Nystagmus is a condition of involuntary (or voluntary, in some cases)

eye movement Eye movement includes the voluntary or involuntary movement of the eyes. Eye movements are used by a number of organisms (e.g. primates, rodents, flies, birds, fish, cats, crabs, octopus) to fixate, inspect and track visual objects of interest ...

. Infants can be born with it but more commonly acquire it in infancy or later in life. In many cases it may result in reduced or limited vision. Due to the involuntary movement of the eye, it has been called "dancing eyes". In normal eyesight, while the head rotates about an

axis An axis (plural ''axes'') is an imaginary line around which an object rotates or is symmetrical. Axis may also refer to: Mathematics * Axis of rotation: see rotation around a fixed axis * Axis (mathematics), a designator for a Cartesian-coordinat ...

, distant visual images are sustained by rotating eyes in the opposite direction of the respective axis. The

semicircular canals The semicircular canals or semicircular ducts are three semicircular, interconnected tubes located in the innermost part of each ear, the inner ear. The three canals are the horizontal, superior and posterior semicircular canals. Structure The ...

in the

vestibule of the ear The vestibule is the central part of the bony labyrinth in the inner ear, and is situated medial to the eardrum, behind the cochlea, and in front of the three semicircular canals. The name comes from the Latin ', literally an entrance hall. Stru ...

sense angular acceleration, and send signals to the nuclei for eye movement in the brain. From here, a signal is relayed to the

extraocular muscles The extraocular muscles (extrinsic ocular muscles), are the seven extrinsic muscles of the human eye. Six of the extraocular muscles, the four recti muscles, and the superior and inferior oblique muscles, control movement of the eye and the othe ...

to allow one's gaze to fix on an object as the head moves. Nystagmus occurs when the

are stimulated (e.g., by means of the

caloric test In medicine, the caloric reflex test (sometimes termed vestibular caloric stimulation) is a test of the vestibulo-ocular reflex that involves irrigating cold or warm water or air into the external auditory canal. This method was developed by Rob ...

, or by disease) while the head is stationary. The direction of ocular movement is related to the semicircular canal that is being stimulated. There are two key forms of nystagmus:

pathological Pathology is the study of the causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in th ...

and physiological, with variations within each type. Nystagmus may be caused by

congenital disorder A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities ca ...

or sleep deprivation, acquired or

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...

disorders,

toxicity Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...

pharmaceutical drug A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy (pharmacotherapy) is an important part of the medical field an ...

s, alcohol, or rotational movement. Previously considered untreatable, in recent years several drugs have been identified for treatment of nystagmus. Nystagmus is also occasionally associated with

vertigo Vertigo is a condition where a person has the sensation of movement or of surrounding objects moving when they are not. Often it feels like a spinning or swaying movement. This may be associated with nausea, vomiting, sweating, or difficulties w ...

Causes

The cause of pathological nystagmus may be congenital,

idiopathic An idiopathic disease is any disease with an unknown cause or mechanism of apparent spontaneous origin. From Greek ἴδιος ''idios'' "one's own" and πάθος ''pathos'' "suffering", ''idiopathy'' means approximately "a disease of its own kin ...

, or secondary to a pre-existing neurological disorder. It also may be induced temporarily by disorientation (such as on roller coaster rides or when a person has been spinning in circles) or by some drugs ( alcohol, lidocaine, and other

depressants, inhalant drugs, stimulants, psychedelics, and

dissociative Dissociatives, colloquially dissos, are a subclass of hallucinogens which distort perception of sight and sound and produce feelings of detachment – dissociation – from the environment and/or self. Although many kinds of drugs are capable of ...

drugs).

Early-onset nystagmus

Early-onset nystagmus occurs more frequently than acquired nystagmus. It can be insular or accompany other disorders (such as micro-ophthalmic anomalies or

Down syndrome Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with physical growth delays, mild to moderate intellectual dis ...

). Early-onset nystagmus itself is usually mild and non-progressive. The affected persons are usually unaware of their spontaneous eye movements, but vision can be impaired depending on the severity of the eye movements. Types of early-onset nystagmus include the following, along with some of their causes: *Infantile: **

Albinism Albinism is the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and pink or blue eyes. Individuals with the condition are referred to as albino. Varied use and interpretation of the term ...

