Nystagmus is a rapid and repetitive involuntary movement of the eyes. The movement is, generally, from side to side (horizontal nystagmus) but it can also be up and down (vertical nystagmus) or circular (torsional nystagmus). The movement can vary between slow and fast and it generally affects both eyes.

Causes of nystagmus

Nystagmus can be a congenital eye disease present from birth. However, nystagmus can also occur, on a temporary basis, when its main cause is related to certain drugs, medications or narcotic substances: anti-seizure drugs, excess alcohol or sedatives.

Nystagmus can also be produced by a head injury as a result of a traffic accident, disorders of the internal ear such as labyrinthitis or Meniere’s disease, cerebrovascular accidents, thiamine or vitamin B12 deficiency. Some brain diseases, such as multiple sclerosis or brain tumours, can result in nystagmus if the damage affects the regions that control eye movement.

Symptoms of nystagmus

The main symptom of nystagmus is the presence of involuntary eye movements. In general, this manifests itself as movement from side to side, which is known as horizontal nystagmus. Vertical nystagmus may also occur with movements up and down, or torsional nystagmus, where the eye moves in circles.

Nystagmus may vary between slow and fast, and it usually affects both eyes. In addition to eye movements, other symptoms of nystagmus include sensitivity to light, dizziness, difficulty seeing in the dark, vision problems, constantly turning the head or holding the head in a tilted position and feeling that the world is spinning or shaking.

Diagnosis of nystagmus

Nystagmus is diagnosed by examining the inside of the eye and performing an eye test. During diagnosis, the ophthalmologist will also look for symptoms of strabismus, cataracts, or anomalies in the optic nerve or retina.

One way of observing nystagmus is to turn the individual around for 30 seconds then stop them and have them stare at an object. If nystagmus is present, the eyes will initially move slowly in one direction, and then they will move rapidly in the opposite direction.

Other tests that can be used to diagnose nystagmus are an ear examination, neurologic examination, computed tomography (x-ray of the brain) and MRI (magnetic and radio waves used to obtain images of the brain).