Convergence insufficiency (CI) is a common condition that is characterized by the inability to maintain proper binocular eye alignment on near objects. An eye teaming problem in which the eyes have a strong tendency to drift outward when reading or doing close work. To prevent double vision, the individual exerts extra effort to make the eyes turn back in (converge). This extra effort can lead to a number of frustrating symptoms which interfere with the ability to read and work comfortably at near.
Under normal circumstances, the eyes must turn inwards to view objects at near. Convergence insufficiency results when an individual has an outward natural or resting eye posture at near which means that they must exert more effort to bring the eyes in while reading. This can make it appear as though words are moving while reading as well as lead to blurred/double vision, impaired concentration, eyestrain, drowsiness, and headaches. It is important to note that individuals with CI can and often have 20/20 vision. Clarity does not guarantee comfort when it comes to vision.
What Causes Convergence Insufficiency?
The exact cause of primary convergence insufficiency is unknown. Convergence insufficiency can arise following infection, traumatic brain injury, certain medications, neurodegenerative diseases (e.g. Parkinson’s), myasthenia gravis, or Graves ophthalmopathy. Diagnosis of primary convergence insufficiency is most common in children and young adults when they begin to experience symptoms from prolonged periods of near work.
What are the Symptoms of Convergence Insufficiency?
It may not always be evident that someone suffers from convergence insufficiency because the symptoms may vary. People with convergence insufficiency often complain of the following symptoms when reading or doing intense near work:
• Eyestrain or tired eyes (especially with or after reading)
• Moving or overlapping words
• Blurred vision
• Double vision
• Inability to concentrate
• Short attention span
• Frequent loss of place
• Squinting, rubbing, closing or covering an eye
• Sleepiness during the activity
• Trouble remembering what was read
• Words appear to move, jump, swim or float
• Problems with motion sickness and/or vertigo
It is not unusual for a person with convergence insufficiency to cover or close one eye while reading to relieve the blurring or double vision. Symptoms will be worsened by illness, lack of sleep, anxiety, and/or prolonged close work.
Many people who would test as having convergence insufficiency (if tested) may not complain of double vision or the other symptoms listed above because vision in one eye has shut down. In other words, even though both eyes are open and are healthy and capable of sight, the person's brain ignores one eye to avoid double vision. This is a neurologically active process called suppression.
Suppression of vision in one eye causes loss of binocular (two-eyed) vision and depth perception. Poor binocular vision can have a negative impact on many areas of life, such as coordination, sports, judgment of distances, eye contact, motion sickness, etc. Consequently, a person with convergence insufficiency who is suppressing one eye can show some or all of the following symptoms:
• Trouble catching balls and other objects thrown through the air
• Avoidance of tasks or sports that require depth perception
• Frequently clumsy due to misjudgment of physical distances
• Trips and stumbles on uneven surfaces, stairs, and curbs, etc.
• Frequent spilling or knocking over of objects
• Bumping into doors, furniture and other stationary objects
• Sports and/or car parking accidents
• Avoidance of eye contact
• Poor posture while doing activities requiring near vision
• One shoulder noticeably higher
• Frequent head tilt
• Problems with motion sickness and/or vertigo
If untreated, in some cases, convergence insufficiency can lead to an outward eye turn that comes and goes (intermittent exotropia).
How Common is Convergence Insufficiency?
Convergence insufficiency is present in one out of every 20 children. Most likely one to two children in every classroom have this condition. Convergence insufficiency has a reported prevalence among children and adults in the United States of 2.5 to 13%. Children with convergence insufficiency are often thought to be lazy or disruptive in the classroom. They tend to have poor attention and often tire more easily when reading.
Detection and Diagnosis of Convergence Insufficiency
Convergence insufficiency is not usually detected on regular vision screenings. Often, the only way it can be properly diagnosed is to see an eye doctor (Optometrist). In fact, Pediatric or Behavioral (Developmental) Optometrists are better experts in dealing with this condition (see covd.org).
There are several characteristics that eye doctors look for when properly diagnosing convergence insufficiency.
Convergence (eye teaming) and accommodation (focusing) tests are the important diagnostic tools. A basic eye exam or screening with the 20/20 eye chart is not adequate for the detection of convergence insufficiency (and many other visual conditions). A person can pass the 20/20 test and still have convergence insufficiency. A comprehensive vision evaluation by an eye doctor who tests binocular (two-eyed) vision and who can refer or provide for in-office vision therapy is recommended for all individuals who do reading and deskwork.
Convergence insufficiency disorder frequently goes undetected in school age children because proper testing is not included in (1) eye tests in a pediatrician's office; (2) school eye screenings; and/or (3) standard eye exams in an optometrist's or ophthalmologist's office.
The good news is that convergence insufficiency responds well to proper treatment, the bad news is that --- due to pervasive lack of testing for convergence insufficiency -- many people are not getting the help they need early in life. And many are never helped. Children, teenagers and adults who remain undiagnosed and untreated tend to avoid reading and close work as much as possible or use various strategies to combat symptoms (such as, using a ruler or finger to keep one's place while reading or taking frequent breaks, etc.).
A Word from Dr. Fulton
Don’t underestimate the influence that a condition such as convergence insufficiency can have on a child's or young adult’s reading ability, concentration, comprehension, and education. If a child is acting out in class, it could be due to a vision problem such as convergence insufficiency. Parents should know that convergence insufficiency can cause numerous symptoms that make it difficult to read and comprehend. However, it is proven that office-based vision therapy with a trained therapist plus at-home therapy reinforcement can treat the condition and eliminate symptoms.
Arnoldi, K., & Reynolds, J.D. (2007). A Review of Convergence Insufficiency: What Are We Really Accomplishing with Exercises? American Orthoptic Journal, 57, pp. 123-130. Retrieved from http://aoj.uwpress.org/content/57/1/123.full.pdf
Cacho-Martinez, P. Garcia-Munoz, & A. Ruiz-Cantero, M.T. Do we really know the prevalence of accommodative and nonstrabismic binocular dysfunctions? Journal of Optometry, 3(4), pp. 185-197. Retreived from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3974377/pdf/main.pdf
Convergence Insufficiency Treatment Trial Investigator Group. (2009). A Randomized Clinical Trial of Treatments for Symptomatic Convergence Insufficiency in Children. Arch Ophthalmol, 126 (10), pp. 1336-1349. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2779032/pdf/nihms-148199.pdf
Convergence Insufficiency Treatment Trial Study Group. (2009). Long-Term Effectiveness of Treatments for Symptomatic Convergence Insufficiency in Children. Optom Vis Sci, 86 (9), pp. 1096-1103. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2780441/pdf/nihms153856.pdf
Cooper, J., & Jamal, N. (2012) Convergence Insufficiency—a major review. American Optometric Association. Retrieved from http://www.coopereyecare.com/studies/CI%20Major%20Review%20copy.pdf
Scheiman, M. & Wick, B. (2014). Clinical Management of Binocular Vision. Philadelphia: Lippincott Williams & Wilkins.
Scheiman et al. (2005). A Randomized Clinical Trial of Vision Therapy/Orthoptics versus Pencil Pushups for the Treatment of Convergence Insufficiency in Young Adults. Optometry and Vision Science, 82 (7), pp. E583-595. Retrieved from http://www.convergenceinsufficiency.net/uploads/citt_adult_pilot_study_manuscript_ovs_82_583-593.pdf