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Your Guide to Exophoria: Everything You Need to Know

Discover what exophoria is, its symptoms, and causes. Learn about treatment options, the difference between exotropia and exophoria, and its prevalence in kids.

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Your Guide to Exophoria: Everything You Need to Know Optometrist

What is Exophoria?

Exophoria is a combination of two terms, exo and phoria. Phoria is the resting position of the eye, meaning when both eyes are not actively looking at something. While exo means outward. Therefore Exophoria is a type of eye condition where the eyes have a tendency to drift outward when the eyes are relaxed, therefore requiring extra effort to keep the eyes pointed together in the same direction. 

Unlike Exotropia, where the eyes are visibly misaligned, people with exophoria can usually control their eye position most of the time. However, symptoms like eye strain, double vision, and headaches can occur, especially when the eyes are tired or during tasks requiring intense focus. For a person with exophoria, the act of keeping their eyes aligned for extended periods of time, for example while reading, requires massive effort, often leading them to dislike activities such as reading. 

While some amount of exophoria is normally fine as long as it does not impact your vision or cause any symptoms, exophoria is one of the most common vision conditions and is often missed in regular vision screenings or eye exams. It's important to consult a functional optometrist for diagnosis and appropriate treatment options if you're experiencing these symptoms. 

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Symptoms of Exophoria

Recognizing the signs of exophoria is the first step toward getting the right treatment. While the symptoms can be subtle, they may grow more noticeable over time, affecting your vision and daily activities.

  • Eye Strain and Fatigue: One common symptom is eye strain, which can cause a feeling of tiredness or discomfort in your eyes. This often happens after prolonged periods of reading, driving, or using digital devices. This is caused by requiring extra effort that your muscles need to put in to keep the eyes aligned. 
  • Double Vision: Experiencing double vision (diplopia) is one of the most common symptoms of exophoria. In cases of exophoria, double vision tends to occur when you're fatigued or when your eyes have been focusing on a task for too long without a break. The reason why you may see double from exophoria is because our brain combines the image from each eye into one image, however when the eyes are not aligned properly the brain is unable to fuse the images into one image, and instead relays two separate images. 
  • Difficulty in Focusing: You may find it challenging to focus on a single point or object, particularly for an extended period. This is often accompanied by a need to squint or close one eye to better focus. This is due to requiring extra effort to keep the eyes aligned. One study at UCSD showed that children who were diagnosed with ADHD had 3 times the incidence of binocular vision problems such as exophoria and convergence insufficiency
  • Headaches: Headaches linked to eye strain can be a frequent symptom. These headaches usually occur after activities that require intense visual focus and might subside when you rest your eyes. As explained above with regard to eye strain and fatigue, when the eye muscles continuously are needing to put in extra effort to keep the eyes aligned, this places extra strain on those muscles, and can lead to tension headaches. 
  • Squinting or Closing One Eye: Some people unconsciously squint or close one eye to minimize the visual disturbances caused by exophoria, especially in bright light conditions or when trying to focus on distant objects. One of the reasons why they may be doing this is to minimize the strain of trying to keep their eyes aligned, or to prevent double or blurry vision. Functional optometrists note that squinting or closing an eye, especially when reading, is an important sign that the eyes are not working together properly. 
  • Trouble with Depth Perception: Difficulty gauging distance or experiencing problems with depth perception can be signs of exophoria. This might manifest as challenges in tasks like catching a ball or parking a car. To see 3D well we rely on both eyes working together through our binocular vision system, when the eyes are not working together properly, this can cause difficulties with depth perception. 
  • Sensation of Eye Drift: You might notice or feel that one of your eyes is drifting outward, especially when you are tired or zoning out. However, you may be able to realign your eyes consciously when you become aware of it.

A simple way to see if you may have exophoria is to look at an image 10 feet away from you. Then cover one eye with your hand and continue to look at the object. Quickly move your hand to cover your other eye, while focusing on the object with the eye that was covered. If the object moved significantly then that is a good indication that your eyes are not aligned.

