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 are
often thought to be the same, but they are not. In blurred vision, a single image
appears unclear. In double vision, two images are seen at the same time, creating
understandable confusion for anyone who has it.
What causes double vision?
There are two possible causes.
- Failure of both eyes to point
at the object being viewed, a condition referred to
as
"strabismus" or "squint". In normal vision,
both eyes look at 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 image seen by each eye
is different and cannot be fused. The result is double vision.
Why might eyes not point in the same direction? Possibly because
of a defect in the muscles which control the movement of the
eyes or in the control of these muscles through the nerves
and brain.
- Refractive. Light from
an object is split into two images by a defect in the eye's
optical system. Cataracts may cause such a defect.
Strabismus is a more common cause
of double vision than is refractive defect.
What
are its implications?
Double vision can be extremely troubling. The brain acts to
alleviate the 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. Doctors
call this condition "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 consists of eye exercises, surgical
straightening of the eye or a combination of the two. Therapy
is aimed at re-aligning the squinting 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. |
