Optic neuritis is the medical term used to describe inflammation of the optic nerve. Normally, the optic nerve sends signals from the retina to the brain. When the optic nerve is inflamed, these signals are disrupted and vision becomes impaired. This condition typically develops between the ages of 20 and 40.
Optic neuritis is commonly seen in patients with autoimmune disorders triggered by an infection, or those with conditions that affect the nervous system, such as multiple sclerosis. Multiple sclerosis damages and inflames the nerves in your brain and spinal cord.
Thankfully, optic neuritis rarely requires treatment, as it usually heals itself. Still, episodes of optic neuritis can range from mild to severe, and treatment is sometimes necessary. In most cases only one eye is affected, although both eyes can develop optic neuritis simultaneously.
Symptoms of Optic Neuritis You Should Know About
Symptoms of optic neuritis may include the following:
- Gradual or sudden vision loss, typically in one eye
- Severe blurred vision that may progress into temporary blindness
- Loss of color vision
- Flashing lights
- Changes in the way your pupil reacts to bright light
Some people report seeing flashing lights or flickering specks in their field of vision. Others lose their perception of color or experience red/green color blindness. Most people with optic neuritis experience pain that worsens with eye movement.
The pain typically lasts several days. In most cases, vision loss occurs. Heat or exercise can worsen the loss of vision, and in some cases, the vision loss may be permanent.
Other symptoms you may be experiencing could indicate an underlying autoimmune disorder. In other words, optic neuritis could be a symptom itself. For example, in 15–20 percent of all cases of multiple sclerosis, optic neuritis is an initial symptom.
Complications of Optic Neuritis That Can Occur
Possible complications of this condition may include:
- Vision loss
- Optic nerve damage
- Body-wide side-effects from corticosteroids
- Inflammation may occur in other parts of your body
- Some people develop multiple sclerosis
What Causes Optic Neuritis?
Your optic nerve is covered in a substance called myelin. Although the exact cause of optic neuritis is unknown, experts believe it develops when the immune system mistakenly targets the myelin, resulting in inflammation and myelin damage.
Common autoimmune disorders that may cause the inflammation of the optic nerve include:
- Multiple sclerosis
- Neuromyelitis optica
- Systemic lupus erythematosus
- Behcet disease
Infections, especially post-infections and upper-respiratory infections, are also thought to cause problems in your immune system. Infections that can cause inflammation of the optic nerve include:
- Lyme disease
- Viral encephalitis
- Chicken pox
- Herpes zoster
- Mycoplasma pneumonia
Additional causes may include:
- Vitamin B deficiency
- Toxicity from drugs such as methanol or ethambutol
- Radiation therapy
- Cranial arteritis
Diagnosing Optic Neuritis – When To See Your Doctor
If you suspect optic neuritis in yourself or someone you know, you should consider visiting an ophthalmologist for a proper diagnosis. Remember, optic neuritis may be a symptom of an underlying condition.
A complete medical exam may be needed to rule out any medical conditions or related diseases. To diagnose optic neuritis an eye doctor may perform the following:
- Routine eye exam: Your eye doctor will check your vision and color perception
- Ophthalmoscopy: Your eye doctor uses this test to look at the back of your eye with a bright light that enhances the structures of your eye. Your eye doctor will pay particular attention to your optic disk, which is the area where the optic nerve enters your retina. In about 33 percent of people with optic neuritis, the optic disk is swollen.
- Pupillary light reaction test: Your eye doctor will wave a flashlight back and forth in front of your eyes to see how your pupils respond to bright light. In eyes with optic neuritis, the pupils do not constrict as much as they should when stimulated by light.
- Visual response test: During this test you sit in front of a screen that displays an alternating checkerboard pattern. Your eye doctor will attach wires with small patches to your head to record your brain’s responses to visual stimuli. Your eye doctor is looking for a decrease in electrical conduction, which can be the result of optic nerve damage.
- Blood test: Blood tests are typically taken to check for antibodies of neuromyelitis optica. Generally, this test is administered to people with severe optic neuritis to see whether they are likely to develop neuromyelitis optica. An erythrocyte sedimentation rate or ESR is a blood test that can detect inflammation throughout your body. Often this type of blood test is used to determine if the optic neuritis is caused by inflamed cranial arteries.
- MRI: Magnetic resonance imaging tests use magnetic fields and pulses of radio wave energy to take pictures of your body. When checking for optic neuritis, your eye doctor will inject a contrast solution to highlight and enhance the optic nerve and other parts of your brain in the pictures. MRIs can also determine whether the myelin has been damaged, and they can rule out tumors and other conditions that may mimic optic neuritis.
How To Treat Optic Neuritis
In most cases, vision returns to normal within two or three days without treatment, unless an underlying condition is causing the optic neuritis. Corticosteroids can be administered through an IV in order to speed recovery, but high doses need to be administered cautiously due to the possibility of side effects.
Oral steroids may also be prescribed. Prednisone is a common oral steroid that is generally used for two weeks. If these options do not work, plasma exchange therapy may help return the patient’s vision.
Plasma exchange therapy involves draining the plasma from your body and replacing it with new plasma. The old plasma contains disease-causing antibodies, immune complexes, and protein-bound toxins. The goal of this treatment is to treat immunological illness such as optic neuritis.
Most people whose optic neuritis is not disease-related have a great chance for recovery. For those with an underlying condition such as multiple sclerosis, the prognosis is poorer.