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 occurs when the optic nerve is inflamed or swollen, leading to the loss of its surrounding myelin sheath (protective coat around the nerve fibres).
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.
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:
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
- Uses of drugs and toxins, e.g. methanol and ethambutol
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
- Pupillary light reaction test
- MRI scan
- Blood tests
- Optical coherence tomography (OCT)2
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 occurs when the optic nerve is damaged from any cause.
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.
As previously mentioned, optic neuropathy includes all forms of damage to the optic nerve. This includes:
- Insufficient blood supply
- Neurological disorder
- Drug abuse
- Dietary deficiency
- Genetic defects, e.g. Leber’s hereditary optic neuropathy or inherited mitochondrial disease
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
- Pupillary light reaction test
- MRI scan
- Blood tests
- Optical coherence tomography (OCT)
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
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.
The symptoms of both optic neuritis and optic neuropathy are similar. The most prominent signs are pain associated with eye movement.
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.
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.
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.
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.
- Behbehani R. Clinical approach to optic neuropathies. Clin Ophthalmol [Internet]. 2007 Sep [cited 2023 Sep 14];1(3):233–46. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2701125/
- Luo W, Huang QS, He JF, Han M, Liu B, Du Y. Clinical differences between young and older patients with optic neuritis. Annals of Eye Science [Internet]. 2017 Oct 27 [cited 2023 Sep 14];2(10):67–67. Available from: https://aes.amegroups.org/article/view/3862
- Mayo Clinic [Internet]. [cited 2023 Sep 14]. Optic neuritis-Optic neuritis - Symptoms & causes. Available from: https://www.mayoclinic.org/diseases-conditions/optic-neuritis/symptoms-causes/syc-20354953
- Pau D, Al Zubidi N, Yalamanchili S, Plant GT, Lee AG. Optic neuritis. Eye [Internet]. 2011 Jul [cited 2023 Sep 14];25(7):833–42. Available from: https://www.nature.com/articles/eye201181