Understanding Strabismus, Tropia & Binocular Vision

What Is Strabismus?

Strabismus is a condition in which the two eyes are not properly aligned and do not consistently point in the same direction.

It is also commonly referred to as an eye turn, squint or crossed eyes.

​

A manifest eye turn is known as a tropia.

One eye may turn inward, outward, upward or downward while the other eye remains directed towards the object being viewed. The misalignment may be constant or may occur only at certain times.

Strabismus can occur in children and adults, and its effect on vision can vary considerably between individuals.

Because our two eyes normally work together as a coordinated visual system, strabismus can sometimes affect binocular vision, depth perception and the ability to maintain comfortable single vision.

​

At Eye Zen Optical in Singapore, we focus on personalised optical solutions for customers experiencing complex visual problems, including spectacle-related difficulties associated with strabismus, tropia, double vision and binocular vision.

​

What Is the Difference Between Strabismus and Tropia?

The terms strabismus and tropia are closely related.

Strabismus is the general term used to describe eye misalignment.

Tropia refers to a manifest eye deviation — meaning an eye is actually misaligned under the viewing conditions in which it occurs.

The direction of the eye turn determines the type of tropia.

​

Different Types of Tropia

Esotropia — Inward Eye Turn

Esotropia occurs when one eye turns inward towards the nose.

It may be constant or intermittent and can occur at different viewing distances.

​

Exotropia — Outward Eye Turn

Exotropia occurs when one eye turns outward, away from the nose.

Some people may notice the outward turn more frequently when they are tired, looking into the distance or not concentrating on a visual target.

​

Hypertropia — Upward Eye Turn

Hypertropia occurs when one eye is positioned higher than the other.

Vertical misalignment can sometimes be associated with double vision, depending on the individual and the circumstances.

​

Hypotropia — Downward Eye Turn

Hypotropia occurs when one eye is positioned lower than the other.

As with other forms of strabismus, the visual effect depends on the degree, cause and duration of the misalignment.

​

Constant vs Intermittent Strabismus

Not every eye turn is present all the time.

​

Constant Strabismus

The eye misalignment is consistently present.

​

Intermittent Strabismus

The eyes may appear aligned at some times but become misaligned under certain circumstances.

For example, an eye turn may become more noticeable when someone is:

• Tired

• Unwell

• Daydreaming or not concentrating

• Looking at certain distances

• Performing prolonged visual tasks

The frequency and circumstances of an intermittent eye turn can provide useful information during a professional assessment.

​

Strabismus and Binocular Vision

Our two eyes normally work together to allow the brain to combine information from each eye into a single visual perception.

This coordinated process is known as binocular vision.

When the eyes are not pointing towards the same visual target, the brain may receive images that do not correspond normally.

How the visual system responds varies from person to person.

Some people may experience double vision.

Others, particularly when strabismus develops during childhood, may adapt differently and may not perceive obvious double vision.

This is one reason why the effect of strabismus cannot be determined simply by looking at the appearance of the eyes.

​

What Symptoms Can Be Associated With Strabismus?

Strabismus does not affect everyone in the same way.

Some people may have an obvious eye turn with relatively few visual symptoms, while others may experience considerable visual discomfort.

Depending on the individual, symptoms may include:

• Double vision

• Intermittent double vision

• Eye strain or visual fatigue

• Headaches associated with visual tasks

• Difficulty maintaining comfortable single vision

• Reduced or uncomfortable depth perception

• Difficulty judging distances

• Visual confusion

• Difficulty concentrating during prolonged visual tasks

• Closing or covering one eye to see more comfortably

• Tilting or turning the head to obtain more comfortable vision

• Difficulty adapting to spectacles

These symptoms can have many possible causes and should not automatically be attributed to strabismus.

A professional assessment is important when symptoms are persistent, new or unexplained.

​

Strabismus and Double Vision

Strabismus can sometimes be associated with binocular double vision, also known as diplopia.

Normally, the two eyes are directed towards the same object and the brain combines their visual information into a single image.

If the eyes become misaligned, the images presented to the brain may no longer correspond normally.

In some individuals, this can result in seeing two images instead of one.

However, not everyone with strabismus experiences double vision.

The effect depends on factors such as when the strabismus developed, whether it is constant or intermittent, the degree and direction of the eye deviation, and how the individual's visual system has adapted.

New or sudden double vision should be medically assessed rather than assumed to be a spectacle problem.

​

Strabismus and Depth Perception

Binocular vision contributes to stereopsis — our ability to use the slightly different images from the two eyes to help perceive depth.

When the eyes are not appropriately aligned, stereoscopic depth perception may be reduced or altered.

However, people can also use other visual cues to judge distance and depth, so the effect of strabismus on everyday activities varies considerably between individuals.

​

Strabismus and Amblyopia in Children

Strabismus that develops during childhood can sometimes be associated with amblyopia, commonly known as lazy eye.

Amblyopia occurs when vision in one eye does not develop normally during childhood.

If the eyes are persistently misaligned,

the developing visual system may favour information from one eye over the other in some cases.

It is important to understand that strabismus and amblyopia are not the same condition, although they can occur together.

Children with suspected strabismus, amblyopia or other developmental vision concerns should receive an appropriate professional eye examination.

Early assessment is particularly important because a child's visual system is still developing.

​

What Is the Difference Between Tropia and Phoria?

Although the terms sound similar, tropia and phoria are not the same thing.

​

Tropia

A tropia is a manifest eye deviation.

The eye is actually misaligned under the viewing conditions in which the tropia occurs.

​

Phoria

A phoria is a latent tendency for an eye to deviate.

