Crossed Eyes (Strabismus): Definition, Types, Causes, Symptoms, and Treatments

What Does Crossed Eyes Look Like?

Crossed eyes look like a person with their eyes going in different directions, or the eyes do not line up. This occurs due to weak muscle control in the eyes. The image below shows what crossed eyes look like.

How Common are Crossed Eyes?

Crossed eyes in children is very common and is less common in adults. According to Eye Research Australia, up to five percent of Australians are affected by crossed eyes.

1. Intermittent Exotropia

Intermittent exotropia is a type of crossed eyes where one eye concentrates on an object and the other eye points outward, therefore, the eyes are unable to coordinate together. Intermittent exotropia symptoms include headaches, double vision, eye strain and difficulty reading. This type of strabismus can occur at any age and treatment may include patching, eye exercises and glasses. Intermittent exotropia is different to accommodative esotropia as the latter is often caused by uncorrected refractive errors.

2. Accommodative Esotropia

Accommodative esotropia is the other type of crossed eyes (strabismus) and often occurs due to uncorrected refractive errors, and is also linked to genetic predisposition, meaning there is a family history of turned eyes. Accommodative esotropia is caused by the eyes trying to focus on distant objects which may lead to the eyes turning inward. The symptoms of this type of crossed eyes include double vision, closing one eye when looking at near objects and turning the head. Accommodative esotropia may be treated with glasses and usually occurs in younger children.

1. Esotropia (Inward Turning)

Esotropia (inward turning) is a category of the eye condition strabismus and is characterised by an inward-turning eye or eyes. Esotropia can appear when a person is fixating on a distant object, a near object or both. The symptoms of this type of strabismus in older children and adults include double vision, the eyes looking in different directions and a minimised visual field. Esotropia may be treated with glasses, patching and eye muscle surgery. It is different from the other types of crossed eyes as the eyes turn inwards rather than outwards or upwards.

2. Exotropia (Outward Turning)

Exotropia (outward turning) is a category of the eye condition crossed eyes and is characterised by outward turning eyes or only one eye deviating outward. Exotropia symptoms according to the American Academy of Ophthalmology include diminished binocular vision, eye strain, double vision and eyes that look in different directions. This type of strabismus may be treated nonsurgically with patching, glasses and convergence exercises. Exotropia differs from the other types of crossed eyes as the eyes turn outwards rather than inwards or downwards.

3. Hypertropia (Upward Turning)

Hypertropia is a category of the eye condition strabismus and is characterised by upward-turning eyes or only one eye turning upward meaning the eyes look in different directions. Hypertropia can appear constantly or only when the person is stressed or tired and it is the least common type of crossed eyes. This category of strabismus can be treated with patching, glasses and surgery and is best treated by an optometrist or ophthalmologist. Hypertropia is different from the other types of crossed eyes as the eyes turn upwards rather than outwards or inwards.

4. Hypotropia (Downward Turning)

Hypotropia (downward turning) is a category of the eye condition strabismus and is characterised by downward-turning eyes or only one downward eye. Hypotropia symptoms include double vision, eyes looking in different directions, blurry vision and binocular misalignment which causes reading difficulties, balance problems and headaches. This type of strabismus is commonly treated with vision therapy. Hypotropia differs from the other types of crossed eyes as the eyes turn downwards rather than inwards or upwards.

What are the Other Classifications of Crossed Eyes (Strabismus)?

Besides intermittent exotropia and accommodative esotropia, the other classification of crossed eyes (strabismus) is infantile esotropia. According to the Cleveland Clinic, this type of crossed eyes occurs in infants and causes a significant amount of inward turning in the eyes. Infantile esotropia can be treated with surgery on the eye muscles to correct alignment.

1. Family History

According to the American Optometric Association, those with family members who have a history of crossed eyes (strabismus) are more likely to develop this eye condition. If there is a family history of strabismus, it is important to recognise the signs and symptoms so that if treatment is necessary, it is started when the eye condition first presents.

