When you wear contact lenses, the expectation is to experience improved vision of the external world — putting faces, screens, and more into focus. But what if you could also monitor the internal world — not the mind, but the vital signs of your body? So far, contact lenses with embedded sensors for measuring intraocular pressure (IOP) are too rigid, bulky, and can even partially block vision. Worse, some even lack the required sensitivity to do the job. Until now.
A breakthrough design was just successfully tested in volunteers: a soft, transparent contact lens capable of taking quantitative measurements of IOP in real-time, using a smartphone, according to a new study published in the journal Biomedical Engineering. Most crucially, the new device successfully performed all functions wirelessly without inducing inflammation for the 10 human participants, and this could have serious benefits for people suffering from glaucoma.
Intelligent contact lens detects a key symptom of glaucoma
The new contact lens uses a wireless antenna, a strain sensor, capacitors, employs a stretchable metal that interconnects, resistors, and an integrated circuit to enable wireless communication. When the device was tested on rabbits, it generated measurements comparable to a commercial tonometer — and it proved perfectly safe when tested on 10 humans, with zero inflammation observed. The device can measure basic vital signs, including heart rate, body temperature, the electric activity of the heart, in addition to glucose, lactate, and alcohol concentrations in bodily fluids like sweat, tears, and saliva. Measuring all of these continually is crucial in the diagnosis of a wide range of illnesses.
Medically speaking, the eyes are an apt choice to measure these vital signs, since they can expose electrical sensors to continuous samples of tear fluids — where a wearable device could record and report signals from the eye. This could diagnose several diseases from eye conditions, but the recent study focused on the technology's capacity to sense Glaucoma.
Glaucoma is an optic neuropathy that often leads to irreversible vision loss, and IOP is the only risk factor scientists are sure we can control — which means the only means we have of treating glaucoma is lowering IOP. Typically, measuring the IOP is done with various forms of tonometry, but they lack the clinical specificity required for fully effective monitoring. To overcome this, the new intelligent contact lens design was put forward as a promising candidate for wearable sensing technology — which is capable of maintaining physical contact with the cornea, and detecting the expansion of the corneal limbus — a key symptom of a jump in IOP.
New contact lens design still faces many challenges
In other words, the new intelligent contact lens can monitor a key signifier of Glaucoma to a meaningful degree of specificity with minimally invasive technology, comparable to ordinary contact lenses. But there are still challenges ahead for the novel design before it can be implemented on a mass scale. For example, conventional sensors using metals or semiconductors lack the sensitivity to detect subtle deformations of the lens that IOP fluctuations create — specifically, lens deformations of only 0.03% in tensile strain per mm Hg.
Additionally, fairly complex circuitry is needed to amplify the modest biosensor's signal, so the data from the lenses isn't drowned out in background electromagnetic noise. Rigid electronic materials in the sensors, metallic antennas, integrated circuits, and interconnecting structures can block human vision — and potentially damage the cornea and the eyelid. No one wants to put a contact lens in their eye if there's a chance it will cut up the interior of your eyelid. Finally, measuring the biosignals from the intelligent contact lenses takes bulky equipment — which would limit the range of motion of a wearer who might prefer to go outside, or anywhere besides a clinical environment.
There's much to accomplish before these intelligent contact lenses can become a reliable diagnostic tool for clinical environments — let alone a popular, market-driven alternative to regular doctor and optometrist visits. But this recent study still represents a laudable breakthrough — one that could signal a new and uncomplicated way of monitoring, diagnosing, and assisting in the treatment of some of the most unwieldy illnesses, including Glaucoma.