Nystagmus — Involuntary Eye Movements
Nystagmus is the medical term used to describe involuntary eye movements. These eye movements may be side-to-side (lateral nystagmus), up and down (vertical nystagmus), or rotary. They are often noticeable while you are gazing at a fixed object in your peripheral view, or when you are watching objects moving at high speeds. Many people describe the eye movements as rapid, uncontrollable, and rhythmic. Depending on the cause, the eye movements can affect one or both eyes.
Some people find themselves turning their head and locking their eyes onto what is called a null point. In this position, the eyes move the least and the focus is clearer. Often, people with a null point adopt a head posture that allows them to get the most from their vision. Some people do things such as sit on one side of a room or blackboard, hoping to improve their vision without having to turn their head. However, doing this reduces the angle at which the screen or blackboard is viewed, causing what is known as crowding. Some experts believe that corrective surgery can eliminate the head turn.
What Causes Nystagmus?
Nystagmus is caused by abnormal function in the part of the brain that controls your eye movements. The labyrinth (the part of the inner ear that senses movement and position) helps to control these movements. For those born with this condition (congenital nystagmus), symptoms are typically mild and do not change in severity. In rare cases this condition is the result of a congenital disease that causes poor vision. Most people with this form of nystagmus do not notice their involuntary eye movements, although some people experience the movements in a severe way and need surgery to improve their visual acuity.
Acquired nystagmus typically is caused by an inner-ear disorder such as labyrinthitis (inflammation of the labyrinth), but many people experience this form of nystagmus after drinking alcohol or experimenting with drugs. Some medications like Dilantin (an anti-seizure medication) can also harm the labyrinth. Most young people acquire nystagmus after a head injury. Older people typically develop nystagmus after a stroke. Diseases of the brain, brain tumors, or multiple sclerosis can sometimes damage the labyrinth, which leads to nystagmus.
Types of Nystagmus
Nystagmus may be optokinetic (eye related) or vestibular (inner-ear related), and it can be either congenital (present at birth) or acquired due to injury or disease. In most cases it appears during infancy or childhood, but it can develop in adulthood. The rhythmic pace of the eye movements can be further broken down into slow and fast phases. Here is a list and brief description of the different types of nystagmus:
- Latent: Symptoms worsen when one eye is covered.
- Manifest: Symptoms are present at all times.
- Fixation: Occurs only when the eyes attempt to focus on an object
- Vestibular: Typically caused by disease of the vestibular apparatus of the ear, or due to normal stimuli produced when the semicircular canals are tested by the rotation of the body.
- Postrotatory: This is a form of vestibular nystagmus and occurs when the body is rotated and then stopped. For example, picture someone who is spinning in a chair then abruptly stops themselves.
- Miner’s: This form of the condition occurs in those who work in darkness for long periods.
- Seesaw: This involves the in-turning eye moving up and the opposite eye moving down, then both eyes moving in opposite directions.
Your healthcare provider will sit down with you and ask you questions about your symptoms, medical history, and family history before performing a physical exam. The physical exam typically involves looking at your nervous system and inner ear. For part of the neurological exam you may be asked to wear Frenzel glasses, which are goggles that illuminate and magnify the eyes. The exact type of nystagmus you have depends on the way your eyes are moving. For example, if your eyes are moving up and down, you may be diagnosed with vertical nystagmus. Your doctor may have you spin around for approximately thirty seconds, stop, and then try to stare at an object. Their eyes will move slowly in one direction, and then move rapidly in the opposite direction. Additional diagnostic testing may include:
- CT scan and/or MRI of your head
- Vestibular testing that records the movements of your eyes and response to caloric stimulation
- Electro-oculography, which uses tiny electrodes to measure your eye movements
In most cases, the cause of the nystagmus determines the type of treatment rendered. There are numerous medical and surgical treatments that are helpful to different people. In some cases, congenital nystagmus does not need treatment; children sometimes grow out of the condition. Eyeglasses and contact lenses can also improve the eye movements, with contact lenses typically being a superior alternative to eyeglasses since the eyes can sweep back and forth over the center of the lenses of a pair of glasses and cause unclear vision. Contact lenses allow the lens center to move with the eyes. Drugs such as Botox® or Baclofen® can improve nystagmus, but results are generally temporary. Regular eye exams can also help to monitor your visual health.
When to See Your Doctor
If you suspect nystagmus in yourself or a loved one, you should contact your doctor for a proper diagnosis. Anytime you have concerns you should contact an eye care professional.
The most common complication is a loss of vision. This condition affects people in different ways. Some treatments may work for some and not for others. In children, nystagmus can lead to learning problems, loss of focus, and problems interacting with other children. Additional complications may include:
- Trouble reading small print or items at an angle
- Trouble reading computer screens
- Poor balance, especially when walking up and down stairs
Questions to Ask Your Doctor
- How severe is my condition?
- How will this affect my vision in the near and distant future?
- If symptoms reappear, what treatment options will I have?
- Do I need to come in for a follow-up visit?
- Are there any eye exercises I can do to improve my condition?
- Can I wear any type of contact lenses, or do you prefer a specific kind?
- American Optometric Association, Nystagmus, http://www.aoa.org/x9763.xml
- American Nystagmus Network, What is Nystagmus?, http://nystagmus.org/new/index.php