It is possible (albeit difficult) to keep our eyes open during a sneeze, said Dr. David Huston, an associate dean at the Texas A&M College of Medicine Houston campus and an allergist at Houston Methodist Hospital.
"The fact that it is possible to sneeze with the eyes open suggests that it is not hardwired or mandatory," Huston said in a statement. It's not entirely clear why people blink while sneezing, but it likely plays a protective role, he said. [Why Do People Sneeze in Threes?]
Sneezing, known to researchers as the sternutation reflex, protects our nasal passageways from foreign particles by forcing a 10-mph whoosh of air from the lungs. (Previous accounts put that speed at 100 mph, but a 2013 study published in the journal PLOS ONE found that six volunteers had sneeze speeds of 4.5 meters per second, or 10 mph).
However, sneezing involves more than expelling air and foreign particles. When stimulated, the brain stem's sneeze center orders muscle contractions from esophagus to sphincter. That includes the muscles controlling the eyelids. Some sneezers even shed a few tears.
Perhaps people close their eyes while sneezing to prevent the expelled particles from entering their eyes, Huston said.
"By automatically shutting the eyelids when a sneeze occurs, more irritants can potentially be prevented from entering and aggravating the eyes," Huston said.
If they're so inclined, people can try to keep their eyes open during a sneeze. Moreover, they don't have to worry about their eyeballs popping out, a tall tale that has no scientific merit, he said. This allegedly happened in 1882, according to a New York Times article about a woman who was said to have dislocated an eyeball (known as subluxation in the medical world) after a fit of severe sneezing.
"There is little to no evidence to substantiate such claims," Huston said. "Pressure released from a sneeze is extremely unlikely to cause an eyeball to pop out, even if your eyes are open."
Rather, increased pressure from a violent sneeze can build in the blood vessels, not in the eyes or the muscles surrounding them. This increased vascular pressure can lead to ruptured capillaries (small blood vessels), which, once broken, are often visible in the eyeballs or on a person's face.
"For example, during childbirth, excessive straining can cause some veins to hemorrhage, leaving a mother's eyes or face to appear red or markedly bruised," Huston said, "but it is irresponsible to claim that such pressure could dislodge the eye from its socket."
Original article on Live Science.