An Eye-Changing Experience

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Researchers, and many people with diabetes, are constantly looking for alternatives to the long-standing practice of pricking fingers to obtain blood for glucose monitoring. While other ways of checking glucose levels exist — such as wearing a continuous glucose monitor (CGM) — no actual alternative to “fingerstick” tests has emerged from years of research. (CGM readings must be confirmed by a meter reading before any action, such as an insulin injection, is taken.) So chances are that a new and somewhat quirky technology won’t be replacing blood glucose meters anytime soon.

But if it did somehow become a plausible alternative to meters, this innovation would certainly be eye-catching: A team of researchers at the University of Akron in Ohio has developed contact lenses that change color based on the glucose level of tears, which constantly circulate on the surface of the eye even when a person is not crying. According to an article in the Daily Mail (UK), researchers created the color-changing system by combining dyes with special “designer” molecules called probes. The probe molecules were designed to be attracted to, and combine with, glucose molecules — so that when a glucose molecule combines with a probe, this reaction releases the molecule of dye that was attached to the probe. The resulting color change would only be visible to other people or by looking in the mirror.

Of course, the color-change mechanism begs the question of whether any dye molecules might leak from the contact. As the researchers note, further studies on this question would be needed to determine that the contacts are safe before they are sold to the public. Also important, of course, is the question of whether the contacts would be an effective source of glucose readings. Since a subtle color change might not be detectable to the human eye, the researchers are developing a smartphone app that they hope will be able to translate colors into estimates of blood glucose levels.

But existing technologies — such as CGM — that measure the glucose concentration of bodily fluids other than blood have proved not to be as reliable as blood glucose meters at providing real-time readings. As David Spero notes in his recent blog entry “Does Self-Monitoring Have to Hurt?” there is often a lag of 20–30 minutes between the fingertip blood glucose level and the blood glucose level as measured just under the skin of other areas of the body. This is why fingertips are used for blood samples rather than, say, the upper arms. Since tears are not even blood at all, they may prove not to be a reliable enough indicator of the current blood glucose level — even assuming perfect accuracy of the contacts and smartphone software. Since even blood glucose meters are not 100% accurate — many manufacturers claim a margin of error no smaller than 20% — it seems doubtful that color-changing contacts could ever be used to make self-care decisions such as how much insulin to inject or glucose to consume.

But it’s still fun to consider the possibilities. If it worked reasonably well, could you see yourself using a product like this one? Would you consider color changes in public or in front of company to be a drawback, a nonissue, or perhaps even a benefit of this technology? If given the option, would you rather stare into your phone than prick your finger for a glucose reading? Do you find taking blood samples from your fingers especially painful or cumbersome? Leave a comment below!

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