Smart contact lenses: what is authorised, what is tested and what is still a prototype

This article is general information, not medical advice.

A smart contact lens is a soft lens with tiny electronics added. Some designs carry a sensor that reacts to something in the tears. Others carry a small antenna and chip, or a micro display that shows an image to the wearer. The attraction is easy to see: a lens that sits on the eye could, in principle, track health signals through the day without a finger prick or a separate device. The difficulty is that the lens has to stay comfortable, let light through and avoid irritating the surface of the eye, which makes it much harder to build than a wrist device.

This article separates three states. Some lenses are authorised for a narrow use. Others have been tested in studies, usually small ones. The rest are prototypes or ideas.

Authorised: a sensing lens for timing eye pressure checks

The only sensing lens with a regulatory authorisation that we could confirm in the sources we checked is Sensimed's Triggerfish. It is a soft lens that detects small changes in the dimensions of the eye over a day. The US Food and Drug Administration (FDA) received Sensimed's de novo request on 6 May 2014 and classified the device on 4 March 2016, according to the FDA's classification letter, which was reissued on 21 April 2016 to correct the original order. The FDA created a new device type for it, the "diurnal pattern recorder system", in Class II. The public announcement came in March 2016, as reported by startupticker.

The authorised use is narrow. Triggerfish is a prescription device for patients aged 22 and over. It is meant to find the time window, over a maximum of 24 hours, when eye pressure peaks, so that pressure can then be measured by conventional clinical methods. The FDA's decision summary calls it an adjunct to standard eye pressure testing and says diagnostic and treatment decisions should rely only on traditional tools. The device does not actually measure eye pressure and is not intended to be a diagnostic tool, according to the startupticker report. Its output is in arbitrary units, not a pressure reading in millimetres of mercury, as a 2012 trial report states.

The evidence in that trial is modest. It reported 40 people, 21 with suspected glaucoma and 19 with established glaucoma. Each wore the lens for two 24-hour sessions one week apart. Across the full day, the patterns from the two sessions correlated at 0.59 in the 36 people with complete data, which the authors describe as fair agreement. For the daytime period alone the figure fell to 0.40. The trial recorded 151 adverse events. Of the 149 that investigators linked to the device, 142 were mild. Five were severe, all redness of the conjunctiva in two patients, and the authors report no serious adverse events. The sponsor, Sensimed AG, took part in designing the study. These are short-term results in a small group.

Tested in studies: lenses that read glucose in tears

Glucose can be measured in tears, but tear glucose follows blood glucose with a delay, and that delay differs from person to person. In 2014 Verily, the Alphabet life sciences company, teamed up with Alcon to develop a glucose-sensing lens. In November 2018 the companies shelved the project, as Engadget reported. Verily said that interference from biomolecules in tears made accurate readings hard to obtain, and that its clinical studies struggled to reach the steady conditions needed for reliable readings. At the time, it said it would continue two other lens programmes with Alcon, one for age-related long-sightedness and one implanted lens for use after cataract surgery. We have not checked their current status.

A later academic pilot, published in Nature Communications in 2024, is more encouraging. It used a wireless lens powered through near-field communication, so it needs no battery, which sends its data to a smartphone app. The human part of the study included 10 healthy and 10 diabetic participants, tested on days 1, 3 and 5. After the lens was put in, readings started once the tear film had settled for 10 minutes. The authors then fitted a personal time lag to each person's data. For a representative healthy participant the correlation with blood glucose was 0.97, and for a representative diabetic participant it was 0.95. The authors report a correlation above 0.9 for every individual. Healthy participants drank a soft drink with 54 g of sugar. The diabetic participants drank a nutritional drink instead, because of concerns about soft drinks for people with diabetes, so the two groups did not receive the same challenge.

Those figures need careful reading. The lag and the conversion from tear to blood glucose were fitted to each person's own data after the tests, so this is not the same as a lens predicting blood glucose on its own. The study covered 20 people, and the authors suggest further research over a longer period with more participants. They also say that an algorithm to set each person's lag automatically would first need further extensive human studies. A 2022 review of wearable glucose-sensing lenses describes animal tests in rabbits and reports no results from people wearing a lens.

Prototype or idea: lenses with displays

Mojo Vision developed a contact lens with a micro-LED display, which is a screen built from very small light-emitting diodes. According to company statements reported by Optometry Times in July 2022, its chief executive had worn the latest prototype, one lens at a time and for one hour at a time, and was then the first and only person to wear it. That is one person, reported by the company.

In January 2023 Mojo Vision stopped work on the smart contact lens, citing difficulty raising capital, and laid off around 75% of its staff. It said it would concentrate on its micro-LED display technology instead, and its news page now presents it as a micro-LED company. We found no multi-person trial of a display lens in the sources reviewed.

Limits and open problems

Accuracy. Tear glucose lags blood glucose, and substances in tears can interfere with readings. Any lens that claims to track glucose has to show that its readings hold up across days, people and glucose swings, not just in a short pilot.

Power and electronics. The 2024 pilot lens is powered wirelessly, but the sources we checked do not give a power budget for a continuously sensing lens or for a display, so we cannot say how close either is to practical use.

Comfort and eye safety. The 2022 review lists several concerns: electric current through the sensor can heat the eye, hydrogen peroxide made by some enzyme sensors may cause irritation, enzymes degrade over a short lifespan, and opaque electronics may block vision and reduce the oxygen reaching the eye.

Data privacy. The sources we checked do not say how data from these lenses would be stored, shared or protected. This will matter for any product that reads health signals from the eye, and it is not answered in the evidence reviewed here.

From prototype to product. Two lens programmes, Verily's glucose lens and Mojo Vision's display lens, ended in 2018 and 2023. Triggerfish is the only one covered here that has reached regulatory authorisation, and that use is narrow.

What to watch next

• Longer, larger tear glucose studies that report accuracy by glucose range and time of day.
• Peer-reviewed publication of full data for any new glucose or sensing lens.
• Regulatory decisions on sensing lenses beyond Triggerfish.
• Any published human trial of a display lens, since the Mojo Vision programme has ended.
• Clear rules for how health data from eye-worn devices is stored and shared.