** Aniridia **Bilateral

congenital cataract Congenital cataracts refers to a lens opacity which is present at birth. Congenital cataracts cover a broad spectrum of severity: whereas some lens opacities do not progress and are visually insignificant, others can produce profound visual impa ...

**Bilateral

optic nerve hypoplasia Optic nerve hypoplasia (ONH) is a medical condition arising from the underdevelopment of the optic nerve(s). This condition is the most common congenital optic nerve anomaly. The optic disc appears abnormally small, because not all the optic nerve ...

Idiopathic An idiopathic disease is any disease with an unknown cause or mechanism of apparent spontaneous origin. From Greek ἴδιος ''idios'' "one's own" and πάθος ''pathos'' "suffering", ''idiopathy'' means approximately "a disease of its own kin ...

** Leber's congenital amaurosis **

Optic nerve In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual information from the retina to the brain. In humans, the optic nerve is derived fro ...

or macular disease **

Persistent tunica vasculosa lentis Persistent tunica vasculosa lentis is a congenital ocular anomaly. It is a form of persistent hyperplastic primary vitreous (PHPV). It is a developmental disorder of the vitreous. It is usually unilateral and first noticed in the neonatal pe ...

** Rod monochromatism **Visual-motor syndrome of functional monophthalmus *Latent nystagmus *

Noonan syndrome Noonan syndrome (NS) is a genetic disorder that may present with mildly unusual facial features, short height, congenital heart disease, bleeding problems, and skeletal malformations. Facial features include widely spaced eyes, light-colored ...

*Nystagmus blockage syndrome X-linked infantile nystagmus is associated with mutations of the gene FRMD7, which is located on the

X chromosome The X chromosome is one of the two sex-determining chromosomes (allosomes) in many organisms, including mammals (the other is the Y chromosome), and is found in both males and females. It is a part of the XY sex-determination system and XO sex ...

. Infantile nystagmus is also associated with two X-linked eye diseases known as complete congenital stationary night blindness (CSNB) and incomplete CSNB (iCSNB or CSNB-2), which are caused by mutations of one of two genes located on the X chromosome. In CSNB, mutations are found in NYX ( nyctalopin). CSNB-2 involves mutations of CACNA1F, a voltage-gated calcium channel that, when mutated, does not conduct ions.

Acquired nystagmus

Nystagmus that occurs later in childhood or in adulthood is called acquired nystagmus. The cause is often unknown, or

, and thus referred to as idiopathic nystagmus. Other common causes include diseases and disorders of the central nervous system, metabolic disorders and alcohol and drug toxicity. In the elderly, stroke is the most common cause.

General diseases and conditions

Some of the diseases that present nystagmus as a pathological sign or symptom are as follows: :* Aniridia :*

Benign paroxysmal positional vertigo Benign paroxysmal positional vertigo (BPPV) is a disorder arising from a problem in the inner ear. Symptoms are repeated, brief periods of vertigo with movement, characterized by a spinning sensation upon changes in the position of the head. * T ...

Brain tumor A brain tumor occurs when abnormal cells form within the brain. There are two main types of tumors: malignant tumors and benign (non-cancerous) tumors. These can be further classified as primary tumors, which start within the brain, and seconda ...

s (

medulloblastoma Medulloblastoma is a common type of primary brain cancer in children. It originates in the part of the brain that is towards the back and the bottom, on the floor of the skull, in the cerebellum, or posterior fossa. The brain is divided into two ...

astrocytoma Astrocytomas are a type of brain tumor. They originate in a particular kind of glial cells, star-shaped brain cells in the cerebrum called astrocytes. This type of tumor does not usually spread outside the brain and spinal cord and it does not usu ...

, or other tumors in the posterior fossa.) :* Canavan disease :*

COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was identified in Wuhan, China, in December 2019. The disease quickly ...

Head trauma A head injury is any injury that results in trauma to the skull or brain. The terms ''traumatic brain injury'' and ''head injury'' are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of inju ...

Lateral medullary syndrome Lateral medullary syndrome is a neurological disorder causing a range of symptoms due to ischemia in the lateral part of the medulla oblongata in the brainstem. The ischemia is a result of a blockage most commonly in the vertebral artery or the p ...

