WHAT IS IT

Double vision, also known as diplopia, is the simultaneous perception of two images of a single object – the patient sees two images of a single thing either all the time, or some of the time.

Normal sight depends on multiple areas of the vision system working together seamlessly.  From front to back:

  • The cornea is the clear window into the eye. It does most of the focusing of incoming light.
  • The lens is behind the pupil. It also helps focus light onto the retina.
  • The retina is like the film inside a camera – images falling onto the retina stimulate light-sensitive cells and create signals that are sent via the vision (optic) nerve to the brain to allow us to see.
  • The vision (optic) nerve carries visual information from the eyes to the brain.
  • Muscles of the eye — extraocular muscles — normally move both eyeballs in a coordinated manner
  • The brain is where several areas process visual information from the eyes.

Problems with any part of the vision system, from front to back, can lead to double vision.

 

CAUSES

Monocular diplopia means double vision occurring in one eye only, and this sort of double vision goes away when the affected eye is covered.  Any disease affecting parts of the eye ranging from the cornea in front to the retina at the back of the eye can lead to monocular diplopia in that eye.

For example:

Cornea problems : The abnormal surface of the eye distorts incoming light, causing double vision. Damage can happen in several ways:

  • Infections of the cornea can distort the cornea.
  • Corneal scars can alter the cornea, creating unequal visual images.
  • Dryness of the cornea (dry eyes) can create double vision.

Lens problems : cataracts are the most common problem with the lens that causes double vision. If cataracts are present in both eyes, images from both eyes will be distorted. Cataracts are often correctable with surgery.

Binocular diplopia is more complex and the causes are often more serious.  Some causes may even be life- threatening!  This kind of diplopia is only present when BOTH eyes are open, and it goes away when either eye is covered.

The causes can be divided into:

Muscle problems
If a muscle in one eye is weak, that eye can’t move smoothly with the healthy eye. The difference in gaze direction between the two eyes leads to two images and double vision. Muscle problems can result from several causes: Grave’s Disease is a thyroid condition that affects the muscles of the eyes. The muscles are swollen in the early stages of the disease and later they become scarred, leaving the eyeballs in non-aligned positions. Graves’ disease commonly causes vertical diplopia. With vertical diplopia, one image is on top of the other.
Nerve problems
Nerve-muscle junction problems
Bone-soft tissue problems
Brain problems

TREATMENT

Treatment of double vision depends on the cause.

Double vision that’s new or unexplained needs urgent medical attention. With so many potentially serious causes for double vision, it’s important to discover the reason without delay as some may be life-threatening!

Your doctor will most likely use multiple methods to diagnose the cause for double vision. Blood tests, a full eye and physical exam, and possibly imaging studies like computed tomography (CT) or magnetic resonce imaging (MRI) are frequently used.

With double vision, the most important step is to identify and treat the underlying cause. In some cases, double vision can be improved by managing or correcting its cause.  For example:

  • If weak eye muscles are the cause, or if a muscle has been pinched as a result of injury, surgery may help.
  • Myasthenia gravis can be treated with medications
  • Graves’ disease is treatable with surgery or medical therapy.
  • Blood sugar in diabetes can be controlled with medicines and/or insulin.

If double vision can’t be reversed, treatments can help people live with double vision. Sometimes, this requires wearing an eye patch or special prism glasses to minimize the effect of double vision.