What is double vision?
Double vision, also known as diplopia, occurs when you see objects duplicated in your vision rather than a single clear representation of each object. Double vision may be temporary or permanent. Double vision can be due to a number of different events or conditions ranging in severity from a minor concern to one that is serious or life threatening. The dual images can appear horizontally, vertically, or at a tilted angle.
Double vision may originate as a problem in one eye or both. Covering one eye eliminates true diplopia, whereas persistence of multiple images with just one eye (monocular diplopia) is usually caused by problems with the eye’s optical system. For example, corneal scarring or cataract may split or double the image you perceive.
A major cause of double vision involving both eyes is misalignment of the eyes such that they cannot focus equally on an object. An eye muscle imbalance or refractive (eyeglass) problem can be responsible. This type of double vision can occur in young children whose eyes are misaligned from birth. Infants don’t tolerate diplopia and the brain involuntary shuts off vision in one eye (amblyopia: a healthy eye that does not see). Diplopia can also occur later in life if injury or disease affects the ability of the eye muscles to work together properly. For example, alcohol intoxication can result in temporary double vision. Serious causes of double vision include brain tumors, stroke and multiple sclerosis, a disease that affects the brain and spinal cord causing weakness, coordination, balance difficulties, and other problems.
Because the causes of double vision are so varied and can range from minor to life threatening, it is important to contact your health care provider promptly for diagnosis of your double vision and treatment of the underlying cause.
Occasionally double vision can be a sign of a medical emergency. Seek immediate medical care (call 911) if you experience double vision along with other serious symptoms, including sudden loss of or change in vision, sudden loss of coordination, change in level of consciousness or alertness, such as passing out or unresponsiveness, severe headache, sudden weakness or numbness on one side of the body, or eye pain.
Seek prompt medical care for diagnosis of the underlying cause of your double vision, or if your symptom of double vision is persistent or recurrent.
What other symptoms might occur with double vision?
Double vision may accompany other symptoms, which will vary depending on the underlying disease, disorder or condition.
Other eye or vision symptoms that may occur along with double vision
Double vision may accompany other symptoms affecting the eye or vision including:
- Abnormal pupils
- Blurred vision
- Droopy eyelids
- Dry eyes
- Eyelid malposition
- Glare or halos seen around lights
- Inability to move one or both eyes (gaze limitation)
- Increased sensitivity to light
- Poor nighttime vision
- Proptosis (eye bulging, as seen in Graves disease)
- Red, sore eyes (bloodshot eyes)
Other symptoms that may occur along with double vision
Double vision may accompany symptoms related to other body systems including:
Serious symptoms that might indicate a life-threatening condition
In some cases, double vision may be a symptom of a life-threatening condition that should be immediately evaluated in an emergency setting. Seek immediate medical care (call 911) if you, or someone you are with, have any of these life-threatening symptoms:
Change in level of consciousness or alertness, such as passing out or unresponsiveness
Fixed, dilated pupil
Loss of muscle coordination
Sudden change in vision, loss of vision, or eye pain
Sudden weakness or numbness on one side of the body
What causes double vision?
Double vision may be caused by a variety of underlying conditions or diseases. Some of these conditions, such as cataracts, are fairly common, particularly in older populations, while others may be serious or life threatening in nature. It may appear in only one eye as a result of refractive errors that split or double the image.
More commonly, double vision results from a misalignment of the eyes (strabismus) that prevents both eyes from focusing equally on an object. Misalignment may be present from birth, occur as a result of injury to the brain or the eye area, or be caused by diseases, including multiple sclerosis and diabetes. Alcohol and drugs can also cause temporary double vision.
Common causes of double vision
Double vision may be caused by conditions including:
- Alcohol intoxication
- Cataracts (clouding or loss of transparency in the lens of the eye)
- Diabetes (chronic disease that affects your body’s ability to use sugar for energy)
- Dry eyes
- Misalignment of the eyes
- Multiple sclerosis (disease that affects the brain and spinal cord causing weakness, coordination, balance difficulties, and other problems)
- Refractive error, such as myopia (nearsightedness), hyperopia (farsightedness), or astigmatism (irregularly shaped cornea)
Serious or life-threatening causes of double vision
In some cases, double vision may be a symptom of a serious or life-threatening condition that should be immediately evaluated in an emergency setting. These include:
- Brain or head injury
- Brain tumor
- Injury to the eye
- Optic neuritis (inflammation of the optic nerve)
- Transient ischemic attack (temporary stroke-like symptoms that may be a warning sign of an impending stroke)
Questions for diagnosing the cause of double vision
To diagnose your condition, your doctor or licensed health care practitioner will ask you several questions related to your double vision including:
- When did you first notice your double vision?
- Is the double vision persistent or does it come and go?
- Is the double vision present in one eye or both eyes?
- Are you having any other symptoms associated with your double vision?
- Do you have any other known medical conditions?
- Are you currently taking any medications?
What are the potential complications of double vision?
Double vision is often due to refractive errors or imbalance in the eye muscles; these conditions are not serious and can be treated by corrective lenses or surgery. However, in some cases, double vision may be caused by serious, or even life-threatening, conditions. If you experience double vision, contact your health care provider promptly to determine the underlying condition. Once the underlying cause is diagnosed, it is important for you to follow the treatment plan that you and your health care professional design specifically for you to reduce the risk of potential complications including:
- Brain damage
- Loss of vision and blindness
- Spread of cancer