Ménière's disease Ménière's disease (MD) is a disease of the inner ear that is characterized by potentially severe and incapacitating episodes of vertigo, tinnitus, hearing loss, and a feeling of fullness in the ear. Typically, only one ear is affected initi ...

and other

balance disorder A balance disorder is a disturbance that causes an individual to feel unsteady, for example when standing or walking. It may be accompanied by feelings of giddiness, or wooziness, or having a sensation of movement, spinning, or floating. Balance ...

s :* Multiple sclerosis :*

Optic nerve hypoplasia Optic nerve hypoplasia (ONH) is a medical condition arising from the underdevelopment of the optic nerve(s). This condition is the most common congenital optic nerve anomaly. The optic disc appears abnormally small, because not all the optic nerve ...

Pelizaeus–Merzbacher disease Friedrich Christoph Pelizaeus, Pelizaeus–Ludwig Merzbacher, Merzbacher disease is an X-linked neurological disorder that damages oligodendrocytes in the central nervous system. It is caused by mutations in proteolipid protein 1 (''PLP1''), a maj ...

:* Superior canal dehiscence syndrome :* Tullio phenomenon :*

Whipple's disease Whipple's disease is a rare systemic infectious disease caused by the bacterium '' Tropheryma whipplei''. First described by George Hoyt Whipple in 1907 and commonly considered as a gastrointestinal disorder, Whipple's disease primarily causes ma ...

Toxicity or intoxication, metabolic disorders and combination

Sources of toxicity that could lead to nystagmus: :* Alcohol intoxication :*

Amphetamines Substituted amphetamines are a class of compounds based upon the amphetamine structure; it includes all derivative compounds which are formed by replacing, or substituting, one or more hydrogen atoms in the amphetamine core structure with sub ...

:* Barbiturates :* Benzodiazepines :*

Ketamine Ketamine is a dissociative anesthetic used medically for induction and maintenance of anesthesia. It is also used as a recreational drug. It is one of the safest anesthetics, as, in contrast with opiates, ether, and propofol, it suppresses ...

Pregabalin Pregabalin, sold under the brand name Lyrica among others, is an anticonvulsant, analgesic and anxiolytic medication used to treat epilepsy, neuropathic pain, fibromyalgia, restless leg syndrome, opioid withdrawal and generalized anxiety diso ...

Lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid ...

MDMA 3,4-Methylenedioxymethamphetamine (MDMA), commonly seen in tablet form (ecstasy) and crystal form (molly or mandy), is a potent empathogen–entactogen with stimulant properties primarily used for recreational purposes. The desire ...

Nitrous Oxide Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and has ...

Phencyclidine Phencyclidine or phenylcyclohexyl piperidine (PCP), also known as angel dust among other names, is a dissociative anesthetic mainly used recreationally for its significant mind-altering effects. PCP may cause hallucinations, distorted percept ...

(PCP) :*

Phenytoin Phenytoin (PHT), sold under the brand name Dilantin among others, is an anti-seizure medication. It is useful for the prevention of tonic-clonic seizures (also known as grand mal seizures) and focal seizures, but not absence seizures. The in ...

(Dilantin) :* Salicylates :* Selective serotonin reuptake inhibitors (SSRIs) :* Other anticonvulsants or sedatives :*

Thiamine Thiamine, also known as thiamin and vitamin B1, is a vitamin, an essential micronutrient, that cannot be made in the body. It is found in food and commercially synthesized to be a dietary supplement or medication. Phosphorylated forms of thi ...

deficiency :** Wernicke's encephalopathy :**

Wernicke–Korsakoff syndrome Wernicke–Korsakoff syndrome (WKS) is the combined presence of Wernicke encephalopathy (WE) and Korsakoff syndrome. Due to the close relationship between these two disorders, people with either are usually diagnosed with WKS as a single syndrome ...

Thiamine deficiency

Risk factors for

thiamine deficiency Thiamine deficiency is a medical condition of low levels of thiamine (Vitamin B1). A severe and chronic form is known as beriberi. The two main types in adults are wet beriberi and dry beriberi. Wet beriberi affects the cardiovascular system, r ...

, or beri beri, in turn include a diet of mostly

white rice White rice is milled rice that has had its husk, bran, and germ removed. This alters the flavor, texture and appearance of the rice and helps prevent spoilage, extend its storage life, and makes it easier to digest. After milling ( hulling), t ...

