What is double vision?

If you see two of whatever you are looking at, you may have a condition known as double vision, also referred to as diplopia.

What causes double vision?

There are two possible causes of double vision. The first is a failure of both eyes to coordinate together, a condition referred to as “strabismus.” In normal single vision, both eyes can focus on the same object. The images seen by the two eyes are fused into a single picture by the brain. If the eyes do not point at the same object, the images seen by each eye are different and cannot be fused. The result is double vision, which may appear to the patient as blurry images, halos around an object or two distinct objects.  The second cause of double vision may be uncorrected refractive error, that is, an object being viewed is split into two images by a defect in the eye’s optical system. Cataracts, uncorrected astigmatism or keratoconus may be the cause.

What are its implications?

Double vision can be extremely confusing. The brain acts to alleviate the visual discomfort by suppressing, or blanking out, one of the images. In young children, if this suppression of the vision persists over a continued length of time, it can lead to an impairment of the development of the visual system. The suppressed eye may get to the point where it is unable to see well, no matter which visual correction or appliance is used. This condition is called amblyopia, or lazy eye. Without immediate and proper intervention at an early age vision may never be restored.

How is it treated?

Treatment of double vision depends on the underlying cause. If the double vision is due to strabismus, it may consist of a program of vision therapy, surgical straightening of the eye or a combination of the two. Therapy is aimed at re-aligning the strabismic eye, where possible, without surgery and re-stimulating the part of the visual pathway to the brain that is not working correctly. If the double vision is due to the presence of cataracts, referral for possible cataract surgery will be undertaken. If it is secondary to astigmatism, corrective lenses will be prescribed to alleviate the double vision.