Nystagmus: definition, causes, symptoms, diagnosis and treatment

Nystagmus is the involuntary movement of the eyeballs. In practice, the eyes oscillate, move rhythmically, in different planes: horizontal, vertical or rotational

It is usually a biphasic movement, characterised by a slow deviation in one direction and a rapid one in the opposite direction.

Nystagmus can be physiological, and therefore not caused by any disorder or disease, or pathological, when it is linked to a malfunction of the areas of the brain responsible for eye movement.

Physiological nystagmus

In the first case, nystagmus is due to natural movements that the eyes make to adapt to visualised images that are themselves in motion.

These are therefore involuntary jerks that are part of the vestibulo-ocular reflex, which stabilises images on the retina.

For example, when we are on a train and we look out of the window, our eyes quickly follow the succession of objects and therefore the bulbs oscillate.

In this case, therefore, it is a temporary event that does not affect vision in any way.

The different types of physiological nystagmus include

  • optokinetic, when it depends on the eye and is caused by repetitive movements of an image within the visual field, such as the example of the train. It is a jerky nystagmus, because the first phase, the one in which the eye follows the image, is slow, while the eyes return to position quickly
  • vestibular, when it is related to the inner ear, usually linked to the displacement of endolymph towards the ampulla on one side, as a result of passive body or head movements or from irrigating the ear with warm water
  • end point or end point/laterality, present in many people and subdivided in turn into fatigue nystagmus, unsupported or supported end point nystagmus

Pathological nystagmus

When nystagmus is pathological, any movement of the bulbs moves the object being observed away from the centre of the retina, the fovea, so that it leaves the central vision zone.

Therefore, pathological nystagmus can significantly reduce vision.

Two types of pathological nystagmus can be distinguished:

  • congenital, when it is present from birth and is usually diagnosed in the first few weeks of life
  • acquired, when it develops in the course of life for health reasons

Nystagmus also differs in the movements it produces, which indicate direction

  • pendular: movements have the same speed in both directions
  • jerky: movements are slow on one side, then become sudden in the opposite direction (indicating direction)

When assessing ocular nystagmus, in addition to evaluating the plane of oscillation and direction, the amplitude (fine, medium, wide) and frequency (low, high) must also be taken into account.

Associated symptoms

While the main symptom is obviously the worsening of vision due to the sudden movements of the eyeballs that prevent central vision, there are other signs that accompany the onset of this disorder, some ocular, such as photophobia, and others related to balance, i.e. dizziness, dizziness, nausea, but also headaches and, in some cases, irritability.

If nystagmus is congenital, it usually does not tend to worsen over the years, but if an eye disease is present, it may worsen over time.

Many people complain of greatly reduced depth perception, which has a major influence on body movements.

Balance may also be affected and some simple operations, such as climbing stairs, may be impaired.

Causes of pathological nystagmus

The causes of pathological nystagmus can vary depending on whether the disorder is congenital or acquired.

In the first case, i.e. congenital nystagmus, it may be a gender-related hereditary disorder and is almost always accompanied by a dysfunction of the visual system, such as strabismus or refractive defects.

In any case, it usually manifests itself in the first few months of life, which is why it is very important to have an eye examination at a very early age, to check with the specialist that there are no abnormalities related to the visual apparatus.

If, on the other hand, the disorder occurs later in life, it may be a consequence of major illnesses.

Patients usually realise that something is wrong because their vision drops drastically, but not only that: they perceive it as unstable and oscillating in relation to the visual field, thus complaining of oscillopsia.

Acquired ocular nystagmus can occur at any time and its causes may or may not be ocular in origin.

Among the reasons for developing nystagmus that can be traced back to the visual apparatus are

  • amblyopia
  • cataract
  • strabismus
  • optic nerve degeneration
  • coloboma
  • severe myopia or astigmatism

Similarly, nystagmus can be caused by pathologies affecting the central nervous system, such as:

  • optic nerve hypoplasia
  • Ménière’s syndrome
  • multiple sclerosis
  • Leber congenital amaurosis
  • Down syndrome
  • stroke

Another area that, if altered, can cause ocular nystagmus is obviously the vestibular area, i.e. the inner ear: infections, inflammations and other disorders can affect eye movement.

Other reasons that can cause ocular nystagmus include albinism, brain tumours, the use of certain medications or even alcohol and drug abuse.

Diagnosis of nystagmus

In the presence of ocular nystagmus it is a good idea to consult an ophthalmologist, who will assess the overall situation in the eyes.

Usually the specialist carries out an analysis of the internal structure with an ophthalmoscope, in addition to the eye test.

It is important that eye movements are also analysed to establish what type of nystagmus is present.

This is usually done by analysing the movement of the eyes while the patient observes a fixed point, using a slit lamp for support, which, by magnifying the image, captures even the slightest movements.

The ophthalmologist can also perform an electrooculography, a test that records eye movements via electrodes.

It is also useful to observe the ocular fundus, pupillary reactivity, visual acuity and eye motility.

Many times, eye and orthoptic tests are accompanied by neurological or vestibular tests.

Among the diagnostic tools used to detect nystagmus are also MRI and computed tomography of the brain.

Treating ocular nystagmus

As is the case with many disorders of the visual apparatus, it is necessary to identify the cause of the problem and then treat the condition.

If it is a question of bad habits such as alcohol abuse and drug use, or even the use of certain medications, it will be necessary to stop in order to see the nystagmus disappear, although it does not always resolve completely.

Possible solutions, at least in part, for ocular nystagmus include

  • medication to reduce its severity, which can, however, have significant side effects
  • surgery to reposition the muscles that move the eyes, improving vision somewhat
  • glasses and contact lenses, which are useful if other defects are present
  • aids for the visually impaired, such as larger fonts or increased illumination

If nystagmus is caused by problems not directly related to the ocular system, the appropriate specialists, such as a neurologist or otorhinolar, will assess the best treatment.

Ocular nystagmus is an involuntary movement of the eyeballs that can be physiological, when the eyes adjust to the image or when it is induced, or pathological.

It can impair vision and be a symptom of major disorders, so it is essential to see your ophthalmologist in the first instance for a thorough examination.

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