New contact lenses may help diabetics monitor blood sugar levels

• Contact lenses that change their appearance according to the wearer's blood-sugar level could one day help people with diabetes keep track of their levels non-invasively, new research suggests.
• Diabetes affects the body's ability to make or use the hormone insulin, which can cause dangerously large swings in levels of blood sugar, or glucose.
• Currently, most people suffering diabetes monitor their blood sugar by pricking their skin and drawing blood.
• But Chris Geddes, the study's lead author and associate director of the Center for Fluorescence Spectroscopy at the University of Maryland, US, has tried to create less painful alternatives.
• Developing a monitoring system through contact lenses makes sense because many people with diabetes also need glasses or contact lenses due to the way diabetes affects the blood vessels in the retina, Geddes says.
• Moisture from the tear ducts contains glucose that binds with the molecules of boronic acid, with the reaction causing fluorescence.
• When they were working on the contact lens, Geddes and his group hit a snag early in the development phase.
• "We had to go back to the drawing board and design molecules that used boronic acid yet survived in a mildly acidic environment," Geddes says.
• Another sugar - fructose - is present in tears, but it exists in much lower concentrations so Geddes says it should not interfere with the glucose readings.
• Most people with diabetes have gaps of hours in between their skin prick tests, so a contact lens approach would still be a more timely and convenient method.
• GlucoWatch, which is worn on the wrist, applies a small electrical current to the skin, drawing the fluid between cells through the skin to test it for glucose.