What is Convergence Insufficiency?
Convergence insufficiency is a treatable binocular vision disorder that affects the ability to maintain clear and single images within arms reach like when you are reading a book. When we look at a book, our eyes point inwards together (converge) and both eyes are to point and focus at the same place in space. When this does not happen, individuals can experience diplopia (double vision) or overlapping of pictures/text or movement of print when focusing on a close object, such as a book, computer, tablet, smartphone, etc. Convergence insufficiency means the eyes struggle to focus easily for near tasks, affecting school work attention and office performance in adults.
For people with normal healthy convergence of the eyes and binocular vision — in other words, people who don't have Convergence Insufficiency — convergence of the two eyes (binocular vision) happens easily, effortlessly, and automatically...without any conscious effort or thought. In contrast, people with the binocular vision disorder of Convergence Insufficiency (CI) do not have normal, stable convergence of the two eyes. That is, the two eyes do not dependably work together to turn in (converge) with consistency, ease, accuracy, etc. As a result, any person with this condition must constantly expend extra effort to force the eyes to turn in to focus on a chosen visual target or to focus and follow changing and/or moving visual targets. Compared to a person with normal convergence of the eyes, the person with Convergence Insufficiency works much harder to clearly see, process, and comprehend all that they are seeing.
It is possible that four children in every classroom may be struggling with this condition! Convergence Insufficiency is present in both children and adults, and is not a condition that people “out grow”. Convergence Insufficiency is most closely associated with reading difficulties. This often leads parents or educators to suspect a learning disability or dyslexia (which is a language based disorder) rather than a vision problem. Diagnosis and treatment of Convergence Insufficiency is essential for your child’s success in reading, learning, sports performance, and more.
Some children with learning difficulties exhibit specific behaviors of impulsivity, hyperactivity, and distractibility. A common term used to describe children who exhibit such behaviors is Attention Deficit Hyperactivity Disorder (ADHD). Undetected and untreated vision problems can elicit some of the very same signs and symptoms that are commonly attributed to ADHD. Due to these similarities, some children with vision problems are mislabeled as having ADHD.
Symptoms of Convergence Insufficiency
Convergence Insufficiency can come with many different symptoms, and some of those symptoms present in the same way as reading difficulties, such as dyslexia. But, while dyslexia is a language disorder, Convergence Insufficiency is a visual disorder.
Symptoms of Convergence Insufficiency may include:
- Blurred vision
- Difficulty concentrating
- Double vision
- Headaches or muscle tension
- Difficulty reading
- Uses finger or ruler when reading
- Avoidance of close work
- Squinting or closing one eye
- Short attention span
- Words that are blurry or seem to "move", "float", or "jump" on the page
- Motion sickness/dizziness
- Anxiety
- Poor hand-eye coordination
Convergence Insufficiency and the Standard 20/20 Eye Test
It is important to understand that a finding of 20/20 vision does not mean perfect or even good enough vision. The 20-20 passing grade simply means that a person can see clearly with at least one eye at the distance of 20 feet only. To repeat for emphasis, only clear vision in at least one eye at a distance of 20 feet is measured in the standard 20/20 eye chart test.
For healthy normal vision, we need to have two eyes working together as a smooth, easy, simultaneous, and coordinated team. This is called eye teaming and the more technical or medical term is BINOCULAR VISION. Convergence Insufficiency is a binocular vision impairment that can affect learning, reading, sports ability, and many areas of life.
What is the best treatment for Convergence Insuffiiency?
It is important to understand that a finding of 20/20 vision does
What is the best treatment for CI?
Office based Optometric Vision Therapy is the most effective treatment for Convergence Insufficiency. Along with weekly office visits with your vision therapist, home skill development training (generally 15-30 minutes of prescribed home reinforcement procedures) are required to develop the lacking visual skills. On average, one can expect 20-26 hours of weekly in office therapy along with the prescribed home skill development training in order to remediate this dysfunction. This time frame may be longer in more severe cases or those associated with concussion or traumatic brain injuries.
Prismatic (prism) glasses may be prescribed to decrease some of the symptoms. This can be a potential management option for individuals who do not wish to pursue office vision therapy; however, for some individuals this will be part of the treatment plan in addition to office based vision therapy.