, as well as

alcoholism Alcoholism is, broadly, any drinking of alcohol that results in significant mental or physical health problems. Because there is disagreement on the definition of the word ''alcoholism'', it is not a recognized diagnostic entity. Predomi ...

, dialysis, chronic

diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin w ...

, and taking high doses of

diuretics A diuretic () is any substance that promotes diuresis, the increased production of urine. This includes forced diuresis. A diuretic tablet is sometimes colloquially called a water tablet. There are several categories of diuretics. All diuretics i ...

. Rarely it may be due to a genetic condition that results in difficulties absorbing thiamine found in food.

Wernicke encephalopathy Wernicke encephalopathy (WE), also Wernicke's encephalopathy, or wet brain is the presence of neurological symptoms caused by biochemical lesions of the central nervous system after exhaustion of B-vitamin reserves, in particular thiamine (vit ...

and

Korsakoff syndrome Korsakoff syndrome (KS) is a disorder of the central nervous system characterized by amnesia, deficits in explicit memory, and confabulation. This neurological disorder is caused by a deficiency of thiamine (vitamin B1) in the brain, and it is ...

are forms of dry beriberi.

Central nervous system (CNS) diseases and disorders

Central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...

disorders such as with a

cerebellar The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cereb ...

problem, the nystagmus can be in any direction ''including'' horizontal. Purely vertical nystagmus usually originates in the central nervous system, but it is also an adverse effect commonly seen in high

phenytoin Phenytoin (PHT), sold under the brand name Dilantin among others, is an anti-seizure medication. It is useful for the prevention of tonic-clonic seizures (also known as grand mal seizures) and focal seizures, but not absence seizures. The in ...

toxicity. Other causes of toxicity that may result in nystagmus include: :*

Brain abscess Brain abscess (or cerebral abscess) is an abscess caused by inflammation and collection of infected material, coming from local (ear infection, dental abscess, infection of paranasal sinuses, infection of the mastoid air cells of the temporal bone ...

(Cerebellar) :* Cerebellar ataxia :* Chiari Malformation :* Multiple sclerosis :* Stroke :* Thalamic hemorrhage :*Trauma :*

Tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

Infantile cerebellar retinal degeneration Infantile cerebellar retinal degeneration is a rare hereditary neurological disorder which primarily affects the eyes and the brain. Presentation Babies with this condition usually appear normal at birth, but start showing symptoms when they a ...

Other causes

:*Non-physiological :*

Trochlear nerve The trochlear nerve (), ( lit. ''pulley-like'' nerve) also known as the fourth cranial nerve, cranial nerve IV, or CN IV, is a cranial nerve that innervates just one muscle: the superior oblique muscle of the eye, which operates through the pu ...

malfunction :*Vestibular Pathology (

, SCDS ( superior canal dehiscence syndrome),

BPPV Benign paroxysmal positional vertigo (BPPV) is a disorder arising from a problem in the inner ear. Symptoms are repeated, brief periods of vertigo with movement, characterized by a spinning sensation upon changes in the position of the head. * T ...

, Labyrinthitis) :*Exposure to strong magnetic fields (as in MRI machines) :*Long-term exposure to low light conditions or darkness, called ''miner's nystagmus'' after 19th-century coal miners who developed nystagmus from working in the dark. :*A slightly different form of nystagmus may be produced voluntarily by some people.

Diagnosis

Nystagmus is highly noticeable but rarely recognized. Nystagmus can be clinically investigated by using a number of

non-invasive A medical procedure is defined as ''non-invasive'' when no break in the skin is created and there is no contact with the mucosa, or skin break, or internal body cavity beyond a natural or artificial body orifice. For example, deep palpation and p ...

standard tests. The simplest one is the

caloric reflex test In medicine Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of ...

, in which one ear canal is irrigated with warm or cold water or air. The temperature gradient provokes the stimulation of the

horizontal semicircular canal The semicircular canals or semicircular ducts are three semicircular, interconnected tubes located in the innermost part of each ear, the inner ear. The three canals are the horizontal, superior and posterior semicircular canals. Structure The ...

and the consequent nystagmus. Nystagmus is often very commonly present with Chiari malformation. The resulting movement of the eyes may be recorded and quantified by a special device called an electronystagmograph (ENG), a form of

electrooculography Electrooculography (EOG) is a technique for measuring the corneo-retinal standing potential that exists between the front and the back of the human eye. The resulting signal is called the electrooculogram. Primary applications are in ophthalmol ...

