Nystagmus

Nystagmus is a severe form of oculomotor disorders, manifested in spontaneous oscillatory movements of the eyes and accompanied by a significant decrease in visual acuity - a vision.

Nystagmus is a repetitive involuntary pendulum oscillation of the eyes, which can be physiological and pathological. So, the nystagmus that appears in response to the rotation of the optokinetic drum or body in space is normal and serves to preserve good vision. The movements of the eyes that perform fixation on the object are called foveiruyuschimi, and those that move the fovea away from the object, are defensive. With pathological nystagmus, each cycle of motion usually begins with an involuntary deviation of the eye from the object followed by a reverse reflexive, jumplike movement. In the direction of nystagmus can be horizontal, vertical, torsion or nonspecific. The amplitude of nystagmus can be small-bore or large-caliber (the amplitude of nystagmus is determined by the degree of eye deflection), and the nystagmus frequency can be high, medium and low (determined by the frequency of the oscillations of the eyes).

[1], [2], [3], [4]

What causes nystagmus?

The development of nystagmus may be due to the impact of central or local factors.

Nystagmus usually occurs with congenital or early acquired vision loss due to various eye diseases (opacification of optical media, atrophy of the optic nerve, albinism, retinal dystrophy, etc.), as a result of which the mechanism of visual fixation is disrupted.

Physiological nystagmus

1. Installation nystagmus is a small, jerky, nystagmus of a small frequency with an extreme gaze. The fast phase is in the direction of the eye.
2. Optokinetic nystagmus is an impetuous nystagmus caused by repeated movements of the object in the field of vision. The slow phase is the tracking movement of the eyes behind the object; the fast phase is the saccadic movement in the opposite direction, so the eyes fix the next object. If the optokinetic tape or drum moved from right to left, the left parieto-occipital region controls the slow (tracking) phase to the left, and the left frontal lobe controls the fast (saccular) phase to the right. Optokinetic nystagmus is used to identify simulators that mimic blindness, and to determine visual acuity in young children. It can also be useful in determining the cause of isolated homonymous hemianopsia (see below).
3. Vestibular nystagmus is a jerky nystagmus caused by an altered entrance from the vestibular nuclei to the centers of horizontal eye movements. The slow phase is initiated by the vestibular nuclei, and the fast one is initiated by the brain stem and front-mesencephalic way. Rotator nystagmus is usually associated with the pathology of the vestibular system. Vestibular nystagmus can be caused by caloric stimulation:
   • When cold water is poured into the right ear, a left-sided pustular nystagmus (ie, a fast phase to the left) appears.
   • When warm water is poured into the right ear, a right-sided pinched nystagmus (ie, a fast phase to the right) appears. In memorizing the direction, the nystagmus is helped by the mnemonic "COWS" (cold-opposite, warm-same), which means: the cold is the opposite, the heat is the same.
   • When cold water is poured into both ears simultaneously, an impetuous nystagmus appears with a rapid upward phase; warm water in both ears causes nystagmus with a fast phase down.

Nystagmus of motor imbalance

Nystagmus motor imbalance appears as a result of primary defects of efferent mechanisms.

Congenital nystagmus

Inheritance can be X-linked recessive or autosomal dominant.

Congenital nystagmus manifests itself 2-3 months after birth and persists throughout life.

Symptoms of congenital nystagmus

• A horizontal nystagmus, usually of an impulsive type.
• It can be weakened by convergence and not noted during sleep.
• Usually there is a bullet point - the direction of view, in which nystagmus is minimal.
• When installing the eyes at the zero point, an abnormal position of the head may be noted.

[5], [6], [7], [8], [9],

Cramping spasm

This is a rare condition between 3 and 18 months.

Symptoms

• • One-sided or two-sided fine-amplitude high-frequency horizontal nystagmus with a nod of the head.
  • Nystagmus is often asymmetric, with an increase in amplitude during lead.
  • Vertical and torsional components can be noted.

Causes

• Idiopathic feeding spasm is spontaneously resolved by 3 years.
• Glioma of the anterior sections of the optic path, the syndrome of the empty Turkish saddle and the porentsefal cyst.

