What is cortical visual impairment?
CVI is the most common form of visual impairment in children. It is the only type of visual impairment that can improve over time, though researchers don’t know exactly why. Other types of visual impairments stem from problems in the eyes themselves. These might include damage to the cornea, lens, and retina. CVI happens when the damage occurs in the visual processing areas of the brain. Think of it as damage to the fiber optic lines that bring cable TV to your house, as opposed to problems with the TV camera that films your favorite show. CVI can co-occur with disabilities such as cerebral palsy, developmental disorders, Rett syndrome, shaken baby syndrome, and some types of epilepsy.
Many of the disorders associated with CVI can also cause difficulties with communication. So, CVI can impair the vision of someone who might benefit from augmentative and alternative communication (AAC).
But how can you use AAC if you can’t reliably see the communication device?
First, folks with CVI experience a range of impact to their vision. As with people with any type of vision impairment, no two people are exactly the same. So how do we get a good feeling for what someone can see? We can observe how the person responds to visual cues in their environment. And we want to work closely with our vision specialists, such as TVIs (teachers of the visually impaired). They can administer batteries, such as Roman’s CVI Range Assessment and tell us a lot about the features of CVI.
There are some traits that are common to many children with CVI. We can take these into account when we determine which communication system to use.
Some of the common features we might observe include:
- Preference for bright colors
- Attracted to movement
- Attracted to light
- Difficulty with a cluttered visual field
- Delayed recognition of visual stimuli
- Trouble recognizing faces
So, can people with CVI use AAC? The short answer is yes! We need to evaluate and observe the individual to see how we can best meet their communication needs. We should match their abilities to the features of AAC an system, as always.
Example of high contrast core icons
Depending on the person, we might try the following features:
- Simple icons with bright colors
- High contrast between the symbol and the background
- Single objects photographed on a black background.
- Increased space between the icons
- A keyguard or other tactile “way finder” on top of the grid
- Auditory scanning
- Tactile icons placed on a light board
With CVI and AAC, we also need to consider the features of the environment, not just the device. You might want to work in a room without a lot of visual distractions, possibly with lowered light levels (if using a back-lit device). You will want to position the device on a table without clutter (hard to find at my house!). As with any AAC system, keep icon placement predictable. If vision isn’t at all reliable, you might focus on using tactile and auditory cues. Project Core has open source, 3D printable core vocabulary symbols.
Collect data, try different systems, and make decisions based on what you observe. There are people with CVI who use a variety of different high tech AAC systems, including eye gaze. Don’t assume an option is off the table until you have the data in hand.
CVI Part Two: Dr. Christine Roman’s CVI Range Assessment. Cerebral Palsy Daily Living. (2014, August 30). http://cpdailyliving.com/cvi-part-two-dr-romans-cvi-range-assessment/.
Mangan, S. 5 essential steps to finding the best AAC system for a learner with CVI. Perkins School for the Blind. https://www.perkins.org/cvi-now/parenting/5-essential-steps-to-finding-the-best-aac-system-for-a-learner-with-cvi#Assessment.
Roman Lantzy, C., & Lantzy, A. (2010). Outcomes and Opportunities: A Study of Children with Cortical Visual Impairment – Christine A. Roman Lantzy, Alan Lantzy, 2010. SAGE Journals. https://journals.sagepub.com/doi/abs/10.1177/0145482X1010401010?journalCode=jvba.
Walker, C. Intensive Eye Gaze Training for AAC Access: A Case Study. KU Scholar Works https://kuscholarworks.ku.edu/bitstream/handle/1808/21909/Walker_ku_0099M_14592_DATA_1.pdf?sequence=1&isAllowed=y.