Optic neuritis (ON) is an inflammatory condition of the optic nerve. The optic nerve sends visual information from the retina to the brain, allowing for vision. Inflammation of the optic nerve disrupts that visual signal causing a sudden decrease in vision and periorbital pain (pain in, around, or behind the eye).
Visual symptoms typically happen in one eye, ranging from minor blurring or a blind spot to total blindness. Other symptoms may include visual field loss, loss of color vision, and flashing lights.
Commonly one suffering from optic neuritis has pain of varying severity when they move their eyes. They also may experience systemic symptoms such as weakness in the arms or legs, tingling, or numbness. But they need not have any of those symptoms.
Optic neuritis is the most prevailing optic neuropathy (harm or dysfunction of one or more nerves) in individuals under 50 years old seen by general ophthalmic practices.
Association with MS
Optic neuritis can be the first sign of Multiple Sclerosis (MS), a disease that causes inflammation and damage to nerves in the brain, spinal cord, and as with ON, the optic nerve. Everyone who experiences optic neuritis does not necessarily develop additional symptoms of MS, but a substantial percentage does.
What causes optic neuritis?
Several conditions may cause optic neuritis, including multiple sclerosis (MS). Other causes include infections, autoimmune disease, injury to the optic nerve, and Vitamin B12 deficiency.
Stress may also be one cause of visual system diseases such as optic neuropathy and glaucoma. Constant stress and elevated cortisol levels can cause imbalance and vascular dysregulation in the autonomous nervous system (sympathetic).
The exact way these diseases result in optic neuritis is not clear. Researchers believe ON may develop when the immune system erroneously targets myelin, the material covering the optic nerve. The myelin helps electrical impulses travel rapidly from the eye to the brain. When the myelin is compromised, it disrupts the transmission of visual information.
Optic Neuritis Prognosis
Optic neuritis usually improves on its own without treatment. The visual loss caused by Optic Neuritis typically degrades for 7-10 days and then increasingly begins to improve in 1 to 3 months. Most patients with Optic Neuritis generally recover 20/20 (normal) visual acuity. Steroid medications can be used in some cases to reduce optic nerve inflammation.
Optic Neuritis risk factors and prevalence
Patients with optic neuritis are typically healthy young adults with a preponderance of females at a ratio of approximately 3:1.
For reasons that remain unclear, the incidence of multiple sclerosis occurring with optic neuritis is highest in people living at higher altitudes and also latitudes (e.g., in the northern USA, northern and western Europe; New Zealand, and southern Australasia) and becomes significantly lower closer to the equator.
ON’s annual incidence is estimated at 5 per 100,000 and found more commonly in Caucasians and rarely in black populations. There are also genetic factors in the risks of developing optic neuritis.
NMO (Neuromyelitis Optica)
Neuromyelitis Optica (NMO), also known as Devic’s disease, is a rare condition that affects both the optic nerve and the spinal cord’s nerves. With NMO, there is persistent and simultaneous optic neuritis and myelitis of the spinal cord.
NMO is commonly misdiagnosed as multiple sclerosis. Damage to the nerves is different from those found in MS, and Neuromyelitis Optica requires a different treatment course. NMO has been determined to be its own disease after much research found that NMO is dissimilar from multiple sclerosis.
Diagnosing Optic Neuritis
First, the ophthalmologist will proceed with a routine eye exam. They will check for the common symptoms of ON, the patient’s vision, their ability to distinguish colors, and measure side (peripheral) vision.
An ophthalmoscopy test is done to look at the eye’s back and check the optic disk where the optic nerve enters the retina. The optic disk becomes swollen in about one-third of people with optic neuritis.
A pupillary light reaction test will be done to see how the patient’s pupils respond to bright light. When the patient’s pupil doesn’t react like their other pupil, it suggests a decrease in their vision in that eye.
When looking at their optic nerve, there may or may not be swelling. This depends on whether the swelling is in the optic nerve’s front part or behind the optic nerve. The critical thing about inflammatory optic neuritis is that it frequently DOES have a different disease association.
Commonly ON is associated with multiple sclerosis. In the case of multiple sclerosis, what is occurring is called demyelination. Myelin is the cover over your optic nerve and nerves in general. Demyelination is a process where antibodies will eat away at this covering, and when that happens, you have damage and inflammation of the optic nerve or other nerves.
Not all optic neuritis forms are multiple sclerosis, which is very important to recognize in a diagnosis. A patient can have optic neuritis that is completely idiopathic, meaning there’s no cause for it whatsoever.
ON can also be associated with other syndromes like lupus or sarcoidosis, an inflammatory disease that affects multiple organs in the body, and sometimes a post-viral inflammatory syndrome.
Other tests can be done to exclude other diagnoses and evaluate the likelihood of other diseases. A magnetic resonance imaging (MRI) study of the brain and orbits (the eye sockets) can check for optic neuritis.
A blood test can also be done to check for infections or specific antibodies that Neuromyelitis Optica is linked to, an antibody that causes severe optic neuritis.
Optic Neuritis treatment options
Optic neuritis usually improves on its own. In some cases, steroid medications are used to reduce inflammation in the optic nerve. Possible side effects of steroid treatment include weight gain, mood changes, facial flushing, stomach upset, and insomnia.
Steroid treatment is usually given by vein (intravenously). Intravenous steroid therapy quickens vision recovery, but it doesn’t appear to affect the amount of vision you’ll recover for typical optic neuritis.
When steroid therapy fails, and severe vision loss persists, a treatment called plasma exchange therapy might help some people recover their vision. Studies haven’t yet confirmed that plasma exchange therapy is effective for optic neuritis.