Medically reviewed on July 15, 2017.
Convergence insufficiency is a condition in which your eyes are unable to work together when looking at nearby objects. This condition causes one eye to turn outward instead of inward with the other eye creating double or blurred vision.
Convergence insufficiency is usually diagnosed in school-age children and adolescents. It can cause difficulty reading, for which parents or teachers might suspect the child has learning difficulties rather than an eye disorder.
Treatments are usually effective for convergence insufficiency.
Not everyone with convergence insufficiency has signs and symptoms. Signs and symptoms occur while you're reading or doing other close work and might include:
- Tired, sore or uncomfortable eyes (eyestrain)
- Difficulty reading — words seem to float on the page, you lose your place or you read slowly — which might cause you to avoid reading or not complete schoolwork
- Double vision (diplopia)
- Difficulty concentrating
- Squinting, rubbing or closing one eye
When to see a doctor
If you or your child has symptoms of convergence insufficiency or problems reading, consult an eye care professional — an ophthalmologist or an optometrist.
The cause of convergence insufficiency isn't known, but it involves a misalignment of the eyes when focusing on nearby objects. The misalignment involves the muscles that move the eye. Typically, one eye drifts outward when you're focusing on a word or object at close range.
Difficulties with reading and concentrating can affect a child's learning. Convergence insufficiency does not cause learning disabilities, but it makes using your eyes difficult and tiring.
Convergence insufficiency typically isn't detected in routine eye exams or school-based vision screenings. Reading difficulties of children with the condition might lead to an evaluation for learning disabilities, but it's important to rule out this eye disorder.
People with convergence insufficiency might have otherwise normal vision, so it's important to mention reading or learning concerns to your eye care provider. To diagnose convergence insufficiency, your eye doctor might:
- Take a medical history. This might include questions about problems you have with focusing, blurred or double vision, headaches, and symptoms.
- Measure the near point of convergence (NPC). This test measures the distance from your eyes to where both eyes can focus without double vision. The examiner holds a small target, such as a printed card or penlight, in front of you and slowly moves it closer to you until either you have double vision or the examiner sees an eye drift outward.
- Assess positive fusional vergence (PFV). During this test, you're asked to read letters on an eye chart while looking through prism lenses. The examiner will note when you begin to have double vision.
- Perform a routine eye exam. If you have any other vision problems, such as nearsightedness, your eye doctor might conduct tests to assess the degree of the problem.
If convergence insufficiency isn't causing symptoms, you generally don't need treatment. But for people with symptoms, treatment with eye-focusing exercises can increase the eyes' convergence ability.
Treatment, which can take place in the office of a trained therapist or at your home, might include:
- Pencil pushups. In this exercise, you focus on a small letter on the side of a pencil as you move it closer to the bridge of your nose, stopping as soon as you see double. The exercise is often done for 15 minutes a day, five or more days a week.
- Computer vision therapy. Eye-focusing exercises are done on a computer using software designed to improve convergence. You can print the results to share with your eye doctor.
- Reading glasses. Glasses with built-in prisms generally haven't proved effective. If you have another focusing or vision problem, such as not seeing well close up (farsightedness), reading glasses might help.
Recent studies indicate that office-based therapy with home reinforcement is the most effective treatment for convergence insufficiency. Home-based treatment with pencil pushups or computer programs hasn't been shown to be as effective. But home treatment costs less and is more convenient and more readily available.
Treatment for convergence insufficiency might take three months or longer. Treatment can resolve convergence insufficiency, but symptoms might recur after illness, after lack of sleep, or when you're doing a lot of reading or other close work. Discuss treatment options with your eye care professional.