Binocular Vision Dysfunction (BVD) — also known as binocular vision misalignment or heterophoria — is an often overlooked visual condition that occurs only during binocular vision (when both eyes are open). It is caused by a subtle imbalance in the eye movement muscles and can lead to a wide range of non-specific symptoms that are frequently not recognized as being related to the eyes.
Many people live for years without knowing that their symptoms are connected to a binocular vision misalignment — or that these symptoms can often be completely and permanently resolved with properly fitted prism glasses.
On this page, you will find a comprehensive overview of the most common symptoms in adults as well as in children and adolescents, the underlying causes, and the available treatment options.
What Is Binocular Vision Dysfunction (Heterophoria)?
A binocular vision dysfunction (BVD) is a visual condition that occurs only during binocular (two-eyed) vision. It is caused by a subtle imbalance in the eye movement muscles. In medical terms, it is considered a form of latent strabismus, because the two eyes are not perfectly aligned on the same point.
As a result, the images on the two retinas do not overlap precisely but are slightly displaced. To fuse these misaligned images into a single picture, the eye movement muscles must constantly compensate. This continuous compensatory effort can place significant strain on the visual system and trigger a wide range of symptoms — even when the eyes themselves are healthy and distance vision is sharp. A binocular vision misalignment is therefore not a disease, but a dysfunction in the way both eyes work together.
When the misalignment is accurately identified and corrected with properly fitted prism glasses, the retinal images are repositioned precisely onto the centers of both retinas. This allows the visual system to relax — and in many cases, the associated symptoms can be completely resolved.
Typical Symptoms of Binocular Vision Dysfunction
A binocular vision dysfunction (BVD) can cause a wide range of symptoms, and these issues can affect people of all ages. Many patients struggle for years to understand their symptoms because they are often not immediately recognized as vision-related.
Typical signs of binocular vision misalignment / heterophoria include:
- Visual strain and rapid eye fatigue: Tasks such as computer work or reading feel exhausting. Text appears unstable, letters blur or seem to “move.”
- Persistent eye strain, burning, or pain: When the misalignment can no longer be compensated, the eye muscles remain constantly tense. This often causes pressure behind the eyes — where the eye movement muscles are located — which can lead to neck tension, tension headaches, migraines, and even cluster headaches.
- Fixation and focus problems: Difficulties occur when shifting focus between near and far, or from right to left and vice versa. Many people also struggle with fast-changing images in TV/cinema or with 3D movies. If the misalignment becomes too strong to compensate, intermittent or constant double vision may occur — sometimes only when looking left or right.
- One eye participating less in the visual process: This can reduce visual acuity in that eye, impair depth perception, and cause dizziness or balance problems, especially during eye movements. In some individuals, this can trigger panic attacks or visual migraines.
- Discomfort in large indoor spaces: Places such as shopping malls or crowded environments can cause discomfort or anxiety. Many patients also have difficulty walking down stairs or escalators, or suffer from fear of heights. Common sensations include mental fog (“cotton wool in the head”), feeling detached, or perceiving the world as if through a film.
- Nausea and motion sickness: BVD is often the underlying cause of nausea, especially in cars or buses, as well as stomach discomfort. A relatively high number of affected individuals are left-handed. In some cases, binocular vision misalignment can even contribute to speech difficulties or stuttering.
- Eye blinking, twitching, rubbing, or squinting one eye: Many people unconsciously tilt their head (often toward the right shoulder) because it makes seeing more comfortable and helps compensate for the misalignment.
- Light sensitivity: Sensitivity to light — even on cloudy days, under neon lighting, or when driving at night — is common.
- Some also experience reduced visual clarity at dusk.
- Symptoms fluctuating with daily condition: Vision and comfort vary depending on daily stress levels — stress typically makes the symptoms worse.
- Other common symptoms: Fatigue, exhaustion, lack of motivation, irritability, teeth grinding, sound sensitivity, and sometimes depression.
