Diagnosing Double Vision

NYU Langone specialists are experts at diagnosing double vision, also called diplopia, in which a person sees two images instead of one. Our team of neurologists and neuro-ophthalmologists—doctors who manage visual problems related to the nervous system—provides a thorough evaluation and develops a treatment plan for people experiencing double vision.

Double vision can have a significant impact on your daily life. It can make basic tasks, such as driving or reading, a challenge. It also increases your risk of falling.

There are two types of double vision—binocular diplopia and monocular diplopia.

Binocular Diplopia

Binocular diplopia occurs when both eyes are open and resolves when either eye is closed. It is caused by a misalignment of the eyes, also called strabismus.

Conditions that affect the cranial nerves supplying the muscles that control the eyes can cause binocular diplopia. They include neurological conditions, such as myasthenia gravis or multiple sclerosis, or may be associated with a systemic disorder, such as hyperthyroidism. Double vision can also be a symptom of a stroke, an aneurysm, or head or facial trauma, especially around the eye socket.

Sometimes, binocular double vision becomes apparent only when a person moves the eyes in a certain direction, such as up or down or far to the left or right. A person with binocular diplopia can eliminate the double image by covering one eye.

Monocular Diplopia

Monocular diplopia is double vision that occurs only in one eye or only when one eye is open.

Common causes of monocular double vision include refractive error, a change in the shape of the eye, which causes vision to become distorted, or the early stages of a cataract, a clouding of the eye’s lens.

In people with monocular diplopia, double vision may persist even when covering one eye.

Medical History

To diagnose double vision, your doctor relies on your medical history, including your symptoms. Your doctor asks if you see a double image with both eyes open or with one closed and if closing one eye makes the double image disappear.

The doctor also wants to know if the double image you’re seeing is horizontal or vertical. This helps the doctor to determine which eye muscles are affected. He or she asks about the severity and duration of your symptoms and any factors that may aggravate or relieve double vision.

Your doctor also asks whether you have any medical conditions, such as diabetes or vertigo, that may be associated with double vision. He or she also wants to know if you have experienced any recent head trauma or a concussion.

NYU Langone specialists use several diagnostic tools to determine whether double vision has a neurological or mechanical cause. It can occur as a result of a problem with the eye muscles, the nerves that control eye movement, or the neuromuscular junction—the space where nerves connect to the muscles they control.

Eye Examination

A series of painless tests helps your doctor evaluate your vision and determine if double vision is binocular or monocular and if your eyes are misaligned.

If your doctor suspects your eyes are misaligned, he or she may ask you to look through a prism-shaped tool, which bends the path of light that the doctor shines into the eye, enabling him or her to measure the degree of misalignment. Knowing the degree of misalignment helps your doctor to determine the cause of the double vision and the best way to correct it.

During an eye exam, your doctor also evaluates how looking in different directions affects double vision. By asking you to follow his or her finger as it moves up and down and to the far right and left, the doctor can determine if there is any eye muscle weakness.

If the diplopia is monocular, the cause may be within the eye, so a doctor may use an instrument called a slit lamp to examine the eye under magnification. This allows the doctor to better evaluate the internal structures of the eyes.

Neurological Examination

If you have binocular double vision, your NYU Langone doctor may ask questions about your symptoms to determine if an underlying condition may be causing it. To find out whether a problem with the cranial nerves—which are responsible for eye movement and facial strength and sensation—is causing double vision, your doctor may ask if you have any pain or numbness around the eye sockets, facial weakness, and swallowing or speech problems.

During a neurological examination, the doctor looks for ptosis—eyelid drooping, which can occur as a result of nerve or muscular disorders, such as myasthenia gravis or muscular dystrophy—or injury to one of your cranial nerves.

MRI Scans

With an MRI scan, a magnetic field and radio waves are used to create two- or three-dimensional images of organs and tissues in the body.

NYU Langone doctors recommend an MRI if they want a better view of the brain, eye socket, and spinal cord. The results can help them to rule out certain causes of double vision, such as a tumor, inflammation along a nerve, or an aneurysm.

Blood Testing

If your doctor suspects that double vision is due to an underlying medical condition, such as Graves’ disease or Lyme disease, he or she may perform a blood test.

Graves’ disease is an autoimmune condition that causes hyperthyroidism. It can cause swelling and thickening of the muscles responsible for eye movement, leading to double vision. Lyme disease is a bacterial infection transmitted by ticks that causes neurological symptoms, including double vision.