Crossing your eyes
Also called: Voluntary convergence · Going cross-eyed
Turning both eyes inward toward the nose on purpose. Most people with normal two-eyed vision can do it. Your eyes will not get stuck that way.
How common
Can you do this?
How it works
Each eye has a muscle on its inner side, the medial rectus, that pulls it toward the nose2. When you look at something close, both muscles pull at once. The eyes turn inward so that each one points at the same object. This is called convergence1.
Convergence is a reflex. It runs whenever you look at something near, along with two other changes. The lens thickens to focus, and the pupils shrink1. Crossing your eyes on purpose means pushing this reflex to its limit. You aim both eyes at your nose and hold them there with no target.
Most people with normal two-eyed vision can do it. People with convergence insufficiency, whose eyes will not hold the inward turn, find it hard or tiring4.
A common warning says your eyes will stick if you cross them too long. There is no evidence for this5. Strabismus comes from muscle imbalance, nerve problems, or unequal vision in the two eyes, not from crossing them on purpose35.
How common it is
Nobody has counted the people who can cross their eyes on purpose. Convergence insufficiency makes the inward turn harder for some people4. It is reported in about 4% to 6% of school and clinic groups when a standard definition is used, and in 13% of fifth and sixth graders in one 1999 study4. Those ranges are wide because studies use different cut-offs4. A survey that simply asked people to try would be better.
Try it
- Hold a finger up at arm’s length and look at it.
- Bring the finger slowly toward your nose. Keep it in focus as one finger, not two.
- When the finger touches your nose, your eyes are fully crossed.
- Take the finger away and try to keep your eyes where they are.
- Look at something far away to release the cross.
Is it a problem?
No. Crossing your eyes on purpose does not damage them and does not cause strabismus. The old warning that your eyes will stick that way is a myth, not a real risk5. A brief headache or double vision after holding the cross is normal and passes quickly. See a doctor if close work such as reading gives you headaches or double vision, or if one eye drifts on its own, since those patterns point at convergence insufficiency or true strabismus34.
Sources and further material
- Wikipedia Convergence insufficiency The condition where the eyes will not hold a turn inward. Prevalence figures from the CITT Study Group, 2008, and Rouse et al., 1999.
- proeyecarecenter.com "If You Cross Your Eyes; They'll Stay that Way" – The Truth Behind Eye and Vision Myths An eye clinic says crossed eyes come from disease, uncorrected vision, or muscle or nerve damage, not from crossing them on purpose.
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Related oddities
Wall-eyed divergence
Turning both eyes outward, away from the nose, on purpose. Nobody has counted how many people can do it. Most people can learn the mild version, parallel viewing, from Magic Eye pictures.
Voluntary nystagmus
About 8% of people can make both eyes shake rapidly from side to side on command. It looks alarming and is harmless. It is tiring and lasts only seconds.
Accommodation reflex
When you look at something close, three things happen at once. The eyes turn inward, the pupils shrink, and the lens in each eye gets fatter. You do not decide any of it.
Independent eye movement
Moving one eye while the other stays still, or moving the two eyes in different directions. Few people seem to manage it, and nobody has counted them. Chameleons do it all day.