- Chronic tension in the eye muscles — and consequently in the jaw and neck — can also trigger or worsen tinnitus. Several patients have told me that all their wisdom teeth were removed because of these symptoms — without any improvement.
All of the visual problems above can also occur when the right and left lenses of your glasses have different strengths — a condition known as anisometropia.
Even in these cases, prism glasses often significantly reduce or even completely resolve the symptoms.
Note: Every symptom listed on this page has only been included after many unrelated patients independently confirmed that their symptoms disappeared or improved significantly once their binocular vision dysfunction was corrected.
Symptoms of Binocular Vision Dysfunction in Children and Adolescents
In children and adolescents (and in some cases even in adults), a binocular vision dysfunction often becomes noticeable through learning difficulties or behavioral patterns. Children may…
- dislike reading because their eyes tire quickly
- mix up letters or swap words
- confuse numbers or misread mathematical symbols
- lose their place while reading and skip lines
- make many careless mistakes
- struggle to understand whole sentences
- need to read the same text multiple times to grasp it
- write and read very slowly
- need frequent breaks while reading or writing
- write with excessive tension and pressure
- have uneven or inconsistent handwriting
- be unable to write small letters
- have difficulty concentrating
- show motor restlessness (fidgeting)
- appear hyperactive
- seem clumsy
- show fear of physical movement
- have poor balance, stumble easily, or fall frequently
- generally appear insecure
In some children, binocular vision dysfunction is mistakenly interpreted as dyslexia or simple “inattention” — even though the actual cause lies in binocular vision.
Once the misalignment is corrected, reading, writing, concentration, and behavior often improve significantly.
Self-Test: Do I Have a Binocular Vision Dysfunction?
If you (or your child) experience several of the symptoms listed above, you should first visit an ophthalmologist to rule out any medical eye diseases.
If no disease is found and your symptoms persist, you can perform a simple self-test to check whether a binocular vision dysfunction may be the cause.
To perform the self-test, cover one of your eyes for a few hours using an eye patch or an adhesive eye pad. If you wear glasses, you can also cover one eye by attaching a small piece of paper to one of the lenses. If you see equally well with both eyes, you may cover either eye; otherwise, choose the eye with weaker vision. Make sure to perform this test only in a safe, familiar environment — never while driving or doing activities that require depth perception.
Then observe whether your symptoms improve significantly or disappear completely during this time. If they do, this strongly indicates a binocular vision misalignment, since monocular vision eliminates the misalignment that causes the symptoms.
If you already wear prism glasses from another optician but still experience symptoms, this self-test can also be valuable: If your symptoms improve when one eye is covered, your misalignment was very likely not measured accurately, and the prism correction needs to be reassessed.
Patients with cluster headaches can find a separate guide to the self-test here: Eye Patch Test for Cluster Headaches.
Treatment: How Prism Glasses Correct a Binocular Vision Misalignment
If the eye patch test suggests that you may have a binocular vision misalignment, the next step is a precise measurement in my practice.
A written registration is required — you can find all information here: Contact & Appointment.
I have been working for many years with my own measurement and correction methodology, which is fundamentally different from the controversial MKH/Haase method. This approach is the result of decades of specialization exclusively in binocular vision misalignments. Because I can exclude all known risks of the MKH method, I offer every patient a guarantee of correction success.
The correction of a binocular vision misalignment takes place in two steps:
- Monocular correction (visual acuity correction): First, the visual acuity of each eye is determined and corrected separately. This ensures that the image formed in the eye lies exactly on the center of the retina — not in front of it (myopia) and not behind it (hyperopia).
- Binocular correction (prism correction): After that, the interaction of both eyes during binocular vision is examined. For optimal binocular function, the images in the right and left eye must fall precisely on the centers of both retinas, without horizontal or vertical displacement. If displacements are present that the eye movement muscles can no longer compensate for, this is classified as a binocular vision misalignment. Such a misalignment can be corrected — after the visual acuity correction — with prism lenses.
Key Principle: Minimal, precise correction: It is crucial to correct only the portion of the misalignment that the visual system can no longer compensate for.