(an electrical method of measuring eye movements using external

electrodes An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials dep ...

), or an even less invasive device called a videonystagmograph (VNG), a form of

video-oculography Video-oculography (VOG) is a non-invasive, video-based method of measuring horizontal, vertical and torsional position components of the movements of both eyes (eye tracking) using a head-mounted mask that is equipped with small cameras. VOG is usu ...

(VOG) (a video-based method of measuring eye movements using external small cameras built into head masks), administered by an

audiologist Audiology (from Latin , "to hear"; and from Greek , ''-logia'') is a branch of science that studies hearing, balance, and related disorders. Audiologists treat those with hearing loss and proactively prevent related damage. By employing vario ...

. Special swinging chairs with electrical controls can be used to induce rotatory nystagmus. Over the past forty years, objective eye-movement-recording techniques have been applied to the study of nystagmus, and the results have led to greater accuracy of measurement and understanding of the condition.

Orthoptist Orthoptics is a profession allied to the eye care profession. Orthoptists are the experts in diagnosing and treating defects in eye movements and problems with how the eyes work together, called binocular vision. These can be caused by issues with ...

s may also use an

optokinetic drum An optokinetic drum—also called catford drum—is a rotating instrument to test vision in which individuals are seated facing the wall of the drum. The interior surface of the drum is normally striped; thus, as the drum rotates, the subject's eye ...

, or

or Frenzel goggles to assess a patient's eye movements. Nystagmus can be caused by subsequent foveation of moving objects,

pathology Pathology is the study of the causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in ...

, sustained rotation or substance use. Nystagmus is not to be confused with other superficially similar-appearing disorders of eye movements ( saccadic oscillations) such as

opsoclonus Opsoclonus refers to uncontrolled, irregular, and nonrhythmic eye movement. Opsoclonus consists of rapid, involuntary, multivectorial (horizontal and vertical), unpredictable, conjugate fast eye movements without inter-saccadic intervals. It is a ...

ocular flutter Ocular flutter is an opsoclonic disorder that results in horizontal saccades. It is caused by damage to the brainstem paramedian pontine reticular formation cells or the cerebellar neurons controlling those cells. See also * Nystagmus * Opsoclo ...

that are composed purely of fast-phase (saccadic) eye movements, while nystagmus is characterized by the combination of a smooth pursuit, which usually acts to take the eye off the point of focus, interspersed with the saccadic movement that serves to bring the eye back on target. Without the use of objective recording techniques, it may be very difficult to distinguish among these conditions. In

medicine Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care pr ...

, the presence of nystagmus can be

benign Malignancy () is the tendency of a medical condition to become progressively worse. Malignancy is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous ''benign'' tumor in that a malignancy is not s ...

, or it can indicate an underlying visual or neurological problem.

Pathologic nystagmus

Pathological nystagmus is characterized by "excessive drifts of stationary retinal images that degrades vision and may produce illusory motion of the seen world: oscillopsia (an exception is congenital nystagmus)". When nystagmus occurs without fulfilling its normal function, it is pathologic (deviating from the healthy or normal condition). Pathological nystagmus is the result of damage to one or more components of the vestibular system, including the

semicircular canal In mathematics (and more specifically geometry), a semicircle is a one-dimensional locus of points that forms half of a circle. The full arc of a semicircle always measures 180° (equivalently, radians, or a half-turn). It has only one line o ...

otolith An otolith ( grc-gre, ὠτο-, ' ear + , ', a stone), also called statoconium or otoconium or statolith, is a calcium carbonate structure in the saccule or utricle of the inner ear, specifically in the vestibular system of vertebrates. The sa ...

organs, and the vestibulocerebellum. Pathological nystagmus generally causes a degree of

vision impairment Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment� ...

, although the severity of such impairment varies widely. Also, many blind people have nystagmus, which is one reason that some wear dark glasses.

