Humans are very visual. We use our eyes to read, watch television, drive, and enjoy a variety of activities. So when diseases such as MS disturb vision, it can have a significant impact on quality of life. People with MS can have many different kinds of vision problems, the most common being optic neuritis, diplopia, and nystagmus.
Optic Neuritis
Optic neuritis is blurry vision or hazy vision affecting one eye. It is usually associated with some eye pain or discomfort, especially with eye movements. When the person looks from side to side or up or down, they may feel an ache or sticking sensation behind the eye. Often the center of vision is most affected, making it difficult to see peoples' faces or creating a “smudge” in the center of vision. This phenomenon occurs when the demyelination that characterizes MS affects the optic nerve, which is essentially a cable that connects the eye to the brain. You can think of the eye as a camera and the brain as the monitor. If we disturb the connection between the eye and the brain, the image that gets through could be blurred and difficult to interpret.
More than half of all people with MS will experience optic neuritis at one point in their lives. In fact, for 15 to 20 percent of people with MS, optic neuritis will be the first presentation of the disease. On examination, a person with optic neuritis often has an afferent pupillary defect (APD), which is an asymmetry in the two pupils’ reaction to light. Initially, the optic nerve head may look normal or mildly swollen. Later on, the optic nerve may develop pallor (paleness).
Intravenous methylprednisolone (also known as Solu-Medrol®) is often given to treat optic neuritis. The steroids do not appear to improve visual outcome in the end, but they do seem to speed up the recovery of vision. The good news is that optic neuritis usually gets better, though the vision in the affected eye may not return 100 percent. Vision in the affected eye might not be as clear as before, and colors may seem faded or “washed out.” Depth perception is often not as good after an episode of optic neuritis, making it more difficult to judge spatial differences, as when climbing stairs.
Double Vision
Normally, both eyes point at the same thing at the same time so that our brain sees only one object. If, because of MS, there is difficulty coordinating the movements of the eyes, one eye may point at one object while the other eye points at a slightly different point in space. The brain then gets two different images, which is very confusing. Typically, double vision, or diplopia, occurs when MS affects the brainstem. This is where the coordination of eye movements is controlled.
One common cause of double vision in MS is an internuclear ophthalmoplegia (also known as an INO) which is a disorder of eye movements caused by a lesion in a certain area of the brain. Rarely, people with MS may develop double vision from a sixth nerve palsy or other neuro-ophthalmologic disorder. Sometimes the person does not see two completely separate images. He or she may report a “shadow” or a “blur” instead of frank double vision. An important question to ask is whether the visual problem goes away if either eye is closed. Because diplopia is caused by the brain receiving two different images, one from each eye, as soon as either eye is closed, this type of visual problem will go away. On examination, there may be an obvious problem with the movement of the eyes, but sometimes the misalignment is not easy to see without special equipment.
Diplopia often resolves on its own. As with optic neuritis, intravenous corti-costeroids are often prescribed, in the hopes of speeding up the recovery. It may be necessary to wear an eye patch temporarily. The eye patch is worn to “cure” the diplopia, since only one eye will be sending an image to the brain, but some people may feel self-conscious while wearing the patch. Sometimes, if recovery is incomplete, eyeglasses with prisms can be used to bring the eyes back into alignment. Prism eyeglasses are similar to prescription eyeglasses for reading. The prism prescription can be added to an already existing eyeglass prescription. In rare cases, strabismus surgery (surgery to correct crossed eye) may be recommended to realign the eyes.
Nystagmus
Nystagmus is an involuntary, rhythmic movement of the eyes. The eyes can jump, jerk, or beat from side to side or up and down. This is often accompanied by a feeling of dizziness. Another symptom, oscillopsia, is the illusion that the world is jumping or swinging back and forth. Experiencing this is similar to watching video footage from an old-fashioned hand-held camera, where the whole image seems to shakes if the screen or camera is shaking. Oscillopsia can make it difficult to read, watch television, or drive, because the visual world is never still. Blurry vision or diplopia may also be present.
Sometimes nystagmus can accompany INO, but it can also be due to any type of MS attack in the vestibular or inner ear part of the brainstem, or to the cerebellum, which is our coordination center. The nystagmus may be visible when the person is looking straight ahead, but sometimes is only present when the person is looking off to the side, up, or down. If the nystagmus is very mild, it may only be perceptible while using an ophthalmoscope.
Nystagmus can be difficult to treat if it does not resolve on its own. Doctors may try various medications to try to dampen down the nystagmus, including clonazepam (Klonopin®), baclofen (Lioresal®), gabapentin (Neurontin®), and memantine (Namenda®). In rare instances, surgery or botulinum toxin (Botox®) may help.
Final Thoughts
In summary, vision can be impaired by MS in many different ways. People with MS who experience visual problems may benefit from an evaluation by both a neurologist and an ophthalmologist, or a neuro-ophthalmologist if one is available. An accurate analysis of the exact visual problem will help lead to possible treatment options.
Dr. Shin received his medical degree from the University of Pennsylvania. He completed a neurology residency and a MS fellowship at the Hospital of the University of Pennsylvania. He also completed a fellowship in neuro-ophthalmology at the Hospital of the University of Pennsylvania and the Scheie Eye Institute before arriving at the University of Maryland as an assistant professor in the Department of Neurology and in the Department of Ophthalmology and Visual Sciences. Dr. Shin has a special interest in visual problems associated with MS, including optic neuritis and double vision. Dr. Shin is involved in many clinical trials for disease modifying therapies in MS. He lectures frequently locally and nationally on MS and neuro-ophthalmologic topics, and has received multiple awards and commendations for his teaching and clinical excellence.
(Last reviewed 11/2011)