What Is It?
Cortical Visual Impairment (CVI) refers to decreased vision resulting from the visual processing parts of the brain (e.g., the posterior visual pathways and/or the occipital lobes) rather than from the eyes themselves. For example, individuals with CVI typically have normal eye exam findings. However, vision loss from CVI can range from mild to total blindness. It is also one of the more frequent causes of visual impairment in children. Regardless, children with CVI often have some level of vision that may improve over time, particularly if they receive therapy to teach them how to integrate the visual signals their brains are receiving.
CVI may be caused by a number of different conditions that damage the visual parts of the brain. Examples include stroke, decreased blood supply to the brain, decreased oxygenation in the brain, brain malformation or infection, hydrocephalus, seizure, metabolic diseases, head trauma, and other neurologic disorders. Conditions such as these make it difficult for the brain to understand and interpret what the eyes see.
In most cases, individuals with CVI do not have other neurological problems, although epilepsy and cerebral palsy are not uncommon. The presence of CVI is not an indicator of the cognitive abilities of the individual; therefore, CVI should be distinguished from vision loss secondary to global neurological damage, where other functional deficits are also present in motor, cognitive, and physical abilities.
Indicators of Cortical Vision Loss
In children, one of the most common indicators of CVI is their poor attention to visual targets, particularly to more complex targets, such as a person’s face. Other indicators are that children with CVI often prefer to look at lights for long periods of time and that when reaching for an object, they will often look away from the object before grabbing it. This is because children with CVI have difficulty integrating visual stimuli (looking at an object) with their motor ability (grabbing the object). The diagnosis of CVI is given based on the combined results of magnetic resonance imaging (also known as an MRI) and an eye evaluation by a pediatric ophthalmologist.
If a child is suspected of having CVI, he or she should be evaluated by a pediatric ophthalmologist as part of the initial evaluation. The pediatric ophthalmologist will assess the child’s eye health as well as the need for glasses to make sure there are no additional factors that may be limiting vision.
Often, there is concern that a child with CVI has little to no vision early in life. However, vision is a learned sense, so as the child matures, he or she may have improved visual responses. As such, early intervention is important for improved visual responses over time, as well as because the treatment period for visual development is limited to the early years of life. State and local educational agencies and early intervention programs should be contacted as soon as a visual concern is noted so that an organized plan of visual stimulation activities can be developed and implemented, based on the specific needs of each child. The professionals involved in the evaluation of a child with vision loss from CVI can include teachers of students who are blind or visually impaired, physical therapists, occupational therapists, speech therapists, and certified orientation and mobility specialists. It is important to note that although the vision of an individual with CVI may improve with intervention, rarely does the vision become totally normal.
The realization and acceptance that a child is visually impaired can be a difficult adjustment for the child’s parents. Fortunately, there are many things that can enhance the functional abilities of individuals with vision loss at any age. To learn about available resources for individuals with vision loss, visit the National Eye Health Education Program low vision program page.
Mark Wilkinson, OD
University of Iowa Carver College of Medicine
Director, Vision Rehabilitation Service, UI Carver Family Center for Macular Degeneration
Medical Director, UI Optical
Chair of the National Eye Health Education Program Low Vision Subcommittee