Nystagmus Definition

Nystagmus refers to bilateral involuntary rhythmic oscillation of the eyes, which can be jerky or pendular (jerk nystagmus and pendular nystagmus).

The various forms of nystagmus are listed in Table 17.5.

Etiology: The etiology and pathogenesis of nystagmus remain unclear. Nystagmus is also a physiologic phenomenon that may be elicited by gazing at rapidly moving objects. An example of this is optokinetic nystagmus, a jerk nystagmus that occurs in situations such as gazing out of a moving train.

Treatment: Where nystagmus can be reduced by convergence, prisms with an outward facing base may be prescribed. In special cases, such as when the patient assumes a compensatory head posture to control the nystagmus, Kestenbaum's operation may be indicated. This procedure involves parallel shifts in the horizontal extraocular muscles so as to weaken the muscles that are contracted in the compensatory posture and strengthen those that are relaxed in this posture.

Table 17.5 Forms of nystagmus

Forms

Onset

Characteristics

Type of nystagmus

Ocular nystagmus

Congenital nystagmus

Latent nystagmus

Fixation nystagmus

Gaze palsy nystagmus

Congenital ❖ Occurs in organic dis-or acquired orders of both eyes, such in early as albinism, cataract, childhood color blindness, vitreous opacification, or macular scarring.

❖ Significant visual impairment.

❖ Secondary strabismus may also be present.

Nystagmus is not curbed by fixation but exacerbated.

Oscillation is usually horizontal.

Intensity varies with the direction of gaze (usually less in near fixation than in distance fixation).

Always associated with congenital strabismus. Manifested only by spontaneously uncovering one eye when fixation changes.

❖ Direction of oscillation changes when fixation changes (see right column).

Acquired ❖ Occurs in disorders of the brain stem or cerebellum due to vascular insults, multiple sclerosis, trauma, or tumors.

Acquired See fixation nystagmus.

Pendular nystagmus.

Congenital or acquired in early childhood (at the age of three months)

Congenital or acquired in early childhood

Constant alternation between pendular and jerk nystagmus.

Right oscillating nystagmus in right fixation.

Left oscillating nystagmus in left fixation.

Nystagmus occurs as jerk nystagmus.

Pendular or other abnormal form of oscillation.

Jerky oscillation. This nystagmus is especially apparent at the onset of muscular paralysis when the patient attempts to use the muscle that is becoming paralyzed.

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