Clinically known as diplopia, double vision can make reading small fonts and completing fine motor tasks difficult. But to fix it, we need to determine what’s causing it—and the answer may range from simple overuse to the clouding effects of cataracts or medical emergencies.
What is double vision?
Under regular conditions, each eye usually gets its own “image feed.” As light passes through the cornea and the pupil, it hits the retina, sending electrical signals to the brain. Then, the brain’s visual cortex merges the signals from each eye, processes all the information, and creates the images you see. Diplopia causes may be related to any step in this process.
Fundamentally, double vision or diplopia results from a misalignment in how the eyes converge and focus on a single point – and the ultimate cause may stem from issues within the eye muscles, the cranial nerves that control them, or even the brain’s processing power.
Types of diplopia
Most of the time, we classify diplopia depending on which eye it affects:
Monocular diplopia originates within a single eye. It is often caused by irregularities inside that specific eye or its optical system. This includes conditions like corneal scars, cataracts, or lens distortions, which can all cause images to split or duplicate even when the other eye is closed. People with monocular diplopia will “see double” even with only one eye open.
Binocular diplopia affects both eyes and usually results from a problem merging the information from each eye. When this happens, the extra “ghost image” disappears after covering one eye.
Understanding the distinction between the different types of double vision is crucial for accurate diagnosis and targeted treatment of the underlying causes.
What are some causes of double vision?
With so many delicate parts and processes working in tandem, it is not unusual for eye conditions to have many possible causes. In the case of double vision, there are so many potential culprits that we can classify them by the organ or function they affect.
Naturally, not every cause of double vision is as likely as all the others. So, take this list with some caution, and remember that the scariest diseases that cause double vision are often the rarest.
Eye structure problems
Most cases of monocular double vision stem from an issue within the eye itself – especially the cornea or the retina. This category includes common chronic vision problems, such as:
- Astigmatism, or an imperfection in the curvature of the eye. It creates an “out of focus” or blurry effect on everything you see, especially at a distance.
- Cataracts, or a progressive clouding of the eye lens. In this case, the problem is more noticeable when looking at close-up objects.
- Keratoconus, when the outer layer of the eye turns cone-shaped instead of ball-shaped.
- Dry eyes, often caused by medications, other eye conditions, or eye surgery, can also cause temporary diplopia.
In addition, a severe eye infection can also create tiny scars or dents in the cornea (keratitis). Sometimes, these scars can be large enough to cause a “spot” of double or blurred vision.
Chronic muscle or nerve problems
We rely on six tiny muscles that control eye movement to gaze in a specific direction. People with strabismus (often misnamed “cross-eyed”) cannot correctly align their eye muscles. As a result, one of their eyes won’t focus precisely where it needs to and will send a “superposed” double image to the brain.
In some cases, strabismus develops in childhood. It can also appear later in life as a result of a chronic condition that affects muscle control or nerve sensitivity:
- Graves’ disease, a chronic thyroid condition
- Myasthenia gravis, a type of chronic muscle weakness
- Diabetes-related neuropathy, a complication of diabetes that can cause nerve damage
- Multiple sclerosis, an autoimmune condition that affects the nervous system
- Guillain–Barré syndrome, a severe type of generalized muscle weakness often triggered by an infection
In addition, some types of head injury (especially near the eye socket) can also damage the eye muscles or lead to cranial nerve palsy – which, in turn, may cause diplopia.
Neurological issues
The final step in the eyesight process happens in the brain, so it should not be surprising that many causes of double vision are neurological.
The following conditions can all affect the way your brain interprets and merges the electrical signals that each eye sends and, therefore, can cause binocular double vision:
- Migraine attacks, especially during the “aura” phase (before the actual pain begins)
- Aneurysms or strokes affecting the occipital lobe
- Brain tumors
- Concussions, although in this case, the double vision will likely be temporary
What to do if you’re seeing double?
The most common causes of diplopia stem directly from the eye. Therefore, if you notice your vision is blurry or you’re seeing double – even if it goes away –your first action should be reaching out to your eye doctor.
Expect a full eye exam during the appointment. For most cases of monocular diplopia, this is all that’s needed; however, if you have astigmatism, cataracts, or keratoconus, it will become evident immediately, and more treatment may be required.
Most cases of binocular diplopia come down to strabismus. However, knowing if there’s a more serious medical condition behind it is still important. This may require advanced imaging tests, such as an MRI, a CT scan, or specialized blood tests.
At AGEI, our ophthalmologists have close relationships with leading specialists in other fields and with advanced diagnostic centers. So, if we see any indication of an undeerlying condition, we will help you diagnose it.
When should you head to the emergency room?
In rare cases, double vision can also be a “red flag” for a medical emergency. Seek immediate medical attention if your double vision starts suddenly and is accompanied by any of the following:
- Severe eye pain
- An unusually strong headache
- Sudden issues with muscle control (for example, you can’t control your fingers)
- Problems speaking or enunciating words
- Facial paralysis or drooping on one side of the face
- Changes in one of your pupils
What are the available treatment options for double vision?
Treatments for double vision will depend on its root cause, and some fall outside the realm of ophthalmology.
In cases of double vision in one eye, treatments may include specialized glasses or contact lenses for astigmatism or keratoconus. Surgery may eventually be necessary to prevent further vision loss in the case of cataracts.
Meanwhile, people with binocular diplopia can also find relief from an eye patch, as this will make the “ghost image” disappear. In addition, eye exercises can also help strengthen eye muscles.
These include:
- Hold a pen at arm’s length and slowly bring it closer while focusing your eyes on it.
- Focus the eyes on a pen at arm’s length for a few seconds, and then rapidly switch to looking into the distance.
- Trace a figure eight with your eyes.
Naturally, if the strabismus is caused by something else, like Graves’ disease, your ophthalmologist will need to work hand-in-hand with your other specialists.
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Are you worried about your eye health? Come to the Assil-Gaur Eye Institute of Los Angeles
The causes of seeing double are often complex and require a precision-oriented approach, access to the latest medical advancements, and an eye doctor willing to go the extra mile.
At the Assil Gaur Eye Institute (AGEI), the team of top ophthalmologists from around the country take pride in combining state-of-the-art technology with thorough consideration for routine eye care.
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