Optic neuritis (ON) is inflammation of your optic nerve. It can cause vision loss and pain when you move your eyes. As the inflammation goes away, your symptoms will usually get better.

The optic nerve carries visual information from your eye to your brain. ON is when your optic nerve becomes inflamed.

The inflammation can cause vision loss in one or both of your eyes. This loss of vision is usually temporary. In some cases, you may also feel pain when you move your eyes.

ON can flare up due to an infection or nerve condition. Early diagnosis and treatment can improve your outcome. As you recover and the inflammation goes away, your vision will likely return over time.

Whenever you notice changes to your vision, it’s important to get it checked out by a doctor or ophthalmologist.

Emergency care

Sometimes, eye problems can require emergency treatment. Reasons to seek emergency care include:

  • severe eye pain
  • sudden loss of vision
  • sudden changes to your vision, such as blurry vision

If your vision changes are accompanied by symptoms of stroke, such as facial drooping, difficulty speaking, or severe headache, get emergency help right away. Call your local emergency services or have someone help you get to the nearest emergency room.

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There are many possible causes of ON. Some cases are idiopathic, which means they have no known cause.

Multiple sclerosis and other nerve conditions

Multiple sclerosis (MS) is the most common known cause of ON. ON is often the first symptom of MS. About 50 percent of people with MS will develop ON at some point.

Other nerve conditions that can cause ON include:

Autoimmune conditions

ON can also be caused by autoimmune conditions, such as:

  • sarcoidosis, a condition that causes inflammation in various organs and tissues
  • Sjögren’s syndrome, a disorder that typically affects tear and saliva glands
  • systemic lupus erythematosus, a long-term condition that can affect different organ systems
  • glial fibrillary acidic protein immunoglobulin G disease, a rare condition

Infections and other causes

Infections that can cause ON include:

Other possible causes include:

  • certain medications
  • exposure to toxic substances
  • alcohol or tobacco use
  • certain nutritional deficiencies

The symptoms of ON can vary, depending on what’s causing it.

The most common symptoms of ON include:

  • vision loss in one eye, which can vary from mild to severe
  • periocular pain, or pain around your eye that’s often worsened by eye movements
  • dyschromatopsia, or the inability to see colors correctly

Other possible symptoms can include:

  • changes in the way the pupil reacts to bright light
  • photopsia, seeing flashing lights or floaters in one or both eyes
  • Uhthoff’s phenomenon, or Uhthoff’s sign, which is when vision worsens with an increase in body temperature

When ON affects one eye only, it’s called unilateral ON. Unilateral ON is more common. But it’s also possible for ON to affect both eyes. This is known as bilateral ON.

Sometimes, conditions other than ON can cause similar symptoms. These include:

  • anterior ischemic optic neuropathy, when part of your optic nerve is not getting enough blood
  • Leber hereditary optic neuropathy, a type of vision loss that is passed down in families

A doctor can assess your symptoms and use tests to help determine whether you have ON or another condition.

Factors that increase the chance of developing ON include:

  • being 20 to 40 years old
  • being assigned female at birth
  • having a diagnosis of MS

The risk of developing MS may be higher for people who live in temperate regions, like western Europe and the northern United States.

A doctor will typically begin by asking you about your symptoms and medical history. They’ll then perform a physical exam. To ensure the best treatment, the doctor may perform additional tests to determine the cause of your ON.

Tests for ON can include blood tests or a cerebrospinal fluid analysis.

The doctor may also request imaging tests, such as:

  • an optical coherence tomography scan, which looks at the nerves in the back of your eye
  • an MRI scan, which uses a magnetic field and radio waves to create a detailed image of your brain or other parts of your body
  • a CT scan, which creates a cross-sectional X-ray image

In most cases, you can treat ON with corticosteroids to help reduce nerve inflammation and swelling.

Steroid medication may be taken orally, injected, or administered intravenously. These medications typically come with some side effects, so be sure to talk with your doctor or pharmacist to learn what to expect.

If your ON is the result of another condition, treating that condition will often help to resolve ON. For example, a doctor may prescribe antibiotics if a bacterial infection is causing ON.

Depending on what’s causing your ON, treatments can also include:

  • adrenocorticotropic hormone
  • intravenous immunoglobulin (IVIG)
  • plasma exchange
  • interferon injections

Experiencing vision loss can be worrisome, but in many cases, the symptoms of ON are temporary. After the ON episode resolves, most people will not have permanent, severe vision loss. However, it can take some time for your vision to recover, from weeks to months.

Sometimes, ON can lead to complications. It’s less common, but optic nerve damage and serious long-term vision loss can happen.

In about 15 to 20 percent of cases, ON is the first sign of MS. If ON comes back repeatedly, you may have a higher chance of developing MS. You may also be at a higher risk of developing NMO spectrum disorder, another nerve condition.

The eye is a very important part of your body. You should always check vision changes with a doctor. Often, vision loss can be treated before it becomes irreversible.