Cortical Visual Impairment (CVI) is a form of visual impairment caused by a brain problem rather than an eye problem.
CVI is sometimes known as Delayed Visual Maturation because the child’s vision can sometimes seem (to an outside observer) to be improving over time.
This can be due to the child’s learning how to make better use of the unusual types of information that their malfunctioning visual system presents to them, while taking into account the context and other clues. Cortical Visual Impairment is also sometimes known as Cortical Blindness, although most people with CVI are not totally blind.
Symptoms of Cortical Visual Impairment
- Variable vision. Visual ability can change from one day to the next, but it can also fluctuate from minute to minute, especially when the child is tired.
- One eye may perform significantly worse than the other, and depth perception can be very limited (although not necessarily zero).
- Many children with Cortical Visual Impairment are able to use their peripheral vision more effectively than their central vision.
- Some objects may be easier to see than others, so your child might have difficulty recognizing faces or facial expressions, but have fewer problems with written materials.
- Children with CVI usually have full perception of colors.
- The vision of children with Cortical Visual Impairment has been described much like looking through a piece of Swiss cheese.
- Your child may have poor depth perception.
- Strong preference for a simplified view. When dealing with text, your child might prefer to see only a small amount of it at once.
- For the same reason (simplified view), your child may also dislike crowded rooms and other situations where their functioning is dependent on making sense of a lot of visual clutter.
Diagnosing Cortical Visual Impairment
Diagnosing CVI is difficult. A diagnosis is usually made when visual performance is poor, but it is not possible to explain this from an eye examination. Usually a child is evaluated by a team of professionals which could include teachers of the visually impaired, physical therapists, occupational therapists, speech therapists, and orientation and mobility specialists.
The Cause of CVI
Numerous conditions cause Cortical Visual Impairment, including a lack of sufficient oxygen in the body cells of blood or not enough blood supplied to the brain. Other causes are developmental birth defects, head injury, and infections such as meningitis and encephalitis.
Help for Cortical Blindness
Therapists use a variety of teaching strategies. Here are a few examples:
- Infants and toddlers will show when and where they see best by their adaptive behaviors. Try different positions and follow your child’s lead.
- Head support should be provided during play or work sessions to avoid involuntary shifting of the visual field.
- Since a child with CVI can often still see colors, use bright fluorescent colors like red, yellow, pink and orange.
- If the child uses a lot of energy for fine motor tasks, work on fine motor and vision separately until integrating the two is possible.
- Use familiar objects (bottle, bowl, plate, bath toy, etc) one at a time. Familiarity and simplicity are very important.
- Look for toys and activities that motivate the child.
- Introduce new and old objects via touch and verbal description.
- Try having the light source behind and/or to the side of your child until you determine which is best.