This preserves the natural compensatory ability of the eye muscles, keeping prism values low and stable.
Important Note: If the prism correction is omitted when new lenses are made in the future, your vision will revert to what it was before the correction — including all previous symptoms and visual strain.
Patient Experiences: When Symptoms Disappear After Prism Glasses
Over the past decades, more than 4,000 people with the symptoms listed above have come to my practice — often after a long journey through various specialists without finding a clear cause. In a very large number of these cases, a properly measured pair of prism glasses was able to resolve the symptoms permanently.
On the following pages, you will find concrete examples and personal feedback from patients — adults, parents, and children — describing how their daily lives changed once their heterophoria was corrected:
- General Patient Experiences: Binocular Vision Dysfunction & Prism Glasses
- Patient Experiences: Prism Glasses for Cluster Headaches
Frequently Asked Questions About Binocular Vision Dysfunction (FAQ)
Many patients have similar questions once binocular vision dysfunction is suspected, or after they have had their first experiences with prism glasses.
Below you will find the most important questions I am regularly asked — together with clear, practical answers based on my daily work with binocular vision misalignments (heterophoria / BVD):
How Common is Binocular Vision Misalignment?
Around 70–80 % of all people have a heterophoria. In most cases, the eye muscles can compensate for this deviation well, so no symptoms occur. However, in about 15 % of affected individuals, the misalignment leads to significant visual strain and discomfort that can have a substantial impact on quality of life. In such cases, a prism correction should be performed.
Why is Binocular Vision Dysfunction so Often Overlooked?
Despite its frequency, binocular vision dysfunction (BVD) often remains undetected. The main reason is that measuring BVD is significantly more complex than determining standard visual acuity. While visual acuity is measured monocularly and with relatively low error, a binocular vision misalignment requires testing both eyes together. This process demands substantial experience — and without it, inaccurate measurements are common. In such cases, prism glasses may be ineffective or even intolerable. For this reason, many professionals avoid binocular measurements altogether and limit their examinations to simple visual acuity correction.
Another contributing factor is that many patients worry about giving “wrong answers” during the eye exam. In reality, inaccurate results are almost never the fault of the patient — they are usually caused by unclear or confusing questions from the examiner. When questions are clear, patients provide clear answers — a crucial prerequisite for precise and reliable prism corrections.
A further cause of frequent misinterpretation is that the term “binocular vision misalignment” (or heterophoria) is largely unknown outside specialized fields.
Most patients first consult an ophthalmologist. There, diseases are ruled out and — if visual acuity is normal — they are often told: “Your eyes are healthy, we cannot find a cause.”
Because binocular vision dysfunction is not classified as a disease and is often not measured correctly during routine examinations, a significant care gap arises. Many people suffer symptoms for years without ever learning the true cause. Later — after finally experiencing relief with prism glasses — many patients ask why ophthalmologists or orthoptists were unable to help. The reason lies in the different professional roles: Ophthalmologists diagnose and treat diseases, while optometrists measure and correct refractive and functional visual errors.
This is exactly why close collaboration between the two fields is essential: to rule out medical conditions and to correctly treat functional misalignments of the visual system.
How Long Does It Take to Adapt to Prism Glasses?
The adaptation period usually corresponds to the amount of time your eyes needed during the initial measurement to fully relax.
Once the visual system has adjusted to the new prism correction, you can expect to see clearly and without strain for many years with these glasses.
Do Prism Glasses Have Thicker Lenses?
No. With my prism corrections, the lenses are usually just as thin as standard lenses that correct only visual acuity. In most cases, other people cannot see from the outside whether your lenses contain a prism correction or not.
How Much Do Prism Lenses for Binocular Vision Dysfunction Cost?
Prism lenses are more expensive than standard single-vision lenses because their manufacturing process is significantly more complex. Two single-vision plastic prism lenses with hard coating and premium anti-reflective coating typically cost around €300. For the actual correction of the binocular vision misalignment (heterophoria), there is an additional fee of around €150 — depending on the time required, the cost may be slightly higher. We generally do not offer “cheap lenses” for children. Children — just like adults — see far better with high-quality lens materials and coatings.
