IN-vision

There are many forms of pathological nystagmus; most are only subtly different from one another which can make accurate diagnosis of a specific form difficult. In general terms however, pathological nystagmus can be grouped into three categories:

• Nystagmus due to a visual defect
• Nystagmus due to an intracranial lesion or drug toxicity
• Nystagmus developing in infancy, but without a known cause

The actual defect of the visual system which causes nystagmus is not fully understood. Pathological nystagmus is the fourth largest cause of registration for partial sight in the UK; its prevalence is estimated at 24 in 10,000 (Sarvananthan et al. 2009).

Nystagmus can also be described by its time of onset. Forms developing in infancy link to Early Onset often have different symptoms to those developing due to an acquired lesion. Some types of nystagmus can be transient, such as those appearing during an epileptic seizure (Epileptic nystagmus under Transient) or drug intoxication. Some ‘normal’ individuals are able to spontaneously produce similar ocular oscillations at will (voluntary nystagmus). (link to Voluntary nystagmus under Transient)