Binocular vision dysfunction

Binocular vision dysfunction (BVD) is one of the more common problems people have with their vision, affecting 10%-30% of people. This is a condition where your eyes struggle to merge the light they pick up into a single unified field of vision because they're sending misaligned images to your brain.  

Understanding binocular vision dysfunction (BVD)

Definitions and basics

BVD is a problem where your eyes are feeding different images to your brain that don't properly merge into a single picture. This happens because your eyes are pointing in somewhat different directions. In normal vision, each eye gets a slightly different image because they're in slightly different positions and looking at the field in front of you at slightly different angles. A really big part of our brains is devoted to merging these two visual feeds into a single 3D image, which usually happens without having to think about it.

Symptoms of BVD

If you have BVD, your eyes are basically feeding images that are so different your brain can't merge them properly. The result is double vision, blurred vision, or confusion. Secondary symptoms can include migraines, dizziness, nausea, and lots of other no-fun issues as your brain struggles to make sense of the pictures your eyes are sending. The split in your vision can make even keeping your balance very hard to impossible.

Causes and risk factors

Your BVD can be caused by almost anything that causes a misalignment of the eyes. This can be a natural misalignment you were born with, the result of an injury, stress, drugs and alcohol, or just being tired.

Developmental factors

Some people are just born with eyes that don't line up. You could have one eye that's higher than the other by a small margin, eyes that are angled a bit inward or outward, or maybe a lazy eye that pulls to one side. In all these cases, the eyes will be looking at such different images that there's really no way for the brain to put them together properly and get a unified image field. If it's something you're born with, you may have been dealing with BVD your whole life. 

Trauma and injuries

Trauma can cause BVD, usually after some kind of injury to the face. Damage to the bridge of the nose caused by a car crash or unfortunate punch can change the geography of your facial bones. If you don't heal just right, the result can be eyes that point in sufficiently divergent directions that you're left with double vision. Basically, anything that pushes or pulls one or both of your eyes out of alignment is potentially enough to cause BVD.

Stress and visual strain

BVD isn't necessarily permanent. You can get double vision if you're under stress or overly tired. This happens because the muscles of your eyes get fatigued and no longer hold your eyes straight forward. In the modern world, you're most likely to get this after a marathon work or gaming session on the computer. It's also pretty common after all-nighters or other extended periods without sleep.

Diagnosis and treatment

You need an eye exam to reliably diagnose BVD, but there are some telltale signs you may be prone to this issue. There are also some treatment options, from special exercises to glasses and even surgery to correct relatively minor physical eye misalignments. 

Diagnosis of BVD

A full BVD exam starts with a questionnaire to find out how you subjectively see the world, followed by a check of your eye resting position and eye movements. Do your eyes work together like a team, or do they pull apart like an old married couple? How do your eyes focus, and do they move together onto a singular target?

Your eye care professional will also probably test your vision directly. They're looking at your visual perception, spatial acuity, and depth perception. These tests can feel a little like a field sobriety test, which is no coincidence. Each eye doing its own thing is one of the symptoms of being really drunk, which is why a lot of the tests police use are borrowed from BVD-related eye exams.

Treatment options

Your treatment options for BVD depend on what's causing it. If you're prone to fatigue or eye strain, the fix is to get rest and limit your screen time. If you have a lazy eye, you might get micro-prism lenses that bend light way more on one side than another. If the issue is a physical misalignment of the eyes, there's even a range of surgical options for fixing it.

 

FAQ

Is binocular vision dysfunction the same as strabismus or lazy eye?

BVD is not the same as these conditions, but they can both cause it. Basically, BVD is the symptom, while strabismus is one of the causes.

Can BVD be managed or corrected in children through vision therapy?

In some cases, kids will grow out of BVD-causing conditions. For others, special glasses or exercises might be prescribed to help. 

Can BVD lead to headaches or eye strain, and how can these be managed?

Headaches and eye strain are among the most common effects of BVD, and they can be managed with rest, exercises to strengthen the eyes, and sometimes just headache medicine to cope in the short term.