Diabetes mellitus

Diabetes is one of the most common diseases of the modern affluent society. According to the International Diabetes Federation (IDF) an estimated 170 Mio. people world wide are affected by this disease. The body of a Diabetes patients is not or only partially able to control the blood sugar level (glucose level). Hence the patient has to measure his glucose level several times a day in order to maintain his diet or to inject insulin to control the level in difficult cases.

These days the measurement of the glucose level is usually done by extraction of smallest amounts of blood. To do so the skin has to be perforated first. This results in a significant strain of the affected skin due to the frequent measurements.

Glucose Monitor

Hence the objective of the sub-project glucose monitor is to develop a compact non-invasive measurement system which increases the acceptance of more frequent measurements as well as the quality of life of the patients significantly.

The measurement itself will be based on a non-contact optical method which is explicit correlated to the blood glucose level.

This intelligent sensor will be integrated into the Personal Health Monitor and is to enable well funded long term analysis of blood sugar level. It is to allow new therapy types as well as to decrease long term damages caused by Diabetes.

Measurement principle

Especially optical measurement schemes are well suited for these non-invasive / non-contact measurement tasks. An intriguing measurements spot with excellent optical properties is the anterior chamber of the eye. The enclosed liquid, the Aqueous Humor, mainly consists of blood serum and hence reflects the blood sugar level to a certain amount considering a short time delay.
Respecting laser safety regulations a measurement light beam can be directed onto the lens of the eye. The reflected beam hence passes through the Aqueous Humor twice and can be detected outside. Analysing this light the glucose level of the Aqueous Humor can be measured and the blood sugar lever can be calculated.

There are two optical characteristics of the glucose molecule which can be well utilized for such measurements:

Absorption
Different wavelengths of the measurement beam will have certain absorption levels depending on the glucose concentration. Using spectral analysis of the reflected light the glucose concentration of the Aqueous Humor can be calculated.
Optical Activity
The polarisation properties of light passing through the Aqueous Humor is influenced according to its glucose concentration. This effect (rotation of the polarisation plane of the incoming light) can be measured by a precise Polarimeter. Again the reflected light is analysed and the glucose concentration can be calculated.

Both effects are being examined within this project