Double Vision

Understanding Double Vision

Double vision is a condition that’s familiar to most. It’s so common in fact, that cartoons and comedies often use double vision as a joke or a gag. While it can set up some funny situations, double vision can cause significant difficulty and frustration, and can even be a symptom of a serious issue. It’s important to know what causes double vision, when it could be an issue, and what to do if it just won’t go away.

What Exactly is Double Vision?

The phrase double vision (known medically as diplopia) describes the doubling of an image. Usually, this doubling overlaps, making the edge of an object appear twice, rather than the entire image. Double vision can be so slight that the patient doesn’t even perceive it as doubling, but rather as blurring. This kind of condition can easily be found and treated through routine eye exams.

Ghost Images

While ghost images are a part of diplopia, they are different from the standard doubling that occurs due to double vision. Rather than just being two overlapping images, ghost images appear as two completely separate images sitting side by side. Ghost images usually only appear in one eye.

Potential Causes of Diplopia

Double vision can come from a variety of sources and sometimes indicates a serious need for medical care. If you’re experiencing consistent, ongoing double vision (or any other sudden vision changes), you should seek emergency eye care. Here are some of the causes of double vision.


In order for the eyes to work properly, they must be perfectly aligned. This comes down to the tension and strength of the muscles in the eye. When the muscles in one eye are stronger than the other, it can cause the eyes to misalign, resulting in double vision at some or all distances.
Sometimes, rather than seeing two images, your brain will start ignoring one eye and rely solely on the other. Strabismus is usually treated with surgery or a process called vision therapy. Vision therapy strengthens the eye muscles; training them to work together.

Neurological Issues

When double vision comes on very suddenly, it could be the result of a stroke, head injury, brain tumour, brain aneurysm, or brain swelling. All of these issues are very sensitive and require immediate medical attention. Your doctor will recommend a course of treatment after diagnosis.

Dry Eye

When the body doesn’t produce enough tears, the eyes cannot be properly lubricated. Likewise, when the body produces enough tears, but without the necessary oils to keep them from evaporating immediately, the eye becomes dry. This lack of lubrication results in double vision or ghost images. There are a number of treatments available for dry eye. Learn more about dry eye, and what treatments are available to you.

Corneal Irregularities

Sometimes, when the cornea is cone-shaped, it results in double vision or ghost images. This can be corrected with special contact lenses, however, some cases require surgery. Your doctor will be able to recommend the best course of treatment for you.
Sometimes, laser refractive surgery leaves irregularities on the cornea, causing double vision. This problem usually resolves on its own within a few months. However, in some cases, a second surgery is required to correct the irregularities.

Written by Lisa Fung

Dr. Lisa Fung is a graduate from the University of Waterloo Optometry program in 1995 and was the recipient of the Excellence in Patient Management Award. She opened up her practice in Keswick in 1996. She completed her externship program at the OMNI Eye Institute in Baltimore, Maryland and is a TLC affiliate. She is a member of the College of Optometrists of Ontario and the Ontario Association of Optometrist.

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