In it’s simplest definition, Convergence Insufficiency is when the two eyes do not converge (direct their aim inward together) strongly enough when someone is looking at something up close. This results in the eyes not being aimed at the same near target and the person seeing double.
The cause of convergence insufficiency, however, is not quite so simple. In order to understand why the eyes are not moving inward together as they should, we have to dive a little deeper.
The first thing to understand is that when we look at an object that is close to us, like a book, we must do two things in order to see it clearly. First, we must focus the lens inside of each eye in the same way a camera refocuses its lens when looking up close versus far. Second, we must move both eyes to aim at the exact same letter of each word together so we don’t see double and continue to keep them aligned as we read across a page.
If this sounds like a lot of work, it is. The immense amount of precision required to do this would be absolutely exhausting if we had to consciously focus on keeping things clear and actively lining up our eyes with each other. Luckily for us, most of this work is done autonomically (without us really having to think about it).
So what is going wrong in convergence insufficiency? Well, in short, the processing system (think of the brain as a computer) that normally coordinates these eye movements autonomically without us having to think about it isn’t working properly.
Each time we bring something closer to our eyes and our brain directs the lens inside of our eye to change it’s shape and focus (bringing clarity), the brain also gauges how close that object is based on how much the lens has to focus. Once the brain has a good idea of how close the object is, it then directs the eyes to move inward to aim at an object that it thinks is at the distance indicated by how much the lenses in the eye had to focus. Hopefully, your head isn’t spinning from this, because it is quite complicated and there are mathematical and optical equations that your developmental optometrist does to really dial in where the weaknesses are.
To simplify, the lens focuses, the brain judges how far the object is based on the amount of focusing power used, and the brain brings the eyes into the distance that it things the object is.
Now that we understand one of the main concepts of what goes on in a healthy and properly working visual processing system, we must ask again, “what is going wrong in convergence insufficiency?”
The error that occurs in convergence insufficiency is in the actually processing done by the brain. A very important concept to understand is that it is NOT a muscle problem with the muscles moving the eyes. It is a BRAIN PROBLEM with how the brain is signaling and directing the eyes.
The more complex, but truest answer to what convergence insufficiency is is that it is a problem with the brain not sending the correct signal to bring the eyes in a sufficient amount.
So what happens when the brain doesn’t send a correct or strong enough signal and the eyes don’t come in enough to look at a near target?
The eyes sit outward slightly and the person has to then work to bring them into the correct point so they don’t see double. And if you are thinking that this sounds exhausting, you are right again. It is literally a headache waiting to happen.
When someone has convergence insufficiency, they are constantly working to bring their eyes in enough to prevent seeing double. They have a limit and the eyes eventually pull back and the person will see double coming in and out until it is constant. This constant work can cause headaches and eye strain. Some people even report nausea as everything is going back and forth from single to double and it can be disorienting.
The sad part is that glasses do NOT help convergence insufficiency. So what do people do to relieve the symptoms? There’s nothing they can do really except to avoid the cause and that is near work.
Obviously avoiding near work isn’t a very helpful suggestion or route to take for a student who must read and study in order to succeed in school. It also won’t work for the majority of adults who’s jobs require some kind of reading or work at a computer. So the obviously better solution is to seek medical help to not just treat, but cure the condition.
What treatment is there for convergence insufficiency?
Vision Therapy. Vision therapy works to improve the processing system of our vision. As we went over earlier, convergence insufficiency is NOT a muscle problem and there is no way to increase the strength of the muscles that move our eyes anyways. Convergence insufficiency is a BRAIN and VISUAL PROCESSING problem and that is what vision therapy so amazingly treats.
Vision therapy is incredibly efficient and has cure rates of 85-95%. I often explain to my patients that vision therapy is like physical therapy, but for the visual processing system. We use customized parameters on each exercise to fine-tune how your brain processes the visional information it is receiving and direct the visual system (the eyes, muscles of the eyes, & processing in the brain) to more efficiently collect and process new visual information.
With the brain working more efficiently, patients no longer have to struggle to read up close. No longer is there the need to force their eyes together to keep things clear as their brain is now autonomically (performing without us having to think about it) doing it for them.
With the brain doing the work, patients and students treated and cured with vision therapy can now focus on the information that they are reading and learning and absorbing the material instead of focusing on preventing double vision and not even knowing what they’ve read.
How prevalent is convergence insufficiency?
According to the Convergence Insufficiency Treatment Trial, convergence insufficiency, or CI, “has a prevalence of 4.2% to 6% in school and clinic setting”. That’s roughly 1 out of every 20 kids sitting in a classroom trying to keep up with their studies.
These numbers are alarming and the sad reason why the public doesn’t hear about it more often is because it is often completely missed. Because children think that everyone sees the world the same way that they see the world, children don’t know how to describe the visual symptoms of blur or double vision. They will still try to avoid reading, but will often sadly be misdiagnosed with ADHD, ADD, or other learning disabilities.
Remembering that vision is MUCH more than just 20/20, as a behavioral optometrist, I can’t help but always want to educate people on the 17 Visual Skills and all the ones that are specifically needed just to read and that when it comes to learning, 80% of what children learn is take in visually.
So it is vital to their academic success and success in everyday activities, as these are not problems children outgrow, that they have well developed visual information processing skills including the visual perception skills here on this page.
If you feel like you or your little one are struggling with reading or any of the visual skills needed to live your life comfortably, don’t worry! Vision Therapy has incredibly high success rates for various vision conditions and lazy-eyes (or eye-turns as we like to call them). Call our office today and schedule a complete and comprehensive vision exam.