Powerpoint presentation. Another common difficulty for those with dual sensory processing issues can be walking and talking. Attempts at having a conversation while walking result in trips and collisions, or the person slows or stops in order to process what is being said.
Other characteristics of CVI include visual latency: it takes the individual more time to make sense of what they are looking at. When presented with new information, they will not be able to react to it straight away. Variability is the hallmark of any neurological condition, and certainly, for a person with CVI, their ability to ‘see’ can vary significantly from one day to the next; just because something was visually accessible one day does not mean it can be seen the next. Finally, for anyone with CVI, seeing is tiring. We need to keep this in mind at all times. Visually demanding tasks need to be kept short, with breaks as needed.
Obviously, with all of these possible issues, it is extremely helpful to have an understanding of exactly which issues a particular person has. Forming an understanding of an individual’s visual profile can help explain unusual behaviours, and allow for tailored adjustments to therapies, learning, and the person’s environment, to minimise the impact of the issues. For people with acquired brain injuries, understanding why they are having particular issues can be extremely validating and help reduce anxiety.
How is CVI identified/diagnosed?
To identify / diagnose CVI we would usually attempt to identify a risk factor, which would explain why the person might have brain-based vision differences. This might be a known condition, such as Down syndrome, or Global Developmental Delay, or a history of a previous traumatic brain injury. Next we look for unusual behaviours suggestive of CVI, this can involve a ‘structured history-taking’ where we ask lots of questions about challenges the person experiences, and unusual behaviours, and we often combine this with a questionnaire, which allows us to collect a wider range of examples of unusual behaviours. The final requirement is to demonstrate the challenges clinically, and we do this through a functional vision assessments. At Special Eyes Vision Services, we regularly perform assessments for people with suspected CVI, and assist in obtaining a diagnosis. Not everyone requires a formal diagnosis; for many, understanding where the challenges lie and how to minimise them is enough, while for others, a diagnosis ensures access to the necessary support services.
I think I might have CVI / someone I support might have CVI?
If some of this sounds familiar and you are keen to learn more, then please get in touch. Our reception is manned Mondays and Thursdays 10-2.30pm, so you can call us, or send us an email. We would love to hear from you and look forward to supporting you.