Can Prism Foils Be Used to Correct a Binocular Vision Misalignment?
Prism foils should only be used in true emergency situations — for example, when the required prism lenses are not yet available.
The reason: prism foils reduce visual acuity and thereby weaken fusion, the brain’s ability to merge both retinal images into one.
A weakened fusion increases the likelihood that symptoms will reappear. For long-term use, a binocular vision misalignment should always be corrected with prism lenses, as they provide significantly better visual acuity and therefore stable fusion.
What Happens When Patients Seek Help From an Ophthalmologist?
Most people who come to me with these symptoms have previously visited one or several ophthalmologists — assuming the cause must lie within the eyes.
However, nearly all of them were told that their eyes were healthy and that no ocular disease could explain the symptoms. Because no cause was identified, many were then referred to neurologists, and — if no findings appeared there either — further to orthopedists or other specialties. This marked the beginning of a long journey through various medical departments, during which, just as before, no disease could be identified as the cause. Some of these patients even underwent MRI scans or lumbar punctures — likewise without results. Since the symptoms persisted despite normal findings, many ultimately received the diagnosis of psychosomatic complaints. However, this assessment proved to be wrong in nearly all cases. For the vast majority of these individuals, symptoms were permanently resolved once a correctly measured pair of prism glasses was provided. The true cause was a previously undetected heterophoria. In total, more than 4,000 people with exactly this medical history have been successfully treated in my practice. Many later returned to their ophthalmologists to report that they had become symptom-free thanks to the prism correction. Unfortunately, only a few ophthalmologists showed genuine interest, and some even questioned the improvement. Patients found this disappointing, as it prevents millions of others from receiving the same help.
These experiences clearly demonstrate a significant gap in care within the healthcare system — particularly in the recognition and proper evaluation of functional visual disorders such as heterophoria.
What Are the Consequences When a Binocular Vision Misalignment Is Not Detected by an Ophthalmologist?
If a heterophoria remains undetected despite normal findings from ophthalmologists and other specialists, the patient’s symptoms often persist — sometimes for many years. Based on the reports of affected individuals, several recurring consequences become apparent:
- Persistent or worsening symptoms: Headaches, migraines, dizziness, light sensitivity, neck tension, and concentration difficulties remain unchanged or intensify over time.
- Reduced academic performance: Many children and students struggle to absorb learning content or have difficulty achieving their educational goals.
- Problems in professional life: Extended screen work becomes nearly impossible for many patients, leading to anxiety about job security — some even lost their jobs or had to stop working temporarily.
- Risk of losing earning capacity: Some individuals were declared unable to work — and only after correct prism correction were they able to return to their professions.
- Psychological stress: When no physical cause could be identified, many were told their symptoms were psychosomatic or received incorrect psychological diagnoses.This often led to emotional strain, hopelessness, and in some cases depressive episodes — even suicidal thoughts (particularly among people with cluster headaches).
- High medication use: Many regularly relied on painkillers or were prescribed stronger medications such as triptans or amitriptyline — usually without lasting improvement and often accompanied by significant side effects.
- Postural problems due to compensation: To compensate for the vertical deviation, some individuals kept their head tilted — usually toward the right shoulder — leading to long-term muscular imbalance.
What If a Binocular Vision Misalignment Was Identified but Not Successfully Corrected?
Some patients receive a confirmed diagnosis of binocular vision dysfunction (heterophoria) but never obtain a correction that truly resolves their symptoms.
Many of these individuals begin to blame themselves, assuming they must be the problem if several specialists were unable to help them achieve symptom-free vision. The persistence of symptoms — combined with self-doubt — often leads to significant emotional and psychological strain. If you have had experiences like these, you are not an exception. Do not doubt yourself: it is not your fault that previous glasses did not help. In nearly all such cases, the binocular vision misalignment was measured incorrectly or imprecisely. With a properly fitted pair of prism glasses, you can achieve comfortable, symptom-free vision.
