Nystagmus: Causes of involuntary eye movements
Nystagmus an involuntary eye movement disorder that affects both eyes. The rapid and repetitive eye movements can be back and forth, up and down, or they can occur in an arc-shaped (partially circular) direction.
Nystagmus typically is accompanied by reduced visual acuity and depth perception, and it can affect balance and coordination.
Often, nystagmus is congenital in origin and becomes apparent between 6 weeks and several months of age, and the condition can be inherited. However, nystagmus can affect people of any age, particularly those with neurological disorders.
The prevalence of nystagmus in the general worldwide population is unknown. However, a study in the UK estimated it to be 2.4 cases per 1,000 people. The study also found that nystagmus was significantly more common among the white European population than in the Asian (Indian, Pakistani, other Asian backgrounds) populations.
Types of nystagmus
Different kinds of nystagmus include:
- Manifest nystagmus
- Congenital nystagmus
- Manifest-latent nystagmus
- Acquired nystagmus
- Latent nystagmus
Congenital nystagmus is present at birth. With this condition, your eyes move together as they oscillate (swing like a pendulum). Most other types of infantile nystagmus are also classified as forms of strabismus, which means the eyes don't necessarily work together at all times.
Manifest nystagmus is present at all times, whereas latent nystagmus occurs when one eye is covered.
Manifest-latent nystagmus is continually present but worsens when one eye is covered.
Acquired nystagmus can be caused by a disease (multiple sclerosis, brain tumor, diabetic neuropathy), an accident (head injury), or a neurological problem (side effect of a medication). Hyperventilation, a flashing light in front of one eye, nicotine and even vibrations have been known to cause nystagmus in rare cases.
Some acquired forms of nystagmus can be treated with medications or surgeries.
Nystagmus causes, symptoms and challenges
As mentioned above, most people with nystagmus are born with the condition or develop it early in life.
Unless induced by trauma or disease, nystagmus almost always is caused by neurological problems.
The two basic types of nystagmus are:
- Optokinetic (eye related)
- Vestibular (inner ear related)
People with inner ear problems can develop something called "jerk nystagmus" — the eyes drift slowly in one direction and then jerk back in the other direction. Because of the motion of the eyes, people with this condition can develop nausea and vertigo.
This type of nystagmus, usually temporary, also can occur in people with Meniere's disease (inner ear disorder) or when water settles into one ear. Taking a decongestant sometimes can clear up this type of nystagmus.
All forms of nystagmus are involuntary, meaning people with the condition cannot control their eyes.
Nystagmus sometimes improves slightly as a person reaches adulthood; however, it worsens with tiredness and stress.
Having nystagmus affects both vision and self-concept. Most people with nystagmus have some sort of vision limitations because the eyes continually sweep over what they are viewing, making it impossible to obtain a clear image.
Some people with nystagmus have so many vision problems that they can be considered legally blind.
If you have nystagmus, not only is your appearance affected, but you literally see in a way that is different from people who don't have the condition. Your eyes are in constant motion.
To see better, you may need to turn your head and lock your eyes into what's called the "null point." This is a certain head angle that makes the eyes move the least, stabilising the image for better vision.
When you have nystagmus, you must deal with the personal and social consequences of this difference.
Nystagmus can affect nearly every aspect of your life, including how you relate to other people, your educational and work opportunities and your self-image.
Counseling may be helpful as you face the social and personal challenges often associated with nystagmus.
Can nystagmus be treated?
Several medical and surgical treatments that sometimes help people with nystagmus are available.
Surgery usually reduces the null positions, lessening head tilt and improving cosmetic appearance.
Drugs such as Botox or Baclofen can sometimes reduce the involuntary eye movements of nystagmus, although results are usually temporary.
Some people with nystagmus benefit from biofeedback training.
If you have nystagmus, make sure you undergo regular eye exams so you can be monitored for both health and vision issues.
Both eyeglasses and contact lenses can help people with nystagmus see better. Because contact lenses move with the eyes, vision provided by contact lenses sometimes is clearer than that provided by eyeglasses. Your optician can advise you which type of vision correction is best for your needs.