Definition

Nystagmus is a visual disorder characterized by rapid, uncontrolled, and repetitive eye movements. These eye movements can be horizontal, vertical, or rotational, leading to blurry and unfocused vision.

Causes

Nystagmus occurs when the brain or inner ear (labyrinth), which regulates eye movements, malfunctions. It can be congenital (present at birth), idiopathic (occurring due to unknown cause), due to neurological diseases, or caused by certain drugs.

The causes of nystagmus are generally divided into two categories: Infantile Nystagmus Syndrome (INS) or early onset nystagmus, and acquired nystagmus. INS is hereditary and more common than acquired nystagmus, typically developing within the first 6 weeks to 3 months of life. INS is usually mild and non-progressive, often unnoticed by parents. It can be triggered by hereditary eye diseases.

For acquired nystagmus, this type results from inner ear disorders (in the ear labyrinth), developing in late childhood or adulthood. Conditions causing acquired nystagmus include:

• Head injury
• Excessive alcohol consumption
• Inner ear diseases (e.g., Meniere's disease)
• Eye diseases (e.g., cataracts, strabismus)
• Brain diseases (e.g., multiple sclerosis, brain tumors, stroke), with stroke generally be the cause of most nystagmus cases found in elderly
• Vitamin B12 deficiency, hypomagnesemia (low serum magnesium)
• Side effects of seizure medications like phenytoin

Risk Factor

Risk factors for nystagmus depend on the underlying condition. For older adults, stroke risk factors include high blood pressure, diabetes, smoking, heart disease, and alcohol consumption. Head injuries can also increase risk, influenced by occupational and environmental factors.

Symptoms

Common symptoms of nystagmus include fast and uncontrolled involuntary eye movements that are circular, horizontal, or vertical. In children, objects may appear blurry, but the environment remains stable. In adults, the environment and objects appear to sway when the gaze shifts. Additional symptoms include sensitivity to light, a sensation of unsteady footing, difficulty seeing in the dark, dizziness, and balance issues. Symptoms usually affect both eyes but can occur in just one eye. The speed of eye movement varies among individuals.

Diagnosis

Diagnosing nystagmus involves a detailed interview about symptoms, history of other health conditions, medications, family medical history, and any environmental factors that can increase the risk of nystagmus. 

Physical examinations include visual acuity measurement, eye refraction examination, overall eye function evaluation that include the ability of the eye to concentrate or focus, and eye movement tests. The patient can also be requested to turn for 30 seconds and then focuses on an object to detect nystagmus by observing eye movements.

Additional examinations may include ear examination to evaluate inner ear function, blood tests to check for vitamin deficiencies or other causes, and nerve examinations to determine if nerve disorders are causing nystagmus. Diagnostic tests such as CT scan or MRI can be requested in some cases to detect structural brain issues if suspected.

Management

The method of treating nystagmus depends on its type. For Infantile Nystagmus Syndrome (INS), nystagmus cannot be cured, but vision can be improved with glasses.

In some cases, congenital nystagmus in children may improve as they grow. When nystagmus is caused by specific conditions, treatment targets the underlying cause, such as switching medications that induce nystagmus, treating vitamin B12 deficiency, or using antibiotics for bacterial inner ear infections. Botulinum toxin injections may be administered to relax eye muscles responsible for abnormal movements.

The final treatment options include eye muscle surgery, it aims to reduce head movements associated with nystagmus. Brain surgery can be performed if nystagmus is caused by central nervous system or brain issues.

Complications

Nystagmus can lead to decreased visual acuity. If it results from serious conditions like head injuries, strokes, or drug poisoning, complications may include brain damage, balance disorders, impaired movement, speech, chewing, and swallowing abilities, paralysis, and even coma.

Prevention

Preventing infantile nystagmus syndrome is not possible due to its hereditary nature. However, acquired nystagmus can be prevented by avoiding risk factors associated with nystagmus. You can maintain a healthy diet by eating nutritious food and staying hydrated, exercise regularly, avoid alcohol and smoking, manage chronic conditions like diabetes and high blood pressure if you have it. Use personal protective equipment, especially in environments with a high risk of head injury. Stop using drugs that can cause nystagmus, and consult a doctor for alternatives.

When to See a Doctor?

Seek immediate medical attention if nystagmus is caused by a serious condition such as a stroke, head injury, or drug poisoning. Nystagmus due to hereditary factors tends to be milder and less dangerous. Go to the hospital immediately if symptoms include partial and sudden body weakness, slurred speech, inability to speak, decreased consciousness or fainting, vomiting, abnormal pupil size and non-reaction to light.

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