What is Convergence Insufficiency (CI)?
Do you think you or your child has reading or attention difficulties at work or at school? It might be convergence insufficiency or other visual problems. At Central Vision Opticians we specialise in diagnosing and treating a range of binocular visual difficulties including CI. To date, we have helped hundreds of children and adults with the condition. I wanted to share some insights into CI including its overlap with, reading difficulties, Dyslexia & Dyspraxia, Visual Tracking Problems and ADHD, so read on to find out!
What is Convergence Insufficiency?
Convergence insufficiency is a common condition that affects near vision and reading vision. It is a leading cause of eye strain, blurred vision and double vision, and occurs when the eyes cannot work well together when looking at close objects.
Convergence is the normal way our eyes move inwards when reading or looking at close objects. In cases of convergence insufficiency the eyes don’t turn inwards adequately to allow both eyes to work together; therefore more effort is required than normal to align the eyes.
Normal Convergence: The eyes are aligned to the word and it appears as one clear word.
Convergence Insufficiency: The eyes do not converge enough, therefore the images do not align, making the word (“THE”) appear doubled or overlapping.
"But my optician said the sight was fine"
Eye tests which involve reading a standard letter chart measure visual acuity. However, convergence insufficiency can occur in children who otherwise have normal vision which means that school screenings and routine sight tests frequently miss it. Glasses only help in a small number of cases.
How can I tell if I have CI?
A recent study by the Convergence Insufficiency Treatment Trial Investigator Group gathered important data about the symptoms of convergence insufficiency in a series of studies (2008 Reference, 2005 Reference ?). These were the first studies that used a scientifically valid and reliable symptom questionnaire.
These studies found that people with convergence insufficiency reported that the following symptoms occurred “fairly often” or “always” while reading or doing close work:
Studies report that CI is present in 15-17% of the general population and in 60% of young people complaining about blurry vision when reading. About 45% of children with CI also complain of difficulties with attention in general.
For adults, the main consequences of having CI are headaches and fatigue. This can mean low performance at work or a propensity to make simple mistakes.
How can I tell my child has CI?
Since vision can be otherwise normal, it is important to let your optometrist know if your child has reading or learning difficulties. Look out to see if they squint or strain their eyes when doing close work such as reading, computer or tablet work, video games or arts and crafts, or have trouble concentrating on these activities.
Children with CI will tend to re-read words or sentences, miss small words or skip lines when reading. This often means they end up having reduced grades at school, a slower than average reading pace which means they may struggle compared to their classmates. Their comprehension can low and they may develop an aversion to reading and generally find academia harder.
What causes CI?
Although the underlying cause of convergence insufficiency could be several difficulties, CI involves the misalignment of the muscles that move the eye, so it is an oculomotor (eye movement/muscle), stamina or binocular vision problem. The good news is that, like with using physiotherapy to solve other muscular problems, CI can also be corrected with eye exercises. Patients are usually permanently cured after vision therapy to strengthen their convergence.
However, if left untreated or undetected, CI can lead to suppression: the neurological ‘shutting down’ of one eye - although both eyes are open and healthy, the brain ignores one eye to avoid the double vision that a convergence problem causes. In these cases, the patient may not complain of double vision or other symptoms related to CI, so an expert opinion comes in handy!
What are the consequences of having CI?
For both children and adults, problems with attention can arise from visual problems. In fact, many symptoms of CI overlap with symptoms of ADHD. A 2005 study investigated this, and the results were that children with convergence insufficiency are three times as likely to be diagnosed with ADHD than children without the disorder.
The professor running the study commented that:
“We don't know if convergence insufficiency makes ADHD worse or if convergence insufficiency is misdiagnosed as ADHD. What we do know is that more research must be done on this subject and that patients diagnosed with ADHD should also be evaluated for convergence insufficiency and treated accordingly.”
Another study showed that students who were rated as poor in motivation and performance by parents and teachers were statistically more likely to have eye teaming, focusing, eye movement, and visual form reproduction problems.
So CI has a strong correlation with attention disorders, although it is unclear whether it is a cause or a consequence. In any case, it is worth checking your child’s eyes if they have ADHD or any kind of attention problems!
How do we test for CI?
CI is to do with binocular function which means keeping the two eyes working together. An assessment of binocular vision will determine whether you or your child has this problem when focusing on near targets. At Central Vision Opticians we specialise in assessing and treating Convergence Insufficiency.
The traditional way to do this is to measure the near point of convergence (NPC), measuring the distance from the eyes to where both eyes can focus without double vision. The optometrist holds a small target in front of you and slowly moves it closer until you either have double vision or the optometrist sees an eye drift outward.
Another test uses prism lenses to assess fusional vergence (FV) or Fusional Reserves (FR). You are asked to read letters on a chart through special prism lenses and the optometrist notes when you begin to have double vision.
Unlike other practitioners, we also use several other methods including assessments for AC/A ratio (how the eyes work together when focusing), binocular vision stability, stamina, and a deep understanding of how the visual system functions.
We also have Okimo, an exclusive computerised test that analyses eye movements while you read in order to investigate convergence and visual tracking.
What can we do about it?
Exercises under a regime of vision therapy are the most effective treatment. Exercises performed regularly and frequently will resolve symptoms in almost all cases.
In the past, suffers of CI were given one simple exercise of bringing a pencil close to the nose (pencil push up exercises). However, this has now been proven to be ineffective. A bespoke range of exercises under the supervision of a vision therapist will yield the largest improvement.
CI can also overlap with other visual difficulties such as accommodative disorders (problems with focusing), and poor visual tracking skills. Therefore a full assessment of visual skills is essential in diagnosing the cause and establishing the best course of treatment.
At Central Vision Opticians we test for all the essential visual skills your child needs to read and for other close work. We can cross reference the strength of each skill to figure out which visual problem your child might be suffering from, and advise you on how best to proceed.