Convergence Insufficiency & The Stroop Effect

Every day in our practice we diagnose and treat patients (both children and adults) with convergence insufficiency and other forms of binocular vision dysfunction. The results and success rate are astounding. Yes we improve several aspects of people's vision, including: eye teaming, eye tracking, eye focusing, visual perception, visual processing speed and working memory. But more importantly we improve their ability to perform real world tasks. This blog talks about one aspect of this improvement, the correlation between vision and Stroo.

Vision is our dominant sense, and a disruption to vision can have massive impacts on one's life. For example, patients who suffer a brain injury often have difficulties returning to work and give up many of their favorite hobbies because of their vision conditions. Sadly there are countless kids who are born with a disrupted visual system that interferes with their ability to learn. Even though 80% or more of learning occurs through the visual system, most kids enter school without ever having a comprehensive eye examination with a residency-trained pediatric optometrist. This leaves many vision conditions undiagnosed and untreated. It is no wonder that 1 in 4 kids have a vision condition significant enough to impact learning.

It may seem logical that vision impacts learning, however there are still doctors who argue against a link between vision and learning (I would ask them if blindfolding them would have made school more difficult, or if wearing their friend's glasses to induce crashing headaches and blurred vision would have limited their ability to stay engaged in the classroom). Multiple studies have reported a link between binocular vision (eye teaming) and problems with learning. The most common challenges for people with binocular vision (eye teaming), accommodative (eye focusing), and oculomotor (eye tracking) conditions is the act of reading. Vision does impact one's ability to learn and too often this barrier goes undiagnosed and untreated.

Why is it important to discuss the link between vision and learning? Because in many cases the vision conditions that impact learning are easily treated by a doctor who is residency-trained in binocular vision. Vision conditions impact about a quarter of students yet little is done to diagnose and treat these conditions. One reason for this may be the confusion surrounding a student's behavior. In addition to being undiagnosed, vision conditions are often misdiagnosed as the child being lazy, having a bad attitude, ADHD, dyslexia (which is a language condition), or not having the intellectual capacity to achieve.

Studies have already shown higher rates of certain vision conditions in people with ADHD. A recent study has taken it one step further and looked for a correlation between binocular vision dysfunction, specifically convergence insufficiency, and cognitive executive functioning.

The Stroop Effect is a demonstration of interference on reaction time. The Stroop Effect is assessed during the Stroop Test. This is a fun and frustrating test where you are asked to read a series of colors as quickly as possible. Yes it is easy look at a series of boxes and tell someone what color each box is. But it is more difficult to tell someone that the word 'red' is written in blue. This is what the Stroop Test does; it is a series of words (all colors) where the text color is mis-matched with the word. The word 'red' is written in blue, the word 'green' is written in pink and so on. This test requires two brain processes – word recognition and color recognition. This mis-match requires selective attention (which all kids have when it benefits them) and attentional focus. This test requires processing speed and difficulties results in prolonged processing time; which is an indicator of attentional processing. The time required to complete the test increases with attentional fatigue or inattentiveness. The link with ADHD is pretty straight forward – difficulties with attention. The error in recognizing the correct color during the Stroop Test is associated with impulsivity (a characteristic of many patients with ADHD).

So what does this have to do with vision again? This study found a correlation between convergence insufficiency (a common binocular vision condition that we treat every day in our practice) and the interference effect on the Stroop Test. That's right, patients with convergence insufficiency had a poor performance on the Stroop Test just like kids with ADHD, learning disabilities and poor executive functioning. Children with convergence insufficiency showed significantly higher interference effect than did students with normal binocular vision skills. The researchers concluded that vergence could be a mechanism for attentional and cognitive functioning.

This highlights a few very important points.

1. It is extremely important that every child receive an eye examination by a Residency-Trained Pediatric Optometrist prior to entering school. An eye exam with a doctor specifically trained in pediatric eye care is the best way to ensure that no vision conditions are missed. Screenings and the pediatrician or a quick exam by the parents' eye doctor can easily miss the conditions that impact learning.

2. Children who are struggling with reading or learning should have a Binocular Vision Assessment with an optometrist who is Residency-Trained in binocular vision, vision therapy or neuro-optometry. A Binocular Vision Assessment tests the aspects of vision that can impact learning, such as convergence insufficiency. The results of this assessment are used to plan appropriate treatment.

3. Vision impacts learning. Not every reading challenge is dyslexia and not every child who has difficulty staying on task has ADHD. ADHD is a diagnosis of exclusion. It is the presence of certain symptoms in the absence of another contributing condition. So can you confidently say a child has ADHD before ruling out convergence insufficiency? The answer is no.