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. Double and blurred vision is often thought to be the same, but they do differ.
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. An uncorrected refractive error is the second possible cause of double vision. An object being viewed is split into two images by a defect in the eye’s optical system. Cataracts may cause such a defect, as can uncorrected astigmatism and keratoconus.
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 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 how good the spectacle or contact lens correction. This condition is called amblyopia. Since it is a result of a defect in the interpretive mechanisms of the eye and brain, it is more difficult to treat than a refractive condition (one having to do with the eye’s ability to bend light).
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 eye exercises, 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.