Section 2: Vision
Nystagmus is an involuntary, rapid, rhythmic movement of the eyeball. The rhythmic movements may be horizontal, vertical, rotary, or mixed. The types of nystagmus that occur before six months of age are called congenital or early onset, whereas those occurring after six months are labeled acquired nystagmus. Early onset nystagmus may be inherited, or the result of eye or visual pathway defects. In many cases, the cause is unknown (Royal Institute for the Blind, 2000). Causes of acquired nystagmus are many and may be a symptom of another condition such as stroke, multiple sclerosis, or even a blow to the head (Royal Institute for the Blind, 2000). Although the prevalence of nystagmus is not accurately known, the condition is believed to affect approximately 1 in 1,000 individuals (Royal National Institute for the Blind, 2000).
The majority of individuals with nystagmus have significant impairments in their vision, with many eligible to be registered as partially sighted or blind (Royal National Institute for the Blind, 2000). However, there is considerable variability in degree of visual impairment. Emotional and physical factors such as stress, tiredness, nervousness, or unfamiliar surroundings have been found to negatively affect visual functioning.
Given the considerable variability in visual impairment among individuals with nystagmus, decisions regarding fitness-to-drive should be determined on an individual basis.