Voluntary nystagmus

How it works

Nystagmus is a repeated, rhythmic movement of the eyes. It usually happens by itself, as a result of an inner ear or brain problem. Voluntary nystagmus is different. A small group of people can switch it on and off at will¹.

The movement is a stream of very fast, very small eye jumps, one after another, left and right⁶. Each jump is a saccade, the same kind of movement your eyes make when you read². In voluntary nystagmus the saccades are packed so close together that the eyes appear to vibrate.

People who can do it describe concentrating hard on the eyes. Many try to blur their vision, or cross the eyes and then relax them⁴. The shaking starts on its own. It is hard work. Most people can keep it going for about 5 seconds. A few can hold it for up to 35 seconds¹. Vision blurs while it lasts⁵.

Voluntary nystagmus runs in families³. It usually first appears between ages 8 and 15⁵. It causes no harm. Eye doctors know it well, because a few patients use it to fake an eye disease.

How common it is

The 8% figure comes from a 1978 survey of college-age people by Zahn, one of the few studies to ask a group of people whether they could produce the shaking on command³. It has not been widely repeated since, so the figure rests on a single, older dataset rather than a broad modern survey. Because the trait runs in families, rates could plausibly differ between populations, but no study has tested this.

Try it

1. Sit in front of a mirror or turn on your phone camera.
2. Hold a finger close to your nose and look at it, so that your eyes cross a little.
3. Tense your eyes as if squinting hard, but keep the lids open.
4. Watch for a fine, fast shake. If you see it, try to hold it for a few seconds.
5. Stop if your eyes ache. Nothing is gained by pushing.

If nothing happens after a few tries, you are probably in the majority. There is no known way to learn it.

Is it a problem?

No. Voluntary nystagmus causes no lasting harm⁴. Vision blurs and the eyes tire while it is happening⁴⁵. It is unrelated to the involuntary nystagmus caused by inner ear or brain conditions, even though the eye movement looks similar¹. Eye doctors know that some patients use it to mimic eye disease, so mention it to a doctor before an eye exam if you can do this. See a doctor promptly for nystagmus that happens on its own, without you triggering it, since that has different causes.