# What is CVI? > CVI (cortical or cerebral visual impairment) is a visual impairment that starts in the brain, not the eyes. The eyes can be healthy, but the brain has trouble making sense of what they send. In the United States it is a leading cause of vision loss in children. Glasses alone do not fix it. Updated 2026-10-03. Canonical: https://cviexplained.com/what-is-cvi/ ## The eye works. The brain builds the picture. Light enters the eye, and the eye turns it into a signal. The signal travels to the brain, and the brain builds the picture you see. With CVI, the brain has trouble with that last step. The National Eye Institute puts it this way: "If you have CVI, your brain has trouble processing and understanding these signals." This is why a child with CVI can pass an eye exam and still not see what is in front of them. ## What CVI can look like CVI is different for every person. These are common patterns, and one child may show a few of them or many. - **Clutter hides things.** On a busy table, wall or page, objects do not separate from each other. - **One thing at a time.** The child takes in one part of a scene, and the rest drops away. - **Faces are hard to read.** Many people with CVI know others by voice, hair or a bright coat. - **The lower part of the view is missing.** Curbs, steps and things on the floor are not seen. - **Depth is hard to judge.** A staircase or a shadow can be hard to read. - **Seeing takes time.** The child needs longer to notice a thing and to know what it is. - **Noise crowds out vision.** In a loud room, the child may look away or close their eyes. - **Vision tires and changes.** A child may see something in the morning and not in the afternoon. None of this is laziness, bad behavior or clumsiness. It is vision. ## Why you cannot tell by looking A child with CVI often looks like they can see. They may walk around furniture and find a favorite toy. Then they miss a step, walk past a parent, or cannot find the pencil on their desk. People around them conclude the child is not trying. Adults with CVI say the deepest harm was not being believed. The most useful thing you can do is believe the child, and then change the space around them. ## Who helps - **An eye doctor who knows CVI**, and sometimes a pediatric neurologist or neuro-ophthalmologist, for diagnosis. - **A teacher of the visually impaired** and an **orientation and mobility specialist**, who work with the child at school and at home. - **Early intervention and school services.** The National Eye Institute says babies and children with CVI need "early intervention and therapy, educational support, and other special services". In the United States, most of this support comes through early intervention and the school system, at no cost to families. ## What helps, in one list 1. Clear the clutter. 2. Show one thing at a time. 3. Say your name when you greet the child. 4. Give extra time, and stop talking while they look. 5. Keep it quiet when they need to see. 6. Mark steps and edges with bright color. 7. When the child says they cannot see it, believe them. ## Questions people ask ### Is CVI the same as being blind? Usually not. Most people with CVI have some vision, and how much they can use changes with the place, the task and how tired they are. A child may see a cup on a plain table and lose it on a crowded one. ### Can glasses fix CVI? No. Glasses correct the eyes, and CVI starts in the brain. Some children with CVI also have an eye condition, and glasses can help with that part. ### Is it cortical or cerebral visual impairment? Both names are in use for the same abbreviation. "Cortical" is the older term in the United States. Many clinicians now say "cerebral" because the cause can lie in the brain's deeper wiring, not only the outer cortex. The US National Eye Institute uses "cerebral visual impairment (sometimes called cortical visual impairment or CVI)". ### Does CVI get better? The National Eye Institute says there is no cure for CVI, and that for some children vision gets better over time, but everybody is different. Support helps a child use the vision they have. ### What causes CVI? CVI is caused by an injury to the brain, most often before, during or shortly after birth. The National Eye Institute lists a lack of oxygen or blood supply to the brain, fluid build-up in the brain, infections that reach the brain, head injury and some genetic conditions. Babies born early are more likely to have CVI. ## Sources - [National Eye Institute, Cerebral Visual Impairment (CVI)](https://www.nei.nih.gov/eye-health-information/eye-conditions-and-diseases/cerebral-visual-impairment-cvi) - [Perkins School for the Blind, What is CVI?](https://www.perkins.org/what-is-cvi/) - [Chang and Merabet 2024, NIH CVI working definition](https://pmc.ncbi.nlm.nih.gov/articles/PMC11588029/) --- CVI Explained gives general information. It is not medical or legal advice and it does not diagnose.