What is nystagmus?

10/12/2024

What is nystagmus?

Nystagmus is an eye condition characterized by involuntary, rhythmic, and repetitive eye movements. These movements can occur side-to-side (horizontal), up-and-down (vertical), or in a torsiona pattern. People with nystagmus cannot control these eye movements, which often impacts their vision.

Types of nystagmus

Nystagmus can be classified based on the time of onset:

• Congenital nystagmus: This type begins before 6 months of age. Its early onset interferes with the normal development of visual function, resulting in reduced vision that varies in severity depending on the underlying cause.
• Acquired nystagmus: This type develops after 6 months of age or later in life. It can be temporary or permanent and is often accompanied by symptoms such as oscillopsia, vertigo, nausea, instability, or other neurological signs, depending on the underlying cause.

Causes of nystagmus

The causes of congenital nystagmus can be grouped as follows:

• Idiopathic: No identifiable underlying pathology is found.
• Genetic: Caused by mutations in specific genes.
• Sensory: Triggered by ocular diseases that lead to low vision in children, which secondarily results in nystagmus. Common causes include:
  • Oculocutaneous or isolated ocular albinism
  • Ocular malformations such as aniridia, foveal hypoplasia, or optic nerve hypoplasia
  • Congenital retinal dystrophies
  • Untreated congenital cataracts
  • Corneal opacities
• Neurological: Caused by neurological conditions, though this is rare in children.

Acquired nystagmus is typically associated with neurological disorders, inner ear lesions, or the use of certain medications or drugs.

It is important to note that nystagmus can be a symptom of other medical conditions. If it appears suddenly, a medical consultation is essential to determine the underlying cause.

Symptoms of nystagmus

The rhythmic oscillation of the eyes can lead to several challenges, including:

• Reduced visual acuity: Children with nystagmus do not fully develop optimal visual acuity. The degree of impairment varies based on the underlying cause, with idiopathic cases often resulting in better visual acuity than those caused by ocular pathologies.
• Oscillopsia: A sensation of constantly moving objects. This occurs in acquired nystagmus but not in congenital nystagmus, as the brain adapts to the rhythmic eye movements.
• Difficulty focusing: Children may struggle to focus on details or nearby objects, perceiving them as blurry or “moving,” especially when reading or viewing something up close.
• Photophobia: Nystagmus associated with albinism often involves sensitivity to bright light, making dimmer environments more comfortable.
• Unusual head posture (torticollis): Some nystagmus cases exhibit a "null point" (a position where eye movements are minimal) in lateral gazes. Patients may adopt an abnormal head posture to achieve clearer vision in the direction of this null point.

In addition to these symptoms, nystagmus can lead to emotional or social discomfort, particularly in situations requiring prolonged eye contact, as the constant movement of the eyes may draw attention.

Treatments for nystagmus

Treatment for nystagmus depends on its cause. In acquired nystagmus, addressing the underlying condition is the priority. For congenital nystagmus with a treatable cause, such as cataracts, removing the cataracts can significantly reduce or even eliminate the nystagmus. Unfortunately, in most congenital cases, there is no effective treatment to stop the eye movements.

In some instances, glasses or contact lenses may be prescribed to maximize visual development. Surgery is another option for severe cases of torticollis, aiming to shift the null point from lateral gazes to the central gaze. This reduces abnormal head posture and improves visual quality.

Nystagmus is a complex condition that requires close monitoring by an ophthalmologist. The goal is to optimise vision using corrective lenses or surgery when appropriate. With proper care, most individuals with nystagmus can lead full and active lives.

Dr. Anna Monés, Ophthalmologist, Barraquer Ophthalmology Centre