What is nystagmus and what causes the eyes to move rapidly?

Nystagmus: Rapid rhythmic repetitious involuntary (unwilled) eye movements. Nystagmus can be horizontal, vertical or rotary.

The term Nystagmus is derived from the Greek word, 鈥渘ystagmus鈥? which was used to describe the wobbly head movements of a sleepy or inebriated individual.

There are various methods of classifying nystagmus. Traditionally nystagmus has been divided into two groups.

Sensory Nystagmus (Congenital)

This type is related to vision loss & usually begins early in life. Studies suggest 1 in every 1000 children have nystagmus. In 80-90% of cases, it is a side effect of vision loss from eye diseases such as albinism, aniridia, optic nerve hypoplasia, achromatopsia congenital cataracts, coloboma or retinopathy of prematurity. This type of nystagmus is usually observed around the sixth to eighth week of life and is rarely seen before then. In about 10-20% of cases, it presents with mild vision loss not associated with other diagnosed ocular diseases. The discovery of nystagmus in a child is reason for an immediate examination!
Most cases of early onset nystagmus are associated with ocular disease many of which are inherited conditions. Genetic counseling can help the patient and family understand the odds of passing the condition to their children. Not all cases of early onset nystagmus are hereditary.

Motor or Acquired Nystagmus

This type is related to the control of muscle function & is associated with neurological disorders occurring later in life.
Nystagmus can be acquired later in life due to neurological dysfunction such as a head injury, multiple sclerosis or brain tumors. Unlike nystagmus acquired from early in life, patients with late onset nystagmus usually notice movement in their vision related to the movement of their eyes. This is called oscillopsia. Oscillopsia causes a person to have vertigo or dizziness related to the new movement they experience in their vision.

Some of the diseases which present nystagmus as a pathological sign are:

Benign Paroxysmal Positional Vertigo
Head trauma
Stroke (the most common cause in older people)
M茅ni猫re's disease and other balance disorders
Multiple sclerosis
Brain tumors
Wernicke-Korsakoff syndrome
Encephalopathy
Lateral medullary syndrome
Aniridia
Optic nerve hypoplasia
Albinism
Noonan syndrome
Pelizaeus-Merzbacher disease
Superior canal dehiscence syndrome
Tullio phenomenon
Horner's Syndrome

Late onset nystagmus is more likely to be directional. The eye will move slowly in one direction, then quickly move back. The nystagmus may change as the patient looks in different directions. The unexplained onset of nystagmus in an adult may indicate a serious neurological disorder and an immediate examination is indicated!


In general, Nystagmus patients often experience fluctuations in their vision. A change in the speed of the nystagmus leading to a decrease in vision can be related to stress, the patient鈥檚 emotional state, fatigue, the direction of view or when one eye is covered. Understanding these issues allows the patient and teachers to create a better environment

Summary
Nystagmus, an involuntary shaking or jerking of the eyes is a very complex ocular condition. It can occur early in life secondary to various ocular diseases or can be acquired later in life in patients who have neurological disorders. Patients with nystagmus often have an abnormal head position called a null position in which their vision is improved. Low vision specialists or other nystagmus specialists may be able to provide special care, eyewear and contact lenses to help patients with nystagmus.

Here's some helpful links:

http://www.nystagmus.org/

http://www.lowvision.org/

Hope this info helps answer your questions.