Maybe you wake up one morning with throbbing pain behind one or both eyes. Maybe you suddenly have a loss of central or color vision. Or, perhaps you have a relentless ache in your eye that gets worse with every passing minute, as your vision goes blurry. While you might be tempted to pop a pain reliever and see if things improve over the next day or two, please follow this advice: Don't wait. First of all, we're talking about your eyes here. Sudden changes to your vision should be checked out ASAP. Among the many reasons why: A serious but rare disorder called neuromyelitis optica spectrum disorder (NMOSD) could be to blame. And if it's not caught and treated quickly, you're at risk for permanent damage to your eyesight.
Sudden, severe eye pain and vision loss are often the first signs of NMOSD, an often disabling autoimmune disease that targets the optic nerves, which send information from the retina to the brain, allowing you to see. An estimated 250,000 people around the world, including about 15,000 people in the U.S., have been diagnosed with the condition, and as many as 50% experience severe visual disturbances in at least one eye from a condition called optic neuritis (ON).
ON occurs when there's damage to the optic nerves' protective coating (called myelin), usually from inflammation. Those lesions interrupt the flow of information, causing symptoms.
“After multiple attacks, if the patient's not on appropriate treatment, the chance of developing permanent legal blindness is quite high,” says Brian Weinshenker, M.D., professor of neurology at the Mayo Clinic in Rochester, MN. “Many patients are permanently blind even after a single attack,” he adds.
So, that's terrifying to hear, especially when the condition can seem to strike out of the blue. But know this: Treatment can help. The key is to get the right diagnosis as quickly as possible.
NMOSD Is Often Mistaken for MS
NMOSD, also known as Devic's disease, can be confused with multiple sclerosis (MS). Both conditions can cause ON, as well as serious mobility issues from damaging inflammation in the central nervous system (CNS), which is comprised of the optic nerves, brain, and spinal cord. There's so much overlap that until quite recently, NMOSD was actually considered a form of MS.
“The older recognition of the disease was based on having both involvement of the spinal cord and the optic nerves,” explains Michael Morgan M.D., director of neuro-ophthalmology at University Hospitals Cleveland Medical Center in Ohio.
NMOSD and MS are now recognized as distinct conditions, says Dr. Morgan. And both require specific and often different treatments to manage attacks and prevent the most serious symptoms from occurring, including blindness.
How NMOSD Impacts the Eyes
Like multiple sclerosis, NMOSD is a relapsing-remitting disease—meaning it causes repeated relapses, called flares, followed by periods of remission, when the immune system calms down and many symptoms, or even all in the case of MS, abate.
However, NMOSD attacks are often much more severe from the get-go, so damage done to the optic nerves can be permanent with each flare—making preventing future flares all the more urgent. Those diagnosed with this condition often experience significant disabilities that never remit, even during a remission.
Along with the increased severity of flares affecting the optic nerves, here are four other ways NMOSD affects the eyes:
Aquaporin-4 antibodies drive an NMOSD diagnosis: Dr. Weinshenker notes that in NMOSD, the immune system produces antibodies that target a specific protein, aquaporin-4, which is responsible for transporting water on the surface membrane of the eyes. Those antibodies, which are not present in MS, appear to be the main cause of the eye pain and inflammation associated with optica neuritis, leading to vision loss. Dr. Morgan notes in an estimated 70% of cases, those with NMOSD have aquaporin-4 antibodies in their blood, which helps confirm the diagnosis.
Dr. Weinshenker adds, “If a patient has severe optic neuritis with poor recovery, it would be important to get these blood tests done because they would have very important treatment implications if they were positive.”
- MOG antibodies offer another clue: A second antibody, myelin oligodendrocyte glycoprotein (MOG), may also be present in NMOSD, creating a similar but distinctive variation of the disease. (If you have MOG antibodies, you won’t have aquaporin-4 antibodies; it seems no one has both.)
Research shows that those with MOG antibodies tend to have serious optic (and less spinal) involvement, including ON in both eyes, but also have fewer attacks and better recovery than those with aquaporin-4 antibodies. It’s also important to note that the presence of MOG antibodies doesn’t always mean you have NMOSD. In fact, scientists are trying to determine if this specific disease course should be categorized as its own, separate disease. But, for now, it's still considered NMOSD.
