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Blindness of the Brain: Explaining CVI

Expert Chats

The leading cause of vision loss at birth, cortical (cerebral) visual impairment (CVI) is blindness related to the brain – not the eyes.

Imagine seeing a tiger stuffed animal. It has orange and black stripes. It’s about the size of your forearm. It is very clearly a tiger stuffed animal.

Now, imagine that someone places it into a box with other toys. Even surrounded by the other toys, the tiger is still easy to pick out. Right?

For people with a condition called cortical (cerebral) visual impairment (CVI), it’s not so easy.

For patients with CVI, it may be difficult to spot Tiger on the right…

Blindness Caused by Damage to the Brain — Not the Eye

To understand CVI, we spoke with Lotfi Merabet, O.D., Ph.D., director of the Laboratory for Visual Neuroplasticity at the Schepens Eye Research Institute of Mass. Eye and Ear, who is researching the condition.

Dr. Merabet explained that, the eyes of a person with CVI are typically healthy and “see” normally. But the brain incorrectly and incompletely processes what is being “seen.”

In the tiger scenario, a person with CVI would be able to identify the stuffed animal on its own. But when placed into the toy box, it would no longer be recognizable. The visual information created by the crowded toy box essentially becomes too complex for the brain of someone with CVI to process, and the tiger goes “unseen.”

A Growing Diagnosis, A Growing Need for Research and Care

CVI is on the rise. In the last two decades, its prevalence has risen dramatically. CVI is most often found in children who are born prematurely, and in the past, many premature babies did not survive past infancy. Thanks to advances in medicine and technology, these children are now living longer. Consequently, CVI is becoming more common. Additionally, as the medical and scientific communities have become more aware of CVI, diagnosis rates are increasing.

Today, CVI is the leading cause of congenital blindness (vision loss at birth) in the United States. It is also the most common cause of visual impairment in children attending schools for the blind.

At the same time, more research is needed to understand the underlying biology of CVI and the unique developmental and educational needs of this growing patient population.

Because children with CVI typically have healthy eyes, their trouble with processing and perceiving the world around them is often attributed to psychological or emotional problems. This knowledge gap contributes to challenging academic and social environments — where children with CVI aren’t getting the support they need.

Vision researchers, including Dr. Merabet, are intent on changing that. 

Using Brain Scans to Uncover a “Hidden Disability”

Brain scans showing the structural visual connections in the brains of individuals with normal vision (left), ocular blindness (center) and CVI (right).

Dr. Merabet advances research aimed at connecting the underlying structural changes in the brains of children with CVI to the resulting developmental and behavioral deficits.

In collaboration with Boston Children’s Hospital, The Perkins School for the Blind and Boston University Medical Center, Dr. Merabet is examining the brain imaging scans of children with CVI, and comparing them to those of children with other forms of blindness and with normal vision.

His major finding so far — that the brains of children with CVI are fundamentally wired differently than the brains of children with other forms of blindness — underscores the need to educate the public on this “hidden disability,” and to recognize CVI as its own unique condition.

Learn more about the Laboratory for Visual Neuroplasticity.

For pediatric ophthalmology care for congenital blindness, request an appointment or call 617-573-3202.

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