Causes of Double Vision (Diplopia)

As the name suggests, double vision, also known as diplopia, occurs when a person sees two images of a single object. It has a significant impact on daily life since it can often affect day-to-day activities such as reading and driving. People with double vision will often experience problems with balance and movement as well.

Diplopia is not a disease but a symptom linked to a range of eye and brain problems or medication side effects. It is more common with advancing age, and it can have both ocular (eye) and neurological causes.

Types of Double Vision

People with diplopia will see double images of a single object side by side or on top of each other. The condition can happen when both eyes are open (binocular diplopia) or when just one eye is open (monocular diplopia).

You can find out whether your double vision is affecting both or only one of your eyes with a simple vision test. If your double vision goes away when you close one eye, then you may have binocular diplopia.

Causes of Monocular Diplopia

Monocular diplopia is double vision out of one eye. People often report that one of the images is clear and the other is blurry. It is often caused by an eye problem and not related to brain diseases.

Causes of monocular diplopia include:

• Cataracts: This condition is a type of age-associated clouding of the lens in the eye, and it is the most common cause of monocular double vision. Although it is not an emergency, your doctor may recommend surgery at some point to improve your vision.
• Dry eye: When the eye produces fewer tears, it becomes less lubricated. Eyes can become dry for different reasons, including aging and staring at a computer for long periods of time. The problem usually improves by blinking, using artificial tears, or pinhole viewing.
• Severe astigmatism: The most common symptoms of astigmatism are blurred or double vision. The condition changes the shape and curvature of the eye, which can cause diplopia.
• Keratoconus: This disease makes the cornea cone-shaped. It can cause many symptoms, including double vision, sensitivity to light, and blurry vision.
• Pterygium: Also known as surfer's eye, it happens when the membrane that covers the white part of the eye overgrows and covers part of the cornea. Double vision is one of the symptoms of this condition.

Causes of Binocular Diplopia

Binocular diplopia occurs when the eyes are not aligned. People with binocular diplopia often report that images in both eyes are clear and one of the images will disappear when one eye is covered. It can be caused by a range of diseases, and some of them can involve the brain nerves.

Each eye has six muscles responsible for controlling eye movements. Problems in these extraocular muscles include weakness or paralysis that prevents one eye from moving in alignment with the other

Causes of binocular diplopia include:

• Diabetes: Among other things, diabetes can cause nerve damage, including to the eye. People who have diabetes are also more likely to have cataracts.
• Guillain-Barre syndrome: This condition can cause muscle weakening due to demyelination of the peripheral nerves, and the first symptoms are often vision-related, including diplopia.
• Myasthenia gravis: This is an autoimmune disease, in which the immune system attacks healthy cells at the junction between the nerves and the musckes. It typically strikes muscles in the face first. Muscles that control the eyelids and eye movements are usually affected early on in this disease. Double and blurry vision are common symptoms.
• Multiple sclerosis: This disease affects the nervous system and can impair control of eye movement.
• Graves' disease: Extreme cases of Graves' disease can swell the eye muscle, which may put extreme pressure on the optic nerve, leading to double vision or vision loss
• Strabismus: This condition, also known as crossed eyes, can cause double vision, but not always. If strabismus has been present since childhood, it doesn't usually cause double vision. Cases of misalignment suddenly occurring during adulthood are usually accompanied by double vision.
• Medication: Medications used for treating seizures and epilepsy can cause diplopia, even when the drugs are used within the recommended dose.

A Word From Verywell

Although some cases of double vision can disappear in a few seconds, it becomes a red flag when it persists for long periods or happens multiple times. The cause of diplopia can be as simple as dry eyes, but double vision can also be a sign of neurological damage.

Schedule a visit with an optometrist or ophthalmologist when you notice that you have double vision. Discovering a disease early makes a whole world of difference in treatment and outcome.