How Can You Tell Whether Prism Glasses Have Been Measured Correctly?
You can very easily determine whether your (or your child’s) prism glasses have been measured correctly.
A properly fitted pair of prism glasses meets five simple criteria:
- You see more clearly than before.
- Your depth perception improves.
- Your visual symptoms and strain-related complaints disappear or are significantly reduced.
- These improvements remain stable over time.
- You do not develop any new symptoms.
If you can answer “yes” to all five points over an extended period of time, your prism lenses were measured correctly. In this case, your visual system will noticeably relax, and you will enjoy wearing the glasses. I offer a guarantee on my prism corrections — even if you previously had other prism glasses that did not help you.
What Risks Are Associated With Correcting a Heterophoria?
In Germany, binocular vision misalignments are almost always measured using the MKH method developed by H.-J. Haase. This method is controversial because it carries several risks:
- the prism glasses may be ineffective,
- they may worsen symptoms,
- they may help only temporarily, or
- the prism values may increase at every follow-up measurement with the Polatest.
In some cases, patients are even advised to undergo an unnecessary eye muscle surgery as a result. Over the past years, thousands of people with MKH prism glasses have come to me — and in many of these cases, these risks were indeed present.
I do not work with the MKH method. Instead, I use a different, more precise procedure that corrects only the portion of the binocular vision misalignment that actually causes symptoms. This approach reliably eliminates all of the risks mentioned above.
What Does a “Prism Build-Up” Under the MKH Method Mean — and Why Is It Problematic?
When MKH prism glasses do not fully resolve symptoms, the prism values are often increased repeatedly in short intervals. The goal is to reach the maximum measurable misalignment of the eye muscles. Once the misalignment becomes so large that it can no longer be corrected with prism lenses (because they would become too thick and heavy), patients are frequently advised to undergo eye muscle surgery.
I consider this approach fundamentally incorrect. Symptoms are never caused by the entire muscular imbalance, but by a small, usually vertical component of the misalignment. This component must be corrected precisely — not less, but certainly not more. A full prism correction of the entire muscular imbalance provides no benefit for the patient and instead creates unnecessary disadvantages.
Hundreds of people have come to me after their MKH prism values were repeatedly increased. All of them reported that they saw worse and with more strain as the prism strength increased. Many rightly questioned the continued escalation of their prism values. In the vast majority of cases, I am able to reduce these excessive values back to the necessary minimum. When only the portion that actually causes symptoms is corrected, patients experience stable, long-term relief — and a supposedly “necessary” eye muscle surgery becomes unnecessary.
When Can Prism Values Be Reduced?
In general, the rule is: A wrong pair of glasses can worsen your vision — this applies both to standard visual acuity corrections and to the correction of a binocular vision dysfunction.
A pair of glasses is considered “wrong” if:
- the visual acuity correction is inaccurate, meaning the image is no longer focused precisely on the center of the retina → vision becomes blurred.
- the binocular vision misalignment is not corrected or corrected incorrectly, meaning the two retinal images are horizontally or vertically displaced → the brain does not receive sharp, matching visual impressions.
If such incorrect glasses are worn for a long period of time, visual acuity may slowly deteriorate. However, if both visual acuity and the binocular misalignment are corrected accurately, this deterioration can usually be fully reversed.
With a correctly fitted pair of prism glasses, the brain once again receives sharp images from both eyes. This allows the brain to “learn to see” again — visual acuity improves, finer details become easier to recognize, and fusion (the brain’s ability to combine both images into one) becomes stronger. Better fusion enhances depth perception and stabilizes the entire visual process.
For people with a binocular vision misalignment, this improved fusion has an additional benefit: the eye movement muscles become better able to compensate for the remaining muscular imbalance. As a result, the misalignment decreases over time, and the prism values can be reduced. Vision with weaker prisms becomes not only more comfortable but also more stable and relaxed.
How Can Prism Values Be Kept Low and Stable?