Variations

*Central nystagmus occurs as a result of either normal or abnormal processes not related to the vestibular organ. For example, lesions of the midbrain or cerebellum can result in up- and down-beat nystagmus. **Gaze induced nystagmus occurs or is exacerbated as a result of changing one's gaze toward or away from a particular side which has an affected central apparatus. *Peripheral nystagmus occurs as a result of either normal or diseased functional states of the vestibular system and may combine a rotational component with vertical or horizontal eye movements and may be ''spontaneous'', ''positional'', or ''evoked''. **Positional nystagmus occurs when a person's head is in a specific position. An example of disease state in which this occurs is

(BPPV). **Post rotational nystagmus occurs after an imbalance is created between a normal side and a diseased side by stimulation of the vestibular system by rapid shaking or rotation of the head. **Spontaneous nystagmus is nystagmus that occurs randomly, regardless of the position of the patient's head.

Physiological nystagmus

Physiological nystagmus is a form of involuntary

that is part of the vestibulo-ocular reflex (VOR), characterized by alternating

smooth pursuit In the scientific study of vision, smooth pursuit describes a type of eye movement in which the eyes remain fixated on a moving object. It is one of two ways that visual animals can voluntarily shift gaze, the other being saccadic eye movemen ...

in one direction and saccadic movement in the other direction.

Variations

The direction of nystagmus is defined by the direction of its quick phase (e.g. a right-beating nystagmus is characterized by a rightward-moving quick phase, and a left-beating nystagmus by a leftward-moving quick phase). The

oscillations Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...

may occur in the vertical, horizontal or

torsional In the field of solid mechanics, torsion is the twisting of an object due to an applied torque. Torsion is expressed in either the pascal (Pa), an SI unit for newtons per square metre, or in pounds per square inch (psi) while torque is expressed ...

planes, or in any combination. The resulting nystagmus is often named as a gross description of the movement, e.g. downbeat nystagmus, upbeat nystagmus, seesaw nystagmus, periodic alternating nystagmus. These descriptive names can be misleading, however, as many were assigned historically, solely on the basis of subjective clinical examination, which is not sufficient to determine the eyes' true trajectory. * Optokinetic (''syn. ''opticokinetic) nystagmus: a nystagmus induced by looking at moving visual stimuli, such as moving horizontal or vertical lines, and/or stripes. For example, if one fixates on a stripe of a rotating drum with alternating black and white, the gaze retreats to fixate on a new stripe as the drum moves. This is first a rotation with the same angular velocity, then returns in a

saccade A saccade ( , French for ''jerk'') is a quick, simultaneous movement of both eyes between two or more phases of fixation in the same direction.Cassin, B. and Solomon, S. ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishi ...

in the opposite direction. The process proceeds indefinitely. This is optokinetic nystagmus, and is a source for understanding the fixation reflex. * Postrotatory nystagmus: if one spins in a chair continuously and stops suddenly, the fast phase of nystagmus is in the opposite direction of rotation, known as the "post-rotatory nystagmus", while slow phase is in the direction of rotation.

Treatment

Congenital nystagmus has long been viewed as untreatable, but medications have been discovered that show promise in some patients. In 1980, researchers discovered that a drug called

baclofen Baclofen, sold under the brand name Lioresal among others, is a medication used to treat muscle spasticity such as from a spinal cord injury or multiple sclerosis. It may also be used for hiccups and muscle spasms near the end of life. It is ta ...

could stop periodic alternating nystagmus. Subsequently,

gabapentin Gabapentin, sold under the brand name Neurontin among others, is an anticonvulsant medication primarily used to treat partial seizures and neuropathic pain. It is a first-line medication for the treatment of neuropathic pain caused by diabeti ...

, an anticonvulsant, led to improvement in about half the patients who took it. Other drugs found to be effective against nystagmus in some patients include

memantine Memantine is a medication used to slow the progression of moderate-to-severe Alzheimer's disease. It is taken by mouth. Common side effects include headache, constipation, sleepiness, and dizziness. Severe side effects may include blood clots ...

levetiracetam Levetiracetam, sold under the brand name Keppra among others, is a medication used to treat epilepsy. It is used for partial-onset, myoclonic, or tonic–clonic seizures and is taken either by mouth as an immediate or extended release formu ...