[10], [11], [12], [13], [14], [15], [16]

Latent nystagmus

It is associated with infantile esotropia and is not combined with vertical deviation. Characterized by the following:

• When both eyes are open, nystagmus is absent.
• A horizontal nystagmus appears when one eye is covered or the amount of light that enters the eye is reduced.
• Fast phase in the direction of the unclosed fixing eye.
• Sometimes the manifest nystagmus is lined with an element of latent, so if one eye is covered, the amplitude of the nystagmus increases (latent-manifest nystagmus).

Periodic alternating nystagmus

Symptoms

• Friendly horizontal jerky nystagmus, periodically taking the opposite direction.
• Each cycle can be divided into an active phase and a phase of immobility.
• During the active phase, the amplitude, frequency and speed of the slow phase of the nystagmus first progressively increase, then decrease.
• Then there is a short, quiet interlude, lasting 4-20 seconds, during which the eyes perform low-amplitude, often pendulum movements.
• This is followed by a similar sequence of movements in the opposite direction, the full cycle lasts 1-3 minutes.

Causes: cerebellar disease, demyelination, ataxia-telangiectasia (Louis-Bar syndrome), drugs such as phenytoin.

Convergence-retraction nystagmus

It is caused by a simultaneous contraction of the extraocular muscles, especially the medial lines.

Symptoms

• The pinched nystagmus caused by the movement of the tape to observe the OKH downward.
• The upper rcfixational saccade leads the eyes to each other in convergent motion.
• It is combined with retraction of the eye into the orbit.

Causes: lesions of the prefectural area, such as pinealomas and vascular accidents.

[17], [18], [19],

Nystagmus, "beating" down

Symptoms: vertical nystagmus with fast phase ,. "Beating" downwards, i.е. Which is easier to call when looking down.

Causes

• The pathology of the craniocervical junction at the level of foramen magnum, such as the malformation of Aniold-Cliiari and sriningobulbia.
• Medicines (lithium compounds, phenytoin, carbamazepine and barbiturates).
• Wernicke encephalopathy, demyelination and hydrocephalus.

Nystagmus, "beating" upwards

Symptoms: vertical nystagmus with a fast phase, "beating" up.

Causes: pathology of the posterior cranial fossa, drugs and encephalopathy Wernicke.

Reciprocal nystagmus Maddox

Symptoms: pendulum nystagmus, in which one eye rises and turns to the inside, and the other eye at the same time falls and turns to the outside; thus, the eyes turn in the opposite direction.

Causes: Parasellar tumors, often causing bitemporal hemianopsia, syringobulbia and stroke of trunk localization.

Ataxic nystagmus

Ataxic nystagmus is a horizontal nystagmus. Arising in the retracted eye of a patient with internuclear ophthalmoplegia {see. Further).

[20], [21], [22], [23], [24], [25], [26], [27]

Nystagmus of sensory deprivation

Nystagmus sensory deprivation (eye) is a consequence of visual impairment. The severity of the condition is determined by the degree of vision loss. The horizontal and pendular nystagmus can decrease with convergence. To reduce the amplitude of the nystagmus, the patient can take a forced position of the head. The reason for the nystagmus of sensory deprivation is severe disruption of central vision at an early age (eg, congenital cataracts, macular hypoplasia). As a rule, nystagmus develops in children under the age of 2 years with a bilateral loss of vision.

Symptoms of Nystagmus

In some varieties of nystagmus, a sufficiently high visual acuity remains, in such cases the cause of its development consists in disturbances in the regulation of the oculomotor apparatus.

Depending on the direction of the vibrational movements, the horizontal (most often observed), the vertical, diagonal and rotational nystagmus are distinguished, the pendulum-shaped (with equal amplitude of the vibrational movements), jerky (for a different amplitude of oscillations: the slow phase in one direction and fast - in the other) mixed (there are some pendulum-shaped, then jerky movements). An angular nystagmus is called left or right, depending on the direction of its rapid phase. With an impetuous nystagmus, there is a forced turn of the head toward the fast phase. By this turn, the patient compensates the weakness of the oculomotor muscles, and the amplitude of the nystagmus decreases, so if the head is turned to the right, the "right" muscles are considered to be weak: the outer straight line of the right eye and the inner straight line of the left eye. Such nystagmus is called right-sided.

