Double vision can impair your ability to drive or read, affect your balance, and make you dizzy or nauseous. It can even be an indicator of a serious health issue. Let’s explore double vision by looking at its potential causes, how people can experience it, and the ways that optometric vision therapy can treat it.
But first, let’s be clear on exactly what it is.
According to the College of Optometrists in Vision Development, diplopia, more commonly referred to as double vision, occurs “if our eyes do not both aim in the same place either at a distance or up close.” The double images that result “may be totally separate or overlap to some degree.”
The hand at the top of this post is a good example of double vision. Below, you can see how text may appear if you have double vision:
If one eye is covered and a person experiences double vision, this is monocular diplopia, a condition that can be caused by:
According to the Mayo Clinic, dry eye syndrome is also a common cause of monocular double vision.
Note that these are all examples of physical problems with the eye. Generally, these are not treatable with optometric vision therapy, which we discuss further below.
To help you understand why double vision occurs, let’s first consider what healthy functional vision is.
Your visual system comprises the eyes, the brain, and the visual pathways that transmit a visual sensation from the retinas of your eyes to the brain. These components all need to work together to produce a single, clear image that has three-dimensional depth.
Functional vision includes the critical visual skill of eye teaming. Normal binocular vision (i.e., two-eyed vision) occurs when both eyes can team together and focus on the same point in space.
But with poor binocular vision, both eyes may not be able to focus on the same point. Because of this, the brain can’t effectively combine the two images it receives into a single image.
As a result, a person may experience double vision.
But what are the underlying causes for double vision? Here are some possibilities:
Strabismus, commonly referred to as “crossed eyes,” occurs when one of the eyes is turned inward, outward, or up or down. This can prohibit normal binocular vision. Not all types of strabismus will cause double vision, but some do.
People with brain injuries such as concussions may experience double vision because head traumas can cause problems with eye teaming.
In “Persistent Visual Disturbances After Concussion,” a review of concussion research, the authors found that “[s]tudies in both adolescent and adult patients have described persistent clinical features affecting the visual system following a concussion,” including double vision.
Note that a stroke, brain tumor, brain swelling, or a brain aneurysm can also cause double vision. See more on strokes directly below.
A stroke can occur when a blood vessel carrying oxygen to the brain becomes blocked or bursts. This can cause damage to the brain, including the areas involved in the visual system.
Because the brain works in concert with the eyes to perceive visual space, a stroke can cause vision problems like double vision. For more information, see Can Vision Therapy Help Stroke Victims with Double Vision?
This is when the lenses of a person’s eyes lose the flexibility to focus on objects within arm’s length, a condition that becomes more common as people age.
As the lenses lose flexibility, longstanding eye teaming problems that were previously compensated for can worsen, resulting in double vision.
Convergence insufficiency. This occurs when a person’s eyes are unable to converge on a near object or they cannot sustain the convergence.
Convergence excess. When a person has convergence excess and looks at a nearpoint target, their eyes converge to a point that is closer than where the target actually is. For example, if a book is held 16” away from the reader, the eyes may be pointing at a spot only 14” away.
With both of these conditions, if double vision occurs, the words on a page may appear to “move around” as the image oscillates between being single and double.
We learned about functional vision above. For more details on double vision and its relationship with functional vision problems, here’s Dr. Kellye Knueppel from The Vision Therapy Center.
Double vision can affect people in a number of ways. Along with actually seeing double, you may also experience the following symptoms:
Headaches or lightheadedness. You may feel lightheaded or have headaches, especially when looking up or looking down.
Nausea, dizziness, and vertigo. In order to maintain balance, the visual input to the brain has to match up with what is perceived by the vestibular system, which gives us a sense of balance and enables us to quickly move and adjust if we feel off-balance.
When vision is doubled, the brain has difficulty integrating the visual and vestibular systems. This can cause nausea, dizziness, and/or vertigo.
People can experience double vision in a variety of ways:
Mild causes of double vision may only produce a slight shadowing effect. At the other end of the spectrum, severe double vision will result in two distinct images that can be fairly far apart.
