Involuntary Eye Movement (Nystagmus) in Dogs

In most cases nystagmus is an indicator of a vestibular system disease, especially if it appears alongside other symptoms such as loss of balance and head tilting
Can also be a sign of ear infection, other infectious diseases, toxins, or tumors
Often appears suddenly and in an acute form
Jerk nystagmus is the most common in dogs and indicates a vestibular dysfunction
Physical exam, blood work, urinalysis, and diagnostic imaging may be used to determine underlying cause
The most common associated conditions are non-life-threatening and most dogs recover fully
Treatment and prognosis depend on the underlying condition

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A closer look: Involuntary Eye Movement (Nystagmus) in Dogs

Nystagmus is most commonly an indicator of Old Dog Vestibular Syndrome (ODVS) which is usually not life threatening. It’s common to think an old dog who suddenly develops nystagmus and trouble walking has had a stroke and is at the end of his life, but this is generally not the case. Nystagmus is associated with various other diseases, most of which are non-life-threatening. If the symptom appears suddenly it is always better to seek veterinary care as it could be an indicator of central nervous system malfunction or brain injury.

Note: It is normal for nystagmus to occur when the head is moving. To assess the symptom it has to be observed when the animal’s head is in its neutral extended position.

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Possible causes

Nystagmus is associated with about one hundred conditions. The most common cause is Old Dog Vestibular Syndrome (ODVS), a spontaneously occurring disease that causes loss of balance, difficulty walking, and circling. ODVS runs its course in a relatively short time (about two weeks) after which most dogs fully recover.

Other possible causes include

Middle and Inner Ear Inflammation (Otitis Media and Interna) in Dogs Babesiosis (Piroplasmosis) in Dogs

Brain tumor

Traumatic head injury

Stroke (Cerebrovascular Accident) in Dogs Rat Bait (Bromethalin Rodenticide) Toxicosis in Dogs Antifreeze Poisoning (Ethylene Glycol Toxicosis) in Dogs

Risk factors

The most common form of this symptom is jerk nystagmus, characterized by a slow phase where the eyes move slowly in one direction, and a quick phase where they return fast to the original position. This type indicates a vestibular dysfunction. Pendular nystagmus occurs without noticeable variations in the eye movement’s speed. This second type is less common in dogs.

Testing and diagnosis

When presented with nystagmus, a veterinarian runs several tests to check whether the cause is a brain abnormality or infectious and determine the overall health status of the dog:

Physical exam
Blood work
Diagnostic imaging

Advanced diagnostic imaging and analysis of cerebrospinal fluid may be indicated in some cases. Referral to a neurologist is sometimes recommended.

Older dogs presenting with sudden onset nystagmus along with ataxia and circling may be presumed to have ODVS, delaying a diagnostic workup until they fail to improve or get worse. Treatment varies depending on the underlying condition and the severity of the symptom. Some dogs with nystagmus get better without treatment, while some underlying conditions are much more serious and difficult - if not impossible - to treat.