Convergence insufficiency (CI) is when the eyes have trouble working together while focusing on an object that is close by.
With normal vision, your eyes make a series of adjustments to work together to form a single image. When you look from an object that is far away to one that is close, the lens inside your eye slightly changes its shape. The dark circle inside the colored part of your eye (the pupil) gets smaller. Your eyes also move slightly toward the center (midline). This is called convergence. Your eye and brain carefully coordinate these changes. The result is that you can see a single, focused image. When you read, your eyes and brain also have to coordinate the quick, complex eye movements needed to scan a page.
If you have CI, your brain and eye may sometimes have trouble coordinating these changes. One of your eyes may sometimes turn out instead of converging toward the midline. This makes it hard for your eyes to work together. It can cause blurred vision, double vision, or eye strain. Or you may need to close one eye when reading.
CI is common. It may be slightly more common in women than in men.
Experts are not yet sure what causes CI. There may be problems in the complex series of actions that the brain and eyes perform. Genes may be partly responsible for CI.
In some cases, a health condition can help lead to CI. These include:
Head injury and concussion
CI tends to run in families. You or your children may be at greater risk for CI if other family members have had it.
If you use a computer for long amounts of time, you may also be at greater risk for CI. Other visually demanding jobs may also raise your risk.
You may also be at greater risk for CI if you have certain health problems.
You are mostly likely to notice symptoms of CI when you do close visual work such as reading. Symptoms are even more likely if you do this for a long period of time. Extreme tiredness (fatigue) also can bring on symptoms. Possible symptoms include:
Sleepiness when reading
Needing to re-read things
Trouble concentrating on what you are reading
Often losing your place when reading
Words seem to move, jump, or float on the page
Motion sickness or vertigo
Others may notice that one of your eyes sometimes turns out as you read. (This might happen at the same time you have blurred vision.) Others also might notice you squinting or closing one of your eyes while you read. (This might make it easier for you to see a single, focused image.)
CI can occur at almost any age. But it is more common in young adults.
Your eye care provider (an ophthalmologist or an optometrist) often begins with a health history. They may ask about symptoms relating to CI.
Your eye care provider will also do a full eye exam. This will include testing for visual sharpness. They will also test how your eyes converge during tasks where you need to look closely. You may need to repeat this test, using each eye separately and then together. Your provider should be able to diagnose the condition with a health history and eye exam alone.
Eye care providers often prescribe certain eye exercises to treat CI. You might do these exercises at home or at the office. Some of these exercises might include looking through prisms. Computer programs are available that can increase convergence ability and measure your improvement over time. Most of the time, symptoms go away after you have regularly practiced the exercises over a fairly short period of time.
Covering one of the eyes does not help correct CI. But it may reduce symptoms for a short time. It doesn’t give you practice working with both eyes together. This is important to correct CI. You may choose to use this method for a short time if you have a lot of close work to perform.
Sometimes the symptoms don't go away, even with treatment. If that happens, your eye care provider may advise using special prism glasses for reading. These glasses may help you read more comfortably. In very rare cases, your provider might advise surgery.
A child with CI may have problems in school. They may have trouble focusing or be a slow reader. These problems may go away once the CI is treated. Think about getting a visual exam for any child having trouble in school.
Exercises to treat CI are very successful for most people. But it is important to practice these exercises sufficiently. If your child has CI, make sure they do these exercises regularly.
It tends to run in families. You or your children may be at greater risk if other family members have had it.
Symptoms can include blurry vision, double vision, headache, eye strain, and trouble reading and concentrating.
Symptoms may only happen when you are tired or have a lot of close visual work.
Eye care providers can diagnose CI with a health history and eye exam.
Most of the time, it will go away if you regularly do special eye exercises.
Tips to help you get the most from a visit to your healthcare provider:
Know the reason for your visit and what you want to happen.
Before your visit, write down questions you want answered.
Bring someone with you to help you ask questions and remember what your provider tells you.
At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.
Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are.
Ask if your condition can be treated in other ways.
Know why a test or procedure is recommended and what the results could mean.
Know what to expect if you do not take the medicine or have the test or procedure.
If you have a follow-up appointment, write down the date, time, and purpose for that visit.
Know how you can contact your provider if you have questions.