Continuous Glucose Monitoring with "tears"
"I heard it on NPR, and I saw it in the Washington Post, and I was hit with multiple emails: a contact lens that can measure glucose in tears! Absolutely amazing and unbelievable! Apparently, Google has developed a computer chip with a sensor that can measure blood glucose levels in tears every second. In addition, Google plans to integrate a LED so that the wearer of these special contact lenses can be notified if blood sugars are out of range. The LED would light up with a "shimmering" look that would indicate that the glucose levels have crossed certain thresholds. The contact lens is apparently powered remotely using a five millimeter-long antennae printed on the lens to receive gigahertz range radio frequency energy from a transmitter placed ten centimeters from the eye. The copper circle around the edge of the lens is most likely an inductive charging coil. Future use of this contact lens will most likely require a face mounted charging antennae. The electronic components are sandwiched between two layers of contact lens material so nothing is touching the eye." (http://googleblog.blogspot.com/2014/01/introducing-our-smart-contact-lens.html) Of course this new technology has yet to be approved by the FDA; however, I understand that multiple trials have been conducted successfully. There are both advantages and disadvantages to this technology.
The advantages are obvious:
1. NO finger pricking to obtain blood sugars.
2. NO glucose meters to carry at all times.
3. NO sensor that has to be placed on any other part of your body.
4. Perhaps more accurate correlation of tear glucose with the actual blood glucose.
5. The sensor is really tiny!
6. Less risk of skin irritation from the sensors.
7. Perhaps easy to change every day as is typical for contact lenses.
8. Fascinating use of technology.
What are the disadvantages?
1. Putting anything on your cornea is not easy- it takes practice and skill; and some individuals simply cannot wear contact lenses.
2. It will be quite a bit of time before the FDA gives approval for this device.
3. Concerns about the correlation of tear glucose with blood glucose- What is the correlation? And will the tear glucose lag behind the blood glucose as interstitial glucose lags behind by 20 minutes?
4. Will the wearer be able to act based on the tear glucose and bolus insulin accordingly?At present, it is recommended that the glucose readings from the CGM are indications that one should actually perform a glucose check with the glucometer. The CGM provides glucose trends and not the actual blood glucose with arrows on the CGM sensor as a visual cue.
5. Will diseases of the eye prevent accurate measuring of tear glucose such as conjunctivitis or there is decreased tear production?
6. What will be the cost of multiple contact lenses?
7. Who will prescribe the lenses? Will it be the pediatric endocrinologist, opthalmologist, or another type of medical professional?
8. Another difficulty may arise in children who do not have the physical dexterity to insert a contact lens.
9. How often will they need to be changed? Daily, weekly?
This is an exciting device and I am looking forward toward its implementation! Keep in mind that 30 years ago we were using chemstrips to measure blood sugar and just starting to introduce glucometers. Prototypes of Insulin pumps appeared shortly thereafter and continuous glucose sensors were then developed.
In summary, until there is a cure, we need to focus on improving the technology and care of people with diabetes and even more importantly, quality of life!