Nystagmus is a complex eye condition, characterised by involuntary movements of the eye. The eyes appear to wobble or flicker from side to side, up and down or round and round. Congenital nystagmus simply means nystagmus which is apparent in the first few weeks or months of life. Acquired nystagmus can occur at any time.
There are two main types of nystagmus, one which appears in the first weeks or months of life and is called congenital or infantile nystagmus and another which develops later in life which is called acquired nystagmus. There are many possible causes of both kinds of nystagmus.
How common is nystagmus?
Nystagmus has an incidence rate of at least 1 in 1,000 people in the general population and is the most common form of visual impairment among school aged children. The condition affects both men and women, although some forms of nystagmus, such as X-linked infantile nystagmus may be more common in boys.
When a child is born with nystagmus they may be the only member of the family who has the condition. As there is a genetic link to some forms of nystagmus, however, there are many families where there is more than one person who has nystagmus.
What causes nystagmus?
Abnormal functioning of the part of the brain or inner ear which regulates eye movement and positioning causes nystagmus. The reason for that abnormality, whether genetic or as the result of a medical condition, needs to be investigated. Nystagmus is regularly seen as a symptom of a variety of underlying conditions.
- Congenital or infantile nystagmus is sometimes, though by no means always, associated with other conditions such as Down’s Syndrome, Leber’s Congenital Amaurosis and albinism or ocular albinism which are genetic conditions. A lot of people who have different eye conditions, such as congenital cataracts or aniridia, also have nystagmus.
- Acquired nystagmus may have any one of many different neurological causes, including stroke, multiple sclerosis or ataxia, or it could arise following a head injury or other accident or after taking certain prescribed or recreational drugs. In some cases acquired nystagmus can come and go over time, so someone might experience oscillopsia for a while, where things appear to move when they are still, and then later the symptoms reduce or disappear and the vision returns to normal.