Double vision (medically known as diplopia) is where you see two images of a single object either some or all of the time. The two images may be one on top of the other, side by side or a mix of both.
The underlying cause of your double vision depends on whether your double vision is coming from one eye or both eyes. This will also affect any treatment you receive.
Treatment options range from special glasses and eye exercises, to surgery to remove a cataract. Read more about treating double vision.
When to see your GP
You should visit your GP as soon as possible if you have developed double vision. If you have not had double vision before, it is very important that you have it checked as it could be a symptom of a serious medical condition.
Read more about the symptoms of double vision.
What causes double vision?
Each eye creates its own, slightly different image because the two eyes are physically located in different positions. However, you usually only see one image. This is because your brain is able to control your eye muscles so that both eyes are pointing accurately at the object you are looking at. Your brain joins the images produced by each eye together into a single image in a process known as fusion.
If your eye muscles or nerves are damaged, the muscles may not be able to control your eyes properly and you may develop double vision. Your eye muscles can also be weakened as a result of a health condition, or your eyes may not be aligned properly. This is sometimes known as a squint.
Read more about the causes of double vision.
Double vision in one eye
Double vision in one eye is known as monocular double vision. You should be able to see normally if the affected eye is covered, but double vision continues when the unaffected eye is covered.
In cases of monocular double vision, the two images are often only slightly separated. This is sometimes referred to as ‘ghosting’.
Double vision in both eyes
Double vision in both eyes is known as binocular double vision. It happens when both eyes fail to work together properly. If you have binocular double vision, your vision will usually return to normal if either eye is covered.
Physiological double vision
You may experience physiological double vision when objects in your background field of vision, which you are not specifically focusing on, appear double.
Your brain usually compensates for this type of double vision and it often goes unnoticed. However, children who complain of having double vision sometimes have physiological double vision.
