Convergence Insufficiency (CI) is a common binocular (two-eyed) vision disorder in which the eyes do not work at near easily. An eye teaming problem in which the eyes have a strong tendency to drift outward when reading or doing close work (exophoria at near). If the eyes do drift out, the person is likely to have double vision .
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.
From Archives of Ophthalmology. 2008;126(10):1336-1349
Convergence insufficiency (CI) is a common binocular vision disorder that is often associated with a variety of symptoms, including eyestrain, headaches, blurred vision, diplopia [double vision] , sleepiness, difficulty concentrating, movement of print while reading, and loss of comprehension after short periods of reading or performing close activities.
A person who has convergence insufficiency may show and/or complain of the following while doing close work (i.e., reading, computer work, deskwork, playing handheld video games, doing crafts, etc.):
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:
If untreated, in some cases, convergence insufficiency can lead to an outward eye turn that comes and goes (intermittent exotropia).
Convergence insufficiency has a reported prevalence among children and adults in the United States of 2.5 to 13%.
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 -- particularly students of any age.
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, ophthalmologist's or optician's office.
According to Dr. M. Bartiss, O.D., M.D.,
Patients typically present [themselves for testing and treatment] as teenagers or in early adulthood, complaining of gradually worsening eyestrain, periocular headache, blurred vision after brief periods of reading, and, sometimes, crossed diplopia [double vision] with near work. Fortunately, in most cases, convergence insufficiency is very amenable to orthoptics and vision therapy.
Regarding Dr. Bartiss' observations: while 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.).
Treatments for CI can be categorized as active or passive:
Pencil Push-ups: While a 2002 survey of ophthalmologists and optometrists indicated that home-based pencil-pushups therapy is the most common treatment, scientific research does not support this method. Studies done on pencil pushups have shown it to be ineffective in eliminating symptoms.
Surgical Care: The decision to proceed with eye muscle surgery should be made with caution and only after all other efforts have failed.