Merck Manual

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Some Causes of Double Vision When Both Eyes Are Open

Some Causes of Double Vision When Both Eyes Are Open


Common Features*

Diagnostic Approach†

Disorders that affect control of eye muscles by the nervous system‡

Often in older people and in people with risk factors for these disorders (such as high blood pressure, atherosclerosis, and diabetes)

Sometimes slurred speech, weakness, and/or difficulty walking

A doctor's examination

MRI or CT of the brain

A mass that presses on a nerve, such as a bulge in an artery (aneurysm) or a tumor

Often pain (sudden if caused by an aneurysm) and often other symptoms of nervous system dysfunction (such as muscle weakness, loss of coordination, and abnormal sensations in the skin)

MRI or CT of the brain

Inflammation or infection of the eye or surrounding structures (for example, abscess, sinusitis, and, rarely, with a blood clot in the cavernous sinus at the base of the skull)

Constant pain

Sometimes fever, chills, fatigue, loss of sensation in the face, and/or bulging eyes

CT or MRI of the orbits and sometimes the brain

Usually periods of relatively good health alternating with episodes of worsening symptoms

Weakness that comes and goes from day to day

Abnormal sensations such as tingling, numbness, pain, burning, and itching


Loss of strength or dexterity in a leg or hand, which may become stiff

As the disorder progresses, shakiness, partial or complete paralysis, and involuntary muscle contractions (spasticity), sometimes causing painful cramps

Slowed, slurred speech

Problems with urination and/or bowel function

MRI of the brain and spinal cord

Double vision that comes and goes

Difficulty speaking or swallowing


Muscles that weaken when they are used repeatedly

A doctor's examination

Antibody testing, electrical testing of muscles, or both

History of long-term alcohol abuse

Clumsiness, poor coordination, and confusion

A doctor's examination alone

Disorders that block eye motion

Graves disease Causes Causes (thickening of muscles and tissues around the eye—called infiltrative ophthalmopathy—that occurs most often in people who also have an overactive thyroid gland and rarely occurs in people with a normal thyroid gland)

Bulging of the eyes, often eye pain or irritation, watering, sensitivity to light, an enlarged thyroid gland (goiter), and thickened skin on the shins

Blood tests to evaluate thyroid function

Injury, such as a fracture of the eye socket (orbit) or a collection of blood (hematoma)


In people who have obviously had a recent eye injury

CT or MRI of the orbit

Often pain unrelated to eye movement, bulging of one eye, and sometimes other symptoms of nervous system dysfunction

MRI or CT of the orbit and sometimes the brain

* Features include symptoms and the results of the doctor's examination. Features mentioned are typical but not always present.

† Although a doctor's examination is always done, it is mentioned in this column only if the diagnosis can be made only by the doctor's examination alone, without any testing.

‡ Whether pain is present varies by cause.

CT = computed tomography; ECG = electrocardiography; MRI = magnetic resonance imaging.