system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do contact lenses stay perfectly centered on your eye and slide/rotate back into place after you move them aside?
gpt
Your eye isn't just a perfect sphere. The lens is actually a bump out from the surface and the contact is curved. Staying on the lens then is preferred because sliding off would require pulling away or deforming the contact.