Optic Neuritis Vs. Optic Neuropathy: What's The Difference?

Introduction

The terms ‘optic neuritis’ and ‘optic neuropathy’ are often confused. It is essential to distinguish these two conditions to better understand and deal with them.

Optic neuritis is the most common form of optic neuropathy. However, optic neuropathy is not necessarily optic neuritis. Optic neuropathy is instead a blanket term for a damaged optic nerve. This term then branches out to different types of damage caused by the optic nerve. For example, ‘optic neuritis’ means the damage to the optic nerve caused by inflammation. While ‘ischemic optic neuropathy’ means the damage in the optic nerve was caused by poor blood flow.¹

Optic neuritis

Definition

Optic neuritis occurs when the optic nerve is inflamed or swollen, leading to the loss of its surrounding myelin sheath (protective coat around the nerve fibres).

Symptoms

Optic neuritis often affects one eye. However, in some cases, the inflammations happen on both eyes’ optic nerves. These inflammations can lead to disruption in eye movement and visual impairment. 

Symptoms of optic neuritis include:

• Pain is often described as a ‘dull ache’ towards the back of the eye. It usually correlates with eye movement
• Loss or reduction in vision, which usually worsens over time, depending on the individual case
• Visual impairment. This includes blurry vision and altered colour perception (Often, colours are duller than usual)
• Flashing lights or flickering lights correlate with eye movement
• Abnormal pupil reaction to light exposure

Some cases of optic neuritis can lead to permanent visual loss, while others can cause temporary visual loss.

Causes

Optic neuritis is a complex condition with no exact pathophysiology. It is often presented among patients with autoimmune disease, i.e. multiple sclerosis (MS). However, it can also be caused by infections. Optic neuritis affects the optic nerve directly. It is believed to develop when the immune system mistakenly attacks the target on the optic nerve. This leads to inflammation in the optic nerve, disrupting the visual process. 

Some of the Autoimmune diseases that are often associated with optic neuritis include:

• Multiple sclerosis
• Neuromyelitis
• Myelin oligodendrocyte glycoprotein (MOG) antibody disorder
• Lupus

All of these cause the autoimmune system to attack the myelin sheath covering the neurons in the optic nerve, spinal cord, and brain. The severity of the attacks can vary among different people based on their age, sex, or other related conditions.

Other conditions that can lead to optic neuritis include:

• Bacterial infection, e.g. Lyme disease and syphilis
• Viral infection, e.g. herpes and measles
• Behcet’s disease
• Sarcoidosis
• Uses of drugs and toxins, e.g. methanol and ethambutol

Diagnosis

The diagnosis of optic neuritis includes:

• Eye tests, which includes examining the visual field, ability to perceive colours, visual evoked response and peripheral vision measurement
• Ophthalmoscopy
• Pupillary light reaction test
• MRI scan
• Blood tests
• Optical coherence tomography (OCT)²

Treatment

Optic neuritis often recovers through time. However, in some cases, steroid medications (intravenous) may be prescribed to reduce inflammation. This type of treatment can speed up the visual recovery but not the amount of vision recovered from an autoimmune disease-induced optic neuritis.

Plasma exchange therapy may be used in severe cases of optic neuritis. However, there is currently not enough evidence to support the effectiveness of this treatment.

Optic neuropathy

Definition

Optic neuropathy occurs when the optic nerve is damaged from any cause.

Symptoms

Symptoms of optic neuropathy include:

• Pain associated with eye movement
• Blurring visual
• Blind spots
• Dull colour perception
• Loss or impaired vision

The visual loss can be sudden or gradual, depending on the cause of the damage. Sudden changes in visual loss are often caused by damages associated with blood flow, i.e. ischemic optic neuropathy. In contrast, the gradual loss of vision is often associated with inflammation, i.e. optic neuritis.

Causes

As previously mentioned, optic neuropathy includes all forms of damage to the optic nerve. This includes:

• Infection
• Insufficient blood supply
• Inflammation
• Neurological disorder
• Drug abuse
• Dietary deficiency
• Genetic defects, e.g. Leber’s hereditary optic neuropathy or inherited mitochondrial disease

Diagnosis

The diagnosis of optic neuropathy includes:

• Eye tests, which involves examining the visual field, ability to perceive colours, visual evoked response, and peripheral vision measurement
• Ophthalmoscopy
• Pupillary light reaction test
• MRI scan
• Blood tests
• Optical coherence tomography (OCT)

Treatment

As mentioned above, optic neuropathy is a blanket term. Therefore, the underlying cause of such damage needs to be identified before determining treatment. If the cause of damage is inflammation, steroids may be used to speed up the recovery. Infection-induced damage can be treated using antibiotics. On the other hand, the damage may not be treatable if it is caused by genetic defects.

Differences between optic neuritis and optic neuropathy

Pathophysiology

The pathophysiology of optic neuritis is most likely to be the inflammatory demyelination of the optic nerve. However, the exact pathophysiology still needs to be fully understood. On the other hand, the pathophysiology of optic neuropathy can be varied. This can include changes in blood flow, causing an oxygen shortage to the optic nerve, dietary deficiency, and even inflammation.

Symptoms

The symptoms of both optic neuritis and optic neuropathy are similar. The most prominent signs are pain associated with eye movement.

Causes

The cause of optic neuropathy can be anything that causes damage to the optic nerve. This can include insufficient blood supply, trauma, infection and inflammation. Meanwhile, optic neuritis can only be caused by inflammation or infection.

Diagnosis

The diagnosis for both optic neuritis and optic neuropathy are the same. The diagnosis aims to identify the cause of optic nerve damage to determine the appropriate treatment for that individual.

Treatment

The treatment for optic neuritis is steroid medications if the symptoms do not recover over time. Other causes of optic neuropathy can be treated through various methods, such as antibiotics.

Summary

Optic neuritis (inflamed optic nerve) is a form of optic neuropathy (damaged optic nerve). Both these conditions can be diagnosed through the same methods and their treatment might change based on the underlying cause.