Diplopia: Double Vision

Seeing double?. Dornveek Markkstyrn

Have you ever seen double? Diplopia is the medical term for double vision. Diplopia causes a person to see two images of the same object. Double vision usually occurs when the eyes are misaligned, or not pointed at the same object, causing us to see two different images. Both images are sent to the brain which we process as double vision. 

Types of Double Vision

There are primarily two types of diplopia: monocular and binocular.

  • Monocular: Double vision that affects only one eye. If one eye is covered, the double vision continues.
  • Binocular: Double vision that affects both eyes. If either eye is covered, the double vision stops.

Why Do You See Double?

Double vision can be very unsettling when it occurs and it can create major problems in your life. Seeing two objects at once is often frightening. Driving a vehicle is not safe if objects are doubled in your field of vision. Fortunately, for most sufferers, our brains help us compensate by suppressing, or ignoring, one of the two images. When suppression occurs, you are really only using one eye. Therefore, you are really not utilizing the information from eye being supressed at all. Your brain is very good at tricking your eyes. 

Causes of Double Vision

Double vision can represent a serious neurological problem since there is a complex network of muscles and nerves that keep our eyes working together.

There are many causes, such as various diseases of the eye muscles, or when various neurological and endocrine diseases (including myasthenia gravis, thyroid disease or diabetes) affect the nerves that control vision. In addition, stroke, aneurysm, brain tumor, swelling of the brain, cataracts. It also may be caused by an injury to the head.

It can be congenital (since birth) or acquired later in life.

Another important cause of double vision is strabismus. Strabismus is a condition that causes the eyes to be misaligned, often referred to as an "eye turn." Most people that have a strabismus have an eye that is pointed inward or outward. Strabismus can also cause one eye to be pointed up or down. In many infants, it is difficult to find a true cause. Children can be born with strabismus and there seems to be no apparent cause. Sometimes strabismus is caused by a large refractive error (need for prescription glasses.) Young children may try to compensate from a large uncorrected refractive error and it cause a disruption of the normal binocular process and one eye turns in. Less commonly strabismus is called by eye or brain tumors.

Lazy Eye

Most young children do not suffer from double vision even though their eyes are misaligned. Our brain often compensates and prevents us from seeing double by suppressing one of the images and making it disappear.

Our brain learns to ignore the extra image, known as suppression. Children seem to adapt quickly and their brains suppress one of the images quickly. However, when one image is suppressed, a child is at risk for developing amblyopia, often referred to as lazy eye, because the eye is not being used properly. When strabismus develops in adults, double vision is more likely to occur. An adult brain has difficulty suppression one image at first because for a large part of their life, both eyes were functioning to their fullest potential.

Besides monocular and binocular disruption, double vision can be vertical or horizontal. If you have  vertical diplopia, you see two diagonally displaced images, one atop the other. In horizontal diplopia the images appear side by side.

What You Should Know

If you ever see double, you need to be concerned. Double vision, or diplopia, can be dangerous and need sot be evaluated. If you have diplopia, you should be evaluated by a medical professional to determine its cause. The underlying cause will determine how to properly treat the condition. Your eye doctor will usually be able to find a treatment plan to help you see normally again.

Also Known As: Double vision

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