High-tech contact lenses: Glucose monitoringSeptember 28, 2012
By Geoffrey W. Goodfellow, O.D., and Dominick M. Maino, O.D.
Patients with diabetes often must check their blood glucose levels using a drop of blood from a finger stick. Fortunately, most patients adapt to this diagnostic test and report that, although unpleasant, the repeated finger sticks are not terribly painful.
However, researchers at the University of Akron in Ohio are developing contact lenses that may make those finger sticks a thing of the past.
How do they work?
High glucose levels don’t just remain in the blood. They rise in other bodily fluids such as urine and tears as well.
Associate Professor of Chemistry Jun Hu has coated a contact lens with a chemical that reacts to glucose in tears, a chemical reaction that is similar to pH paper changes. The coating causes the lens to change color.
It’s this color change of the contact lens in response to the patient’s blood glucose levels that provides for a non-invasive measurement. (See photo.)
Hu developed a probe molecule that binds well to glucose.
The probe is then combined with a dye that causes the color change.
When glucose levels rise, the sugar binds to the probe and releases the dye.
Once the glucose in the tears returns to normal, the probe binds back to the dye, and the color returns to normal.
Patients wear the color-changing lens in only one eye.
The blood sugar is recorded by the patient using a smartphone to take a picture of his/her own eyes.
A free cell phone app compares the color difference between the two eyes to produce a blood glucose calculation.
“No special light source is needed; all you need is a smartphone with a camera,” said Hu.
What does this mean for the patient?
Hu reports that “the lens feels exactly like a regular contact lens because the molecules that we use to detect the glucose are [in] such a low concentration.”
This low amount of color also means that the patient’s vision won’t be affected in a significant way.
Hu’s team has been working on the glucose-sensing chemical since 2003, and he has held a patent for the idea since 2011.
Their recent work has been to ensure that the dye binds fully to the contact lens material and does not wash off.
Since the lenses are relatively inexpensive and the process is so non-invasive, it would be possible for a patient to check his/her glucose levels many times during the day, something not usually afforded by traditional finger sticking.
Is it a reality for my patients?
Even though the University of Akron has been using the innovation in its marketing campaign this past year, the lenses are still in the early phases of testing and not approved for human use.
It could be three years or longer before the glucose-sensitive lenses are available for commercial production.
All of the normal regulatory and funding difficulties of the research process apply.
Optometrists will want to exercise similar cautions with the lenses as they would while fitting any contact lens to a diabetic patient.
We know that the cornea in diabetics has decreased sensitivity, so the patient will become aware of contact lens problems much later than a person with normal corneal sensitivity.
There’s also the problem of diabetic corneas recovering and healing more slowly.
The color changing technology is up against other researchers who are working to outfit contact lenses with electronic sensors that can measure tear glucose levels and transmit the information to a wireless device.
Microsoft and the University of Washington are trying to solve some of the same bio-compatibility issues with their design.
No matter what the method, it seems that the familiar contact lenses that we routinely prescribe and fit may have a new purpose in the future.
This also means that the AOA and its state affiliates will need to ensure that optometrists are able to prescribe and/or fit these types of contact lenses.
Optometrists frequently prescribe and fit lenses for vision enhancement.
We also currently use contact lenses as therapeutic devices – fitting bandage contact lenses, implementing orthokeratology, or treating amblyopia or iris dysfunctions.
However, the use of contact lenses for diagnostic processes may require some legislative language changes in some states.
Dominick M. Maino, O.D. is a professor of pediatrics and binocluar vision at the Illinois College of Optometry (ICO) and a recipient of the Leonardo da Vinci Award of Excellence in Medicine. He can be contacted at email@example.com. Geoffrey G. Goodfellow, O.D., is an associate professor of optometry at ICO and the college’s assistant dean for curriculum and assessment. He can be contacted at firstname.lastname@example.org. Both practice in the ICO’s Illinois Eye Institute clinics.