Nystagmus is a clinical sign that refers to oscillatory, rhythmic, involuntary movements of ocular globes, and it manifests itself for several causes:
• Inner ear (vestibular) problems
• Inability to main gaze position
• Disorders of central myelin
• Drug intoxication
The vestibular and optokinetic nystagmus are physiological.
Named in the past as congenital nystagmus, it occurs in patients with ocular motility disorder. They may exhibit visual impairment for albinism, achromatopsia, and hypoplasia of the optic nerve. The cause is still unknown. The intensity of the disorder decreases with inattention and, often, in convergence. It manifests itself at birth or in the first 6 months of life. The oscillations (shaking) are involuntary, conjugated, and often, in a horizontal direction. The characteristic of Infantile Nystagmus is the presence of a “null point”. It is the direction of the gaze where the intensity of the disorder is decreased with improved vision. In fortunate cases, the null point is at the straight-ahead position, so the patient should not assume an abnormal head position. Strabismus and high refractive defects are often associated. There is no oscillopsia, except in rare cases where there is a worsening of the nystagmus due to an associated pathology. Sometimes head nodding, an expression of motor instability, is evident.
Fusion Maldevelopment Nystagmus
In fusion maldevelopment nystagmus, which was called latent nystagmus in the past, all patients have reduced or absent fusions, with no binocular vision abnormalities. It is benign nystagmus that begins in early childhood, with involuntary and conjugated bilateral oscillations, and is easily observed by covering an eye. The movements are horizontal. Patients will rotate the head from the side of the eye so that it will lead to adduction where the nystagmus is reduced. There is no oscillopsia.
Spasmus Nutans Syndrome
Spasmus Nutans is acquired in childhood in the first 2 to 8 years of age. It is often associated with an abnormal head position, squinting, and amblyopia. Some forms of head bobbing and neck posturing are also present. Ocular “quivers” are usually horizontal in direction but may also be vertical or torsional, and it is often described as intermittent nystagmus that is asymmetric or even monocular, and the cause is still unknown. Since some neoplastic forms have similar manifestations, RMN or TB should be performed to exclude diencephalic tumors.
Treatment of Nystagmus
Treatment of nystagmus involves correction of refractive defects, preferably with contact lenses, for increased visual capability and correction of the abnormal head position. Possible strabismus may be addressed through various surgical techniques allowing the patient to receive optimum correction.