Researchers have said that computer simulations that map the way tears move across the eye's surface could one day lead to the treatment for dry eye - a burning, gritty condition that can impair vision and damage the cornea.

To understand dry eye, Kara Maki, assistant professor in Rochester Institute of Technology's School of Mathematical Sciences, had to begin with the physics and chemistry of tears. Tear film consists of a layer of water sandwiched between an oily layer of lipids on the outside to prevent evaporation and an inner mucous layer to spread the water over the eye.



Maki developed a mathematical model to simulate the direction tear film travels when entering the eye from the lacrimal glands above the upper eyelid. Using the software program Overture, she recreated the flow of tears on the surface of an open eye, moving from the upper corner and draining through the ducts at the opposite corner.

The tears, Maki explains, climb up the eyelid and join a column of fluid that travels along the lids. Lower pressure sucks the fluid into the meniscus and away from the center, creating the black line and dry spots in the tear film that can compromise vision and irritate the cornea.

Maki saturated the eye with liquid to penetrate the black line. She wanted to know if the fluid would travel down the front of the eye and relieve the thinning of the tear film.

She said they found that they had to really flood the eye in our simulations. The fluid would rather travel in the meniscus.

Maki said it splits traveling along the upper lid and the lower lid and confirmed that blinking is necessary to stop this thinning from happening. Every time they blink, the tear film gets repainted on the front of the eye.

The study has been published in the journal Physics of Fluids.