This is achieved through the three parts of orbicularis oculi muscle. (emedicalhealth.net)
No more than one in 10 people can voluntarily control the outer orbicularis oculi, the muscles surrounding the eye sockets, with that much precision. (discovermagazine.com)
The Hotz - Celsus technique involves the removal of strip of skin and orbicularis oculi muscle parallel to the affected portion of the lid and then the skin is sutured. (en.wikipedia.org)