Eye Conditions That Cause Strabismus

Dr. Russel Lazarus, April 7, 2020

The following is a brief guide to the common eye conditions that can lead to an eye turn.

Eye turns affect over 3 people in 100 and can be successfully treated by eye doctors, often without needing surgery.

Amblyopia (Lazy Eye)

A vision problem in which an eye fails to achieve normal visual acuity, even with prescription eyeglasses or contact lenses. Amblyopia typically begins during infancy and early childhood. In most cases, only one eye is affected.


A condition in which each eye has a different refractive error (optical prescription). For example, one eye is mildly nearsighted (myopic) while the other is significantly nearsighted. Or one eye is nearsighted and the other eye is farsighted. There are many variations. When associated with farsightedness, anisometropia is a common cause of amblyopia.

Convergence Insufficiency

A common eye muscle condition in which the two eyes are unable to easily turn inward to see close objects. This visual condition is the leading cause of eyestrain, blurry vision, double vision (diplopia), and/or headaches. A recent multi-site scientific study funded by National Eye Institute has proven that the most effective treatment for convergence insufficiency is in-office Vision Therapy with home reinforcement. Surgery is not recommended.

Double vision 

Double vision occurs if both eyes are working, but are not aimed at the same target.


A tendency for one or both eyes to drift inward. When both eyes are open, each eye points accurately at the target. However, when one eye is covered, it causes an inward eye turn as a result of over-convergence.


An inward eye turn in one eye, when both eyes are open. The eye turn can be constant or intermittent. It is usually congenital and may respond well with surgery, Vision Therapy, or prisms.


A tendency for one or both eyes to drift outward. When both eyes are open each eye points accurately at the target. However, when one eye is covered, it causes an outward eye turn, as a result of under-convergence. Exophoria can be associated with convergence insufficiency.


An outward eye turn in one eye, when both eyes are open. The eye turn can be constant, or intermittent.  It is usually congenital and may respond well with surgery, Vision Therapy, or prisms.

Eye tracking problems

Accurate eye movements are required for reading— providing the ability to read every word in a sentence, so you don’t easily lose your place.

There are two basic types of eye movements:

  • Pursuits- a smooth tracking motion
  • Saccades- a jump from one target to another

Grave’s disease

Grave’s disease or hyperthyroidism may result in protrusion of one or both eyes, dry eye due to cornea exposure, convergence insufficiency, and/or hypertropia.

The first sign of Graves disease is usually a convergence insufficiency, which causes eye strain, fatigue or diplopia (double vision).

In more advanced cases, the muscle thickens and may not work properly, and resulting in a vertical deviation.  For mild cases, vision therapy is an effective treatment, while more complex cases usually require prisms. Rarely, if the hypertropia is too large, surgery may be required.

It is important to understand that treating the thyroid condition does not guarantee non-progression of the eye condition.

If you notice an eye turn, schedule an appointment with a vision therapy eye doctor to start a treatment program.

SEE RELATED: What Is Strabismus (Crossed-Eyes)?

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Brown’s syndrome

Brown’s syndrome is an eye muscle problem in which an eye fails to elevate upon adduction (turning inwards).  It is usually congenital, and in severe cases does not respond well with surgery vision therapy, or prisms. Unless problematic, it is best left alone.

In rare cases, this condition can develop as a result of trauma or inflammation.

After cataract surgery

Upon the removal of a cataract, some patients will experience double vision. This may be due to a hidden eye muscle problem that occurs from covering an eye, or from toxicity to the injected anesthetic.

Many cataract surgeons now use topical anesthetic drops to avoid this problem. Eye surgery should always be co-managed by a primary care provider, such as your Optometrist.

Visual consequences of cataract surgery often respond well to prisms. Vision Therapy might be helpful in some cases. Surgery should be reserved as a last resort.

After retinal detachment

In some cases, after repair for a retinal detachment, double vision can develop. If it doesn’t get better in two weeks, prisms are generally used to eliminate the double vision. Many times, vision therapy is used in conjunction with prisms to further eliminate the double vision.

If the image from the eyes is not parallel then surgery will be necessary.

Myasthenia Gravis

Fleeting bouts of double vision that worsen as the day goes on may be due to myasthenia gravis. The key feature with myasthenia is the variability of the findings.

Very mild cases may benefit from vision therapy. However in moderate to advanced cases, vision therapy may temporarily exacerbate symptoms.

Myasthenia is often the culprit of eyelid ptosis (dropping of an eyelid), diplopia (double vision), focusing problems, eyestrain, and/or generalized fatigue. Therapy generally includes oral medications or steroids.

Paralysis due to diabetes or hypertension

Diabetes or high blood pressure may cause a relative ischemia, a deprivation of blood supply. Fortunately the double vision is not permanent and can be temporarily eliminated with press-on prisms. No surgical treatment should be performed since the condition usually heals on its own, within 3-4 months time. When the condition resolves, you or your doctor can peel off the press-on prism.

Orbital fracture (blowout fracture)

Traumatic contusion to the bone surrounding the eyeball (orbit), may result in a fracture of the floor of the orbit known as a blow-out fracture. Diagnosis is best made with a CAT scan. Antibiotics are typically prescribed for a couple of days, and ice is recommended to reduce swelling.

You should wait at least two weeks to allow for spontaneous recovery of symptoms before considering intervention. Repair of the orbital floor by slipping in a supportive plate, should only be performed if symptoms of double vision or cosmesis persist.

Vision therapy for strabismus

Vision therapy trains the entire nervous system and reflexive behavior, thus resulting in a lasting cure for strabismus and other vision conditions.

LEARN MORE: Guide to Eye Turns

Contact an optometrist who can provide vision therapy to improve the functioning of the visual system and the neurological control of the eyes.

Vision therapy for eye turns is effective, especially when performed with a trained vision therapist in an optometrist’s office, together with home-based exercises.