Though CVI may be considered more of a sensory or perceptual problem rather than a vision problem, a TVI with experience and education on the understanding of CVI and it’s educational impact (especially for a nonverbal student whom can not express their visual strengths and challenges) can be helpful to a CVI student and the student’s teacher. Since most CVI students’ functional vision is unique from one another, it is important for a TVI to consider the below common characteristics and behaviors while looking at the individual child as a whole (including other disabilities) to incorporate the appropriate below teaching strategies (along with other strategies). Most of these below teaching strategies are strategies that TVI’s are trained on using with VI students along with the below adaptations and educational considerations.
Common characteristics of visual function demonstrated by children with CVI:
- Vision appears to be variable: sometimes on, sometimes off; changing minute by minute, day by day.
- Many children with CVI may be able to use their peripheral vision more effectively than their central vision.
- One third of children with CVI are photophobic, others are compulsive light gazers.
- Color vision is generally preserved in children with CVI (color perception is represented bilaterally in the brain, and is less susceptible to complete elimination).
- The vision of children with CVI has been described much like looking through a piece of Swiss cheese.
- Children may exhibit poor depth perception, influencing their ability to reach for a target.
- Vision may be better when either the visual target or the child is moving.
The behaviors of children with CVI reflect their adaptive response to the characteristics of their condition
- Children with CVI may experience a "crowding phenomenon" when looking at a picture: difficulty differentiating between background and foreground visual information.
- Close viewing is common, to magnify the object or to reduce crowding.
- Rapid horizontal head shaking or eye pressing is not common among children with CVI.
- Over stimulation can result in fading behavior by the child, or in short visual attention span.
- The ability of children with CVI to navigate through cluttered environments without bumping into anything could be attributed to "blindsight", a brain stem visual system.
- Children are often able to see better when told what to look for ahead of time.
- Children with CVI may use their peripheral vision when presented with a visual stimulus, appearing as if they are looking away from the target.
- Some children look at an object momentarily and turn away as they reach for it.
- A great deal of energy is needed to process information visually. The child might tire easily when called upon to use his visual sense. Allow for intermittent "break" times.
- Positioning is important. Keep the child comfortable when vision use is the goal in order that "seeing" is the only task.
- Head support should be provided during play or work sessions, to avoid involuntary shifting of the visual field.
- Try many different positions to find the one in which the child feels most secure. Infants and toddlers will demonstrate when and where they see best by their adaptive behaviors.
- If the child needs to use a lot of energy for fine motor tasks, work on fine motor and vision separately, until integration of the modalities is possible.
- The simpler, more constant and more predictable the visual information, the better the child with CVI is likely to deal with it. Keep toys and environment simple and uncluttered. Use books with one clear picture on a contrasting simple background.
- Use familiar/real objects (bottle, bowl, plate, bath toy, diaper, cup, spoon, favorite toy) one at a time. Familiarity and simplicity are very important.
- Since the color system is often intact, use bright fluorescent colors like red, yellow, pink, and orange. Colored mylar tissue seems to evoke visual responses.
- Repetition is very helpful: use the same objects and same process each time to provide familiarity and security for the child. Familiarity breeds response.
- Look for toys and activities that motivate the child.
- Vision is often best stimulated when paired with another sensory system. For example, auditory cues from the handling of mylar may help attract the child's attention.
- Introduce new and old objects via touch and verbal description.
- Try different lighting situations to assess optimal conditions for viewing. Try locating a light source behind, and/or to the side of the child.
- Try moving the target that you want the child to see. Try different visual fields.
- Allow lots of time for the child to see and to respond to what is being seen.
- Learn to interpret each child's subtle response cues: such as changes in breathing patterns, shifts of gaze or body position, etc.
High illumination, bright contrast in materials, using consistent visual cues throughout different settings such as school. A combination of reading media may be necessary
Pair best sensory system with vision, visual input must be controlled to prevent “visual overloading”, Visual images should be simple and presented in isolation, provide repetition and routine, color coding simple pictures or shapes give an additional cue for recognition, restrict # of people involved in intervention. When preparing reading materials, use a contrasting paper, template, or marker to block out visual information or space objects farther apart on a page. Demonstrate how to use a finger to move from one object to another on a page. Simplify illustrations. Reduce visual fluctuation and performance by eliminating tiredness, extraneous noise and distracters. May be necessary to turn off a light or use diffused lighting to get student to focus on a task.