by Tanni L. Anthony, Anchorage, Alaska
Cortical visual impairment (CVI) occurs when there is damage to the visual cortex, or to the posterior visual pathways, or to both places in the brain. The eye generally does not have any internal damage although CVI can also be evident in children who do have ocular damage. The reduction of vision is due to neurological damage which hinders visual stimulation from being organized and interpreted by the brain. It is analogous to an imperfect computer chip which cannot fully process the input from the keyboard.
The diagnosis of cortical visual impairment can be made by an ophthalmologist and/or neurologist. The child should have a complete eye examination and a visual evoked potential (VEP) test. Children who are cortically visually impaired have a medical history that involves neurological impairment due to conditions such as asphyxia, cerebral hemorrhage, infection of the central nervous system, and/or trauma.
Dr. James Jan, a pediatric neurologist in British Columbia, has worked with children with a sight loss for over two decades. He has been involved with research in particular on the subject of cortical visual loss as it is a neurological based problem that results in visual impairment.
Just under 10% of the current population of visually impaired children in British Columbia are cortically visually impaired according to Dr. Jan. His practice has included many children with this diagnosis and he and his colleagues have made several observations about the “visual behaviors” associated with cortical visual impairment.
It is important to understand the base of information known about CVI must be analyzed to each child as an individual. Each characteristic of CVI may or may not fit an individual child. The information that does “fit” will help parents and teachers to design a home and/or school program that is tailored to each child’s needs. Dr. Jan’s and his colleagues at Children’s Hospital have noted the following behaviors associated with cortical impairment:
- Visual performance can be quite variable, simply put, some days are better than others. Visual functioning can even change from hour to hour with some children. Factors which might influence the fluctuation include: fatigue, noisy environments, illness, medications, seizure activity, and unfamiliarity of environment.
- Visual field defects may also be associated with CVI due to specific neurological damage.
- Movement cues, especially in the peripheral fields can often stimulate a visual response. Visual interpretation of the environment may be improved for some children when they are actually moving as opposed to standing still. Parents of some children with CVI have reported improved visual responsiveness when the child is riding in a car.
- Color vision does not seem to be affected. In fact, some colors appear to be “better received” that others such as red, orange, and purple.
The process of visual habilitation is in many ways different for the child with CVI than for the child who experiences an ocular impairment. The focus is for the CVI child to control visual input to avoid overstimulation. In view of the aforementioned characteristics of CVI, the following guidelines are recommended for consideration in home and/or school programming:
- Reduce extraneous sensory information from the child’s “working/playing environment”. Eliminate unnecessary noise or visual distractions. Present one item at a time as much as possible.
- The use of touch should be a primary means of introducing information. Continue to place the objects of daily care or “learning activities” in the child’s hand when presenting the item.
- Language is very important for information about the object or visual situation. Use labels that include description words. Tell the child what she/he is “seeing”. Voice intonation is important as far as providing meaning to a situation. When disciplining, for example, a firm voice should be used to match the words being used.
Familiarity is also an extremely important consideration. Parent and teacher experience has shown objects that are familiar often result in increased visual attention to that object as opposed to one that is new to the child. Think about what objects the child is involved with during his/her daily care activities. Make these objects part of his/her vocabulary (touch, function, sight). Examples might include:
- bottle/cup – drinking
- bowl/plate/spoon – eating
- comb – morning grooming
- washcloth or favorite bath toy – bathing
- music toy – bedtime
- diaper – diaper changes
- “security toy” – time to go somewhere outside of the home
Parents and teachers should decide what objects are typically used with the child during everyday activities or routines. To establish familiarity, the same object(s) should be used each time. The object should be visually, tactually, and verbally presented at the onset of the activity and then talked about as the child experiences their function. The exact style of presentation will vary according to each child’s general learning style and needs.
- The colors red and yellow are thought to be more readily perceived so may be used to enhance a visual target.
- Repetition is important for all children, practice is how they learn to integrate their new knowledge and put it to use. This especially is true for children who experience a sight loss.
- Be aware the child might fatigue easily in situations which require visual/auditory/tactile deciphering of information. Build in breaks and allow for extra response time before giving the child more information.
- Proper positioning is important for the child. If she/he is not in an aligned or supported body posture, the child cannot fully concentrate on the task at hand. This is true for all children, but especially important for the child with CVI and cerebral palsy. Consultation with a therapist should be utilized to promote optimal positioning.
- Each child’s family knows their child the best, their knowledge of what he/she likes, dislikes, etc. should be built into his/her learning activities.