A prototype contact lens can flag how stressed you are by reading serotonin levels in your tears.
Engineers built a soft contact lens fitted with a biosensor tuned to detect serotonin, the neurotransmitter tied to mood, in tear fluid. The idea builds on years of attempts to turn contact lenses into wearable health sensors, following earlier prototypes aimed at glucose and eye pressure. Because the sensor sits directly on the eye, it can in theory pick up chemical signals continuously, without a blood draw or a lab visit. The result, reported by IEEE Spectrum, is a lens that could double as a stress gauge.
That matters because stress monitoring today is mostly self-report: surveys, mood apps, or a smartwatch inferring anxiety from heart rate variability. A lens reading an actual neurotransmitter would be a more direct signal, if it holds up outside a lab. That is a big if, and the kind of claim that has sunk smart contact lenses before.
Google's glucose-sensing lens, developed with Novartis, spent years in development before the companies quietly shelved it in 2018 because the readings were not reliable enough. This lens is chasing a harder target than glucose, and it has the same road to walk from an interesting sensor to something a doctor, or an eye, can actually trust.