Nystagmus

Nystagmus is an involuntary rhythmic movements of the eyes from side to side (Horizontal Nystagmus), up and down (Vertical Nystagmus), circular (Rotatory Nystagmus), back and forth (Pendular Nystagmus) or a combination of these. Nystagmus may be congenital or acquired. Nystagmus may or may not be associated with decreased vision and neurological problems. It often has a "null point" – a direction of gaze in which the oscillations slow down or stop. Nystagmus has been mapped to chromosome 6P. Nystagmus may cause affected individuals to have head turns to compensate for the eye movements and there may be other signs of pathology present. Most forms of Nystagmus have no available treatment.

Certain eye diseases in which the eye has been deprived of vision may cause nystagmus; some of these conditions include ocular albinism and Leber’s Optic Atrophy. Nystagmus due to vision deprivation is usually pendular in nature.

Motor Nystagmus is usually hereditary and present shortly after birth. It is due to a disturbance in the ocular-motor system (Cranial nerve 3 and Edinger -Westphal Nucleus of the Brain) and is usually horizontal in nature. Motor Nystagmus decreases when the eyes converge together and may disappear during sleep

Convergence-Retraction Nystagmus is present in people with midbrain lesions, increased intracranial pressure syndromes and multiple sclerosis. It appears as a "jerk", or sharp movement inward and backward and happens when the extra-ocular muscles contract and converge together.

Dissociated Nystagmus is when nystagmus is different for each eye. This can arise as a result of disease of the posterior part of the brain.

Downbeat Nystagmus is associated with mid-brain lesions and multiple sclerosis. It usually disappears in upgaze and increases in intensity as the eyes look downward

Drug-Induced Nystagmus is usually in the horizontal plane of gaze and increases as horizontal gaze angle increases. Barbituates and tranquilizers are most often the cause of this, but alcohol may also cause increase in horizontal gaze nystagmus

Opsocionus Nystagmus (Saccadomania); unpredictable, fast jerk nystagmus which disappears during sleep; often associated with viral encephalopathies in children

Periodic Alternating Nystagmus: appears in individuals with cerebellar disease and is extremely rare. It may change direction and force cyclically. It may cease for several seconds and resume thereafter.

See-Saw Nystagmus may occur after head trauma or stroke. One eye rapidly and repeatedly turns down and in and the other eye rapidly turns up and out.

Spasmus Nutans Nystagmus manifests itself in a triad of symptoms. First of all it appears monocularly (in one eye), the head will nod and the head will turn sideways. It first appears in young children from 4 months to about 1 year and may disappear before the 4^th year, unless a neurological lesion is present and a doctor should be consulted in such a case.

Upbeat Nystagmus; eyes flick upwards when looking straight ahead. Null point is in downgaze. May be caused by brainstem lesion or drug intoxication

Vestibular Nystagmus is Horizontal in nature and may or may not have a rotatory componenet. May also have other neurological symptoms including vertigo, ringing in the ears (tinnitus), possibly deafness and may be due to a lesion affecting a nerve.