- Both eyes are attacked in NMOSD: Optic neuritis from MS tends to affect one eye at a time (and may only ever affect one eye and never the other), while ON in NMOSD has a much stronger tendency to attack both eyes at the same time.
Vision loss from MS is usually temporary: While ON symptoms can come on suddenly in both conditions, Dr. Weinshenker says that vision loss associated with NMOSD is distinct—and may be permanent, even with treatment, while people with MS generally regain their full vision within a few weeks after a relapse that includes an ON attack.
“An NMOSD patient might say, ‘I notice some pain when I move my eye,’ and, by the next morning, they get up and say, ‘I can barely read,’ or, ‘There's a black spot in front of my vision in the center. When I look at your face, I can see around the edges, but I can't see the center.’ [Without treatment], over several days, it could progress even to the point of losing all ability to [see] light and dark, or maybe just a small crescent of vision [is all] that's preserved.”
It’s Difficult to Detect NMOSD Nerve Damage
The sudden onset of vision symptoms in NMOSD, combined with the severity of episodes, make early diagnosis and treatment especially important. What's confounding is that NMOSD damage is rarely visible during a conventional eye exam. In fact, the eyes can look normal.
“With this condition, you look in the eye and don't see anything wrong,” Dr. Weinshenker says. “You may see swelling of the optic nerve if it is very close to the eyeball, but, more often than not, the eye looks healthy. There is no macular degeneration, no diabetic retinopathy, no venous thrombosis. Once you rule out those other causes, it raises concerns that there is a disease involving the optic nerve.”
The most common diagnostic tests that ophthalmologists use to confirm NMOSD, in addition to antibody testing, include:
- Ocular coherence tomography (OCT): This is a clinical test that measures the thinning of the retinal nerve fiber layer to assess the degree of damage.
- Magnetic resonance imaging (MRI): “The MRI shows intense inflammation along one or both optic nerves, or also potentially involving that optic chiasm,” says Dr. Morgan. “It's one of the ways that we help become more suspicious that this disease might be neuromyelitis optica. And if the inflammation involves a very long segment of the nerve, involves both nerves, stretches all the way back to the optic chiasm, or involves the optic chiasm, tan NMO spectrum disease is more likely than another kind of optic neuritis.”
NMOSD Treatments Tame Symptoms and Prevent Relapses
The sooner an NMOSD diagnosis is made, the sooner treatments can begin. However, treating NMOSD with MS medications can actually worsen symptoms, not make them better—another reason getting the correct diagnosis is so important.
“It's quite different than in MS. The treatment we use to prevent attacks of MS don't work in NMO, but other treatments do,” Dr. Weinshenker says. Those treatments include:
- Injectable and oral steroids in high doses are often the first line of defense against an NMOSD attack. A 2019 study in the journal Neurology, Neuroimmunology and Neuroinflammation showed that those who received treatment with injectable steroid medications within seven days of an attack had a greater likelihood for restoring their vision than those who delayed treatment.
- Preventative, NMOSD-specific medications were first approved in June 2019 by the U.S. Food and Drug Administration (FDA) to treat people with aquaporin-4 antibodies. Soliris (eculizumab) was initially approved, followed by Uplizna (inebilizumab), with Enspryng (satralizumab) widely expected to gain approval in 2020. Clinical trials for all three showed significant reductions in NMOSD relapses and hospitalizations.
- Plasma exchange is also a treatment option. The process involves filtering out the part of the blood that carries inflammation-causing antibodies. This can help shorten an attack, Dr. Morgan explains. To be effective, the plasma exchange process must be repeated in multiple sessions, often five times over a period of 10 days. The treatment has good success rates for restoring vision, the doctor notes.
- Corticosteroids and monoclonal antibody therapies are additional treatments used for NMOSD to quell the haywire immune system response. Because more than 90% of those living with this disease experience multiple, severe attacks, these drugs are used to help prevent relapse.
Early Detection Delivers the Best Prognosis
“Almost everyone gets some improvement with these treatments, but the degree of response varies,” Dr. Morgan says. “For some patients, vision is never restored. Even for patients who do get good recovery of their vision, and even if they are able to see colors or read 20/20 in the clinic, they still [notice] that something about their vision is different following an NMOSD attack.”
The best prognosis comes with early treatment, he stresses. “In the event of sudden or very rapid vision loss and eye pain, see an eye doctor as soon as possible. We wouldn’t want someone to go several days without getting good evaluation and treatment.” It just might save your sight.