Strabismus

Strabismus is a condition in which both eyes do not look in the same direction, e.g. when one eye looks straight ahead, and the other eye looks in a different direction.
If left untreated, strabismus can lead to amblyopia in the affected eye (eye not looking straight ahead) in children and/or lose the ability to see three-dimensionally with both eyes.
This article describes following topics.

・Types and causes of Strabismus
・How to examine Strabismus
・How to treat strabismus

The appropriate treatment differs depending on the type of strabismus and its symptoms.

Strabismus is a condition in which the gaze of both eyes is not aligned toward a target object. One eye looks straight ahead while the other looks in a different direction such that the gaze direction of the right and left eyes looks misaligned.
Many people with a large degree of strabismus are more concerned cosmetically about how they look to others. However, with strabismus, functionally the two eyes don’t work together, and 3D vision isn’t possible. Therefore, if strabismus develops early, there is a possibility that the development of binocular vision function will be disturbed, or that the vision of only one eye will not develop sufficiently, resulting in amblyopia.

Amblyopia: A condition in which the desired level of vision cannot be achieved even with correction. It’s often correctable with early treatment.

Symptoms of strabismus in adults may be accompanied by fatigue and diplopia, a condition in which objects appear double. This can be caused by childhood strabismus that worsens with age, trauma, head disease, diabetes, high blood pressure, or other factors. If symptoms of diplopia suddenly appear, it’s advisable to have a blood test and/or head examination to determine the cause of the strabismus.

Strabismus is categorized according to the direction of the eye that doesn’t align properly. In all of the above illustrations, the left eye is normal, and the right eye is looking in different directions.

When the right eye is
・Inward-deviation = Esotropia
・Outward-facing = Exotropia
・Upward-facing = Hypertropia
・Downward-facing = Hypotropia

The types and characteristics of strabismus most common in children are as follows.

Each eye has six extraocular muscles that help maintain eye position. Strabismus occurs when there is an imbalance in the commands from the brain to the external ocular muscles or an imbalance in the muscle tension of the eye.

The following are possible causes of strabismus.

・Hyperopia (far sightedness)
・Visual impairment
・Age-related changes
・Head disease such as cerebral aneurysm or brain tumor
・Systemic diseases such as diabetes, hypertension, thyroid dysfunction, myasthenia gravis, etc.

Another recent problem is the increasing number of patients who develop esotropia due to prolonged use of smartphones.

Strabismus may be noticed due to changes in appearance caused by misalignment of the eye position.
In the case of children, it’s recommended that parents observe the child and see an ophthalmology as soon as possible if any of the following symptoms are observed that raise suspicions of strabismus.

First, a routine vision test, refraction, slit-lamp exam, and fundus exam will be performed. If strabismus is suspected, eye position tests, eye movement tests, and binocular vision function tests are also performed. MRI and blood tests may be necessary to evaluate head and systemic diseases.

Visual Acuity Testing

Vision tests are regularly performed to evaluate the degree of eye disease, amblyopia, and the effectiveness of treatment; the C-shaped Landolt ring test can be performed at around 3 years old, while children under 3 years old are tested using pictures or striped visual targets.

Refraction Examination

Refraction examinations are performed to check for short sightedness (myopia), far sightedness (hyperopia), and astigmatism. Early detection of hyperopia and astigmatism is important, as these conditions can lead to amblyopia.
Some types of strabismus are caused by refractive error, so this test is also essential for examining strabismus.

Binocular vision function test

This test examines the visual status when both eyes are used, and whether it has been maintained or improved by treatment. Stereopsis and the ability to see with both eyes as one (fusion) are tested using instruments such as the “Titmus stereo test” and the “major amblyoscope.”

Eye Position Examination

The degree of ocular misalignment can be examined using the corneal reflex method, in which both eyes are illuminated with a penlight, or the cover test, in which one eye is covered, and eye movement is observed.
A prism is used to examine the angle of ocular misalignment in the cover test.

In the treatment of strabismus, different tests are performed to determine which method is appropriate.
(eye misalignment, function of the external ocular muscles, refractive examination, binocular vision function test, etc.)

Surgery

Surgery is performed to improve eye position by repositing the extraocular muscles. In cases where the eye is outward-facing, the lateral rectus muscles are separated from the eyeball and sutured backward.
The surgery takes about 20 to 30 minutes per muscle, and generally only one or two muscles are operated on in one eye. Adults can undergo day surgery under local anesthesia, while infants and children under school age are operated on under general anesthesia.

Correction with spectacles or contact lenses

The goal is to correct the hyperopia or myopia which are the causes strabismus with spectacles or contact lenses to promote normal binocular vision. This is an effective method when there is an unequal left and right power difference in exotropia and, in accommodative esotropia caused by hyperopia.

Occlusion method

This method is used to treat strabismus and amblyopia by using an eye patch or frosted spectacle lens. This is a training method to improve the ability to see with the strabismic eye by shielding the normal eye.

Prism prescription

A prism is added to the spectacles to refract light so that the eye with strabismus can see the target at the same time as the non-strabismic eye.
Prism spectacles do not cure strabismus itself, but they can improve eye fatigue and diplopia because they facilitate binocular function.

I want to know how to cure strabismus and how to do training at home.

In adults, wearing prism spectacles to refract light makes it easier to use both eyes, thereby reducing double vision and eye strain. In children, covering the normal eye with an eye patch and training to use the strabismic eye is effective in to recover from amblyopia.

What causes strabismus?

Strabismus can be caused by a variety of factors, including hyperopia, binocular vision abnormalities, poor vision, and other conditions related to brain or systemic diseases. If you have any strabismus symptoms that concern you, you should see an ophthalmologist as soon as possible to determine the cause.

Is strabismus inherited?

The development of strabismus is thought to be related to both genetic and environmental factors. People who have a family history of are more likely to develop the condition, but genetics aren’t the only cause.