Internuclear Ophthalmoplegia

Internuclear ophthalmoplegia (INO) happens when your eyes don’t move together when you look to the side. “Inter-” means how parts of your body work together. Internuclear is a medical term that refers to the connection between two nerves. Ophthalmoplegia is weakness in your eye muscles.

INO prevents one of your eyes from looking in the direction opposite the side of your face it’s on.

For example, if you have INO in your left eye, it can’t move with your gaze to the right. If you have right-side INO, your right eye can’t look to the left.

You might be able to see this in a mirror or camera. Your affected eye will stay looking straight ahead while the other one moves back and forth quickly.

You can have INO in one eye (unilateral internuclear ophthalmoplegia) or both eyes at the same time (bilateral internuclear ophthalmoplegia).

Some people with internuclear ophthalmoplegia make a full recovery. Others have symptoms for the rest of their lives. How it affects you depends on lots of factors, especially the cause.

Symptoms of internuclear ophthalmoplegia

The most obvious symptom of INO is one eye not moving when you look to the side. Other common symptoms include:

• Double vision, especially when you’re looking to the side (and sometimes when you’re looking up)
• Blurry vision
• Vision that’s worse than usual
• Dizziness

Internuclear ophthalmoplegia causes

INO happens when something damages your medial longitudinal fasciculus (MLF).

The MLF is a fiber pathway. It connects the nerves that control your eye movements, including the abducens and oculomotor nerves. If these nerves are damaged, they can’t help control the muscles that move your eyes the way they should.

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.

The most common causes of INO include:

• Multiple sclerosis (MS)
• Strokes, especially if one damages your brainstem
• Autoimmune diseases like lupus, Sjögren’s syndrome and sarcoidosis
• Hemorrhage
• Infections like Lyme disease, herpes zoster, syphilis or HIV
• Traumatic brain injuries (TBIs)
• Tumors

How doctors diagnose this condition

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 like it should.

Providers might also diagnose it during tests for other conditions, especially if you experience a stroke or trauma.

Your provider might use an MRI or a CT scan to look for the damage that causes INO. They might also order blood tests or a lumbar puncture to check for infections or other issues that can affect your brain.

Internuclear ophthalmoplegia treatments

Your healthcare provider will treat the cause of internuclear ophthalmoplegia. Your provider will tell you which treatments you’ll need and what to expect.

Some causes, like strokes and multiple sclerosis, require both short- and long-term treatment. You might need to manage these conditions for the rest of your life. Your provider will suggest ways to prevent another episode of INO.

INO from infections will usually get better after the infection is treated.

If you experience INO symptoms for a long time, your provider might inject botulinum toxin into the muscles around your eyes. This will relax them. It can help relieve double vision and reduce uncontrolled eye movements.

Your provider may also suggest temporarily wearing an eye patch or prisms (a special type of glasses).

When should I see my healthcare provider?

See a healthcare provider or eye doctor 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:

• You can’t move your eyes
• A sudden loss of vision, either partial or total
• Severe eye pain
• You see new flashes or floaters in your eyes

INO is sometimes a symptom of a life-threatening medical emergency, including a stroke. Call 911 or your local emergency services number if you think you or someone you’re with is having stroke symptoms.

What can I expect if I have this condition?

Internuclear ophthalmoplegia might be a temporary issue. But you may have some symptoms for the rest of your life. It depends on the cause.

If you developed INO because of an infection, you should get better with no long-term effects.

You’re more likely to have lasting INO symptoms from more serious causes, including:

• Strokes
• Multiple sclerosis
• Traumas

Talk to your provider about what to expect. They’ll help you set goals and expectations that fit your unique circumstances.