What is Optic Neuritis?

A condition in which the optic nerve becomes inflamed is called optic neuritis (ON). It often causes pain, vision loss, and other symptoms. In most cases, it is linked with other chronic (long-term) conditions, including multiple sclerosis (MS) and other autoimmune disorders. The only way to prevent serious complications of optic neuritis is early diagnosis and proper treatment.

In general, this condition is a type of neuropathy (nerve disease) that may cause serious vision changes and eye pain. Usually, it occurs due to inflammation that negatively affects the optic nerve. This nerve is responsible for sending signals between the eyes and the brain. The cells that make up this nerve also have a fatty coating (protective layer) called a myelin sheath. However, in people with optic neuritis, this protective layer is deteriorated, which impacts the optic nerve’s ability to send signals.

ON is common in the U.S., and it affects about 5 per 100,000 people each year.

Types of Optic Neuritis

Healthcare providers have divided this disorder into 3 main types. For example:

Typical – This type often affects only one eye, and most people notice improvements within a few days, even without treatment.
Atypical – In such cases, the condition often affects both eyes, and people do not recover quickly. According to some research, atypical optic neuritis is linked with other complex neurological disorders.
Pediatric – This type occurs in children and causes the same health problems. However, pediatric optic neuritis has a better outlook compared to the previous type.

Symptoms

This disorder often causes vision problems, but it may also cause other symptoms. Check below some examples:

Eye pain – About 90% of people with ON experience this symptom. It often worsens when you move the affected eye.
Vision acuity loss – It means the vision is less clear or sharp. Furthermore, in the pediatric type, this symptom tends to be more severe.
Visual field defects or vision loss – These include gaps or other decreases in vision that negatively affect a part of the visual field only.
Dyschromatopsia (loss of color vision) – When this symptom occurs, you may not see the colors, especially red.
Sensitivity to light
Changes in pupil size or reactivity
Headaches
Nausea
Vomiting

Do not hesitate to see a doctor if any of the previous symptoms occur.

Causes

There are a lot of factors that may cause optic neuritis. These include autoimmune and inflammatory disorders, infections, drugs, toxins, and other diseases. Sometimes, it is not possible to identify what exactly has caused ON. In such cases, the condition is called idiopathic optic neuritis.

Autoimmune and Inflammatory Disorders

According to some research, autoimmune and inflammatory disorders are a major cause of ON. Check below some examples:

Typical optic neuritis – The primary condition linked with the ON is multiple sclerosis. According to some studies, a lot of people develop optic neuritis as a primary symptom of MS. Moreover, roughly 50% of people with typical optical neuritis will also develop this autoimmune disorder within 15 years.
Atypical optic neuritis – This type of ON is often linked with neuromyelitis optica (NMO) and MOG-antibody-associated disease (MOGAD). Previously, healthcare providers thought MS, NMO, and MOGAD were the same disorder until they found different antibodies in the NMO and MOGAD.

Infections

In general, all nerves are vulnerable to damage caused by infections. Usually, the following infections are a triggering event that causes pediatric optic neuritis. Check below some examples:

Viral Infections

This type of infection is the most common cause of optic neuritis (especially in children). For example:

Varicella-zoster virus (it causes chickenpox and shingles)
Herpes simplex virus (including types 1 and 2)
Cytomegalovirus
HIV
Mosquito-carried viruses
Childhood viruses (such as measles)

Bacterial Infections

These infections are caused by bacteria that often pass to humans from animals and insects. Check below some examples:

Cat scratch fever
Lyme disease caused by ticks
Tuberculosis
Syphilis

Fungal Infections

These include:

Cryptococcus neoformans (cryptococcosis)
Various Candida species (candidiasis)
Histoplasma capsulatum (histoplasmosis)
Multiple types of Aspergillus (aspergillosis)

Sometimes, people may develop ON due to certain parasites that spread from pets, especially cats and dogs. For example, Toxoplasma gondii (toxoplasmosis) from cats, and Toxocara canis (toxocariasis) from dogs.

Drugs and Toxins

There are some over-the-counter (OTC) and prescription medicines that may cause nerve damage, which eventually will lead to ON. Check below the most common types:

Medicines used to treat infections (such as Ethambutol, Chloramphenicol, Isoniazid, or sulfa-type antibiotics)
Arrhythmia medicines (such as amiodarone or Digoxin)
Quinine-type malaria medicines (including Hydroxychloroquine and Chloroquine)
Cancer medicines (such as Methotrexate, Vincristine, and Tamoxifen)
Tobacco and nicotine products
Alcohol or methanol

Other Causes

Sometimes, people develop ON due to the following conditions and health problems. For example:

Ischemia (lack of blood flow) – When the optic nerve does not get enough oxygen-rich blood, it may begin to work improperly. Usually, it leads to nerve damage.
Vitamin deficiencies – Low B vitamin levels (especially vitamin B12) can cause permanent and severe damage to the optic nerve.
Nerve compression – Usually, it occurs when a tumor or health condition (such as hydrocephalus) puts pressure on the optic nerve, and it becomes inflamed.
Metabolic conditions – One of them is type 2 diabetes, and it may worsen an existing condition or contribute to ON.

