Recent advances in medical technology have facilitated the integration of wireless communication and portable devices to promote improved health monitoring. In the field of diabetes, many patients are becoming more experienced with using advanced technology in both insulin delivery and the monitoring of blood glucose. New to the proposed technology toolbox is a smart (soft) contact lens capable of monitoring glucose in tear fluid and other relevant physiologic data in real time, thus facilitating disease management.

While previous efforts have been made to launch smart contact lenses, criticism over the opacity and rigidity of the material, which could potentially damage the eye, resulted in a seemingly insurmountable barrier to success. That is, until now. Scientist Jihun Park and colleagues from South Korea at the Ulsan National Institute of Science and Technology have developed a new device that has been tested on rabbits, and the findings were published in January 2018 in Scientific Advances.

The earlier concerns about the rigidity and potential damage to eye tissue have been addressed by the research team. They accomplished this by placing the operational components (including the glucose sensor, flexible wires, and antenna) around the edge of the lens and away from the pupil. When glucose is elevated, the LED light turns off and the user can look in the mirror to view this change. Although current research has focused on the ability to detect glucose changes in the tears, the lens in this study is equipped with sensors that can collect other biomarkers found in the blood, such as cholesterol, sodium ions, and potassium ions, thus potentially providing additional monitoring capacity.  

Researchers point out that the collection of the tears in the lens results from natural secretion and normal activity, such as blinking, thereby avoiding invasive collection methods such as finger sticks for blood samples. The team states that the difference in the amount of glucose in the tears when compared to that found in the blood was factored in. According to the scientists, average glucose levels of tears for nondiabetic subjects range from 0.2 to 0.6 mM. This average can exceed 0.9 mM for people with diabetes, however, and lag time between tear glucose levels and blood glucose levels can also range 10 to 20 minutes, which was also factored into the study.

While acknowledging that more work must be done before the prototype can be used in the human eye, the team sounded optimistic about the future, writing, “The in vivo tests using a live rabbit, including the monitoring of the temperature change on the rabbit’s eye, provided the substantial promise of future smart contact lenses for noninvasive health care monitoring using human eyes and tears.”

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