What is cortical visual impairment (CVI)?
Cortical visual impairment (CVI) — more recently referred to as cerebral visual impairment — occurs when parts of the brain that process vision are damaged or develop atypically. It is more common in children than adults, though it may persist throughout life.
Unlike ocular visual impairment, which occurs due to issues in the eyes, CVI is a neurological condition. Individuals with CVI can have healthy eyes, but their brains have trouble understanding what their eyes see. This can lead to a range of vision difficulties.
CVI often develops when a baby’s brain is affected by injury or other problems before, during or shortly after they are born. It is one of the primary causes of childhood visual impairment in the United States.
What is the difference between cortical visual impairment and cerebral visual impairment?
The terms “cortical visual impairment” and “cerebral visual impairment” are often used interchangeably. But they are not quite the same. The cortex is the outer surface of the brain that provides complex processing, while the cerebrum includes the cortex as well as deeper brain structures.
Medical professionals increasingly favor the term "cerebral visual impairment.” This is because the scientific community has begun to recognize that CVI affects many parts of the brain, not just the cortex (the outer layer). The newer terminology reflects how various areas of the brain contribute to vision problems in CVI.
What causes CVI?
CVI is most often caused by damage to the brain before, during or soon after birth. Causes of brain damage in babies and newborns include:
- Hypoxic-ischemic encephalopathy (HIE) – Brain damage due to a lack of oxygen to the brain (this is the most common cause of CVI)
- Periventricular leukomalacia (PVL) – Injury to the white matter of the brain that is most common in babies who are born very prematurely
- Hydrocephalus – Fluid buildup in the brain
- Infectious diseases – Conditions such as meningitis or pneumonia that can result in brain damage
- Epilepsy – Neurological seizure conditions
- Trauma to the head – Trauma such as an injury from shaken baby syndrome
CVI can also be caused by:
- Congenital brain malformations
- Hypoglycemia
- Metabolic disorders
- Stroke
- Brain tumors
- Defects of the central nervous system
- Cardiac arrest
- Complications from a twin pregnancy
- Prenatal drug use by a baby’s mother
Premature babies have a higher risk of developing CVI because of the complications associated with preterm birth.
Diagnosis
There is no single test for CVI, so making a diagnosis can be difficult. However, there are three main criteria that are used to diagnose CVI:
- A history of neurological issues, which could have occurred due to trauma, brain damage or abnormal development, to name a few.
- Irregular eye behavior that cannot be explained through an eye exam.
- The child presents unique visual and behavioral characteristics that are typically seen with CVI.
Overlapping conditions
A variety of health conditions often overlap with CVI, which can also make diagnosis challenging.
Cerebral palsy is a disorder that affects movement, balance and coordination. The most common visual condition seen in people with cerebral palsy is CVI. Studies have shown that 50% to 70% of children with cerebral palsy also have CVI.
Additional conditions often seen in people with CVI include:
- Developmental disabilities
- Down syndrome
- Epilepsy
- Autism
- Hearing loss
What are the symptoms of CVI?
Symptoms of CVI are not typically detected during a standard comprehensive eye exam, though they may have abnormalities in the optic nerves. Strabismus, or crossed eyes, is also common. However, most children and adults with CVI appear to have healthy eyes and normal vision. This is because the problem is in their brain and not their eyes.
Certain behavioral characteristics are often associated with CVI. They include:
- Preference for looking at objects that are certain colors. It’s common for a child with CVI to show preference for toys and other items that are red, yellow, or in rich, saturated colors.
- Either excessive interest in light that can cause a child to gaze directly at a light or sensitivity to light (photophobia).
- Preference for looking at moving objects versus static objects. You may need to shake an object in front of the child in order to get their attention.
- Difficulty reaching for objects. Using peripheral vision may be preferred when reaching for an object. A child may also look at something, look away, and then reach for the object without looking at it.
- Slower processing time when looking at objects. This is referred to as visual latency.
- Difficulty with visual complexity. In other words, it’s difficult to focus on something in a busy environment with lots of people and/or activity.
- Having abnormal visual reflexes. If something moves toward the child’s face, they may not instinctively blink like someone who does not have CVI. This may be more apparent in a noisy environment.
- Difficulty with vision in unfamiliar places but better vision at home. This is called visual novelty.
- Preference for certain visual fields. A child may only look at something that is in a specific position, such as left, right, up or down.
- Difficulty seeing objects at a distance. A child may prefer to look at items that are close by, even though their eye exam shows they have normal vision.
Someone with CVI may also:
- Become tired after doing visual tasks
- Have inconsistent responses to familiar objects
- Prefer to use their sense of touch over their sense of sight
- Avoid tactile stimulation
- Avoid direct eye contact
Phases of CVI
Three CVI phases and their associated scores are used to help describe a patient’s level of visual function in addition to their strengths and needs.
- Phase I – This phase ranges from 0 to 3. Patients in this range have the lowest level of visual functioning.
- Phase II – This phase ranges from 3 to 7. Patients in this range have a moderate level of visual functioning.
- Phase III – This phase ranges from 7 to 10. Patients in this range have the highest level of visual functioning.
This information is also used to determine which interventions, techniques and adaptations will be most beneficial to an individual patient.
How is CVI treated?
There is no specific treatment to cure CVI, but there are rehabilitation techniques that can help improve a CVI patient’s quality of life. Many of these can be done at home after discussing what will work best for your child with their medical team.
For example, you or your child’s rehab specialist can:
- Perform light reflex stimulation therapy in a quiet and dark room. Shine a flashlight in their eye for a brief moment. After pausing for five seconds, shine the flashlight in the other eye. This is done for one minute at a time and is repeated 30 times a day.
- Make an object’s outline easier to see by shining a penlight on it for one minute in a darkened room.
- Help with shape recognition by cutting shapes out of white cardboard and placing them onto a black background. The shapes can also be cut out of black cardboard and placed on a white background. These can be shown to your child 10 times a day.
- Keep your home environment uncluttered and use high-contrast colors to make it easier to identify different objects.
- Look for large-print and double-spaced books to help your child read more easily.
- Help your child with facial recognition by asking family members and other regular visitors to wear the same color each time they come over.
It can also help a child with CVI to:
- Allow extra time to complete a task
- Use sound or touch to get their attention
- Dim the lights in their room
- Avoid giving them visual tasks when they are tired, hungry or getting frustrated
- Avoid overstimulation
Rehabilitation and treatment varies from one person to the next. An individualized and multidisciplinary approach is important. In some cases, a child’s vision can improve on its own over time, but early intervention is important to ensure a child can get the most out of their vision.
Is cortical blindness the same thing as CVI?
Cortical blindness (CB) is vision loss that happens when the part of the brain called the occipital cortex is damaged. CB is a different condition from CVI.
In the past, the term “cortical blindness” was used to describe CVI, but this is not an accurate description. In children with CVI, the brain is still growing and developing. This allows for the development of alternative pathways for processing what the eyes see. Because of this, it is possible that children with CVI can enhance their vision over time.
How can I support my child?
Early intervention and therapy can benefit children with cerebral visual impairment (CVI). With support from parents and healthcare professionals, many children with CVI can work on their visual skills.
Advocate for your child and apply practical strategies at home and school. The Pediatric Cortical Visual Impairment Society (PCVIS) can offer additional guidance and resources.
