Convergence Insufficiency

Binocular vision disorders are conditions affecting how the eyes work together. Convergence insufficiency is one of the most common disorders of binocular vision.1 In convergence insufficiency, the eyes struggle to converge, or look inward. It can affect people of all ages and becomes noticeable when the strain of trying to look inward causes headaches and sore eyes (known as asthenopia) or double vision.

What is convergence?

Binocular vision is the ability to use both eyes as a unit. It relies on communication between the motor system (muscles)and sensory system (light detection, resolution and processing).1 When switching from looking in the distance to near, the components of the binocular vision system need to adapt to this change. One of these adaptations is fusion. To avoid seeing double, the eyes pivot inward toward the nose – a process known as convergence. When looking in the distance, they pivot out – this is divergence.

What causes convergence insufficiency?

People with convergence insufficiency have difficulty converging, or looking in, to focus on something up close. This can occur for a number of different reasons, but typically arises if the position of the eyes when relaxed (not trying to maintain fusion) is naturally turned out. This is known as exophoria. Most people have some degree of exophoria when looking at a near object. It only becomes a problem with low fusional range –when the strength of the muscles that position the eyes can’t overcome the degree of misalignment. Rarely, convergence insufficiency can result from more seriouscauses.1 It therefore requires a thorough check with a comprehensive eye exam.

What are the symptoms?

• Sensation of tension in and around the eyes
  ‍
• Blurry vision, especially with near work
  ‍
• Moving words on the page or screen
  ‍
• Double vision
  ‍
• Inability to focus for long periods of time
  ‍
• Improvement with one eye closed

How is convergence insufficiency managed?

Convergence insufficiency is a binocular vision disorder, not a refractive disorder (like long- and short-sightedness), so glasses not usually the first option. Management is aimed at strengthening ocular muscles with exercises instead, in a process known as vision training. This can include jump convergence (trains the eyes to move quickly from a more relaxed, turned out position to a turned in position), gradual convergence (trains the eyes to follow an object smoothly as it comes closer) and loose base-out prism exercises (similar to jump convergence). These strategies relieve symptoms by increasing the maximum amount the eyes can turn in, which improves their ability to overcome misalignment. With vision training, symptoms improve in more than 75% of patients.2 Spectacles with base-in prism can be used, although this tends to be a last resort. Fatigue and anxiety contribute a great deal to convergence insufficiency, which is why it can worsen in many people during stressful periods. Avoiding exacerbating factors can provide some relief.

References

1) Von Noorden, G. and Campos, E., 2002.Binocular Vision And Ocular Motility: Theory And Management Of Strabismus. 6thed. St. Louis, Mo.: Mosby.

2) Convergence Insufficiency Treatment Trial Study Group. Randomized clinical trial of treatments for symptomatic convergence insufficiency in children. Arch Ophthalmol Chic Ill 1960. 2008Oct;126(10):1336–49