Do you know the most common cause of vision loss in children? You may have never heard of it. Cortical visual impairment (CVI) is the most common cause of permanent visual impairment in children. Although it always affects both eyes, the eyes themselves are normal. In children with CVI, the eyes function normally and send the correct massages to the brain, but something goes wrong in the parts of the brain responsible for vision.
CVI has many causes and different children are affected differently. Most children with CVI are not blind but their vision is abnormal. The first sign of CVI in a baby may be a failure to recognize or respond to faces and make eye contact. CVI can range from mild to severe, but most children will have some improvement in vision over time. Visual training can help stimulate visual development and improvement. Visual strategies can help a child deal with visual deficits.
What Causes CVI?
CVI used to be called cortical blindness. The cortical area of the brain is the densely packed area just below the brain surface. The name was changed because most children with CVI are not blind. Researchers now know that the brain problem may be in the pathways behind the eyes that lead to the cortical area.
Causes of CVI usually occur before birth or soon after birth. Babies who are born prematurely are at higher risk for CVI. The main cause is a lack of oxygen supply to the brain during birth, called hypoxia. Other causes include:
- Brain injury from trauma, such as a head injury or shaken baby syndrome
- Severe seizures
- Very low blood sugar (hypoglycemia) in the first few days after birth
- Fluid buildup in the brain (hydrocephalus)
- Maternal drug or alcohol use
- Brain infection (meningitis or encephalitis) before or after birth
Causes of CVI often cause other brain problems. These include cerebral palsy, epilepsy, developmental delays, and learning disabilities. About two-thirds of children diagnosed with cerebral palsy also have CVI.
Diagnosis of CVI
CVI has become the most common cause of visual loss in children because more and more children are surviving premature births. The other cause of vision linked to prematurity – retinopathy of prematurity – has decreased as diagnosis and treatment for this condition has improved. Even though CVI is the most common cause of vision loss in children, it is still rare. It may affect between 10 to 22 children under age 16 out of 10,000.
Doctors that diagnose CVI include pediatricians, pediatric eye specialists, and pediatric neurologists. Eye exams are usually normal, but vision exams are usually abnormal. Brain imaging studies may help with the diagnosis. In most cases, the signs and symptoms of CVI are the most important part of the diagnosis. Signs and symptoms can be different for each child but may include:
- Not recognizing or responding to faces
- Not making eye contact
- Not making visual contact with objects, eyes may drift away
- Having a blank face
- Avoiding new faces or unfamiliar objects
- Not recognizing objects at a distance
- Wanting to look at objects from the side or up close
- Moving the head from side to side to see
- Reaching for an object while looking away from it
- Having better vision while moving or when viewing objects that have bright colors
- Staring directly at lights or avoiding bright lights (photophobia)
Treatment of CVI
Some causes of CVI – like hypoglycemia or hydrocephalus – can be treated and CVI may improve. In some cases, glasses can be helpful. In most cases, the best treatment is not medical. Children should be referred to a low vision therapist as soon as possible. Early visual stimulation can help the brain make new connections. A skilled low vision educator can help school age children. Parents can also play an important role. These are some of the ways to stimulate better vision in a child with CVI:
- Move visual stimulation objects. Children with CVI see better when objects are in motion. A brightly colored mobile above the crib or bed is a good example.
- Use sounds and touch to help the child focus vision.
- Present visual cues in an uncluttered way. Children with CVI have trouble seeing when there is a lot of background.
- Present visual cues with different lighting, different angles, and different colors to see what works best.
- Avoid overstimulation.
- Avoid working on visual stimulation when a child is tired, hungry, or cranky.
CVI is rare but it is the most common cause of vision loss in children. CVI can be tricky to diagnose because the symptoms can fluctuate and they can be subtle. If your child does not make good eye contact, does not seem able to focus vision well, or has any of the other signs of CVI, talk to your child’s pediatrician. Treatment does help when started early and many children with CVI improve.