How nystagmus testing works and what to expect

What is a nystagmus test?

During a nystagmus test, a doctor looks at how your eyes move in various contexts. They need to know if the nystagmus occurs with certain gaze directions, body positions or head movements. Knowing when it does or doesn’t occur can tell them a lot about what is causing it.

Why are nystagmus tests important?

Many nystagmus tests are technically vestibular (inner ear) function tests. This is because nystagmus is often caused by inner ear or neurological issues. It’s also related to alcohol or drug use (illicit, recreational and prescription).

Vestibular tests assess how your inner ears, brain and eyes work together to create spatial orientation and balance. They can tell doctors if nystagmus is related to the inner ear, brain, substance use or something else.

Sometimes, eye and vestibular tests can’t pinpoint the exact cause of nystagmus. Your doctor may also need to do other types of tests, including genetic testing, a CT scan or an MRI. 

Beyond testing, it’s important to understand whether nystagmus starts from early infancy or develops later. Infantile nystagmus syndrome (INS) is when both eyes together show nystagmus symptoms with onset prior to six months of age occurring possibly on its own or alongside other findings. For these cases, it’s recommended to talk to your doctor about genetic testing. It’s increasingly part of the workup. 

One thing to know is that diagnostic measurements are higher when genetic testing is guided by clinical findings (around 80%) and in patients with a family history (up to 88%). Nystagmus that appears later in life is more commonly acquired and points toward an inner-ear, neurological or medication-related cause. 

How to test for nystagmus

In the majority of cases, people who have nystagmus are aware that something is off. You may feel dizzy or nauseated, have double vision or notice the telltale sign of nystagmus — involuntary eye movements. Depending on your symptoms, you might go to a primary care provider (PCP) to find out what’s going on.

These doctors will often do a basic eye movement screening as part of a full exam, especially if you are dizzy or have certain vision symptoms. If they detect signs of nystagmus, they’ll usually refer you to an eye doctor or specialist. 

An eye doctor will do a comprehensive eye exam and other tests to rule out any eye disease that may be causing the nystagmus. Depending on their results, they may refer you to another specialist. 

The nystagmus “finger test”

One part of a basic eye movement screening is the horizontal gaze nystagmus (HGN) test. It’s also known as the “finger test,” a familiar part of field sobriety testing.

For the finger test, you follow the movement of a pen, penlight or finger with only your eyes.

• The doctor or law enforcement (military police or town/state police officer) will ask you to stand or sit with your arms to your sides and face forward.
• They’ll hold up their finger or penlight and move it slowly from side to side (testing horizontal gaze nystagmus) and then up and down (testing vertical gaze nystagmus) a few times.
• As you follow it with your eyes, they’ll check the smoothness and range of your eye movements.

For law enforcement, horizontal gaze nystagmus is considered the most reliable of the three standardized field sobriety tests for detecting alcohol impairment. It’s a screening tool rather than a definitive measurement. Chemical (breath or blood) testing would confirm intoxication.

A doctor generally does the finger test as one step in an eye movement, or ocular motility, screen. The other steps are similar but involve covering and uncovering the eyes one at a time. 

If they see abnormal eye jerking or movement, they’ll do further tests and/or refer you to a specialist.

Nystagmus testing with a specialist

A specialist will do several tests to narrow down the kind of nystagmus you have and what’s causing it. Nystagmus often stems from an issue in the inner ear or the brain, so that’s where the most common tests focus. Many types of doctors specialize in eye, vestibular (inner ear) and brain function, so you may be referred to one of the following: 

• Neuro-ophthalmologist
• Neurologist
• Otolaryngologist (ENT)
• Vision therapist
• Orthoptist
• Audiologist

Often, though not always, the specialist will ask you to wear a pair of “nystagmus goggles” during a video head impulse test (vHIT). 

These are special goggles that make it easier to assess your eye movements. Depending on the vHIT, the goggles might:

• Magnify and/or light up your eyes to make them easier for the doctor to see.
• Make your vision a little blurry so the doctor can see if nystagmus occurs when your eyes aren’t focused.
• Track and record your eye movements so the doctor has as much data as possible.

In some cases, the doctor may also place stick-on electrodes near your eyes to measure their activity.

Spontaneous nystagmus test

This test checks for spontaneous nystagmus. Essentially, this is nystagmus that occurs when you look straight ahead. It doesn’t have a “trigger,” such as looking right or left or turning your head. The results of this test can impact any following tests, so doctors usually do this one first.

