All About Strabismus
by Dr. Jeffrey Cooper & Rachel Cooper (no relation). © 2001-2008

Conditions Associated with Strabismus

Amblyopia (Lazy Eye)
See What is Amblyopia?

Anisometropia
A condition in which each eye has a different refractive error (prescription). For example, one eye is mildly nearsighted (myopic) while the other is very nearsighted. There are many variations. When associated with farsightness, this visual condition is a common cause of Amblyopia.

Convergence Insufficiency
An eye muscle condition in which the eyes do not cross (converge) or look at near with ease and efficiency. This visual condition is the leading cause of eyestrain, blurry vision, double vision (diplopia), and/or headaches. It is treated with orthoptics or vision therapy. Surgery is not recommended.

See a more detailed definition with links at What is Convergence Insufficiency?

Read stories written by children, parents and teachers about successful treatment of convergence insufficiency.
See 20/20 is Not Enough! and Success with Visual Disabilities: Convergence Insufficiency.

Read an article by an eye doctor about problems with reading and learning caused by convergence insufficiency.

Double vision (binocular diplopia)
If the two eyes are not aimed at the same target and both eyes are working, the patient will report seeing two of everything. Read a detailed page on Double Vision.

Esophoria
A muscle condition in which when both eyes are open each eye points accurately at the target. However, upon covering one eye the covered eye turns inwards. Also known as over-convergence.

Read an article by Dr. Donald Getz which explains and illustrates the problems with reading and learning that can be caused by esophoria.

Esotropia
A muscle condition in which when both eyes are open one eye is turned inwards. The eye turn may occur 100% of the time and is called constant or some of the time and is called intermittent. See our detailed page on esotropia.

Exophoria
A tendency for one or both eyes to drift outward. When both eyes are open each eye points accurately at the target. Upon covering one eye, the covered eye turns outwards. Exophoria usually is also known as under-convergence and can be associated with convergence insufficiency.

Read an article by Dr. Donald Getz which explains and illustrates the problems with reading and learning that can be caused by exophoria.

Exotropia
A muscle condition in which when both eyes are open one eye is turned outwards. The eye turn may occur 100% of the time and is called constant or some of the time and is called intermittent. See our detailed page on exotropia.

Orthophoria
A muscle condition in which when both eyes are open or one eye is covered, both eyes point accurately towards the target.

Orthoptics
The medical term for vision therapy. However, technically there are broad distinctions between vision therapy and orthoptics. Orthoptics looks at muscle problems only in regard to strength. Treatment is home based. Optometrists who provide vision therapy look at the neurological control system and thus are treating the whole system and altering reflexive behavior, which results in a lasting cure. Also, most Optometrists rely on office based therapy that they believe is more accurately performed and monitored, with home therapy as an adjunct.

Eye Tracking Problems
There are two basic types of eye movements. One is a smooth tracking motion (called a pursuit) and the other is a jump from one target to another (called a saccade). Accurate movements are required so as not to skip words or lose one's place while reading.

Read an article by Dr. Donald Getz which explains and illustrates the problems with reading and learning that can be caused by eye tracking problems.

Grave's Disease
Grave's disease or hyperthyroidism may result in protrusion of one or both eyes, dry eye to cornea exposure, convergence insufficiency, and/or hypertropia. The first muscle sign of Graves disease is usually a convergence insufficiency, which causes eyestrain, fatigue or diplopia. In more advanced cases the muscle thickens and may not work appropriately. The most common muscle involvement is the inferior rectus. This results in a vertical deviation as seen in failure of the left eye to elevate in the picture above. The mild muscle problems may be treated with vision therapy, while more complex problems with require prisms. Rarely, if the hypertropia is too large surgery may be required. It is important to realize that normalization of the thyroid does not guarantee non-progression of the eye condition.

Brown's Syndrome
Brown's syndrome is an eye muscle problem in which an eye fails to elevate upon adduction (turning inwards). The picture above depicts a Brown's Syndrome of the left eye. It is usually congenital and does not do well with surgery, vision therapy, or prisms. Unless problematic, it is best left alone. Rarely, it is acquired and may be due to trauma or inflammation.

Brown's Syndrome

After Cataract
Upon the removal of a cataract some patients will see double. This may be due to a hidden eye muscle problem that occurs from covering an eye or from toxicity to the injected anesthetic. (Today's more sophisticated cataract surgeons use topical anesthetic drops and avoid this unhappy problem. Eye surgery should always be co-managed by a primary care provider, such as your Optometrist). Visual consequences of cataract surgery often respond fairly well to prisms. Vision therapy might be helpful in some cases. Surgery should be reserved as a last resort.

After Retinal detachment
Some times after repair for a retinal detachment the patient has double vision. If it doesn't get better in two weeks, prism should be tried to eliminate the double vision. If the image from the eyes is not parallel then surgery will be necessary. If the prism eliminates the double vision, vision therapy may be necessary to eliminate further double vision. However, you should not suffer for a long time before help is provided.

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. There are simple tests that help confirm or deny the existence of myasthenia gravis. Very mild cases may benefit from vision therapy. However in moderate to advanced causes vision therapy may temporarily exacerbate symptoms. Myasthenia is often the culprit of changing ptosis (dropping of an eyelid), diplopia (double vision), focusing problems, eyestrain, and/or generalized fatigue including breathing. Therapy generally includes oral medications such as Mestinon or steroids.

Myasthenia Gravis

Paralysis due to diabetes or hypertension
Diabetes or high blood pressure may cause a relative ischemia (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 in this population since time usually heals the condition within 3-4 momths. When the condition resolves, you or your doctor can peel off the press-on prism.

Orbital Fracture -- Blow-Out Fracture
Traumatic contusion to the orbit (the bone surrounding the eyeball) 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 not a MRI. The patient with this fracture should be put on antibiotics for a couple of days and ice. One 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 done if symptoms of double vision or cosmesis persist.