Schrader W. F.

Universitätsaugenklinik, Würzburg

The eye is a good target for the optical determination of ist anatomic structures, but also for functional measurements. With the application of spectrometric methods the range for further diagnostic methods can be expanded. The anterior chamber of the eye is accessible for the examination of its optical properties within a spectral range between 350 and 1300 nm and 1600 to 1800 nm. The non inavasive determination of the glucose content is choosen as an example to demonstrate the possibilites and limits of these non invasive methods. To examine, how the glucose concentration in the anterior chamber of the eye is mirroring the blood glucose levels, we determined both concentrations just before intraocular surgery with classical methods (hexokinase method). The glucose concentration in the aqueous humor is about 75% of the plasma levels and is highly correlated with it. However the spectrometric determination of serum glucose levels requires an individual calibration: We used the reflection on the anterior surface of the lens (3rd Purkinje picture, 0.3‰ of the radiation) to register spectra in the UV-, VIS- and NIRrange. We succeeded to determine glucose concentrations with a standard deviation of ±30 mg / dl. So far this is not enough to recognize potential life threatening situations caused by very low or very high glucose levels. We also tried to determine glucose concentrations with other optical methods as polarization. This is basically possible with blue light, but is technically too difficult to realize. In conclusion, the anterior chamber of the eye offers a valuable target for non invasive spectrometirc measurements. The non invasive monitoring of blood glucose levels is possible but not yet clinically available. A lot more of scientific work is necessary.

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