Diplopia (double vision)

You may have a condition known as double vision if you see two of what you are looking at. It is often thought that blurred and double vision is the same but they are not. Blurred vision causes the person to see a single image unclearly whereas with double vision, two distinct images appear of the same thing which can be quite confusing for obvious reasons.

What causes double vision?

There are two possible causes.

The inability for the eyes to properly align with each other (Strabismus).

With normal vision, both eyes focus on the same object. The two images seen are fused into one image by the brain. When the eyes do not look at the same object, the image is seen by each eye individually and the brain is unable to fuse them. The result is double vision. Why don’t the eyes look in the same direction? Perhaps there is a fault in the muscles that control the eye movement or a fault in the muscle’s control of the nerves to the brain.

Refractive error.

The light reflecting from an object is split into two images due to a defect in the eye’s optical system. Cataracts may cause this type of error. Double vision is most often caused by strabismus than by a refraction error.

What are its consequences?

Double vision can be very disturbing. The brain will alleviate discomfort by suppressing or ignoring one of the images. Over time, this suppression may cause permanent damage to children’s visual system. The suppressed eye may begin to have difficulty seeing no matter the quality of the corrective glasses or contact lenses. This is known as amblyopia (lazy eye) as it stems from a defect in the way the eye and brain work together. It is more difficult to treat than a refractive error which involves the ability of the eye to refract light.

How can it be treated?

Double vision can be treated through eye exercises, surgical realignment of the eye or a combination of the two. The therapy is meant to realign the eye while avoiding surgery when possible and to stimulate the path to the brain that is weaker. Should the double vision be caused by cataracts, surgical intervention may be required.