, 3,4-diaminopyridine (available in the US to eligible patients with downbeat nystagmus at no cost under an expanded access programMuscular Dystrophy Association Press Release
/ref>), 4-aminopyridine, and

acetazolamide Acetazolamide, sold under the trade name Diamox among others, is a medication used to treat glaucoma, epilepsy, altitude sickness, periodic paralysis, idiopathic intracranial hypertension (raised brain pressure of unclear cause), urine alkal ...

. Several therapeutic approaches, such as

contact lenses Contact lenses, or simply contacts, are thin lenses placed directly on the surface of the eyes. Contact lenses are ocular prosthetic devices used by over 150 million people worldwide, and they can be worn to correct vision or for cosmeti ...

, drugs, surgery, and

low vision Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment� ...

rehabilitation have also been proposed. For example, it has been proposed that mini-telescopic eyeglasses suppress nystagmus. Surgical treatment of congenital nystagmus is aimed at improving head posture, simulating artificial divergence, or weakening the horizontal recti muscles. Clinical trials of a surgery to treat nystagmus (known as tenotomy) concluded in 2001. Tenotomy is now being performed regularly at numerous centres around the world. The surgery aims to reduce the eye oscillations, which in turn tends to improve visual acuity.

Acupuncture Acupuncture is a form of alternative medicine and a component of traditional Chinese medicine (TCM) in which thin needles are inserted into the body. Acupuncture is a pseudoscience; the theories and practices of TCM are not based on scientif ...

tests have produced conflicting evidence on its beneficial effects on the symptoms of nystagmus. Benefits have been seen in treatments in which acupuncture points of the neck were used, specifically points on the sternocleidomastoid muscle. Benefits of acupuncture for treatment of nystagmus include a reduction in frequency and decreased slow phase velocities, which led to an increase in foveation duration periods both during and after treatment. By the standards of evidence-based medicine, the quality of these studies is poor (for example, Ishikawa's study had sample size of six subjects, was unblinded, and lacked proper controls), and given high quality studies showing that acupuncture has no effect beyond placebo, the results of these studies have to be considered clinically irrelevant until higher quality studies are performed. Physical or occupational therapy is also used to treat nystagmus. Treatment consists of learning strategies to compensate for the impaired system. A Cochrane Review on interventions for eye movement disorders due to acquired brain injury, updated in June 2017, identified three studies of pharmacological interventions for acquired nystagmus but concluded that these studies provided insufficient evidence to guide treatment choices.

Epidemiology

Nystagmus is a relatively common clinical condition, affecting one in several thousand people. A survey conducted in Oxfordshire, United Kingdom found that by the age of two, one in every 670 children had manifested nystagmus. Authors of another study in the United Kingdom estimated an incidence of 24 in 10,000 (c. 0.240%), noting an apparently higher rate amongst white Europeans than in individuals of Asian origin.

Law enforcement

In the United States, testing for ''horizontal gaze nystagmus'' is one of a battery of field sobriety tests used by

police The police are a constituted body of persons empowered by a state, with the aim to enforce the law, to ensure the safety, health and possessions of citizens, and to prevent crime and civil disorder. Their lawful powers include arrest and th ...

officers to determine whether a suspect is driving under the influence of alcohol. The test involves observation of the suspect's

pupil The pupil is a black hole located in the center of the Iris (anatomy), iris of the Human eye, eye that allows light to strike the retina.Cassin, B. and Solomon, S. (1990) ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing ...

as it follows a moving object, noting # lack of smooth pursuit, # distinct and sustained nystagmus at maximum deviation, and # the onset of nystagmus prior to 45 degrees. The horizontal gaze nystagmus test has been highly criticized and major errors in the testing methodology and analysis found. However, the validity of the horizontal gaze nystagmus test for use as a field sobriety test for persons with a

blood alcohol level Blood alcohol content (BAC), also called blood alcohol concentration or blood alcohol level, is a measurement of alcohol intoxication used for legal or medical purposes; it is expressed as mass of alcohol per volume or mass of blood. For example ...

between 0.04 and 0.08 is supported by peer reviewed studies and has been found to be a more accurate indication of blood alcohol content than other standard field sobriety tests.

Explanatory notes

References

{{DEFAULTSORT:Nystagmus Eye diseases Medical signs Neurological disorders