Convergence insufficiency is a common condition in children and young adults with eyes that cannot maintain binocular vision when viewing nearby objects. Binocular vision refers to both eyes working together. In a normal eye, both eyes turn inward when focusing on nearby objects, creating fusion where the eyes maintain one image. In convergence insufficiency, however, one eye turns outward instead of turning inward together with the other one. The effect is blurry or double vision. This condition often affects school-going children and adolescents and may be mistaken as a learning disability instead of an eye condition. Although the disorder is common among children, people of all ages can develop it following trauma to the brain.
In the classroom setting, these children encounter difficulties with belonging. Teachers and caregivers think they are lazy and disruptive. Such children have problems maintaining attention in class because they get tired quickly when trying to read. One out of 20 children is said to have the disorder.
Causes & Risk Factors
It is not known what exactly causes convergence insufficiency. However, it is believed that a malfunctioning of the muscles that help with eye movement may be responsible. The eyes are said to be misaligned when a person tries to focus on objects close by.
Signs & Symptoms
The signs and symptoms of convergence insufficiency may not affect all. Some present with symptoms, while others do not. The symptoms may include:
- Headache when reading
- Diplopia or double vision
- Difficulties in concentrating
- Eyestrain or tired, sore eyes
- Closing one eye or squinting while reading
- Problems with reading where words appear to be floating on a page leading to slow reading or stopping to read altogether
An eye specialist will diagnose the disorder in the following ways:
- Ophthalmic evaluation or routine eye examination - The doctor checks whether refractive errors exist, whether there are weaknesses in focusing, and if the muscles are functioning
- Taking a medical history of the patient, especially the history of the symptoms - The doctor also inquires about symptoms like headaches, double vision, focusing problems, or other symptoms
- Positive fusional vergence test - Here, the patient looks through prism lenses and reads letters from an eye chart. As the patient does this, the examiner checks the point at which double vision occurs
- Measurement of convergence ability or point of convergence - The test determines the distance from the eyes to the point of focus without diplopia. The examiner holds a target in front of the eye, which s/he slowly moves closer to the eye till the eye drifts outward or double vision occurs. Prims are also used to measure the degree to which the eyes deviated outward at near and distance vision
Only those with symptoms require treatment. Various methods can treat convergence insufficiency. They will be selected based on the patient’s age, expense involved, distance to the therapist’s office, and patient’s preference. They include:
- Convergence exercises - A specialist in binocular vision and ocular muscle function or an ophthalmologist can prescribe eye-focusing exercises. One example is the pencil push-ups, where a pencil with a small letter on the side is moved closer to the nose's bridge. The patient follows the letter until they see double vision. These can be done at home for 15 minutes per day. Exercises can also be facilitated by a specialist at the office/clinic
- Base-out prism glasses - These are only used during short periods since they can be very tiring to the eyes. This method only helps to facilitate reading but doesn’t cure the problem of convergence insufficiency. The eyeglasses are fixed with a special power that causes the displacement of images
- Patching will not solve the issue of convergence but can help relieve double vision whenever a patient needs to complete large amounts of work at near vision
Surgery can be considered if prism glasses or exercises do not work. It is the last resort.
A program can be installed on the home computer which helps to increase convergence ability. The doctor uses printouts from these programs for follow up
Prognosis & Long-Term Outlook
The exercises can permanently cure convergence insufficiency where adequate convergence is maintained even with discontinuation of treatment. It may take three or more months to resolve convergence insufficiency. However, there are circumstances such as illness, lack of sleep, and increased near work that can cause a return of the symptoms. However, the symptoms can disappear after treatment.
Prevention & Follow Up
Some patients may be diagnosed with convergence insufficiency but lack symptoms. They will need follow-up.