What is double vision?
Medically referred to as diplopia, double vision is seeing two images of a single object. The images may be side by side, on top of one another, or a mixture of both. On some occasions, you may even see more than two images of the same object.
Depending on the cause, double vision can either be a temporary issue or a long-term condition.
What causes double vision?
Double vision can affect either one eye (monocular) or both (binocular), which usually dictates which kind of treatment you’ll require.
Temporary moments of double vision can be caused by a blow to the head, drinking too much alcohol or extreme tiredness. This is short term and usually disappears quickly.
There are also a number of other conditions that can cause long-term double vision, these include:
A head injury, tumour, swelling or aneurysm in the brain can cause sudden double vision, and will usually continue until the problem is treated. After an eye examination, you’ll be referred to a neurologist or neurosurgeon for more comprehensive tests and diagnosis.
Cranial nerve palsies
Paralysis or loss of coordination of the muscles that control how the eyes work together can also cause double vision, and can both be a result of cranial palsy. Cranial nerve palsies can be caused by a number of things, such as: diabetes, a tumour, meningitis, high blood pressure, a head injury, a brain aneurysm or a blockage in an artery.
A squint (strabismus is the medical term) refers to a condition in which your eyes point in different directions. This is usually because the muscles controlling your eyes are either too strong, in which case they are prevented from moving smoothly, or too weak, in which case they are unable to move. Not all squints cause double vision and they are particularly common in young children.
Abnormalities of the eye’s lens due to cataracts, or the retina due to macular degeneration, as well as refractive surgeries to correct these conditions, can cause double vision. Vision usually goes back to normal after a patient has recovered.
Dry eyes, particularly more severe conditions such as Sjogren’s syndrome, can cause ghost images. Eye drops can help this.
Usually caused by astigmatism, the irregular shape of the cornea affects how light passes through the eye, resulting in images appearing blurry.
How is double vison treated?
As most double vision is the result of underlying issues, once these conditions are treated, your vision will usually balance out.
While some causes of double vision can be treated easily at home, such as astigmatism being corrected by toric contact lenses, a lot of times you must seek medical advice from your ophthalmologist.
Do I need an eye test?
A guide to light sensitivity
A guide to cataracts