Monocular Diplopia: Double Vision in One Eye

Double vision in one eye is known as monocular diplopia.

While there are many reasons why you may have double vision in one eye, not all of them are causes for concern.

Various conditions can cause double vision, such as eye problems related to your eye’s cornea or lens.³ The muscles and nerves that control your overall eye function can also cause double vision, as well as brain injuries. 

What Can Cause Double Vision in One Eye?

A few common eye and health problems can lead to double vision in one eye. If you see a double image in either eye, the following could be the culprit:

Keratoconus

Keratoconus refers to an eye condition in which the cornea thins out and gradually bulges outward in a cone-like shape.

Keratoconus typically affects both eyes but can also happen in one eye. The condition may progress and get worse for a decade or more.

Cataracts

A cataract is an eye problem characterized by a cloudy lens.

Clouded vision caused by cataracts may make it difficult to see, giving you what appears to be double vision. Cataracts can be an underlying cause of monocular diplopia, as they can occur in just one eye.

Pterygium

Pterygium refers to a growth of fleshy tissue in the eye that can start as pinguecula, a yellow and raised growth on the eye’s conjunctiva.²

Pterygium can grow big enough to cover part of the cornea, affecting how a person sees. It may only affect the vision in one eye.

Astigmatism

Astigmatism refers to an imperfection in the curvature of your eye that causes symptoms like blurry vision. You may have blurry distance and near vision if you have astigmatism. Your eye doctor can perform an eye exam to determine a diagnosis.

Dry Eye Syndrome

Dry eye syndrome is a common condition when your eyes cannot produce enough lubrication to keep them wet.

Dry eyes can cause discomfort, and you may feel like you are seeing two images at once. Because your eyes are dry, the surface can also become inflamed.

Health Conditions

Other health conditions that can cause double vision include:

• Myasthenia gravis
• Multiple sclerosis
• Hyperthyroidism (Grave’s disease)⁴

These can cause weak eye muscles, eye movement difficulties, the effect of seeing two images, and more.

Monocular Diplopia vs. Binocular Diplopia

Monocular diplopia is different from binocular diplopia. The main difference refers to the persistence when the eye is shut.¹

Monocular diplopia happens in one eye even if you cover the other eye. You can typically correct it using a pinhole. On the other hand, binocular diplopia usually happens when both eyes are open, and you can typically correct it by covering either eye.

Monocular diplopia may be caused by: 

• A refractive error
• Early stages of cataracts
• Clouding of your eye’s lens
• Other eye conditions 

The symptoms of monocular diplopia include, but are not limited to, the following:

• Difficulty seeing
• Double vision
• Blurry vision
• Discomfort with eye movement
• Trouble reading

Binocular diplopia may be caused by a misalignment of the eyes, known as strabismus. It can also result from cranial nerve damage, the nerves that control your eyes.

Listen In Q&A Format

Monocular Diplopia: Double Vision in One Eye 

Vision Center Podcast

When to See a Doctor

You should see a doctor if you notice the vision in one of your eyes is poor or worsening. While the causes of double vision may be nothing serious, like a refractive error, they can also be life-threatening, like a brain aneurysm.⁷

In addition, double vision can be a sign of a stroke. One common symptom of a stroke is vision changes, which means you can lose vision in one of your eyes.⁶

Diagnosing Monocular Diploma in Adults

There are a few ways your regular healthcare doctor or eye doctor can diagnose you with monocular diplopia. Tests that can help diagnose monocular diplopia include: 

• Eye test. Your doctor will check your vision and look for any signs of eye disease
• Neurological test. Your doctor may perform a neurological exam to check your reflexes, muscle strength, and coordination
• MRI scan. An MRI scan can help detect any abnormalities in the brain or other parts of the body that could be causing double vision
• Blood tests. Blood tests can help rule out any underlying medical conditions causing double vision.

Treatment for Double Vision in One Eye

Talk to your doctor about your treatment options if you have binocular double vision or monocular double vision.

• If you have an eye problem like astigmatism, the solution may be as simple as contact lenses or glasses 
• If you have a more serious reason, like a cataract, you may explore other treatment options like surgery
• If you have had brain tumors, a stroke, or another life-threatening condition, you will need to seek immediate medical attention

Summary

Monocular diplopia is a condition in which a person sees two images instead of one in one eye. Treatment for monocular diplopia depends on the underlying cause. 

It’s important to seek medical attention if you experience any of these symptoms, as they can be signs of a more serious condition.