Convergence insufficiency is an eye condition that affects how your eyes work together when you look at nearby objects. This can cause blurry or double vision when you look at things up close, like a book or a smartphone screen.

Convergence insufficiency usually starts in childhood, but it can happen in people of all ages after a brain injury, like a concussion.

If you have convergence insufficiency, getting early treatment can help your eyes work together. 

Convergence insufficiency happens when the nerves that control your eye muscles don’t work the right way.

Normally when you focus on something up close, both of your eyes turn in. When people with convergence insufficiency look at something up close, 1 eye turns out.

In many cases, doctors don’t know what causes convergence insufficiency. But research shows that convergence insufficiency is common after a brain injury or concussion.

People with convergence insufficiency often have vision problems when they do close-up activities, like reading or using a computer. The most common symptoms are:

• Tired or sore eyes
• Blurry vision
• Double vision
• Headaches
• Trouble concentrating

You may also have trouble reading. You might lose your place, read slowly, or feel like the words move or float around on the page. 

If your child has convergence insufficiency, you may notice that they have problems when they read or do other close-up activities. They may:

• Squint
• Rub their eyes
• Close 1 eye

If your child has any of these symptoms, it’s important to talk to their eye doctor. Parents and teachers might think kids with convergence insufficiency have trouble reading or learning — but it’s actually a vision problem that needs to be treated.

Your eye doctor may start by asking you about your symptoms. They may ask if you have blurry or double vision, headaches, tired eyes, or trouble focusing when doing close-up activities.

They’ll also do some tests to measure:

• How much your eyes turn in toward your nose before you have double vision or 1 eye starts to turn out
• How likely your eyes are to turn out when you look at things that are up close and far away
• How well your eyes can switch from focusing on things up close to things far away

You can have perfect vision and still have convergence insufficiency — that’s why a regular eye exam won’t catch it.

Convergence insufficiency can be treated with a type of vision therapy called convergence exercises. This often includes working with a specialist to practice focusing on objects at different distances. You can also do exercises at home. Sometimes a special type of glasses called prism glasses can be used in treatment. In rare cases, surgery can help make the eye muscles stronger.   

You may not notice an improvement with treatment right away. It can take 12 weeks or more to notice a change in your vision. Your symptoms may come back after being sick, not getting enough sleep, or doing a lot of close-up activities.

Scientists are studying other treatments for convergency insufficiency to see if we can treat it better, including new eye exercises and the use of virtual reality headsets.