Prism values remain permanently low and stable when only the portion of the binocular vision misalignment that the eyes can no longer compensate for is corrected. This is the decisive difference.
Every person can comfortably move their eyes horizontally and adjust them to different distances. When focusing on near objects, the eyes turn slightly inward; when looking into the distance, they return to a parallel position. For this reason, most people can compensate for horizontal binocular vision misalignments without symptoms. A horizontal prism correction is therefore often unnecessary—or significantly weaker than the measurement results on the Polatest might suggest.
Vertical misalignments, however, cannot be compensated for consciously. No one can intentionally move one eye slightly upward and the other slightly downward. Even very small vertical deviations can cause pronounced visual discomfort and must be corrected with prisms. This vertical “alignment” of the eyes cannot be learned or trained — not through vision therapy, not through orthoptic exercises, and not in any vision training program.
Because vertical deviations are generally very small, they can usually be corrected with very low prism values — often in the range of 0.25 to 0.75 prism diopters. These minimal deviations are often not detected by ophthalmologists or opticians using standard prism bars, because those typically start measuring at 1.00 prism diopter. As a result, many patients are mistakenly told that their symptoms are “not coming from the eyes,” even though that is precisely the case.
When only the portion of the misalignment that the person can no longer compensate for is corrected, the natural compensatory abilities of the eye muscles remain fully intact — and the prism values stay permanently low and stable. I have not had a single case in which prism values increased or an eye muscle surgery became necessary. This is especially important for individuals who worry that prism glasses inevitably lead to continuously rising or very high prism strengths — which is simply not true when the correction is done correctly.
Is There Really a Dispute About Prism Glasses — and Who Is Right?
It is often said that there is a fundamental dispute between ophthalmologists and optometrists regarding prism glasses and the significance of binocular vision dysfunction. From my perspective, this dispute does not truly exist. I do not claim to “be right,” nor do I deny anyone else the possibility of being right. I always leave that judgment to the people who matter most: the patients themselves.
Ultimately, only one thing counts: If someone can see comfortably and without symptoms over the long term with their prism glasses, then those glasses are correct. If not, they are not.
If everyone involved consistently listened to what patients actually experience — how they see with their glasses and how their symptoms change — many misunderstandings and this supposed dispute would quickly disappear.
What Should I Know About Double Vision (Diplopia)?
Double vision can have many different causes. For this reason, it is essential to undergo comprehensive medical examinations first so that potential diseases can be ruled out or treated. However, if neither an ophthalmologist nor any other specialist finds a medical cause, the underlying reason for the double vision is often a pronounced imbalance in the eye movement muscles. In such cases, the visual system is no longer able to merge the images from both eyes into a single, unified picture. This imbalance usually existed long before the double vision appeared and had been compensated for over many years. Visible diplopia often appears only when the body becomes physically weakened, during illness, or when visual acuity is not corrected accurately.
In correcting double vision, I address only the portion of the binocular vision misalignment that the patient can no longer compensate. This keeps the prism lenses as weak as possible — a strategy that has proven highly successful in practice. Many people who come to me have suffered from double vision for months or even years, often accompanied by additional symptoms. Almost all had undergone extensive diagnostic testing, including MRI scans or lumbar punctures, without any conclusive findings. Some were even diagnosed with trochlear nerve palsy, although their double vision could be completely resolved through precise prism correction. In all these cases, the true cause was a previously undetected binocular vision misalignment.
For double vision not caused by disease, I can provide a guarantee for symptom-free vision; whether this is a full guarantee or a partial one can only be determined after the examination. If double vision is caused by a medical condition and persists despite treatment, everything should still be done to correct it with appropriate lenses — prism glasses can often help in these cases as well, and I always work closely with ophthalmologists when dealing with disease-related diplopia.
Where Can I Find More Information About Binocular Vision Dysfunction and Vertical Heterophoria?
A highly recommended source is the work of Dr. Debby Feinberg„ an optometrist from the United States who also specializes in the correction of vertical heterophoria. Her educational resources provide many additional explanations, case examples, and in-depth information on this topic.