14 DAY TRIAL // A new study led by Kara Maki, a mathematics grad student at the University of Delaware, demonstrated the physics behind the tear phenomenon, providing new insight, such as the fact that, contrary to previous beliefs, tear fluid can cross the surface of the middle of the eye. Thorough computer simulations have offered new hints on the fluid mechanics going on at eye surface level. The new results could aid breakthrough treatments in ophthalmology, for dry eye symptoms, for instance.
During the blinking process, the whole eye surface changes drastically, as new fluid secreted by glands near the temple is poured in within a quarter of a second, and is brushed by the lid in order to leave a coating, protecting layer. This shields the eye from harmful particles in the air, such as dust. The excess fluid is drained into the nose; when blinking again, the process starts anew.
"The reason why we're interested in studying this is because it's a highly dynamical system," shared Maki. "If we can try to understand and gain insight into tear film dynamics, we can aim at trying to find better treatments for dry eye." Richard Braun, her advisor, explained for LiveScience that "Every time you blink, it's like a paint brush that moves fluid around and leaves a coating of fluid like a coating of paint on the wall."
When external factors (like a highly-emotional state or slicing onions) alter the process, the balance is broken and too much fluid is released. This exceeds the surface tension and is collected and directed out of the eye in the form of teardrops. The scientists' computer model also took into consideration gravity, surface tension and viscosity factors in order to get more accurate results, showing that tears can reach middle-eye regions.
"Most people think of this as a barrier, that tears can't get across to the middle of the eye," stated Braun. "Most of the time that's true. But Kara found that if there's enough fluid, the tear can cross the middle of the eye, instead of staying at the edges. No one had computed that before."