Cortical Visual Impairment (CVI)
Cortical Visual Impairment (CVI) is a temporary or permanent visual impairment caused by the disturbance of the posterior visual pathways and/or the occipital lobes of the brain. The degree of vision impairment can range from mild to severe visual impairment. The degree of neurological damage and visual impairment depends upon the time of onset, as well as the location and intensity of the insult. It is a condition that indicates that the visual systems of the brain do not consistently understand or interpret what the eyes see. The presence of CVI is not an indicator of the child’s cognitive ability. The terms Cortical Visual Impairment, Neurological Visual Impairment, and Cerebral Visual Impairment, are sometimes used interchangeably.
The major causes of CVI are asphyxia, perinatal hypoxia ischemia (“hypoxia”: a lack of sufficient oxygen in the body cells of blood; “ischemia”: not enough blood supply to the brain), developmental brain defects, head injury, hydrocephalus, and infections of the central nervous system, such as meningitis and encephalitis.
Initially, children with CVI appear blind. However, vision tends to improve. Therefore, Cortical Visual Impairment is a more appropriate term than Cortical Blindness. Most children show some recovery after being diagnosed with CVI but very few recover completely. Usually the most dramatic improvement happens in the first two years after the diagnosis. Improvement is related to children’s brain plasticity, development and degree of neurological damage. A great number of neurological disorders can cause CVI, and CVI often coexists with ocular visual loss so the child should be seen by both a pediatric neurologist and a pediatric ophthalmologist. The diagnosis of Cortical Visual Impairment is a difficult diagnosis to make. It is diagnosed when a child has poor or no visual response and yet has normal pupillary reactions and a normal eye examination. The child’s eye movements are usually normal, however nystagmus can be present in some children. The visual functioning will be variable. The result of an MRI (Magnetic Resonance Imaging) in combination with an evaluation of how the child is functioning visually, provide the basis for diagnosis.
Additional information is available in the Blind Children’s Center Pediatric Visual Diagnosis Fact Sheets.