Binocular Vision Dysfunction: The Weird Reason Your Eyes Might Be Giving You Headaches
Let’s do a weird little test. Don’t worry, it’s quick and no one’s watching.
Step 1: Stare directly at this red dot.
Step 2: Cover one eye with your hand. Keep staring.
Step 3: Switch eyes, cover the other one.
Step 4: Repeat a few times.
Now ask yourself: Did the dot move? Just a little, side to side?
If yes, congratulations, you’ve just caught your eyes red-handed not agreeing on where “straight ahead” is. Weird, right?
Let me explain what’s going on.
Your Eyes Are a Team… But With Trust Issues
Under normal conditions, when both eyes are open and working together, they play nice. That’s called binocular viewing. Your brain forces your eyes to align so that what you see becomes a single, unified picture.
But the moment you cover one eye, the other one relaxes and moves to its default “rest” position. The same happens when you switch eyes. If the dot shifted, that means your eyes each have a slightly different idea of what “straight ahead” means when left to their own devices.
Now, don’t panic. This doesn’t mean your eyes are broken. Everyone has some natural misalignment, and your brain is usually great at compensating for it. But sometimes, the cost of that constant compensation adds up.
And that’s where things get interesting.
The Eye Muscles Are Strong, They Can Handle This
Your eye muscles, known as the extraocular muscles (EOMs), are pound-for-pound some of the strongest in your body. Seriously, if your leg muscles were as dense with myosin (that’s the protein that helps muscles contract), you could squat like 20,000 lbs. Not that you should. But the point is: pulling your eyes into alignment should be easy.
So why do people with tiny misalignments sometimes get headaches, eye strain, and even neck pain?
Because it’s not the muscles that struggle, it’s the brain that has to track all of this.
The Hidden Bandwidth Tax
Every time your eyes realign themselves, tiny sensors in the muscles called proprioceptors, send signals to your brain, telling it where your eyeballs are in 3D space.
Those signals travel along the trigeminal nerve, a big important nerve that also handles things like facial sensation and parts of your headache pathways. So when it’s getting spammed with constant “eye muscle update” messages, that bandwidth gets clogged.
And that’s when you can start feeling the effects: pressure behind your eyes, light sensitivity, neck tension, even migraines.
“But it’s not like my eyes are constantly realigning themselves,” you say.
Oh, but they are.
The Saccade Secret
Every time you move your eyes from one point to another, your brain does a neat trick: it temporarily turns off your visual processing.
Why? Because if it didn’t, you’d see the world as a smeary, disorienting mess every time you shift your gaze. Don’t believe me? Try looking back and forth between your eyes in the mirror. You’ll never catch them moving, it’s like a weird visual blackout. Or film yourself doing it. You’ll see it on playback, but not in real life.
These rapid eye jumps are called saccades, and you do them all the time, especially when reading. Every word, every line shift? Saccade. That’s dozens, even hundreds of times a minute that your binocularity is temporarily broken… and then reset.
Each reset? More proprioceptive noise through the trigeminal nerve. More work for your brain. More opportunity for symptoms.
This is why extended near work, either on the computer or reading a book, can cause such discomfort for so many people. It’s not tired eye muscles, it’s an overwhelmed trigeminal nerve being spammed after every saccade.
So, What Can You Do?
Enter: Neurolens… and microprism.
A few years ago, a group of optometrists and neurologists started noticing something odd: patients with perfect vision on paper were still dealing with headaches, neck pain, eye fatigue, and that “I’m cooked after 30 minutes of screen time” feeling. The culprit ended up being tiny, hard-to-detect misalignments in how their eyes work together, a pattern now called Binocular Vision Dysfunction (BVD).
To solve this, they created Neurolens, glasses with a contoured prism built directly into the lenses. The prism gently guides the eyes back into their natural, relaxed alignment so the visual system doesn’t have to fight to keep both eyes teamed. Think noise-cancelling headphones, but for your eyes and brain. Less visual “static” means less trigeminal nerve irritation, and for many people, fewer headaches, less neck tension, reduced fatigue, and more comfortable screen time.
In some cases, especially when the misalignment includes a vertical component, microprism can be added to the prescription as well. Even a tiny vertical correction (far smaller than what would show up on a regular exam) can substantially reduce symptoms if your eyes are subtly sitting above or below each other. Vertical microprism is often the missing piece for people whose discomfort seems mysterious or out of proportion to their test results.
If this is all sounding uncomfortably familiar, it may be worth getting checked properly. The red-dot alignment test you just did can hint at BVD, but in-clinic we take it further: we use an eye-tracking VR headset to measure exactly how your eyes behave when they’re allowed to drift to their natural resting position.
Your eyes (and your head and neck) will thank you.
Dr. Burke is an optometrist practicing at Calgary Vision Centre. He has a special interest in Neuro-Optometry and how the brain and eyes work together. Opinions above do not constitute medical advice, and readers should consult with their optometrist and health care team if they have questions or concerns about their eye health