What is Double Vision?
Double vision is the perception of two images of a single object seen adjacent to each other (horizontally, vertically, or obliquely) or overlapping. Diplopia is the medical term for double vision. Polyplopia is the perception of three or more images of a single object overlapping each other.
Double vision is called “monocular” when the double image is perceived by an eye that is tested alone. In “binocular” double vision, each eye sees a single image when tested alone, but a double image is present when both eyes are open.
What Causes Double Vision?
There are lots of causes of double vision, ranging from benign to life-threatening. It is important for a doctor to carefully review your history and perform an examination to determine the cause and initiate appropriate treatment when necessary.
Most causes of monocular diplopia stem from poor focusing of light by the eye. Refractive errors (myopia, hyperopia, astigmatism) are causes. Dry eye (from a variety of causes such as meibomitis, Sjögren’s syndrome, and decreased tear production following refractive surgery) can produce diplopia that varies with blinking.
Cataracts (clouding of the natural lens) and posterior capsule opacification (which can occur after cataract surgery) are common in people over 60 years of age and can produce diplopia along with other vision problems. Other conditions that interfere with the proper focusing of light include corneal irregularity from keratoconus, swelling or scars, and retinal conditions such as epiretinal membranes. Rarely is the underlying cause a medical emergency in cases of monocular diplopia.
What Are The Symptoms And Signs Of Double Vision?
Images may appear to overlap each other or may appear adjacent to each other. This can lead to other symptoms, such as blurred vision and dizziness. The double vision may be monocular (one or both eyes sees multiple images when tested individually) or binocular (double vision is seen only when both eyes are open, but each eye sees a single image when tested individually).
Double vision can be constant or variable. For example, double vision that varies with blinking is often related to irregularities of the eye’s surface. Binocular diplopia may vary depending on the direction of gaze or with tilting or turning of the head. Fatigue may also contribute to variable double vision.
If you suffer from double vision, your treatment will depend entirely on the type and cause of your diplopia. Treatment can be as simple as wearing an eye patch, or special glasses or contacts. Botox® injections or eyelid surgery may be used to correct a squint that causes double vision. Similarly, a cataract operation may be necessary if a cataract is a cause, or dry eye treatment may help if dry eye is the cause.