Scientific research, as well as optometric and ophthalmological clinical trials, agree that the primary treatment of CI should be vision therapy.
Convergence Insufficiency and Attention Deficit Disorder
Undiagnosed Convergence Insufficiency is often mistaken by individuals, teachers, friends and family as "laziness", "clumsiness", "day dreaming" or even Attention Deficit Disorder or Attention Deficit Hyperactive Disorder.
Consider if you are seeing doubling when reading, how long will you persist with your reading or desk tasks? Not very long. In a classroom setting, what is there to do? Often it would be talking to the classmate beside you or getting up and sharpening the pencil again or yet another bathroom break.
A 2005 study published in Strabismus 13:164-168, 2005 reported an apparent three time greater incidence of ADHD among patients with CI when compared with the incidence of ADHD in the general US population.
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Additional Information
Other Binocular Vision and Accommodative Dysfunctions
There are other Binocular Vision and Accommodative Disorders other than convergence insufficiency that may cause a significant increase in effort required to maintain clear and single images, to be able to read and comprehend what you have read and to be able to direct your action with your visual system accurately.
Some such examples are convergence excess (over pointing of the eyes), accommodative insufficiency,
“Convergence excess” is the term used to describe an eye muscle imbalance, which causes a tendency for the eyes to want to aim more inwardly than needed. Usually, this mismatch between where the eyes aim and where the object is located in space has more of an effect on vision up close (within arms reach), as opposed to looking farther away.
When a convergence excess exists, it requires the muscle coordination system to work harder to maintain alignment of the eyes. Sometimes, the extra-ocular muscles are taxed beyond their power to maintain single, binocular vision and can result in episodes of diplopia (double vision), or even to a point where using both eyes is not possible. In cases like these, people will either see double most of the time; the brain wants to reject this, and learns to suppress at least the central vision from one eye. This can occur in individuals that still have 20/20 eyesight
In the milder forms of convergence excess, we refer to it as “esophoria”. Symptoms of esophoria may include blurred vision at distance, near or both; headaches; intermittent diplopia; ocular fatigue; a drawing or pulling sensation around the eyes; excess blinking and head tilting. Dizziness, a tendency for motion sickness and an avoidance of near tasks such as reading, writing or computer use are also reported. Obviously, academic performance will suffer when children are esophoric.
Accommodative Dysfunctions
Accommodation is the ability to change focus from a distant to a near target (and vice versa). It is a complex process in which the crystalline lens (i.e. the "camera lens" positioned on the inside of the eye) alters its shape to bring an object into focus. Accommodation allows one to quickly bring a distant or near target into sharp focus. An accommodative dysfunction is an eye focusing problem that affects a child or young adult's ability to focus their eyes properly. The eyes' ability to accommodate is a vital visual function that allows us to read and perform many daily tasks.
Accommodative infacility is a condition in which the eyes have difficulty shifting focus from a distant to a near target (and vice versa). Some people like to think of it as a "poorly working camera" that takes several seconds to come into focus.
Accommodative infacility may be functional in nature, in which the child fails to develop normal eye focusing abilities. It may also be due to acquired brain injury such as in a concussion. In both cases, vision therapy is the treatment of choice.
To effectively read with accuracy and efficiency in the classroom or perform in the work environment, the eyes need to accommodate (focus) in three essential ways. First, the eyes must have the strength to sustain focus on the printed material for an extended period. Second, the eyes must have a high degree of precision to see the print clearly. Third, the eyes must have the flexibility to change focus from near to far to properly acquire visual information in the environment. Therefore, for efficient reading, learning, and working our eyes must engage in these accommodation (eye focusing) abilities. An individual can have 20/20 eye sight but still have problems in one or more of these areas. Fatigue can set in quickly as a result. Treatment may include prescription glasses and/or office based optometric vision therapy.
Unfortunately many eye care practitioners do not routinely assess these visual skills. If you feel you would benefit from an extended visual assessment including these areas, contact Calgary Vision Therapy at 403-242-1800 to begin the process to schedule an appointment. A referral is not required.