What causes Exophoria?

What causes Exophoria?

The origins of exophoria can vary and are often a result of a combination of factors. Knowing the underlying causes can help in formulating a targeted treatment plan.

  • Genetic Factors: A family history of eye alignment problems can increase your likelihood of developing exophoria. If close relatives have had similar issues, it's essential to get regular eye check-ups.
  • Muscle Imbalance: In some cases, the muscles that control eye movement aren't working in harmony, causing the eyes to drift outward. This muscle imbalance can be congenital or acquired later in life due to various factors like injury or illness.
  • Binocular Vision Dysfunction: Binocular Vision Dysfunction (BVD) can be a contributing factor to the development or exacerbation of exophoria. BVD refers to the inability of the eyes to work together correctly, resulting in vision that is slightly misaligned. In a well-functioning visual system, both eyes aim at the same point and send one clear image to the brain. However, in cases of BVD, each eye sends a slightly different image, causing the brain to struggle to form a single, focused picture.
  • Refractive Errors: Issues like nearsightedness, farsightedness, or astigmatism can exacerbate eye alignment problems. In such cases, exophoria may be more noticeable when the person is not wearing their corrective lenses. Specifically myopia or nearsightedness significantly increases the likelihood of exophoria in school aged children. 
  • Neurological Conditions: Certain neurological issues, such as stroke or head injury, can affect the muscles and nerves that control eye movement, leading to exophoria.
  • Age-Related Changes: As you age, the risk of developing exophoria can increase due to a natural weakening of the eye muscles or as a side effect of other age-related vision changes. One example of age related eye changes is presbyopia (best described as needing reading glasses), which is significantly correlated to increases in exophoria. 
  • Eye Strain: Prolonged periods of close-up work or screen time can lead to eye strain and exacerbate exophoria symptoms. This is particularly true for individuals whose work or lifestyle involves extensive use of digital devices.
  • General Fatigue and Stress: Overall fatigue and stress can weaken your eye muscles temporarily, making it more challenging to control eye alignment. People often report that their exophoria symptoms get worse when they're tired or stressed.
Study Highlights on Exophoria Prevalence in Seventh-Graders

Study Highlights on Exophoria Prevalence in Seventh-Graders

A comprehensive study done in 2020 examined 2,260 students in the seventh grade, split evenly between male and female students, to understand the prevalence of eye alignment issues. The study had an impressive response rate of 95.64%, making the findings highly relevant.

  • Over 22%, or 479 students were diagnosed exophoria when focusing on objects up close.
  • 8.5% of students had large heterophoria (≥10 PD)
  • When looking at distant objects, 82 students were found to have exophoria, accounting for about 4% of the total participants.
  • The study also revealed that nearsighted (myopic) children were significantly more likely to have exophoria, both at close and far distances.

(https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7201350/)

Another study highlighted the increased incidence of binocular vision problems such as exophoria as we age. Notably this same study showed an even better predictor of binocular vision problems is the use of antidepressants.

(https://iovs.arvojournals.org/article.aspx?articleid=2190045)

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Diagnosing and Treating Exophoria

Diagnosing and Treating Exophoria

Exophoria is often less severe than other forms of eye misalignment, but it still requires appropriate treatment to manage symptoms and improve eye coordination. Luckily exophoria is treatable in almost all cases. 

There are several treatment options available that can make a significant difference in your vision and comfort.

Vision Therapy

The groundbreaking CITT study by the National Eye Institute (NEI) demonstrated that office based vision therapy was by far the most effective treatment option for exophoria. In that study 75% of patients had normal vision or significantly reduced symptoms after only 12 weeks of office based vision therapy. 

Vision therapy goes beyond just correcting eyesight; it's about teaching the brain and eyes to work together more efficiently. This improved coordination among the eyes, brain, and body enhances essential skills like tracking, focusing, and visual processing.

For binocular vision conditions such as exophoria, the goal is to get the eyes working together as a team without requiring extra effort to do so. 

