Binocular Vision, Strabismus & Amblyopia

The human visual system is a complex network including the eye, ocular nerves, and key brain areas that process visual information. Under most circumstances, we use information from both eyes to create a single visual image. This ability to converge information from both eyes is called binocular vision. In some cases, the eyes fail to seamlessly meld visual information into a coherent image. We can assess vision to determine if there are problems with binocular vision that require further care.

What is Binocular Vision?

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How Does Binocular Vision Work?

Unlike some other animals, humans’ eyes are both set on the front of the face, permitting binocular vision. Each eye has a field of view, which is the area that you can see when you close one eye. The center of the eyes’ fields of view overlap with one another, although visual information in the periphery can only be detected by one eye. This information is transmitted to an area of the brain in the back of the head, which synthesizes the overlapping visual information to make a single coordinated image.

Binocular Vision and Depth Perception

One of the reasons that binocular vision is so important is that it allows us to perceive depth and relationships between objects. Each eye sees slightly different spatial information and transmits these differences to the brain. The brain then uses the discrepancies between the two eyes to judge distance and depth. The result is the ability to see a 3-D image and distinguish the relationships between objects. Depth perception is technically called stereopsis or stereoscopic vision.

Causes of Binocular Vision Problems

If the eyes can no longer maintain their correct position or focus on the same object, the result is problems with binocular vision. In cases of strabismus, or cross-eye, the eyes are not properly aligned, with one is drifting from its normal position. Strabismus causes the brain to have difficulty synthesizing visual images from each eye, resulting in impaired binocular vision and depth perception. Amblyopia, or lazy eye, is another condition that causes binocular vision problems. Amblyopia occurs when the brain ignores input from one eye, affecting depth perception and other visual abilities.

Fortunately, most problems with binocular vision are easily treated through eyeglasses, vision therapy, or surgery. Receiving a thorough annual optometry exam -- especially during childhood when the visual system continues to develop -- is essential to detect and correct these eye problems. We can recommend treatment options that correct or manage problems with binocular vision.

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Binocular vision dysfunction is an ocular condition that occurs when the eyes don’t align properly with one another. Although our brains may try to correct this misalignment, it isn’t without considerable effort and this results in a range of symptoms that are associated with the condition. Exactly what some people develop BVD and others don’t often isn’t clear. However, some research has found that BVD is often genetically inherited and so if you have members of your family who suffer from similar symptoms to you, it may be that they too have BVD and it hasn’t been diagnosed.

Symptoms of Binocular Vision Dysfunction

Visual Symptoms

  • Sore eyes and eye strain
  • Painful vision, aching face
  • Trouble with night vision
  • Difficulty with close-up vision
  • Blurry vision at near or far distances

Effects on Reading

  • Eye fatigue when reading
  • Trouble concentrating
  • Difficulty with reading comprehension
  • Skipping lines when reading
  • Seeing letters shimmering or moving
  • Words appearing to run together
  • Headaches
  • Eye movements hurt

Other Symptoms Involving Both Eyes

  • Blurry, shadowed, or double vision
  • Trouble holding eye contact
  • Poor hand-eye coordination
  • Poor depth perception
  • Light sensitivity
  • Difficulty with glare or reflection
  • Covering or squinting one eye to enhance vision

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What is Strabismus?

Strabismus is a visual condition where the eyes do not look in the same direction at the same time. It is commonly diagnosed in children due to an underlying condition but may also occur later in life as a result of injury or physical disorder.

When your eye muscles work together, both eyes aim at the same spot, allowing the brain to take the images and form a single 3D image, giving us depth perception. If you have strabismus, two different images are sent to the brain leading to a loss of depth perception and visual confusion.

In young children, the brain may learn to ignore images from the misaligned eye. However, the condition will result in a loss of depth perception. If strabismus is developed later in life and you are diagnosed as an adult, double-vision is often developed as the brain has already learned to receive images from both eyes.

Types of Strabismus

There are different types of strabismus and they are often described by the direction or alignment of the eyes.

  • Esotropia – Refers to the inward turning of the eyes and is what most people associate when they imagine crossed eyes.
  • Exotropia – Occurs when the eyes turn outward and are often called wall-eyed.
  • Hypotropia – Used to describe vertical misalignment where the abnormal eye sits higher.
  • Hypertropia – A vertical misalignment where the abnormal eye sits lower.

It is important to note that the misalignment can be either intermittent or consistent.



Did you know that there are six muscles attached to your eye to control eye movement? If one or more of the muscles is weakened or underdeveloped, vision problems may occur. A common condition that often occurs due to weakened eye muscles is strabismus, often identified as "cross-eyed".

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Signs & Symptoms of Strabismus

The main sign of this condition is misaligned eyes. Children may squint one eye to see clearly or tilt their heads to use their eyes together. Adults often describe having double vision and headaches from straining their eyes to try to see clearly. Strabismus needs to be treated as soon as possible, especially in children, as it may result in permanent vision impairment if left untreated.

Once suspected, visit an optometrist for a comprehensive eye exam and diagnosis. It can be caused by problems with eye muscles, the nerves that transmit information to the muscles and brain, or within the portion of the brain that controls eye movement.