Nystagmus can be large-caliber (with an amplitude of vibrational movements of the eye more than 15 °), a medium-sized (with an amplitude of 15-5 °), a small-bore (with an amplitude of less than 5 °).

To determine the amplitude, frequency and nature of oscillatory nystagmoid movements, an objective method of investigation is used - nystagmography. In the absence of a nystagmograph, the nature of the nystagmus amplitude can be determined from the degree of displacement of the light reflex from the ophthalmoscope on the cornea. If the light reflex moves from the center of the cornea to the middle of the distance between the center and the edge of the pupil when vibrating eye movements, one speaks of a small-bore, small-scale nystagmus, if it goes beyond these limits - large-caliber. If the movements of both eyes are not the same, such nystagmus is called dissociated. It is very rare.

Types of Nystagmus

1. A pinched nystagmus with a slow deflecting "drifting" motion and a fast correcting reflexive jerky movement. The direction of the nystagmus is indicated by the direction of the rapid component, so the jerky nystagmus can be right-sided, left-sided, upper, lower or rotatory. The spasmodic nystagmus can be subdivided into the setting (vestibular) and nystagmus with the gaze of the eye (slow and usually a sign of brainstem damage).
2. Pendulum nystagmus, in which both foveirujushchie, and defoeveirujushchie movements are slow (speed nystagmus is identical in both directions).
   • Congenital pendulum-shaped nystagmus, - horizontal and tends to move into an ankle when viewed sideways.
   • Acquired pendulum nystagmus has horizontal, vertical and torsion components.
   • If the horizontal and vertical components of the pendulum nystagmus are in phase (ie, occur simultaneously), the perceived direction looks oblique.
   • If the horizontal and vertical components are not in phase, the direction looks elliptical or rotational.

Mixed nystagmus includes pendulum nystagmus in the primary position and pustular nystagmus when viewed sideways.

Diagnosis of nystagmus

When examining patients with nystagmus, the results of electrophysiological studies (electroretinogram, visual evoked potentials, etc.) are important, allowing to clarify the diagnosis, determine the extent of organic lesions, the presence of amblyopia and determine the tactics of treatment.

With nystagmus, the visual acuity of each eye is examined in glasses and without glasses, with the direct and forced position of the head. In this position, the amplitude of the nystagmus usually decreases and the visual acuity becomes higher. This criterion is used to decide the expediency of performing surgical intervention on the oculomotor muscles. It is important to determine visual acuity with two open eyes (in glasses and without glasses), since with binocular fixation the amplitude of the nystagmus also decreases and the visual acuity becomes higher.

[28], [29], [30], [31], [32], [33]

Treatment of nystagmus

The system of measures to increase visual functions in nystagmus includes a carefully selected optical correction for distance and proximity. In albinism, retinal dystrophy, partial atrophy of the optic nerves, it is advisable to select the color filters (neutral, yellow, orange, brown) that protect the visual acuity and increase the visual acuity.

With nystagmus, the accommodative capacity is also impaired and relative amblyopia is noted, therefore, pleoptical treatment and accommodation training exercises are prescribed. Useful light through a red filter (on a monobinoscope), selectively stimulating the central zone of the retina, stimulation with contrast-frequency and color test objects (device "Illusion", computer exercises in the programs "Zebra", "Spider", "Crosses", "EYE" ). These exercises can be performed consistently for each eye and with two open eyes. Very useful are binocular exercises and diploptic treatment (the "dissociation" method, binarimetry), which also contribute to a decrease in the amplitude of nystagmus and an increase in visual acuity.

Medical treatment of nystagmus is used to improve the nutrition of eye tissues, retina (vasodilator drugs, vitamin complex).

Surgical treatment of nystagmus is performed to reduce the vibrational movements of the eyes. In the jerky nystagmus, when the forced turn of the head is diagnosed with an increase in visual acuity and a decrease in the amplitude of the nystagmus in this position ("rest zone"), the purpose of the operation is to transfer the "rest zone" to the middle position. To do this, weaken stronger muscles (on the side of the slow phase) and strengthen weaker muscles (on the side of the fast phase). As a result, the position of the head is straightened, nystagmus decreases, and visual acuity is increased.