Approximately 14 percent of the world's population suffer from dry eye disease (DED) but treatments are limited because it's difficult to model the complex human eye for drug development. Now though, University of Pennsylvania bioengineers developed an "eye-on-a-chip" complete with a motorized blinking eyelid. The hope is that the artificial eye will lead to a deeper understanding of dry eye disease, enable drug screening, and even become a testbed for contact lens technology and eye surgery. Their technology also received the 2018 Lush Prize awarded for innovations that could help eliminate animal testing for shampoos and other beauty product. From Eurekalert:
In this study, (Dan) Huh and (Jeongyun) Seo focused on engineering an eye model that could imitate a healthy eye and an eye with DED, allowing them to test an experimental drug without risk of human harm.
To construct their eye-on-a-chip, Huh's team starts with a porous scaffold engineered with 3D printing, about the size of a dime and the shape of a contact lens, on which they grow human eye cells. The cells of the cornea grow on the inner circle of scaffolding, dyed yellow, and the cells of the conjunctiva, the specialized tissue covering the white part of human eyes, grow on the surrounding red circle. A slab of gelatin acts as the eyelid, mechanically sliding over the eye at the same rate as human blinking. Fed by a tear duct, dyed blue, the eyelid spreads artificial tear secretions over the eye to form what is called a tear film.
"From an engineering standpoint, we found it interesting to think about the possibility of mimicking the dynamic environment of a blinking human eye. Blinking serves to spread tears and generate a thin film that keeps the ocular surface hydrated. It also helps form a smooth refractive surface for light transmission. This was a key feature of the ocular surface that we wanted to recapitulate in our device," says Huh.
