A smart contact lens can repeatedly measure levels of the hormone serotonin in tears, offering a convenient and accessible way to monitor psychological stress.
It is applicable to commercially available soft contact lenses, allowing the innovation to be incorporated into existing technology.
Following the emergence of smart contact lenses as wearable biosensor platforms, researchers examined their value as an easily accessible medium for repeated serotonin sampling.
They further note that electrochemical measurements were performed primarily using a wired configuration rather than a fully integrated wireless contact lens, which may not fully reflect real-world on-eye deployment.
“With further development, wireless integration, and clinical validation, tear-based contact lens biosensors could enable noninvasive longitudinal monitoring of biochemical dynamics in daily-life settings,” the team suggested.
A smart contact lens can repeatedly measure levels of the hormone serotonin in tears, offering a convenient and accessible way to monitor psychological stress.
The “lab-on-a-contact-lens” platform, described in Science Translational Medicine, demonstrates how wearable diagnostic tools can be used to track health remotely.
It is applicable to commercially available soft contact lenses, allowing the innovation to be incorporated into existing technology.
“This work provides a foundation for future development of wearable, noninvasive ocular platforms for monitoring tear serotonin dynamics,” reported Minwoo Kim, PhD, from Terasaki Institute for Biomedical Innovation in Los Angeles, California, and co-workers.
Stress-related endocrine responses are critical for understanding human performance and mental health.
Conventionaly assessment relies heavily on self-report questionnaires, which can be subjective, or invasive sampling such as venipuncture.
Serotonin is a neurotransmitter that acts as a key regulator of stress and is commonly targeted in antidepressants. It is present in tears, but these are conventionally sampled invasively—involving test strips, microcapillaries, or sponges that can affect tear chemistry—and provide only snapshots of specific timepoints.
Following the emergence of smart contact lenses as wearable biosensor platforms, researchers examined their value as an easily accessible medium for repeated serotonin sampling.
The team created a soft hydrogel lens that integrated printable, stretchable electrochemical sensors to detect serotonin in tear fluid. An electrochemically refreshable redox surface restores the baseline between repeated measurements.
Firstly, Kim and co-workers calibrated the reversible lab-on-a-contact lens platform with artificial tears, which established a limit of detection of 72 picomolar and a dynamic range of 0.1 to 500 nanomolar.
The lenses were able to maintain function and stability for more than four weeks in a tear-like environment as the lenses underwent repeated flipping, folding, stretching, and twisting.
Safety and biocompatibility in eyes were demonstrated through assessment in pigs, with tear serotonin concentrations in a mouse model of chronic stress inversely correlating with cortisol in both serum and tears.
A first-in-human pilot study involving 30 participants revealed that the lenses captured serotonin changes in tears during stressful tasks such as speaking and arithmetic, supporting the relationship between tear serotonin and stress.
However, the researchers acknowledge that these human tests were “offline” and did not involve the participants wearing the lenses.
They further note that electrochemical measurements were performed primarily using a wired configuration rather than a fully integrated wireless contact lens, which may not fully reflect real-world on-eye deployment.
“With further development, wireless integration, and clinical validation, tear-based contact lens biosensors could enable noninvasive longitudinal monitoring of biochemical dynamics in daily-life settings,” the team suggested.
“Such platforms may complement existing approaches for assessing stress-related physiological changes, support personalized monitoring, and expand the role of SCLs beyond vision correction toward wearable diagnostics and remote health monitoring.”
