Why Are My Dog's Eyes Darting Back and Forth?

You are relaxing with your dog and all the sudden notice his eyes are darting back and forth while his head is still. This can obviously be scary to see as a dog caregiver, and it is important to know this is not normal and to contact your veterinarian as soon as possible.

What Is Nystagmus?

Nystagmus is a medical term that describes when your dog’s eyes move rapidly and uncontrollably. They can move up and down or in a circle, but most commonly seen is side-to-side movement. 

The movement can vary between slow and fast, and it generally occurs in both eyes. The eyes may shake more after a sudden movement or position change. Dogs with nystagmus may have a head tilt or turn that accompanies the abnormal eye movement.

Nystagmus, in and of itself, is not a disease but rather a symptom of an underlying problem with the vestibular system, which controls balance. There are a variety of reasons your dog may exhibit problems with this system.

Vestibular disease refers to a sudden, non-progressive disturbance of balance, and nystagmus is commonly seen with this. Problems with this are most commonly seen in senior dogs, with a disease referred to as old-dog vestibular syndrome or canine idiopathic vestibular syndrome.

The vestibular system is responsible for maintaining normal balance, coordinating eye movements, and sensing the position of the head and body in space.  The vestibular system has central components located in the brain and peripheral components located in the inner and middle ear.  Determining if the problem is originating from inside or outside of the brain will be one of the first steps your vet takes in finding the cause.

Other potential causes for nystagmus including the following:

• Middle/Inner infections 
• Head trauma
• Hypothyroidism
• Encephalitis (inflammation of the brain)
• Neoplastic tumors
• Inflammatory and viral infections such as canine distemper
• Exposure to toxins 
• Stroke (loss of blood flow to part of the brain)

Depending on the underlying cause you may or may not see any other signs accompanying the nystagmus. Dogs with nystagmus may also have other symptoms, including loss of balance, head tilt, vomiting, walking in circles, falling over/disorientation, standing with their legs wide apart, or decreased activity.

Diagnosing the Reason For Your Dog’s Nystagmus

If your dog suddenly starts showing any of the symptoms mentioned above, contact your veterinarian immediately. Your veterinarian will start by performing a thorough exam and obtaining a history on your dog. Your vet may want to run blood work, perform a urinalysis, take radiographs, or obtain a blood pressure reading to check for any concurrent diseases. The examination and testing can help determine if the nystagmus is more consistent with central (in the brain) or peripheral (inner ear or idiopathic) vestibular disease.

Most sudden-onset episodes of nystagmus are caused by idiopathic vestibular disease. "Idiopathic" means that the exact cause of the disease is unknown, This syndrome affects the balance system in your dog's inner ear. A dog suffering from vestibular disease will commonly develop a head tilt, a circling gait, and may not want to eat their food any more. The symptoms are alarmingly similar to those of a stroke, but idiopathic vestibular disease is far more common in elderly dogs than a true stroke.

Unfortunately, because some causes of nystagmus occur within the brain, a definitive diagnosis can only be made by specialized imaging, such as an MRI or CAT scan in those cases. While these tests are available in veterinary medicine, an owner usually has to go to a referral hospital to have them performed, and the tests can be cost-prohibitive for some.

Treating your Dog's Nystagmus 

How best to treat your dog's nystagmus depends on the severity and cause. Some dogs with mild symptoms may be treated at home with basic supportive care with anti-nausea medications, activity restriction, and supported walks. Hospitalization for supportive care with IV fluids and medications may be recommended for dogs that are more severely affected until they are able to eat and walk on their own. Uncomplicated cases often make good progress toward recovery in the first 2-3 days. Some dogs can be left with a mild head tilt for life, though it generally does not affect their overall quality of life.

If a specific cause is found for the nystagmus, treatment will be tailored to that. Medications may be recommended for problems like ear infections, hypothyroidism, or high blood pressure. Evaluation by a veterinary neurologist may be recommended for dogs that are showing a central (brain-related) causes for their nystagmus.

Regardless of the reason for your dog's nystagmus, seeking immediate veterinary attention is vital for your dog's health. Whether you see an emergency veterinarian or your regular veterinarian, they can help you figure out what is causing your dog's troubling eye symptoms and how best to tackle the problem.