During vision therapy sessions, the emphasis is on enhancing the ability to converge the eyes. The therapy involves a range of tasks and exercises that target eye coordination, the skill to focus inward (convergence), and the ability to focus outward (divergence). Furthermore the eye muscles will also be developed to better control eye alignment. Tools like computer games, vectograms, lens or prism flippers, and brock strings may be used to aid the process. Vision therapy supervised by an optometrist and a vision therapist has been found to be more effective than simple at-home exercises, often showing substantial improvement after approximately 30 in-office hours, although the exact number can vary based on individual needs.

Goal of Vision Therapy

A personalized vision therapy plan, sometimes in combination with specialized lenses, is typically the most effective way to handle exophoria. 

The therapy aims to:

  • Minimize or even reverse the symptoms of exophoria
  • Improve the skills needed for convergence and accommodation
  • Integrate vision with other sensory functions like hearing and balance
  • Boost visual stamina and focus
  • Incorporate good binocular vision into motor activities

Eyeglasses

The first step in treating exophoria often involves prescribing eyeglasses, particularly for patients with significant refractive errors like nearsightedness or farsightedness. Correcting these issues can sometimes alleviate some exophoria symptoms, although glasses alone usually don't solve the entire problem.

Prisms

For some patients, prism lenses can offer relief. These lenses are set up in a way that reduces the need for the eyes to converge, making it easier to focus. However, prisms generally serve as a short-term solution, as they don't address the underlying issue of poor convergence ability.

Surgery

Surgical interventions are rarely considered for exophoria because non-invasive options are usually effective and less risky.

What is the Difference Between Exotropia vs Exophoria?

Understanding the difference between Exotropia and exophoria is crucial for identifying the right treatment options. Both conditions affect eye alignment but manifest in distinct ways.

What is Exophoria?

On the other hand, exophoria is a tendency for the eyes to drift outward, but the eyes can realign themselves when the person is conscious of it or during focused activities like reading. This condition is often less noticeable to others because it's intermittent and the individual can usually control it.

What is Exotropia?

Exotropia is a form of strabismus where one or both eyes turn outward away from the nose. This eye misalignment is constant, meaning it occurs all the time. Exotropia can be evident in various situations—whether the person is focusing near or far, and it usually requires surgical treatment.

Key Differences

Consistency: Exotropia is constant, while exophoria occurs intermittently.

Control: Exophoria can often be controlled voluntarily, unlike Exotropia.

Visibility: Exotropia is usually more noticeable to others, whereas exophoria can go undetected for long periods.

Treatment: Exotropia often necessitates surgical intervention, while exophoria may be managed with eye exercises and sometimes corrective lenses.

What Are the Types of Exophoria?

Exophoria is not a one-size-fits-all condition; it varies in terms of its impact on your vision and daily activities. Knowing the types of exophoria can help in understanding the condition better and seeking appropriate treatment.

Convergence Insufficiency Type

This form of exophoria occurs when your eyes have difficulty turning inward to focus on near objects. It's particularly noticeable during activities like reading or working on a computer. Symptoms can include eye strain, headaches, and difficulty maintaining focus on the text.

Divergence Excess Type

In divergence excess type exophoria, the eyes have difficulty maintaining proper alignment when looking at distant objects. You may experience symptoms like double vision and eye strain when focusing on something far away, such as a road sign while driving.

Basic Exophoria

This type affects both near and distant vision equally. It's generally present all the time but can vary in severity. The symptoms are similar to the other types, including eye strain, headaches, and double vision, but they occur regardless of whether you're focusing on near or distant objects.

Simultaneous Exophoria

This rare form of exophoria occurs when one eye focuses on the intended object while the other eye simultaneously focuses on another object at a different distance. It can cause double vision and extreme difficulty in maintaining focus.

Decompensated Exophoria

This is when a person who has been able to control their exophoria for a long time starts to experience symptoms. Usually, this happens due to aging, extreme fatigue, or other eye issues. Symptoms can include more frequent bouts of double vision and eye strain.

