According to Dr. Roman-Lantzy, CVI “is the leading cause of visual impairment in children today”. There are many conditions that can cause CVI, including anoxic brain damage, periventricular leukomalacia (PVL), hypoxic brain damage (including hypoxic ischemic encephalopathy) , meningitis, encephalitis, head injury, intraventricular hemorrhage, structural abnormalities, and metabolic conditions. As more critically ill babies are surviving the incidence of CVI is increasing. This makes it even more important that people know about and understand CVI.
Once we started to understand what CVI is, and gained some strategies to help Little Bear, we found we wanted to know more about why certain characteristics are so common for children with CVI. Here is what we have learned.
Preference for a specific color
Many children with CVI have a definite color preference with red and yellow being the most common. No one is 100% sure why this is. Color vision is often preserved in children with CVI because it is located deep in the brain and in both sides, making it harder to damage. Red and yellow may be the most commonly preferred colors because they have the longest wavelengths and the human eye has more receptors for long wavelengths.
Preference for familiar objects
Because it is difficult for children with CVI to process visual information, they often prefer familiar objects that the brain easily recognizes and has processed before. For example, Little Bear’s Elmo was a constant companion when we first learned that he had CVI. Each exposure to this simple red object strengthened the neural pathways for seeing that object. He now looks at it immediately and for longer periods of time.
Need or preference for movement
The part of the brain that interprets motion and peripheral vision is often not damaged in children with CVI because this area is small and located in the back of the brain on both sides. For this reason, movement, especially in the peripheral field, can often trigger a child to begin using their vision. For many children with CVI an object placed in the center of their field of vision will be too difficult to see. Some children will move themselves to create motion and stimulate their vision. You can use motion in the periphery to help a child see until this characteristic is resolved.
Visual latency and need for simplicity
Children with CVI may find it very difficult to use their vision. They need to be given plenty of time and a quiet uncomplicated environment to maximize their ability to process visual input. Furthermore, the object presented to the child needs to be visually simple. If there are too many distractions, the child may be unable to use their vision or may need even more time to respond. These delayed responses may be seen as disinterest on the part of the child, but often if you wait long enough you will see a response. With experience, the brain gets better at processing information from the eyes and the visual latency and need for simplicity may resolve.
Light gazing and non purposeful gazing
It is not entirely clear why this is a common characteristic among children with CVI. Children with CVI might gaze at light in order to visually stimulate themselves. Conversely, both light gazing and non purposeful gazing may be ways to avoid visual stimulation. Another theory is that because many children with CVI have difficulty processing vision and sound at the same time, they may turn away from an object when trying to listen and may therefore appear to be gazing at light or gazing without purpose. It may appear that a child who looks away from a person or object is not interested, when in fact they are trying to focus on listening.
Visual field preferences
Because CVI is the result of injury to the brain, areas of the brain that correspond to the visual pathways and processing centers may be damaged, which results in damage to certain parts of the visual field. Since the extent and location of injury is different in each person, the effect on the visual field will also be different. For example, some children may prefer to view objects on the left side or have trouble viewing objects placed in the lower visual field. Little Bear often does not notice objects if they are located below his chin.
Distance vision impaired
Many children with CVI appear to be very near-sighted. For example, Little Bear will often bring objects inches away from his face to look at them. This may be connected to the need for visual simplicity. The closer an object is, the more the background clutter disappears, allowing the child to simply focus on the object.