New model of tears may lead to more comfortable contacts

Researchers built a model of the eye to allow manufacturers and researchers to better design and test tear films on contact lens surfaces.

By Stephen Feller

STANFORD, Calif., March 25 (UPI) -- Stanford researchers created a model of the eye that could allow them to create more comfortable contact lenses, they report in a new study.

Researchers working to understand why contacts, and users' eyes, dry out after several hours of use, found they needed a better understanding of how tears keep the eye wet, resulting in the design of the model.


The discomfort felt by contact lens wearers occurs when the tear film, a coating on the surface of the eye, breaks up. The researchers theorized the lipid layer, an oily coating that protects the eye's surface, could be reinforced in order to prevent dry eye irritation.

The researchers compare the lipid layer to a pool cover: You can't run across the surface of water, but with a thin cover on top, you can run across the pool -- so why not add an additional cover to contact lenses to help prevent the dewetting process when the tear film breaks up?

"We recognized early-on that the fluid mechanical responses of the lipid layer were just as important as the conventional view that its role was to control evaporative loss," Gerald Fuller, a professor at Stanford University, said in a press release. "And it's been gratifying to realize that the combined role of these two forces is now accepted."


For the study, published in the journal Investigative Ophthalmology and Visual Science, researchers created a device that mimics the surface of the eye called the Interfacial Dewetting and Drainage Optical Platform, which reproduces the tear film on the surface of a contact lens.

The researchers say the device could help doctors and manufacturers create better contact lens surfaces that include a secondary tear film to test how quickly it breaks up, as well as make contacts overall more comfortable.

"Some people are studying contact lenses by holding them up to a light, dipping them in water, and looking at them to see if the tear film breaks up," said Dr. Saad Bhamla, a bioengineering researcher at Stanford. "We felt we could definitely do better than that."

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