The Dr. Bill Takeshita Foundation

Last Modified: Sat, 18 Aug 2007

View other Common Causes of Vision Impairment

Neurological vision impairment (NVI) is one of the leading causes of legal blindness among children in the United States today. It is a neurological condition in which the visual cortex in the occipital lobe of the brain does not process visual information normally. The most common causes of neurological insult to the brain include lack of oxygen (hypoxia, anoxia, asphyxia), seizure disorders, mirconium aspiration, and intra-ventricular brain hemorrhage. Although there are no surgical or medical treatments to reverse the damage to the occipital lobe of the brain, many children with neurological vision impairment develop higher levels of vision after receiving vision stimulation therapy.

The diagnosis of neurological vision impairment (NVI) has been inconsistent. For many years, children who had vision impairment that was caused by damage to the brain and not the eyes were diagnosed as having cortical blindness. This diagnosis was often misleading because many of these children were not totally blind while others developed very high levels of vision with time. Today, neurological vision impairment is classified as one of three different diagnoses. Cortical blindness is the term used to describe children and adults who are totally blind due to damage to the visual cortex of the brain. Their vision does not improve and there is no medical treatment. Delayed visual maturation is a different form of NVI in which children who are born with very low levels of vision develop high levels of vision by the age of 36 months. In many cases, their vision is normal by the age of 4 years. Cortical vision impairment is the third and most diverse form of NVI.

Cortical vision impairment (CVI) accounts for the majority of cases of legal blindness due to neurological vision impairment among children. At the Center for the Partially Sighted, a low vision center in Los Angeles, CA, over ninety percent of the cases of congenital NVI are due to CVI. These children have vision but their vision does not improve to normal. Their visual acuity may range from the ability to perceive light to 20/100. They frequently have fluctuating vision where their vision may be different at various times of the day. Their central vision may have spotted blind spots and their vision may be analogous to looking through Swiss cheese. Consequently, they often do not make eye contact and their eye hand coordination may be poor.

Children with CVI often have many interesting behaviors. Aside from not making eye contact, they are highly stimulated by high contrast, rotating, and moving objects. They frequently look at ceiling fans, the scrolling credits on videos, and some stare at blinking and flashing lights. A small percentage are extremely sensitive to glare and bright light and will keep their eyes closed or turn away and stare into a corner of the room. Children with CVI frequently have very sensitive peripheral vision and they can become overwhelmed when they are in crowded places that have a lot of visual noise. Department stores, amusement parks, and confined quarters can be very stressful for these children. Their visual attention fluctuates tremendously and they may demonstrate short periods where they use their central vision to focus and identify objects but their attention quickly weakens and they then glance at objects with their peripheral vision. During these times, they appear totally blind and use their hands to interact with their environment rather than using their vision to guide their hands.

Children with CVI often have many other problems that interfere with their general development. Because the entire brain is often involved, they frequently have motor, language, feeding, and cognitive problems. These neurological problems often present a major challenge to parents, teachers, and therapists. The neurological and cognitive problems of children with CVI are usually the greater limiting obstacle that interferes with their development as compared to the vision impairment. The cognitive deficits create unique difficulties in attempting to teach children how to use non-visual clues for learning.

Recommendations

• An evaluation by a neurophthalmologist is recommended to obtain an accurate diagnosis. This diagnosis plays an important role in determining the most appropriate early intervention treatment program.
• A low vision examination by a pediatric low vision specialist is recommended to prescribe a program of vision stimulation. Glasses and other low vision aids may be prescribed to maximally stimulate the development of vision. Specific toys and modifications to the home should also be recommended by the doctor to further enhance the development of vision.
• Vision stimulation is recommended during the first five years of life to maximize the development of vision. Use high contrast patterns, stripes, and paints to provide a visually stimulating environment for children with CVI. For more information on vision stimulation, see Developing Your Child’s Vision.
• Consult with the Regional Center and your local school district’s special education programs to ask for assistance with early intervention therapies and treatments.
• Children over the age of 7 years of age who have not made significant gains with their vision development should begin learning non-visual tools to perform daily activities independently and to read and write with the use of low vision aids, Braille, or other non-visual methods.
• For more information, please see Low Vision Rehabilitation