Exophoria

What is exophoria?

Exophoria is when covering one of your eyes makes it drift outward (away from your nose) and out of alignment. For context, phoria is when covering an eye makes it drift out of alignment.

Smaller misalignments from phoria are normal, and almost everyone has this. But exophoria becomes an issue when the misalignment is big enough. That’s because your eyes and brain have trouble compensating, which disrupts your vision and can lead to constant eye misalignment (strabismus).

Why eye alignment matters

Your vision depends on proper eye alignment. When your eyes align properly, your brain can “fuse” the input from both eyes into the single big-picture 3D view that you see. That’s called binocular vision (stereopsis).

When you have significant exophoria, your brain may struggle to fuse the two pictures. That can cause other, more disruptive symptoms like:

• Double vision (diplopia).
• Eye pain.
• Eye strain.
• Headaches.
• Dizziness or vertigo.

What are the most common causes of exophoria?

When you’re using both eyes, your brain uses what each eye sees to make subtle adjustments to align and focus them. When you cover one eye, that eye can’t use the same reference points as the uncovered eye, so it has trouble staying aligned. That’s why a small amount of phoria is normal.

A few other contributing factors can make exophoria more likely to develop, including:

• Your anatomy. Exophoria is something you can have when you’re born or develop during childhood. Exophoria can also happen if your eyes aren’t the same distance from the center of your face, or if you have weakness in some of the muscles that control your eye movement.
• Your eyesight. Exophoria is more likely to happen in people with nearsightedness (myopia).
• How you use your eyes. You might be more prone to exophoria if you frequently rely on just one eye for a job or hobby. Examples include frequently using a microscope or telescope, a transit level (a special scope that engineers or surveyors use), a magnifying glass or a jeweler’s loupe.
• Medical conditions. You can get exophoria with head injuries, especially concussions and traumatic brain injuries (TBIs) and — less commonly — with stroke.
• Sex. Some research studies show that men and people assigned male at birth (AFAB) are more likely to have exophoria. But more research is necessary to confirm if and why this is the case.

How is exophoria treated?

Exophoria often doesn’t need treatment unless it becomes severe enough to cause other symptoms. It can also worsen and cause tropias, which are misalignments that happen without covering an eye.

The most common treatment options include:

• Vision correction. Prescription glasses or contact lenses might be all it takes to correct your exophoria.
• Vision therapy. Just like physical therapy helps you strengthen muscles in your arms, legs and core, vision therapy helps strengthen your eye muscles. Vision therapists guide you through specific exercises to help strengthen the muscles that help your eyes align.
• Prism lenses. These can be built into eyeglass lenses or come as an attachable layer you put on the lenses of your eyeglasses. They shift the way light beams enter your eyes, so it takes less effort for your eyes to align. That can help keep exophoria from getting worse.
• OnabotulinumtoxinA (Botox®). This medication interferes with the nerve signals that control muscles, causing weakness or paralysis. Precisely injecting it can treat exophoria because it causes just enough muscle weakness to compensate for eye muscles that pull too strongly away from your nose.
• Surgery. Certain procedures deliberately weaken muscles that rotate your eyes outward, reducing or eliminating exophoria. This isn’t reversible, so it’s usually only an option when other treatments don’t work.

What can I do at home to treat exophoria?

Exophoria isn’t a condition you can self-diagnose, so you need to see an eye specialist to get this diagnosis. You shouldn’t try to self-treat it. If you think you have it, an eye care specialist can guide you on how to manage it.

What are the possible complications or risks of not treating it?

Exophoria is usually not a major issue. But when it’s more severe, it can get worse over time. That’s known as “decompensated exotropia.” If it decompensates enough, the misalignment can start happening without covering an eye. That’s known as exotropia, and it can be much more disruptive and unpleasant because it can happen without covering an eye.

Even if that doesn’t happen, exophoria can still be unpleasant. Every time your eyes have to realign, your brain and eye muscles have to work a little harder than usual to readjust. That can cause brief moments of double vision, which can cause headaches and eye strain.

One way to think about it is like the wheels on a shopping cart. If the wheels don’t line up right, the cart becomes much harder to control. That means you have to work harder to keep it moving straight, which tires out the muscles in your arms and legs faster. Likewise, misalignment from exophoria can tire out your eye muscles, especially with larger misalignments.

When should an eye care specialist treat this symptom?

Most people with exophoria don’t know they have it, and it’s rare to notice it on your own. Instead, other symptoms that happen because of exophoria are why people see a healthcare provider or eye care specialist, which leads to the diagnosis. It’s also something an eye specialist or other provider might notice during a routine eye exam (or during routine pediatrician visits for children).

If you have frequent headaches, eye strain or fatigue, or notice vision changes, it’s a good idea to see an eye care specialist. They can check your eye alignment and offer treatment recommendations if necessary.

What’s the difference between exophoria and esophoria?

Exophoria and esophoria are both horizontal (side-to-side) misalignments that happen to an eye when you cover it. Exophoria is when the covered eye turns away from your nose. Esophoria is when the covered eye turns toward your nose.

What’s the difference between exophoria and exotropia?

Exophoria is an outward-pointing eye misalignment that only happens to a covered eye. Exotropia is when an eye misaligns away from your nose without covering it. While they’re very different, exophoria can become exotropia. That’s because your eye tries to compensate for the misalignment and ends up causing a more severe and more frequent misalignment.