Why glucose
Glucose is the sugar that people with diabetes need to track, and for decades the standard way to measure it was a finger-prick blood sample. The idea of reading glucose without needles has long been attractive, and researchers have looked at many body fluids and sites over the years, including sweat, saliva, the skin and the eye. The eye drew attention because tears contain glucose and a contact lens can sit in them.
This article is history. It does not say whether any approach is suitable for managing diabetes, and anyone with the condition should rely on devices their clinician recommends.
The scientific starting point
Glucose in tears had been measured in laboratory studies for many years, and the results suggested that tear glucose tends to rise and fall with blood glucose. The relationship, however, was loose. Tear glucose is present at far lower concentrations than in blood, and the delay between a change in the blood and a change in the tears can be uneven. Collection of tears can itself change their composition, for example through irritation.
From these findings came two hopes: that a sensor in the lens could track the trend, and that a lens would be a comfortable platform for it. Both are reasonable ideas, but they depend on the link between tears and blood being strong enough to guide health decisions, which remains unproven.
Early lens prototypes
Research groups in universities began reporting lens-based glucose sensors in the 2000s. Many were optical: a lens containing a molecule that changes its fluorescence when it binds glucose, read out with a handheld instrument. Others were electrochemical, based on the enzyme approach used in blood glucose test strips. In the late 2000s and early 2010s, work on flexible circuits and wireless power opened the way to lenses that could include a tiny sensor and an antenna.
A line of research at the University of Washington, led by Babak Parviz, explored lenses with electronics, and Parviz later moved to the technology company that would announce the best-known glucose lens project. Other academic groups kept working in parallel, including teams in Korea, the United States and Europe.
The 2014 announcement
In January 2014, Google announced that it was developing a smart contact lens to measure glucose in tears, using a tiny glucose sensor and a wireless chip sandwiched between two layers of lens material. The prototype was described as having an antenna thinner than a human hair. Later that year, a pharmaceutical company with an eye care division announced an agreement to license the technology, with the aim of developing it into a product. The project was later placed under a life sciences unit, Verily.
Public attention was intense. News stories described it as a possible replacement for finger-pricks. The company’s statements emphasized that the project was at an early stage and that many questions remained, though media reports often skipped that part. Prototype lenses were reported to have been tested in small clinical studies, but detailed results were not widely published.
The setback
In 2018, the life sciences unit announced that it would not continue the glucose lens project. Reports at the time said that the lens had not been able to show a reliable enough relationship between the glucose reading from tears and the level in blood. In the same period, other approaches to continuous monitoring were moving ahead quickly: small sensors worn on the skin that measure glucose in the fluid beneath it were becoming widely used, making the lens a harder sell. These skin-worn systems, in turn, are used with insulin delivery in closed-loop systems, a development that changed expectations about how glucose should be tracked.
The ending was an instance of a familiar pattern in medical technology. A clever idea attracted attention and large investment, ran into a scientific obstacle that was not fully visible at the start, and gave way to a different approach.
What has reached the market
To date, no contact lens that measures glucose has been approved and widely sold as a medical device. The lens products that exist on the market are for correcting vision, plus a lens that records changes in eye pressure, used in some clinics. Prototypes continue to appear in journals, often with new materials or improved sensors, but moving from a prototype to a regulated device requires evidence of accuracy, safety over long wear and benefit to patients.
The wider diabetes context
The glucose lens story belongs beside other developments in diabetes care. The insulin discovery of the 1920s changed the outlook for people with the condition, and the following century brought home blood testing, insulin pumps and, more recently, continuous sensors. Some devices, such as implantable drug pumps, were developed in research programs for delivering insulin, though they have been used only to a limited degree. The lens was an attempt to join this line, which is why it attracted attention far beyond ophthalmology.
Wearable devices that measure health data, such as wearable watches, have also prompted interest in glucose sensing without needles. Claims for such devices have sometimes run ahead of the evidence, and regulators in several countries have warned consumers about products that claim to measure blood glucose without a validated method.
A measured conclusion
The glucose-sensing lens is a good example of why history is useful in reading technology news. The chemistry is real, the engineering was impressive, and the goal was worthwhile. Yet the work ran into limits that engineering alone could not remove, and for now the lens has not become a medical tool. Whether improved sensors or new analysis methods will change that is uncertain.