Diplopia

Diplopia is a vision problem commonly known as double vision. A person with diplopia sees a double image of a single object. The condition occurs in several forms and can affect one or both eyes. The many causes of diplopia range in severity from minor to life-threatening. Treatment depends on the cause and severity. In addition to the obvious disorientation that a person with diplopia experiences, the condition can cause problems with reading and balance.

Background

The ability to see things—vision—results from light reflecting off an object and entering the eye. The eye translates the light reflections into impulses that the brain interprets as sight. Many parts of the eye have to work in coordination to make this happen.

First, the iris, or colored portion of the eye, helps the pupil—the small dark area in the center of the eye—open to the right size to allow the available light to enter. This light is refracted, or bent, as it passes through the clear outer part of the eye known as the cornea. The light is further bent as it goes through the eye's lens.

In much the same way that a camera lens focuses light so that it can be captured on film or a digital card, the lens of the eye focuses the light on an area on the inner back surface of the eye called the retina. The retina is made up of many tiny cells known as rods and cones. Cones capture bright light and are responsible for detecting details and colors, while rods help the eye detect movement, see to the side of the eye (peripheral vision), and assist with seeing objects at night or in dim light. The cones and rods convert the information they capture into nerve impulses that travel to the brain through the optic nerve. What people perceive from this information is sight.

Each eye creates its own image, which the brain focuses into a single image. When something interferes with this process, a phenomenon known as diplopia, or double vision, can result. A problem with one eye, both eyes, or the brain can cause diplopia.

Overview

Diplopia may result from a malfunction in any part of the eye. Damage to the cornea from an injury, such as a blow to the eye that causes a bruised or "black eye," an infection, or excessive dryness can warp the light entering the eye and cause double vision. A condition known as a cataract, when the lens becomes cloudy, is another possible cause. Any problem that affects the muscle of the eye, including issues with nerves or health conditions that directly affect how the muscles work, can result in double vision. Diabetes, high blood pressure, and other conditions can affect the workings of the eye. Conditions that affect the brain, such as aneurysms, strokes, tumors, migraine headaches, or injuries or illnesses that cause swelling and pressure in the brain may affect how the brain interprets images and result in diplopia.

Sometimes double vision is a short-term condition. For instance, it may be caused by the use of alcohol or recreational drugs or by excessive eye fatigue. Diplopia from these causes will resolve on its own when the cause is removed.

The most obvious symptom of double vision is a visual image that is repeated, with images appearing next to or above each other or overlapping. To determine whether diplopia is affecting one eye or both eyes, a person can take turns covering each eye to see how this affects double vision in the eye that remains uncovered. Double vision can occur on its own or with other problems. Problems associated with double vision include eye weakness or eyes that are not aligned, such as crossed eyes or one eye that moves independently of the other ("wandering eye"). Pain can occur in or around the eyes or as a headache, and one or both eyelids might droop. The disorientation that results from the mixed signals the eyes send to the brain may cause nausea.

The development of diplopia is a potentially serious medical condition, and the patient should see a physician as soon as possible to determine the cause and begin treatment. Tests and procedures for diagnosis will depend in part on the suspected cause. These may include an eye exam to determine whether the cause is an injury or illness in the eye itself, blood tests to check for infection or other problems that can cause diplopia, or imaging tests such as magnetic resonance imaging (MRI) or computerized tomography (CT) scans.

In deciding where to begin, the physician will likely ask a number of questions regarding when the symptoms began and which symptoms the patient is experiencing in addition to double vision. The physician will likely ask whether the patient has experienced recent injuries to the eye or head and whether anything makes the double vision better or worse. During the exam, the physician will likely ask the patient to try different vision tasks, including looking up, down, and to the sides, covering the eyes, and tilting the head to see how this affects the condition.

The treatment and eventual outcome for diplopia depends on its cause. If an illness has caused it, treating the illness may resolve the diplopia. For instance, lowering blood sugar levels can eliminate double vision caused by diabetes. Medications to treat conditions such as Graves' disease, which affects the thyroid, or myasthenia gravis, which causes muscle weakness, can also help restore normal vision. Double vision resulting from an injury may resolve as the injury heals, or it may require surgical treatment to help with healing.

In cases for which the primary cause cannot be resolved or for which resolving the cause does not restore normal vision, adaptive measures may make it easier to adjust to diplopia. These measures may include wearing a patch over one eye when only one is affected or wearing special prism eyeglasses that minimize effects. Eye exercises can help improve the effects of diplopia.

Bibliography

Bainter, Patricia S. "Double Vision (Diplopia)." MedicineNet,www.medicinenet.com/double‗vision/article.htm#what‗is‗the‗prognosis‗for‗double‗vision. Accessed 25 Sept. 2017.

Brady, Christopher J. "Vision, Double (Diplopia)." Merck Manuals, www.merckmanuals.com/home/eye-disorders/symptoms-of-eye-disorders/vision,-double. Accessed 25 Sept. 2017.

"Double Vision." American Academy of Ophthalmology, www.aao.org/eye-health/symptoms/double-vision-2. Accessed 25 Sept. 2017.

"Double Vision—Causes." National Health Services, www.nhs.uk/Conditions/Double-vision/Pages/Causes.aspx. Accessed 25 Sept. 2017.

Dudee, Jitander. "Diplopia (Double Vision)." Medscape, 13 Apr. 2017, emedicine.medscape.com/article/1214490-overview. Accessed 25 Sept. 2017.

"How Your Eyes Work." American Optometric Association,www.aoa.org/patients-and-public/resources-for-teachers/how-your-eyes-work. Accessed 25 Sept. 2017,

Newman, Tim. "Double Vision (Diplopia): Causes, Symptoms, and Treatments." Medical News Today,1 Nov. 2016, www.medicalnewstoday.com/articles/170634.php. Accessed 25 Sept. 2017.

"What Is Double Vision?" WebMD, www.webmd.com/eye-health/double-vision-diplopia-causes-symptoms-diagnosis-treatment#1. Accessed 25 Sept. 2017.