2. Medical Conditions

People with certain medical conditions such as Cerebral Palsy and Down Syndrome often have crossed eyes due to the difference in strength in their eye muscles. Cerebral palsy is a disorder that affects motor function with one of the many symptoms including crossed eyes which can be treated with glasses and in some cases surgery. It is also common for people with Down Syndrome to have crossed eyes, most commonly eyes that turn inward.

3. Refractive Error

Uncorrected refractive errors are a cause of crossed eyes (strabismus), especially farsightedness as the eyes are overcompensating due to excessive focusing efforts. Refractive errors are a category of visual issue that affects a patient’s ability to see clearly. Refractive errors include myopia, hyperopia and astigmatism. By trying to keep vision clear, people with refractive errors may develop crossed eyes which can be treated by correcting the vision issue with glasses.

What are the Other Causes of Crossed Eyes (Strabismus)?

There are other causes of crossed eyes (strabismus) besides family history, medical conditions and refractive errors such as injuries to the head, hydrocephalus, stroke and nervous system problems. These other causes of strabismus and their definitions are listed below.

• Injuries to the head: Head injuries can cause strabismus as there could be damage to the part of the brain that controls eye movements.
• Hydrocephalus: This congenital disease occurs due to a buildup of fluid in the brain, which can cause strabismus.
• Stroke: A stroke is the lead cause of crossed eyes in adults according to the Cleveland Clinic.
• Nervous System Problems: Crossed eyes may be caused by the part of the nervous system that controls the muscles in the eyes.

1. Double Vision

Double vision is a common symptom of crossed eyes (strabismus) and occurs when the eyes are not working together which causes a person to see two completely distinct or overlapping images. If crossed eyes are left untreated, the brain corrects the double vision by ignoring the image seen from the weaker eye; this condition is called lazy eyes (amblyopia). Double vision can be recognised when a person is looking at one image and sees two images instead. Double vision may be a sign of another medical condition, so it is important to seek medical help if you have this symptom.

2. Misaligned-Looking Eyes

Misaligned-looking eyes are a cosmetic symptom of crossed eyes where one or both eyes may be looking inwards, outwards, upwards or downwards. Misaligned eyes are the reason people with strabismus have double vision as the two eyes are not looking in the same direction. Misaligned-looking eyes can be recognised as the eyes are not in alignment with each other.

3. Turning the Head to View Objects

The eye condition strabismus may cause people to turn their head to view objects as one or both eyes are not looking straight ahead. This symptom may be treated with patching to strengthen the weaker eye that is not seeing straight. If this symptom occurs, it may be a sign of crossed eyes therefore you should see an optometrist for diagnosis.

4. Improper Depth Perception

Improper or reduced depth perception is a symptom of strabismus and occurs due to misaligned eyes not looking at the same spot or object. Depth perception is important as it is how we tell how near or far objects are from us, allowing people to walk without bumping into objects and people, play sports and drive a car. This symptom often occurs in young children as their brain learns to ignore the image the weaker eye sends to the brain, therefore, reducing their depth perception.

5. The Eyes are not Moving Together

Eyes that do not move together is a common symptom of crossed eyes (strabismus). When the eyes are not moving together and working in unison, it may create double vision and make vision unclear. This symptom can result in poor depth perception, misaligned eyes and having to turn your head to view objects.

When do the Signs and Symptoms of Crossed Eyes (Strabismus) Start to Show Up?

The signs and symptoms of crossed eyes, or strabismus, typically start to show up in infants and often by the time the child is three years of age according to the Cleveland Clinic. Additionally, according to Kids Health Organisation, children are commonly diagnosed with crossed eyes between the ages of 1 and 4.

What are the Different Ways to Diagnose Crossed Eyes (Strabismus)?

There are multiple different ways that eye care professionals diagnose crossed eyes (strabismus), these include patient history, visual acuity, refraction, focusing and alignment testing and eye health examination. The ways crossed eyes are diagnosed and their definitions are listed below.