 

What causes Exophoria?
Study Highlights on Exophoria Prevalence in Seventh-Graders

How Can Exophoria Be Diagnosed?

Identifying exophoria early is essential for effective management and treatment. The diagnostic process involves a series of tests conducted by an eye care professional to assess eye alignment and other visual factors.

Comprehensive Eye Exam

An initial comprehensive eye exam is usually the first step. This exam checks for refractive errors, eye health, and other vision-related issues. Your eye doctor may ask about any symptoms you've been experiencing, such as eye strain, headaches, or double vision.

Cover-Uncover Test

In this test, your eye doctor will ask you to focus on a distant object. While you’re focusing, they'll cover one eye and then uncover it, observing how the uncovered eye moves. This helps to determine whether your eyes are properly aligned and how they react when one eye is covered.

Alternate Cover Test

This test is similar to the cover-uncover test but involves rapidly switching the cover between both eyes while you focus on a target. The eye doctor observes how your eyes move and adjust in response to being covered and uncovered, which helps identify any tendency for outward drifting.

Convergence Testing

To test your eyes’ ability to converge (move inward), your eye doctor may move an object or light towards your nose and ask you to follow it with your eyes. Difficulty in doing this could indicate convergence insufficiency, a form of exophoria.

Prism Adaptation Test

A prism is placed in front of your eyes while you look at a target. The prism bends the light, making it easier for misaligned eyes to focus on the target. This test helps to quantify the degree of eye misalignment and is useful for planning treatment, especially if prisms are being considered as a treatment option.

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Common Questions

Exotropia is often confused with "lazy eye," but they are different conditions. Lazy eye, or amblyopia, is a vision development disorder where one eye fails to achieve normal visual acuity, even with prescription glasses or contact lenses. Exotropia, on the other hand, involves the outward turning of an eye. However, untreated exotropia can lead to amblyopia, especially in children, as the brain might start ignoring the image from the misaligned eye to avoid double vision.
The management of exotropia varies based on its type and severity. In many cases, it can be effectively treated with vision therapy, corrective glasses, and sometimes surgery. The goal of treatment is to improve eye alignment and visual function. An eye doctor will assess the specific needs of the patient and recommend the most appropriate treatment. Early intervention, particularly in children, can lead to better outcomes.
Glasses can be a part of the treatment for exotropia, especially if the condition is associated with refractive errors like farsightedness. In some cases, prism lenses are prescribed to help align the images seen by each eye, reducing the outward turning. However, glasses alone may not completely correct exotropia, and additional treatments like vision therapy or surgery might be necessary. An optometrist can provide a comprehensive evaluation to determine the best treatment approach.
Exotropia may not go away on its own, especially if it is constant or worsening over time. Intervention is often necessary to manage the condition and prevent complications like amblyopia. The treatment success depends on several factors, including the type of exotropia, its severity, and the patient's age. With appropriate treatment, many individuals can achieve improved eye alignment and visual function. Regular follow-ups with an eye doctor are crucial for monitoring and adjusting treatment as needed.
Exophoria and exotropia are both types of outward eye deviations, but they differ in their manifestation. Exophoria is a latent condition where the eyes tend to drift outward only when binocular vision is disrupted, like when one eye is covered. In contrast, exotropia is a more noticeable and constant outward turning of one or both eyes. An optometrist can diagnose these conditions through a comprehensive eye examination and determine the extent of the eye turn.
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Visit a Functional Optometrist Today!

If you or your child have symptoms of exophoria, don’t wait, effective treatment is available.  The Convergence Insufficiency Treatment Trial, a study by the National Eye Institute (NEI) as part of the National Institutes of Health, demonstrated clearly that office based vision therapy was the most effective treatment for exophoria. In that study, 75% of patients showed normal vision or significantly reduced symptoms after only 12 sessions of office based vision therapy. What is important to note is that other methods of treatment such as software based treatment and simple exercises were less than half as effective.

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