Double vision, also called diplopia, can be disorienting and scary when patients experience it for the first time. Whether it’s a new condition or a more chronic issue, seeing two images of a single object significantly impacts your daily life.
A few conditions can cause double vision; some require immediate medical attention. If the double vision is new, your doctor will order tests to determine the cause.
Let’s look into what causes double vision and the potential treatments.
What is double vision?
Double vision occurs when a person sees two images of a single object. These images can be side by side (horizontal diplopia), on top of each other (vertical diplopia), or a combination of both.
Some patients with a high amount of astigmatism will think they have double vision, but they see the smeared, blurred edges of the image and not an actual second image. This secondary image can be corrected with their glasses.
Double vision can affect one eye (monocular) or both eyes (binocular). Understanding these two types’ differences is essential for a doctor to diagnose and treat diplopia.
Monocular diplopia
Monocular double vision affects only one eye. When the unaffected eye is closed, the patient will still see double. This diplopia is caused by a problem within the eye itself, such as an issue with the cornea or lens.
Binocular diplopia
Binocular double vision affects both eyes, but it disappears when one eye is closed. This form is typically due to a misalignment of the eyes; they are not working together properly. Binocular diplopia is often related to issues with the muscles or nerves that control eye movement.
Common causes of double vision
Several factors lead to double vision, from relatively benign causes to more serious medical conditions.
Causes of monocular diplopia
Monocular double vision usually stems from an issue with the eye’s structures, such as the cornea, lens, or retina.
- Astigmatism is an irregular cornea curvature that causes light to be focused improperly on the retina, leading to distorted or double vision.
- Cataract is a clouding of the eye’s natural lens and is a common cause of monocular double vision, particularly in older adults.
- Keratoconus is a condition where the cornea thins and bulges outward into a cone shape. Keratoconus leads to distorted vision and may cause double images.
- Retinal conditions like macular degeneration or a retinal detachment can affect how light is processed by the eye, resulting in monocular diplopia.
- Dry eye syndrome is a lack of adequate moisture in the eye that can cause surface irregularities, which may result in double vision. Dry eyes can be caused by environmental factors, medications, or autoimmune conditions like Sjogren’s syndrome.
- Lens displacement (also called ectopia lentis) is a dislocation of the lens of the eye due to trauma or a genetic condition like Marfan syndrome, leading to double vision in one eye.
Causes of binocular diplopia
Binocular double vision occurs when the eyes are not properly aligned or coordinated. This form of double vision often has neurological or muscular causes.
- Strabismus is a condition where the eyes are misaligned and fail to work together. It is often called an eye turn. This can cause double vision because each eye is focusing on a different point.
- Cranial nerve palsy occurs after damage to the nerves that control eye movement. There are three cranial nerves responsible for eye movements (the oculomotor, trochlear, and abducens nerves), and any injury or disease affecting these nerves can cause misalignment of the eyes. Diabetes is the most common cause.
- Graves’ disease is an autoimmune disease that affects the thyroid gland resulting in inflammation of the eye muscles and leading to restricted eye movements.
- Strokes can affect the brain’s ability to control eye movements.
- Myasthenia gravis is an autoimmune disorder that affects the muscles that control voluntary movements. The disease results in the weakening of the eye muscles resulting in double vision.
- Trauma to the head or face can damage the muscles or nerves that control eye movements.
- Brain tumors, particularly those that affect the brainstem or cranial nerves, can interfere with eye coordination and cause diplopia.
- Multiple sclerosis (MS) an autoimmune condition that affects the central nervous system, including the optic nerves and the part of the brain that controls eye movements.
Diagnosing double vision
If you have double vision, you should see an eye doctor especially if it occurs suddenly or is accompanied by headaches, dizziness, or eye pain. A thorough eye exam will help determine the type of double vision (monocular or binocular) and its underlying cause.
Your eye doctor will use several diagnostic tests including:
- Refraction: To check for refractive errors like astigmatism or cataracts
- Corneal topography: To assess the shape of the cornea and diagnosis keratoconus
- Eye alignment tests: To evaluate how well your eyes work together and to assess your binocularity
- Imaging (MRI or CT scans): If strokes, tumors, or other problems are suspected
- Blood tests: To check for conditions like Graves’ disease or myasthenia gravis
Treatment options for double vision
The treatment for double vision depends on the underlying cause. First, corrective lenses like glasses or contacts lenses can be used to treat refractive errors by realigning the light entering the eye. Prism glasses may also be used to bend light and compensate for eye misalignment in strabismus or nerve palsy cases.
Second, surgery may be necessary for conditions like cataracts, retinal detachment, or eye muscle problems (strabismus). Cataract surgery replaces the clouded lens with a clear artificial one, while eye muscle surgery realigns the eyes to eliminate double vision.
Third, if the double vision is caused by conditions like myasthenia gravis, Graves’ disease, or multiple sclerosis, medications can help control symptoms. Steroids can reduce the inflammation in Graves’ disease, while immunosuppressants can treat myasthenia gravis.
Lastly, for temporary or minor cases of binocular diplopia, an eye patch may be used to block the vision in one eye, preventing double vision. Patching is typically a short-term solution while a more permanent treatment is being sought.
Double vision can be a disorienting and scary symptom but understanding the causes and treatments can be reassuring. Whether it’s due to a simple refractive error or a more complex neurological issue, early diagnosis and treatment are key. Double vision must be treated to improve one’s quality of life, prevent eye strain, and maintain vision alignment.