Risk Factors

Healthcare providers have also identified some factors that may put you at increased risk of developing ON. Check below some examples:

Sex – According to some data, females are more prone to ON than males. The only exception is atypical optic neuritis, which occurs more commonly in men.
Age – In most cases, people develop ON between the ages of 20 and 40. While the atypical optic neuritis mostly occurs before 18 years old or after 50 years old, the pediatric type of the condition happens before 10 years old.
Race – Some research shows that people of Asian descent are less likely to develop MS after having ON.
Location – People who live farther from the Earth’s equator have an increased risk of developing ON. Some experts think it is linked with sun exposure and vitamin D levels.
Other autoimmune disorders – For example, systemic lupus erythematosus, sarcoidosis, Behcet’s disease, and others.

What Are The Long-term Effects of Optic Neuritis?

People with optic neuritis may also experience some complications, especially if the condition is left untreated. These include:

Vision loss
Optic nerve damage
An increased risk of developing multiple sclerosis (MS)
Other demyelinating diseases
Recurrent ON
Reduced visual acuity
Other vision problems (including reduced contrast, blurred vision, reduced depth perception, loss of visual field, and others)
Treatment complications, such as from a high dose of corticosteroids (including weight gain, mood swings, hyperglycemia, increased risk of infection)

The previous list does not contain a complete list of ON complications. In any case, you can talk with your doctor about measures to reduce the risk of developing them.

How to Prevent Optic Neuritis?

Commonly, ON occurs for unpredictable reasons. However, doctors may recommend some tips to reduce the risk of developing it. Examples include:

Stop smoking – If you face problems with smoking cessation, discuss it with your healthcare professional.
Get treatment as soon as possible if you get infections
Administer prescribed medicines exactly as recommended by your doctor. Otherwise, it may lead to unpleasant outcomes.
Dietary changes – It is advised to make nutrition a priority to prevent vitamin deficiencies (especially vitamin B12).
Limit or avoid alcoholic beverages
Manage chronic health conditions (such as autoimmune or inflammatory disorders)

Diagnosis

Usually, ON is diagnosed by an eye care specialist based on your symptoms, medical history, and existing health conditions. Your doctor may also perform an eye and slit lamp examination to check your visual acuity and field, ability to see color, and pupil reflexes. Doctors may also perform the following tests. For example:

Visual evoked potentials
Optical coherence tomography.

When the previous tests indicate a condition that better explains your symptoms, you may be referred to a neurologist or neuro-ophthalmologist for further testing. Therefore, they will perform additional imaging tests, including MRI (magnetic resonance imaging) scans that involve contrast, to get more clues about the disease. Commonly, an MRI is the primary test used to diagnose ON. This imaging test can also detect brain lesions that may indicate MS.

If your physician suspects ON occurs due to other disorders, they may also perform blood and urine tests to check for infections or autoimmune antibodies.

Treatment

Usually, doctors recommend the following treatments to address optic neuritis. Examples include:

Intravenous (IV) anti-inflammatory drugs – These medicines are often steroids that help reduce inflammation to the optic nerve. It also helps ease pain and improve vision problems. Most people get a standard treatment course that involves high-dose IV or oral steroids for about 5 days. Once the symptoms improve, doctors may reduce the dose of oral steroids.
Treatment for underlying causes and other contributing factors – For example, antibiotics to treat bacterial infections, plasma exchange (PLEX) to reduce the immune system activity, and others.

Frequently Asked Questions

What is the outlook for optic neuritis?

The prognosis for this disorder is different because it depends on several factors. For example, the severity and type of the condition, other health problems, and age.

Typical optic neuritis – Approximately 90% of people with this type of optic neuritis will have normal or near-normal vision within 12 months. However, chronic loss of vision is also possible, but it is usually not common.
Atypical optic neuritis – The prognosis for this type of optic neuritis also varies among people. It depends on the underlying cause. Generally, the outlook depends on when you start the treatment.
Pediatric optic neuritis – In most cases, the prognosis in children is better than in adults. Moreover, long-term problems rarely occur in children with this disorder.

Does optic neuritis always mean MS?

No, but if you have optic neuritis, you are at increased risk of developing MS. That’s why early diagnosis and proper treatment are vital. For more details, discuss it with your doctor.

What are the symptoms of optic neuritis?