Smart lenses can detect glaucoma wirelessly

Most people with early stage glaucoma are unaware of their condition, although early treatment is critical to reducing vision loss. Detection of slight increases in intraocular pressure helps doctors diagnose glaucoma, but continuous monitoring of this pressure is difficult, especially given the variety of temperatures to which the eyes are exposed. Now researchers from ACS Applied Materials & Interfaces announces the creation of a prototype of a smart contact lens that accurately measures intraocular pressure regardless of temperature.

According to the Centers for Disease Control and Prevention (CDC), about 80 million people worldwide suffer from glaucoma, a group of diseases that damage the optic nerve and lead to vision loss. Doctors use a "pneumotonometry test" during an eye exam to take a one-time measurement of intraocular pressure. A slight increase in pressure, a subtle symptom caused by the accumulation of fluid around the cornea, may lead to a diagnosis of glaucoma. P>

Researchers are testing ways to continuously and more comfortably detect these small pressure fluctuations, such as contact lenses that transmit signals to special glasses. However, changes in temperature, such as going out into the cold, can skew lens measurements. So researcher Dengbao Xiao and his colleagues decided to develop a contact lens that accurately measures and wirelessly transmits real-time intraocular pressure data over a wide temperature range.

Xiao's team initially developed two miniature helical circuits, each with a unique natural vibration pattern that changed when stretched, such as by changes in pressure and diameter of the eye. To create pressure-sensing contact lenses, the researchers sandwiched these small circuits between layers of polydimethylsiloxane, a standard contact lens material.

They then read the vibration patterns of the embedded circuits using a coil connected to a computer and located next to the lens. The transmitted signals were not subject to distortion in tests simulating eye movement, prolonged exposure to moisture (to simulate wet conditions in the eye), and daily wear and tear.

In laboratory tests, the researchers placed the new lenses on three samples of pig eyes, monitoring intraocular pressure and temperature. The contact lenses monitored and wirelessly transmitted pressure data at temperatures ranging from 10 to 50 degrees Celsius. When pressure was calculated from the signal from only one circuit in the lens, the results deviated by up to 87% from the true values. However, when using information from both circuits, the pressure readings differed by only 7% from the true values, since the combination of circuits eliminated temperature-related errors.

Researchers say their dual-circuit smart lens design has the potential for accurate early detection and monitoring of glaucoma, even over a wide temperature range.