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Eye sensor simplifies glucose tests

07 Oct 2005

Optical sensor could offer diabetics a convenient alternative to blood testing.

Blood glucose measurements could be as simple as holding a small sensor up to a person’s eye and pressing a button if a UK start-up is successful. Lein Applied Diagnostics is developing an optical sensor that determines the glucose level of a diabetic via the eye’s aqueous humor.

The attraction of the technique is that it involves no drawing of blood, is rapid (0.1s), and requires no consumables aside from a battery. In contrast, glucose measurements are currently performed by pricking the finger and placing a finger stick with a blood sample into a small analyser 4 or 5 times a day. The problem is that this approach is that is painful, inconvenient and can be unhygienic.

“The goal is to have a non-invasive device that is quick and easy to use,” Dan Daly, a director of Lein Applied Diagnostics, told attendees during a Biophotonics seminar at the Photonex 05 trade show yesterday in Coventry, UK. “Other people have explored optical techniques but they nearly all go through the skin. The problem is that the skin’s properties are very variable due to changes in temperature and sweat for example, and this leads to inconsistent measurements.”

Lein was formed in May 2003 by Daly and Graeme Clark, two former telecoms professionals working for PerkinElmer and Agilent Technologies. The firm has filed two patents for its idea and built a lab-based prototype device. It is working closely with SIRA, the University of Manchester and the Institute of Photonics at the University of Strathcylde.

To protect the firm’s IP, Daly wouldn’t go into details concerning the optical design but explained that the meter uses a confocal arrangement to localise the measurement in the anterior chamber of the eye. Light from a low power 670 nm source is focused into the eye and the intensity of the light reflected back is analysed. From this analysis the glucose level in the body is obtained.

“The glucose concentration in the aqueous humor is about 80% of that of blood and tracks it with a time lag of no more than 5-10 minutes,” said Daly. “We’ve tested a couple of dozen people and now want to extend testing to a large sample and build a more advanced prototype.”

According to Daly, the technique is inherently safe as it requires an optical power in the microwatt level and the measurement time is only about 0.1s. He also believes that it should be compatible with contact lenses.

Making Light Work In Healthcare was a biophotonics technology seminar at Photonex 05. It was jointly organized by the Photonics Cluster (UK) and the University of Strathcylde.


Oliver Graydon is editor of Optics.org and Opto & Laser Europe magazine.

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