- Congenital – most often develops by 2 to 3 months of age. The eyes tend to move in a horizontal swinging fashion. It is often associated with other conditions such as albinism, congenital absence of the iris (the colored part of the eye), underdeveloped optic nerves, and congenital cataract.
- Spasmus nutans – usually occurs between 6 months and 3 years of age and resolves spontaneously between 2 and 8 years of age. Children with this form of nystagmus often display head nodding and a head tilt. Their eyes may move in any direction. This type of nystagmus usually does not require treatment.
- Acquired – develops later in childhood or adulthood. The cause is often unknown, but it may be due to central nervous system and metabolic disorders or alcohol and drug toxicity.
- Pendular nystagmus – the speed of movement of the eyes is in same in both directions.
- Jerk nystagmus – the eyes move slowly in one direction and then quickly “jerk” back in the other direction.
What causes nystagmus?Nystagmus results from the instability or impairment of the system responsible for controlling eye movements. When nystagmus develops in early childhood, it can be caused by a problem with the visual pathway from the eye to the brain. Often the child has no other eye or medical problem. Acquired nystagmus, which occurs later in life, can be the symptom of another condition such as stroke, multiple sclerosis or a blow to the head. Other causes of nystagmus include:
- Lack of development of normal eye movement control early in life
- Very high refractive error, e.g. nearsightedness (myopia) or astigmatism
- Congenital cataracts
- Inflammation of the inner ear
- Medications such as anti-epilepsy drugs
- Central nervous system diseases
How is nystagmus diagnosed?Nystagmus can be diagnosed through a comprehensive eye exam. Testing for nystagmus, with special emphasis on how the eyes move, may include:
- Patient history to determine any symptoms the patient is experiencing and the presence of any general health problems, medications taken, or environmental factors that may be contributing to the symptoms.
- Visual acuity measurements to assess the extent to which vision may be affected.
- A refraction to determine the appropriate lens power needed to compensate for any refractive error (nearsightedness, farsightedness, or astigmatism).
- Testing how the eyes focus, move and work together. In order to obtain a clear, single image of what is being viewed, the eyes must effectively change focus, move and work in unison. This testing will look for problems that affect the control of eye movements or make it difficult to use both eyes together.