Convergence insufficiency occurs when your eyes don't turn inward properly while you're focusing on a nearby object. When you read or look at a close object, your eyes should converge — turn inward together to focus — so that they provide binocular vision and you see a single image. But if you have convergence insufficiency, you won't be able to move your eyes inward to focus normally.
Convergence insufficiency is usually diagnosed in school-age children and adolescents. Convergence insufficiency can cause difficulty with reading, which may make parents or teachers suspect that the child has a learning disability, instead of an eye disorder. Treatments are usually effective for convergence insufficiency.
Not everyone with convergence insufficiency experiences symptoms. Signs and symptoms occur while you're reading or doing other close work and may include:
- Tired, sore or uncomfortable eyes (eyestrain)
- Blurred vision
- Difficulty reading — words seem to float on the page, you lose your place or you read slowly
- Double vision
- Difficulty concentrating
- A "pulling" feeling around your eyes
- Squinting, rubbing or closing one eye
When to see a doctor
If you or your child experiences symptoms of convergence insufficiency or has problems reading, consult an eye care professional, such as an ophthalmologist or an optometrist. A technician called an orthoptist may assist the eye care professional in evaluating and treating convergence insufficiency.
Convergence insufficiency results from misalignment of the eyes when focusing on nearby objects. The exact cause isn't known, but 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 adversely affect a child's learning. Convergence insufficiency typically isn't detected in routine eye exams or school-based vision screenings. A child with the condition may be evaluated for learning disabilities because of his or her reading troubles.
Tests and diagnosis
People with convergence insufficiency may have otherwise normal or "20-20" vision, and the condition may not be detected during a routine eye exam. To diagnose convergence insufficiency, your eye doctor may do the following, including special eye-focusing tests:
- Take a medical history. This may include questions about problems you have with focusing, blurred or double vision, headaches, and other signs 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. For this simple test, the examiner holds a small target, such as a glass ball, printed card or penlight, in front of you and slowly moves it closer to you until either you experience double vision or the examiner recognizes that your eyes can no longer focus together.
- 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 ophthalmologist or optometrist may conduct tests to assess the degree of the problem.
Treatments and drugs
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 may take place in the office of a trained therapist or at your home. Treatments may include:
- Pencil pushups. In this simple 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 the movement if you have double vision. 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 special software designed to improve convergence. You may print out the results to share with your eye doctor.
- Reading glasses. Glasses with built-in prisms force your eyes to work harder to align and are sometimes used for people who need help with their reading vision. But they can be tiring to your eyes and generally haven't proved effective.
A study sponsored by the National Eye Institute of the National Institutes of Health compared home-based treatment with doctor office-based treatment for convergence insufficiency in children ages 9 to 17. Study results showed that the most effective therapy was a weekly hourlong session of in-office vision therapy with at-home reinforcement exercises. Other studies have also found that office-based treatment is effective about 75 percent of the time.
Home-based treatment with pencil pushups or computer programs hasn't been shown to be as effective — in some studies, it works only about one-third of the time. But home treatment costs less and is more convenient. Only a small percentage of eye care providers offer in-office therapy for convergence insufficiency. Many people who can't find or can't afford in-office therapy opt for home-based treatment.
If you choose home treatment, many experts recommend using computer software programs along with pencil pushups. The combined approach may be more effective, and the computer therapy is more engaging for children.
Treatment for convergence insufficiency may take three months or longer, though you'll likely start to see improvement in your symptoms after four weeks. After your convergence ability has improved, you can help maintain your improved vision by continuing to read and do other near tasks. Treatment can permanently cure convergence insufficiency, but symptoms may come back after an illness, lack of sleep or when you're doing a lot of reading or other close work. In rare cases, eye-focusing exercises don't work and your doctor may recommend surgery.