• Patient History: A patient will be asked about their family medical history, any symptoms they are experiencing and any other health problems they are facing.
• Visual Acuity: A visual acuity test is performed to measure a patient's visual acuity to assess their vision and how it is being affected.
• Refraction: A refraction test will be conducted to determine the prescription needed to correct a refractive error.
• Focusing and Alignment Testing: The focus and alignment of the eyes can tell an eye care professional how well the eyes are working together to see a single, clear image.
• Eye Health Examination: An eye exam will include a test of eye health which looks at the external and internal health of the eye using a multitude of tests.

1. Eyeglasses and Contact Lenses

Eyeglasses and contact lenses are common nonsurgical treatments to fix cross eyes in children and adults. Eyeglasses may be used in patients who developed strabismus due to uncorrected refractive errors as they help to reduce the effort it takes for the eyes to focus and as a result keep them straight. The benefit of eyeglasses is that, in many cases, corrective eyewear is the only treatment needed for people with crossed eyes, helping the eyes work together in alignment.

2. Prism Lenses

Prism lenses are a type of corrective eyewear that can be worn to treat crossed eyes (strabismus). In the context of how to fix crossed eyes, prism lenses work by correcting double vision, changing the direction of light towards the retina, perceiving objects as a single image. Prism lenses also provide benefits such as increased comfort, reduced stress and increased duration of near tasks.

3. Medications

Medications may be used to treat crossed eyes (strabismus) when less invasive options are not successful and in place of surgery. Some medications include eye drops which work in a similar way as patching by blurring the straight eye. Injections of botulinum toxin A may be used to fix cross eyes as it can weaken overactive eye muscles.

4. Vision Therapy

Vision therapy is a program designed to improve a person’s visual skills and can be used to fix cross eyes. This non-invasive treatment includes eye exercises that help to treat the nervous system and the brain as they control the eye muscles. The benefits of vision therapy are that it is effective for children and the results are often noticed within a few months.

5. Patching

Patching is a way to fix cross eyes by wearing an eye patch over the straight eye in order to force the weaker eye to be the main source of vision. Over time, patching assists in strengthening the vision and muscles of the weak eye, therefore, treating crossed eyes (strabismus). Eye patches may be worn a few hours a day which benefits the wearer as it develops the skills and acuity needed for a functional eye.

6. Eye Muscle Surgery

Eye muscle surgery is another way a person can fix cross eyes. The surgery involves changing the position and length of the person’s eye muscles in order to align the eyes correctly. Following eye surgery, the patient may need to undergo vision therapy to ensure the eyes do not become misaligned again. According to the American Academy of Ophthalmology, surgery is a common treatment for adult strabismus to help restore proper vision.

What Happens When Crossed Eyes are not Treated?

If crossed eyes are not treated, it may result in another eye condition called amblyopia also known as lazy eyes. Amblyopia is defined by Health Direct as a condition that occurs when one eye develops abnormally at an early age although it can rarely affect both eyes. Strabismus may turn into amblyopia because the brain ignores the images seen by the weaker eye. Lazy eyes appear as one eye moves inwards or outwards and can lead to vision loss in the affected eye if not treated. If a person presents with crossed eyes, it is important to seek treatment from an eye care professional instead of assuming it will get better on its own.

What are Eye Diseases that May Result if not Treated on Time?

Amblyopia is an eye disease that may result if strabismus is not treated. Amblyopia (lazy eye) occurs when the eyes do not work together properly due to the brain ignoring the visual signals from the weaker eye. Other symptoms that can occur if strabismus is not treated include blurry vision, headaches, double vision and poor three-dimensional vision which are listed below.

• Blurry vision: Vision is not clear which can affect performance in school and is a common symptom of many eye conditions.
• Headaches: Headaches are among the symptoms of intermittent exotropia.
• Double vision: Double vision occurs when the eyes aren’t working together and causes a person to see two distinct or overlapping images.
• Poor three-dimensional vision: Strabismus may limit three-dimensional vision causing people to bump into objects.