Double vision, also known as Diplopia, can be a symptom of a binocular vision disorder. When a person has double vision, it means that both eyes are not working together. Double vision is a result of the two eyes not pointing in the same place at the same time.
Double vision, especially with sudden onset, can be a sign of a very serious medical problem. See a doctor immediately if you experience sudden double vision.
The experience of double vision is often seeing two distinct or overlapping images of what you’re looking at, when you should only see one. The term “Ghost Image” can be used to describe the less dominant image when double vision is occuring.
There are different kinds of double vision:
Horizontal: two images where two images overlap or are side-by-side.
Vertical: two images where one appear higher or lower than the other.
Monocular: when double vision persists even when one eye is closed.
Double vision can happen temporarily, intermittently, or permanently. Some temporary causes like drinking too much alcohol or extreme exhaustion, are not cause for serious concern, and will resolve when the underlying reason for it is no longer affecting your body.
However, double vision that doesn’t go away, or keeps coming back frequently without an obvious cause, may be signs of something more serious.
Injury to your brain that affects your visual processing may cause double vision. Double vision accompanied by other neuromuscular symptoms, pain, disorientation or impairment may be a sign of neurological damage.
Disorders or injury to the eye(s) itself may cause double vision. The most common eye problems that can cause double vision are keratoconus, cataracts or dry eyes. When double vision occurs in just one eye, it may be caused by a problem with the cornea or the lens of the eye. Damage to the cornea or lens can distort the image that comes through your eye and into your brain.
Cranial nerve palsy can lead to paralysis or loss of coordination of one or more muscles that control the position of the eyes, and how they work together. There are various underlying causes of CNP, including diabetes, brain injury, infections or high blood pressure.
If you’ve had corrective laser surgery, like LASIK, double vision may occur as a side effect to the change of shape in your cornea. And irregular cornea may cause a distortion of light entering your eye. While this often resolves by itself within a few weeks, if it persists, a second corrective surgery may be necessary to compensate.
Sometimes when struggling on work that requires focusing the eyes constantly, like reading, people (especially children) can experience double vision as a result of muscle fatigue or mental exhaustion.
When your eyes are working properly, it requires the coordination of complex systems of nerves, muscles, your eyeballs, and your brain. Usually, your eyes are able to focus, point and fixate on things in the world in sync with each other and the two images that each eye sees are fused together in your brain to present a three dimensional view of the world.
However, if for any reason, one or both eyes cannot synchronize, then double vision is likely to occur, as the brain is receiving two very different images that it cannot fuse together into a three dimensional scene.
One of the main causes of double vision is Strabismus, or when the eyes are not properly aligned together, usually do to a physiological problem. People with Strabismus usually suffer from one eye being too far inward or outward, up or down.
Interestingly, when double vision occurs because of a persistent condition like strabismus, the brain may automatically adapt by shutting down or ignoring the information from one eye, in order to have less confusing visual information. This is called suppression. Surgery and Vision Therapy can help treat people with Strabismus.
It’s very important to see a doctor if you have double vision that is not clearly related to a temporary condition like intoxication or tiredness. Double vision can be among the most noticeable symptoms of a more serious underlying medical problem that needs immediate attention.
Persistent double vision that is left untreated, but then goes away, may be a sign that your brain has adapted by suppressing the image from one of your eyes (Amblyopia). While this may seem to be an improvement, it does not necessarily mean the problem has fixed itself - indeed, it can simply be an evolution of a new, different condition. Suppression can be masking the need for treatment of the underlying cause. Also, suppression also results in losing binocular vision and depth perception. In order to regain depth perception, the cause of the suppression will have to be addressed.
The most effective treatments for Strabismus are surgery to correct the eyes’ misalignment, and then vision therapy to unsuppress the visual information from the eye the brain decided to “turn off”. It’s important that the physical alignment of the eyes are functioning properly before vision therapy is administered, or double vision may re-emerge! The ultimate goal is to regain normal depth perception and coordination of the eyes in their movement and focusing ability.
Unfortunately, some causes of double vision are irreversible, like stroke, nerve palsy, tumors or other brain injury.
If the underlying cause cannot be corrected, some treatments, like prism glasses, may help you live with the symptoms at a more tolerable level.
Remember: Double Vision (Diplopia), can be the result of a life threatening problem that requires immediate attention.
When you see your doctor, be prepared to answer questions about the context surrounding the first onset of symptoms. They may administer a physical exam, blood tests and imaging tests to determine the root of the problem.