Liquid-based lenses that automatically focus on what a person is seeing could replace reading glasses and bifocals in the near future. The human eye has a lens inside that adjusts the focal depth depending on what is being viewed. But as people age, the lens loses its ability to change focus, which is why many people ultimately require reading glasses or bifocals to see objects up close, and regular eyeglasses to see far away. Close-up of a liquid-based lens that can automatically adjust the focus on what a person is seeing. Courtesy of Carlos Mastrangelo. A team of researchers from the University of Utah are working to correct this problem with a novel pair of adaptive “smart glasses.” "Most people who get reading glasses have to put them on and take them off all the time,” said Carlos Mastrangelo, professor of electrical and computer engineering. "You don't have to do that anymore. You put these on, and it's always clear." The eyeglass lenses are made of glycerin — a thick colorless liquid enclosed by flexible rubber-like membranes in the front and back. The rear membrane in each lens is connected to a series of three mechanical actuators that push the membrane back and forth like a transparent piston, changing the curvature of the liquid lens and therefore the focal length between the lens and the eye. The lenses are then placed in special eyeglass frames — also invented by the researchers from the University of Utah — with electronics and a battery to control and power the actuators. In the bridge of the glasses is a distance meter that measures the distance from the glasses to an object via pulses of infrared light. When the wearer looks at an object, the meter instantly measures the distance and tells the actuators how to curve the lenses. If the user sees another object that's closer, the distance meter readjusts and tells the actuators to reshape the lens for farsightedness. This changing of focus from one object to another takes place in 14 milliseconds. University of Utah electrical and computer engineering professor Carlos Mastrangelo, right, and doctoral student Nazmul Hasan have created “smart glasses” with liquid-based lenses that can automatically adjust the focus on what a person is seeing, whether it is far away or close up. The lenses are placed in battery-powered frames that can automatically adjust the focal length of the lenses based on what the wearer is looking at. Courtesy of Dan Hixson/University of Utah. Before putting the smart glasses on for the first time, the user inputs their eyeglasses prescription into an accompanying smartphone app, which then calibrates the lenses automatically via a Bluetooth connection. Currently, the team has constructed a bulky working prototype, but expects to constantly improve the design to make them smaller, lighter and more attractive. Theoretically, eyeglass wearers would never have to buy another pair of glasses since these constantly adjust to changing eyesight. The eyeglasses could be available as soon as three years from now. Research on the adaptive lenses is available in the journal Optics Express (doi.org/10.1364/OE.25.001221).