Cortical visual impairment
form of visual impairment caused by a brain problem
Cortical visual impairment (CVI), also known as cerebral visual impairment, is a form of visual impairment that is caused by a brain problem rather than an eye problem. (The latter is sometimes termed "ocular visual impairment" when discussed in contrast to cortical visual impairment.) Some people have both CVI and a form of ocular visual impairment.
CVI is also sometimes known as cortical blindness, although most people with CVI are not totally blind. The term neurological visual impairment (NVI) covers both CVI and total cortical blindness. Delayed visual maturation, another form of NVI, is similar to CVI, except the child's visual difficulties resolve in a few months. Though the vision of a person with CVI may change, it rarely if ever becomes totally normal.
The major causes of CVI are as follows: asphyxia, hypoxia (a lack of sufficient oxygen in the body's blood cells), or ischemia (not enough blood supply to the brain), all of which may occur during the birth process; developmental brain defects; head injury; hydrocephalus (when the cerebrospinal fluid does not circulate properly around the brain, and collects in the head, putting pressure on the brain); a stroke involving the occipital lobe; and infections of the central nervous system, such as meningitis and encephalitis.
Visual and behavioural characteristics
Individuals' visual and behavioural characteristics vary and may include several (but not necessarily all) of the following:
Vision fluctuations likely to appear can involve a variety of factors including but not limited to:
environment
visual complexity of target
utilise simplified views e.g. larger text
familiarity of target
other sensory factors
level of fatigue
personal state of well-being (i.e. comfort, sickness)
Visual performance may vary eye to eye, impacting on depth perception
Field of view
tunnel vision
nystagmus
Movement
depends on speed, reflective properties
cognitive overload
scotomas
blindsight, not always effective, but an intuitive way of knowing surroundings without seeing them
Eye contact
Affecting social acceptance in Western cultures
Photophobia
sensitivity to changes in light and vision
one third of people with CVI are affected
possible compulsive staring at light sources
task lighting
Colour vision
colour perception often intact
colour coding often utilized
high contrast can increase clarity.
The public source identifies “Cortical visual impairment” as form of visual impairment caused by a brain problem. This brief keeps that definition visible, then builds a research path around Cortical, visual and impairment.
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