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Internuclear ophthalmoplegia is the medical term for one (or both) of your eyes not moving when you look to the side. When you look to one side, your affected eye won’t move past center or be able to turn all the way in the direction you’re looking. It’s caused by damage to the pathway that holds the nerves that regulate your eye movements.
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Internuclear ophthalmoplegia (INO) is the medical term for one (or both) of your eyes not moving when you look to the side. Internuclear refers nerve bundles called nuclei. “Inter-” is a prefix that means how parts of your body work together. INO affects how nuclei that control your eye movements connect and work together to move your eyes.
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INO is sometimes a symptom of a life-threatening medical emergency, including a stroke. Call 911 (or your local emergency services number) as soon as you notice yourself or someone you’re with having symptoms of a stroke.
INO happens when something damages your medial longitudinal fasciculus — the pathway that holds nerves that regulate your eye movements. INO prevents your affected eye from looking in the direction opposite the side of your face it’s on — your affected eye won’t turn to look past your nose. It’s a type of nystagmus (uncontrollable eye movement). INO can affect one of your eyes (unilateral internuclear ophthalmoplegia) or both eyes at the same time (bilateral internuclear ophthalmoplegia).
If you look to one side, one of your eyes will stay looking straight ahead, or not move all the way in the direction you’re looking. For example, if you look to the right, your left eye won’t move with your gaze. Or, if you look to the left, your right eye won’t move all the way past center.
Some people with internuclear ophthalmoplegia make a full recovery. Others have symptoms for the rest of their life. How long it takes you to recover depends on many factors, especially what caused it.
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The most obvious symptom of INO is one eye not moving when you look to the side. Other common symptoms include:
INO can be caused by anything that damages your medial longitudinal fasciculus. The medial longitudinal fasciculus is a fiber pathway that holds the nerves that control your head and eye movements, including your oculomotor nerve (the third cranial nerve). It’s like the wiring in your home — it’s an important part of your daily routine that you’ll probably never think about unless something is wrong with it.
Some people develop INO after experiencing a stroke that damages their brainstem. The brainstem is the stalk-like part of your brain that connects your brain to your spinal cord (the column of nerves that runs down your spine). It sits toward the bottom of your brain and is part of your central nervous system.
The most common causes of internuclear ophthalmoplegia include:
A healthcare provider will diagnose INO with a physical exam. They’ll look at your eyes and watch how they move. They’ll ask you to perform movements that will show if one of your eyes isn’t turning as it should.
It might also be diagnosed during tests for other conditions, especially if you experience a stroke or trauma.
Your provider might need one of a few imaging tests to confirm damage to your medial longitudinal fasciculus, including:
Your provider may also recommend other tests if imaging tests aren’t helpful. These include:
How INO is treated depends on what causes it. Your provider will treat the underlying cause instead of the INO itself.
Some causes of INO, like strokes and multiple sclerosis, require long-term treatment — maybe for the rest of your life.
Internuclear ophthalmoplegia caused by infections will usually get better after the infection is treated.
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If your symptoms are persistent (last a long time), your provider might inject botulinum toxin to relax muscles around your eyes. This can help relieve double vision (diplopia) and reduce uncontrolled eye movements (nystagmus).
Your provider will tell you which treatments you’ll need and what to expect.
You can’t prevent INO because it’s caused by sudden, unpredictable conditions or infections.
In general, make sure you always wear protective eyewear and proper safety equipment while working with tools or doing any activity that could injure your head or eyes.
Having your eyes and vision checked regularly can help your eye care specialist identify problems right away. How often you should get your eyes checked usually depends on your age:
You might need your eyes checked more often than this if you have a condition that might affect your brain’s ability to control your eyes. People with diabetes need their eyes checked more often than what’s listed here.
Ask your eye care specialist how often you need an eye exam.
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Internuclear ophthalmoplegia might be a temporary issue, but you might also have some symptoms for the rest of your life. It depends on what caused it initially. Conditions like multiple sclerosis and some autoimmune diseases can cause longer-lasting internuclear ophthalmoplegia, too.
People with internuclear ophthalmoplegia caused by an infection usually get better after the infection is treated and have no lasting effects.
You’re more likely to have long-term symptoms if you’ve experienced a stroke, hemorrhage or traumatic brain injury, or if you have multiple sclerosis. How your eyes and vision recover will depend on how long the blood supply to your brain and nerves was interrupted.
Talk to your provider about what to expect and how you can manage your symptoms.
See your healthcare provider as soon as you notice any changes in your eyes or vision.
Go to the emergency room if you have any of the following symptoms:
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Internuclear ophthalmoplegia happens when something damages your medial longitudinal fasciculus and the nerves that control your eyes’ movement.
Strabismus (crossed eyes) is the broad term for any condition that makes it so your eyes can’t line up with each other. Usually, the six muscles that control eye movement work together and point both your eyes in the same direction. People with strabismus have problems controlling their eye movement because something affects those muscles.
Pseudo-internuclear ophthalmoplegia (pseudo-INO) causes similar symptoms that sometimes seem like internuclear ophthalmoplegia, but it’s a different disorder that affects your eyes.
Pseudo-INO is usually caused by myasthenia gravis. Myasthenia gravis causes muscle weakness throughout your body. If that weakness affects muscles around your eyes, you might lose your ability to control your eye movements. Visit a healthcare provider if you notice any new muscle weakness.
A note from Cleveland Clinic
Internuclear ophthalmoplegia affects your eyes and their ability to move smoothly like they usually do. It’s typically caused by a serious condition or sudden trauma. Your provider will work with you to find treatments that work for you — no matter what caused your symptoms. Don’t be afraid to ask your provider lots of questions along the way.
Last reviewed on 03/07/2023.
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