In “Red Flags in Neuro-Ophthalmology,” the author calls the sudden onset of double vision a “red flag symptom” because it could be a sign of pathology (i.e., disease) in the brain. If you’re experiencing a sudden onset of double vision, you need to be evaluated by an eye care professional or neurologist immediately.
Once the possibility of pathology has been ruled out or treated, you can explore treatment options for any remaining double vision.
Double vision does not have to be constant. When a person experiences double vision some but not all of the time, this is known as intermittent double vision. It tends to occur more frequently from eye fatigue.
For example, it can be triggered by doing an extensive amount of near work. In “Management of Diplopia,” researchers state, “Patients usually present with diplopia ... after sustained near tasks (reading, writing, computer working) and ... eye contact.”
Vertical diplopia is when the images split up and down from one another, as opposed to the more common horizontal diplopia, where double images appear side-by-side, with varying degrees of overlap.
Note that it’s possible to have horizontal and vertical double vision at the same time.
Rotational double vision occurs when one image appears to be turned, or rotated, compared to the other.
People can experience diplopia when looking at something from any distance -- near, intermediate, and far. It’s also possible for double vision to occur only at certain distances.
Double vision can be an ongoing condition and can vary in its severity. Some people can actually learn to live with the condition.
For example, a person with constant double vision may learn which image is “real” and only pay attention to that image while carrying out daily activities.
A person with intermittent double vision may simply close one eye in order to temporarily function when they are experiencing it.
It’s also possible that a person’s brain will suppress or ignore one of the two images, preventing double vision from happening.
But these are hardly good solutions because in all cases the person loses binocular vision, which is necessary for three-dimensional depth perception, or stereopsis.
Fortunately, you don't have to live with double vision. Many cases can be treated with optometric vision therapy. Learn more on that below.
With a Functional Vision Test, our doctors can test all aspects of your visual system. The test is the first step in determining the extent of your double vision and the types of treatment that may be available to correct it.
In “Nonsurgical Treatment of Neurologic Diplopia,” the authors state, “Surgical intervention for [diplopia] is not always warranted, possible, or even safe for some patients, and nonsurgical and orthoptic treatments can provide significant relief.”
Here at The Vision Therapy Center, we use a non-surgical, non-invasive treatment option for double vision known as optometric vision therapy, which is designed to work on the underlying problem and, in best cases, eliminate it.
Watch the video below to learn how optometric vision therapy helped Nancy’s double vision following a stroke. You can also read about her success story.
Vision therapy is a specialized area of optometry and is practiced by developmental optometrists, who have received extensive training in this field.
A typical individualized program of vision therapy lasts six to nine months with weekly in-office sessions with a vision therapist. Between sessions, the patient completes activities at home to support their progress.
Other treatment tools may include prism glasses and/or partial occlusion of one or both eyes. These may be used alone or in conjunction with vision therapy for the best outcome.
The approach to treatment and results will vary depending on the specific nature of your double vision. If you’re experiencing double vision, schedule a Functional Vision Exam with one of our doctors. After a thorough assessment of your visual system, they can determine what treatment approach would be best for you and what results to expect.
Gunasekaran, P., Hodge, C., Rose, K., & Fraser, C. L. Persistent visual disturbances after concussion. Aust J Gen Pract 2019; 48(8):531-536.
Iliescu DA, Timaru CM, Alexe N, et al. Management of diplopia. Rom J Ophthalmol. 2017;61(3):166-170.
Ogun O. Red flags in neuro-ophthalmology. Community Eye Health. 2016;29(96):64-65.
Singman EL, Matta NS, Silbert DI. Nonsurgical treatment of neurologic diplopia. Am Orthopt J. 2013;63:63-68.
The content above was written by professional writers and then reviewed and edited for medical accuracy by Dr. Brandon Begotka of The Vision Therapy Center. Learn more about Dr. Begotka's medical background.
The content on this website has been created by The Vision Therapy Center. It was written by professional writers and then reviewed and edited for medical accuracy by the Developmental Optometrists at The Vision Therapy Center.