Involuntary Eye Movement (Nystagmus) in Horses

Key Takeaways

Nystagmus is involuntary, erratic movement of the eyes. 

• Nystagmus is a very rare symptom in horses, but when present indicates a brain injury or disorder and requires urgent medical attention 

• Potential causes vary but include rabies, West Nile virus, meningitis, temporohyoid osteoarthropathy, and skull fracture

• Diagnostics involve medical and neurological history, spinal tap, blood work, and x-rays of the skull

• Treatment varies based on the root cause but can involve surgery, palliative care, and euthanasia

A Closer Look: What is Nystagmus in Horses?

Involuntary eye movement is a very rare symptom in horses, but it is indicative of brain injury or disorder and requires rapid intervention as some of the associated conditions are life-threatening. Horses with nystagmus are a fall risk and potential bite risk and should not be handled outside of a veterinary care position. Due to the risk of rabies as a cause, horses with nystagmus need to be handled with caution.

Possible Causes

Nystagmus is a sign of nervous system disease or injury. Possible causes include:


• Temporohyoid osteoarthropathy

• Hepatic encephalopathy

• Meningitis

Equine viral encephalitis

West nile virus

• Skull fractures

• Equine protozoal myeloencephalitis

• Tetanus

Risk Factors

Nystagmus is rare in horses. Any horse at risk of nervous system disease or injury may have an increased risk of developing this symptom. The symptom indicates a serious neurological problem and requires prompt veterinary attention.

Testing and Diagnosis

After a physical examination and medical history additional diagnostics to investigate nystagmus include

• Neurologic examination

• Cerebrospinal fluid examination (spinal tap)

• Blood work

• Skull X rays

Treatment varies depending on the root cause but can include:

• Surgery

• Symptomatic management

• Palliative care

• Euthanasia

Similar symptoms

Nystagmus is not often mistaken for other symptoms, but it can be mistaken for normal eye movement. If the eyes are moving slightly while the horse is moving its head, this is likely to be normal behavior. Nystagmus is when the eyes rapidly and involuntarily move and often is best identified when the head is still.

Associated Symptoms

Nystagmus is associated with other nervous system symptoms, including


• Fever

• Difficulty chewing

• Seizures

• Coma

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