When both eyes are working together effectively, the visual system may maintain normal-looking alignment.

The deviation becomes more apparent when binocular fusion is disrupted, such as when one eye is covered.

Both can be relevant when investigating binocular vision problems,

but their visual effects and management may be different.

​

Can Glasses Help With Strabismus or Tropia?

Spectacles can play an important role in the visual management of some forms of strabismus, but they are not appropriate as a complete solution for every type of eye misalignment.

The appropriate approach depends on factors such as:

• The type of strabismus

• The direction and degree of the eye deviation

• Whether it is constant or intermittent

• The person's spectacle prescription

• Whether double vision is present

• Binocular vision

• Age

• Visual symptoms

• The underlying cause

For some people, accurately correcting the refractive prescription may help support more comfortable vision.

​

Why Can Spectacles for Strabismus Be Difficult to Get Right?

For someone experiencing strabismus, double vision or another binocular vision problem, spectacle comfort may involve more than obtaining the correct prescription.

Several factors can influence the final visual experience, including:

• Prescription accuracy

• Differences between the two eyes

• Lens design

• Optical centration

• Pupillary measurements

• Frame size

• Frame positioning

• Vertex distance

• Previous spectacle adaptation

• Near and distance visual requirements

This is why someone may occasionally have a prescription that appears correct

but still experience visual discomfort when wearing the finished spectacles.

For complex visual requirements, how the prescription is translated into the finished pair of spectacles can be important.

​

How Eye Zen Optical Approaches Complex Strabismus-Related Spectacle Problems

At Eye Zen Optical, we look beyond the prescription alone.

Our focus is on understanding the relationship between your symptoms, prescription, binocular vision, lenses, frame and everyday visual requirements.

Depending on your situation, we may consider:

​

Your Visual Symptoms

We first want to understand what you are experiencing.

For example:

• Is the eye turn constant or intermittent?

• Do you experience double vision?

• Is the problem worse when tired?

• Does it occur more at distance or near?

• Do you feel more comfortable closing one eye?

• Are your existing spectacles comfortable?

Understanding when and how the symptoms occur helps provide context for the optical problem.

​

Your Current and Previous Prescriptions

Your current prescription is considered together with previous spectacles and your experience wearing them.

This can be particularly important when there have been significant prescription changes.

​

How Your Two Eyes Work Together

Where appropriate, binocular vision and eye alignment need to be considered rather than looking at each eye completely independently.

​

Lens Design and Optical Positioning

Lens power is only one part of the finished spectacle.

Lens design, optical centration and the position of the spectacles in front of the eyes can influence visual comfort.

​​

Your Daily Visual Requirements

The visual requirements for reading, computer work, driving and general everyday activities can be very different.

The optical solution should therefore be considered in relation to how the spectacles will actually be used.

​

When Should You Seek Medical Attention?

A longstanding, previously assessed strabismus is different from a new or suddenly developed eye turn.

Seek prompt medical assessment if you experience:

• Sudden onset of strabismus or eye misalignment

• New or sudden double vision

• Sudden changes in vision

• Severe or unusual headache

• Drooping of an eyelid

• Weakness, numbness or difficulty speaking

• Significant dizziness or loss of balance

• Eye pain

• Strabismus following a head or eye injury

• Other new neurological symptoms

These symptoms should not simply be treated as a spectacle problem.

​

Eye Zen Optical provides optical consultations and personalised spectacle solutions.

We do not replace medical diagnosis or treatment,

and referral to an appropriate eye-care or medical professional may be recommended when necessary.

​

Frequently Asked Questions

​

Is tropia the same as strabismus?

Tropia refers to a manifest eye deviation and is a form of strabismus. Strabismus is the broader term used for eye misalignment.

​

What is the difference between tropia and phoria?

A tropia is a manifest eye deviation, while a phoria is generally a latent tendency for the eyes to deviate that may remain controlled while both eyes are working together.

​

Can strabismus cause double vision?

Yes, strabismus can be associated with double vision in some individuals because the two eyes are not directed towards the same visual target.

However, not everyone with strabismus experiences double vision.

​

Can you have strabismus without knowing it?

Some eye deviations can be intermittent or relatively subtle.

Others may have been present for a long time without causing obvious symptoms.

A professional assessment is required to determine whether an eye alignment problem is present.

​

Can glasses help strabismus?

Glasses can form part of the management of certain forms of strabismus, particularly when refractive error contributes to the visual problem.

However, spectacles do not correct every type of strabismus.​

​

Is strabismus the same as lazy eye?

No.

Strabismus refers to eye misalignment.

Lazy eye, or amblyopia, refers to reduced vision caused by abnormal visual development during childhood.

The two conditions can occur together, but they are not the same.

​

Should adults with a new eye turn get it checked?

Yes.

A new eye turn or sudden double vision in an adult should be appropriately assessed because there are many possible causes, some of which require medical investigation.

​

Personalised Optical Solutions for Strabismus & Tropia in Singapore

If you have strabismus, tropia, double vision or difficulty achieving comfortable vision with your current spectacles, the optical solution may involve more than simply changing the prescription.

At Eye Zen Optical, we take a personalized approach to complex spectacle requirements.

We consider how your:

prescription + binocular vision + lens design + optical positioning + frame + lifestyle

work together.

Our aim is to determine whether an appropriate spectacle solution can provide clearer and

more comfortable vision for your individual visual needs.

​​

​

​

Eye Zen Optical
71 Kallang Bahru #01-529D
Singapore 330071

WhatsApp / Call: +65 8048 8379

Book a consultation with Eye Zen Optical to discuss your visual concerns.