Diplopia or ‘seeing double’, can have many causes ranging from the severity of an intracranial tumour to more benign causes such as dry eye. It can be a common presenting complaint in ophthalmology therefore it is important to have a good approach to this. There are two types of diplopia; monocular diplopia is usually the result of a refractive error, whilst binocular diplopia is commonly due to impaired extraocular muscle function.

Diagnosis of Diplopia
The first step is to determine whether your double vision is monocular or binocular. To do this, your doctor will ask you to cover one eye and then the other. If you have monocular diplopia, your doctor will evaluate you for conditions, such as cataracts, that could be causing the problem. You will then need to see an eye specialist (an ophthalmologist). If the problem is binocular and there has been no facial trauma, then your doctor will want to know if you have Diabetes, Graves' Disease or neurological disorders.

In diagnosing binocular diplopia, your doctor has to determine which eye muscles are affected. To do this, you will be asked to look at the doctor's finger as he moves it up, down, left and right. This lets the doctor see how far your eye can move in each direction. Your doctor also will cover one eye and then the other, while you focus on a target. If the doctor sees your eyes shift as the eye cover is moved, it means your eyes are not aligned properly. Prisms may be placed over your eye to shift the image, and the test is repeated. The prisms allow the doctor to measure the amount or degree of your double vision when you look in different directions. This helps to diagnose the problem and monitor the problem over time. Your doctor will use the results of this exam, together with your medical history and additional symptoms, to determine if you need more tests.

Treatment for Diplopia
Treating double vision depends on its cause. For example, people with astigmatism that causes double vision can wear special contact lenses. Sometimes, simply updating your prescription eyeglasses takes care of the problem. Surgery is used to treat cataracts and pterygium, and surgery on the eye muscles can treat certain types of double vision. Often, adjustable stitches are used so that the position of the eyes can be fine-tuned a few hours after the surgery. That way, the patient is alert for the adjustment and can report whether the double vision is gone. Prisms also may be used in the glasses to fine-tune the surgery by moving the image seen with one eye to coincide with the other eye.

For children with strabismus, treatment includes wearing prescription eyeglasses, prism vision therapy to train the eyes to align properly, or surgery. Double vision caused by a medical or neurological disease may improve by treating the disease. Eye specialists may consider other strategies to help improve the eye movements. Injections of botulinum toxin (Botox) can weaken strong eye muscles opposite the weakened one to help balance vision.