These contact lenses with a pattern of conductive silver wires could be used to measure pressure inside the eye and study glaucoma, a major cause of blindness. (Credit: Tingrui Pan/UC Davis photo)

In glaucoma, drainage of the fluid that normally delivers nutrients to and removes metabolic waste from the eye is blocked. Elevated pressure in the eye ultimately presses on the retina, compromising neural activity and damaging the optic nerve, resulting in loss of vision. Current treatments of glaucoma include the measurement of patients' IOP and prescription of drugs to lower it. James Brandt, a professor of ophthalmology at UC Davis and Pan's collaborator, explained the complexity involved: "It's very different from situations like cardiac disease or diabetes, where patients can wear devices that measure heart rate or blood pressure 24 hours a day for a week or more to get a better idea of what's going on; we don't have that for glaucoma, and that's one of the biggest clinical frustrations we have."  

Wireless implantable micro-nanosystems (Credit: UC Davis)

The next step was the creation of a negative cutout in the pattern of a small circuit. UV light was shone through the cutout onto a layer of a polymer mixture. As expected, areas exposed to light gelled while those under the cutout did not. Thus, researchers were able to easily wash away the liquid polymer leaving an imprint of a small nanoscale circuit within the solidified polymer. Afterwards Pan filled the pattern with a solution of powdered silver, which is a nontoxic metal conductor. After polymerization, the silver formed a continuous circuit within the soft polymer. 

During initial laboratory tests it was found that the voltage within the tiny circuit changed slightly as the polymer bent. Using this technique the change is measured and according to Pan it could be a good indicator for IOP since when pressure within the eye increases the shape of the contact lens will distort, causing a change in voltage within the wires. "This device is really a breakthrough in real-time IOP monitoring," says David Calkins, associate professor of ophthalmology at Vanderbilt University Medical Center, who was not involved in the research. "We don't have a means right now to measure pressure in real time outside of the clinic. Because of that, we are missing the fluctuations in IOP that could be pertinent to the pathogenesis of glaucoma." 

Although the prototype seems promising, several hurdles remain before it can be practically used as a contact lens. In the current version, the silver circuit is opaque and would obviously obstruct vision. Pan says that such a visible circuit could still be used for short-term, sit-down tests in the clinic, but nevertheless he looks for materials that could be made into transparent circuits for longer-term use. 

TFOT has also covered the new bionic eye that could restore sight, developed at the Boston Retinal Implant Project, and the SIAFU, a computer designed for the blind by industrial designer Jonathan Lucas. TFOT also features an extensive article entitled “Shedding Light on Blindness,” written by Gadi Howard. 

More information on the new smart contact lenses can be found on UC Davis’s website.