Diplopia

Diplopia is the medical term for double vision. It means you see a single object as two separate images, either side by side, one above the other or at an angle to each other. This can occur in one eye (monocular diplopia) or only when you look with both eyes at the same time (binocular diplopia).

Monocular diplopia means that you still see double even when one eye is closed. This may indicate a problem within the eye itself, such as an abnormality of the cornea, the lens or the retina. Possible causes include an irregular cornea, early-stage cataracts or a problem with the eye’s lens.

Binocular diplopia disappears as soon as you close one eye. This type usually indicates a problem with the coordination between the two eyes. The cause often lies with the eye muscles, the nerves that control the eye muscles, or the brain. Examples include paralysis of an eye muscle, nerve damage, thyroid disorders, myasthenia gravis, or neurological conditions such as a stroke or multiple sclerosis.

Diplopia can occur suddenly or develop gradually. It may be constant or only occur when looking in certain directions. It is sometimes accompanied by other symptoms such as headaches, tiredness, pain when moving the eyes, or a drooping eyelid.

Double vision is always a reason to contact your GP, optician, optometrist or ophthalmologist. It is particularly important to seek a prompt examination if it starts suddenly, or if you are also experiencing headaches, nausea, weakness, speech difficulties or a drooping eyelid.

The specialist will assess whether the diplopia is monocular or binocular, and in which direction of gaze it occurs. This is often followed by further investigations, such as an ophthalmological consultation, blood tests, imaging of the brain or eye sockets, or a referral to a neurologist.

Treatment depends entirely on the underlying cause. In the case of a refractive error, a pair of prescription glasses or prism lenses may help. If there is a problem with the eye muscles, surgery may sometimes be necessary. In the case of a nerve or brain problem, treatment focuses on the underlying condition.

Contact lenses rarely cause true diplopia. However, a poorly fitting or damaged lens can sometimes cause temporary blurred or distorted vision, but this is different from true diplopia. If you experience double vision, you should always have it assessed by an eye specialist.