Treatment will vary depending on the severity and underlying cause of your condition. Most often treatment focuses on straightening the eyes and restoring binocular vision. Visual exercises can help to strengthen weakened muscles and corrective lenses can help to straighten the misalignment. Surgery can be considered if necessary, during which the unbalanced eye muscles may be removed to restore proper alignment and function to the eye.

A Note About Adult Strabismus

Strabismus is a condition in which the eyes are not properly aligned with one another. You may have heard this referred to as “cross-eyed”, “wall-eye” or “lazy eye”. An adult patient may have had this condition since childhood (that was either never diagnosed or unsuccessfully treated), experienced an illness or injury later in life, or in some cases,

there is no identifiable reason that caused misalignment of the eyes.

Do I have strabismus?

Adults with strabismus may experience any or all of the findings/symptoms below:

  • eye(s) cross in, wander out, float up or down
  • the eyes do not move together
  • double vision
  • use a head position to relieve double vision
  • eye fatigue
  • overlapped or blurred images
  • reading difficulty
  • loss of depth perception

If you have any of these findings/symptoms, you should be evaluated.

Who treats misaligned eyes in adults?

Many ophthalmologists are highly qualified to treat all forms of eye misalignment in adults. The doctors we work with not only have training in general ophthalmology, they have also completed additional education and training in the fields of pediatric ophthalmology and adult strabismus.

Which adults are at higher risk of
having or developing strabismus?

  • if you have a family history of strabismus
  • if you had strabismus in childhood
  • if you have thyroid disease (Grave’s Disease)
  • if you have Myasthenia Gravis
  • if you have a history of a brain tumor
  • if you have had a stroke or aneurysm
  • if you have had a head injury
  • if you have had an injury to the bone surrounding the eye (orbital fracture)
  • if you have a low vision or non-seeing eye
Can anything be done for adults with strabismus or misaligned eyes?

Absolutely! As an adult with eye misalignment, you may have been told by a physician or friend that nothing can be done to re-align the eyes. This is simply not true. Eye muscle surgery is safe, effective and highly successful and it is never too late to make a decision for surgical correction. In some cases, non-surgical treatment, such as prism glasses, is an effective alternative to surgery.

What is Amblyopia?

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Amblyopia must be treated as early as possible as there is no chance that it will resolve by itself. Untreated amblyopia can lead to permanent vision loss in that eye and reduced depth perception. Amblyopia needs to be treated promptly so that your child can have the best vision possible in childhood and later in life. When amblyopia is diagnosed and treated before age 9, the weaker eye can often develop significantly better vision. The most critical time to treat amblyopia is from 3 to 6 years of age. If you or anyone sees any signs of amblyopia, go to your eye doctor to find the best treatment for your child.

Amblyopia, which is also called “lazy eye”, is a disorder that affects the visual development in children. Amblyopia is difficult to correct just with the use of contact lenses, or eyeglasses. Ambylopia can cause vision loss if it is not treated early and properly. This vision disorder affects 2-3% of the population.

What are the symptoms of Amblyopia?

Usually for children that are born with amblyopia, the symptoms start in early childhood. Some signs of amblyopia in children are squinting, closing one eye in order to see better, poor general vision, headaches, and eyestrain. Usually caretakers such as parents, caregivers, doctors, or nurses notice these symptoms and recommend the child for treatment.

What are the causes of Amblyopia?

Strabismus is usually the cause of amblyopia. Strabismus is the eyes aligning incorrectly. Amblyopia can also be caused when there is a large difference between the eyes in refractive errors (prescription much higher in one eye than the other). For example, one eye is nearsighted, while the other is farsighted. If amblyopia is not treated, the brain will learn to disregard the vision in the eye with amblyopia. The eye that is disregarded does not grow with clear image and vision loss can be permanent. This is why it is very important to get early treatment and take your child to see your eye doctor if any signs are apparent.

How is Amblyopia treated?

There are several treatments for amblyopia, depending on the cause. Often children are treated using vision therapy, which usually includes a patch on the better eye. Other treatments are atropine eye drops, corrective prescription eyeglasses, or surgery.

Vision Therapy

Vision therapy consists of eye exercises, which aim to teach the eyes to work together. In cases of amblyopia, the exercises require the brain to recognize the affected eye, which restores vision in that eye. Some doctors place a patch over the more functional eye, which forces the less functional eye to work harder and become stronger. The patch is generally worn for a few hours a day. Depending on the severity of the condition, treatment can last for weeks or months. Some children refuse to wear a patch, in those cases, a prosthetic contact lens is available. These contact lenses look like the regular eye and are designed to block vision in that eye.

Atropine drops

Some doctors use atropine eye drops to treat amblyopia. These drops blur vision in the child’s better eye, forcing the weaker eye to work harder and get stronger. In the morning, one drop is instilled under eye doctor’s instructions. The advantage to this method of treatment is that the patch is avoided.

Prescription Eyeglasses

If your child has developed amblyopia because of uncorrected vision, sometimes all that is needed is a pair of eyeglasses. When there is strong uncorrected prescription, or when there is a large difference in prescription between the two eyes, sometimes amblyopia can result. Your eye doctor may recommend eye patch therapy in addition to corrective lenses.


Strabismus surgery is usually required if the amblyopia is due to a large eye turn. This type of surgery aligns the eyes and corrects the problem within the eye muscles. After the surgery the eyes will be able to focus better. Additional vision therapy may be required after strabismus surgery.

Want to learn about how we can help your child with binocular vision issues?

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