The doctor will ask you to look straight ahead for about 30 seconds. Then, you’ll repeat that process looking up, down and to each side. Looking straight ahead checks for spontaneous nystagmus, while shifting your gaze up, down and to each side checks for gaze-evoked nystagmus which appears only in certain eye positions. 

In some cases, they may cover your eyes and go through the steps again. This allows them to compare any eye movements that occur when you are and are not looking at a target.

Positional nystagmus test

In this test, the doctor observes relaxed eye movements (not focusing on an object) in two positions.

First, they will have you sit up on the edge of an exam table. Then, they will turn your head 45 degrees to the right and lay you down rather quickly. As you lie with your head turned and neck extended, they will watch your eye movements for nystagmus. After about 60 seconds, they’ll repeat the process on the other side. 

This test, also known as the Dix-Hallpike maneuver, is the best way to diagnose benign paroxysmal positional vertigo (BPPV). BPPV is caused by the movement of tiny calcium crystals in the inner ear.

There is another version called the Pagnini-McClure maneuver (supine head-roll test) which is performed while laying flat on your back.

Optokinetic nystagmus test

Optokinetic nystagmus is how your eyes track objects that rapidly move across your field of view. A good real-life example of this is looking out the window in a moving car. Your eyes are constantly moving to keep track of the objects as they fly by.

This type of nystagmus is supposed to happen. The tests check for anything abnormal, which can point to a neurological issue.

Typically, the “objects” in the test are a series of vertical black and white stripes. There are a few different methods a doctor might use:

• You might sit in a rotating chair and look at stripes projected onto the wall.
• You might look at a striped, spinning drum you hold at arm’s length.
• You might sit or stand inside a large drum with striped walls that rotate around you.

Head-shaking nystagmus test 

In this test, the doctor tries to induce nystagmus by using specific head motions. You’ll need to keep your eyes open but relaxed (not focused on an object).

First, they’ll ask you to look straight ahead from your seated position. After a few seconds, they’ll gently tilt your head down about 30 degrees. From there, they will move your head from side to side, like shaking your head “no,” 20 times. The target speed is about two no’s per second.

At the end, you’ll look straight forward again, and the doctor will watch your eyes for about a minute to see if any nystagmus occurs. If so, it can indicate a vestibular imbalance, such as vestibular neuritis in one ear.

Caloric Test

During caloric testing, the doctor places warm and then cool water or air into each ear canal and records the eye movements that result. The caloric test assesses the function of the lateral (horizontal) vestibular canal. It is one of the few tests that can measure each inner ear separately, making it the gold-standard measure of one-sided vestibular weakness.

Can you do a nystagmus test on your own?

It’s possible to do simplified versions of some of these tests at home. If you’re curious, you may even be able to capture some of your eye movements with your phone’s camera.

However, only an eye doctor or specialist can diagnose nystagmus. They have the expertise and tools to interpret the eye movements within the context of the tests. 

If you or your child has new, nystagmus-like eye movements, it is recommended to see an eye doctor as soon as possible. 

Tips for patients

If you’re having nystagmus testing soon, try not to be nervous. They are all non-invasive, and the doctors and staff will walk you through each step.

It’s important to ask ahead of time if you need to do anything special to prepare, but a few general tips include:

• Avoid alcohol, sleeping medication and recreational drugs for at least 24 hours before testing.
• Don’t wear any eye makeup; it can disrupt the eye movement recordings.
• It’s best to stop taking any medication for dizziness a few days beforehand, but definitely ask your doctor first.
• Be sure to eat something, even if your tests are in the morning and you don’t normally have breakfast.
• Bring a list of your current medications, episodes of vertigo or dizziness and any past ear or brain issues.

It’s also a good idea to write down any questions you think of and bring them with you.

When to talk to a doctor

It’s important to see an eye doctor right away if you notice any visual symptoms related to nystagmus or an ENT, neurologist or audiologist when an inner-ear or neurological cause is suspected. These symptoms may include:

• New, involuntary eye movements
• Frequent episodes of dizziness or vertigo
• Dizziness or nausea with head movements
• New or more frequent episodes of losing your balance

In most cases, the first step in a nystagmus diagnosis is having a comprehensive eye exam. An eye doctor will assess your total eye health to determine if an eye disorder is causing your symptoms.

If they rule out an eye disorder as the cause, they’ll need to refer you to a specialist. Then, they and any other specialists will work together as part of your care team to manage and treat your condition.

LEARN MORE: How nystagmus is treated