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Eyes give easy access to glucose levels

11 Jul 2008

People with diabetes could soon have a non-invasive way of measuring their glucose levels if a clinical trial underway in the UK proves successful.

A clinical trial that is comparing the performance of a laser-based glucose sensor against gold-standard testing methods has been launched in the UK. The non-invasive optical device measures glucose levels by shining a low-power laser beam into the eye, and can record other important information such as the thickness of the cornea and the lens.

"Our sensor provides information on more than just glucose," Dan Daly, co-founder and director of Lein Applied Diagnostics told optics.org. "We also get dimensional information that can be used by opticians and optometrists. This takes us from being a company focused on glucose, to a company looking at various diagnostics via the eye."

Current estimates put the number of people with diabetes across the globe at 240 million. To check their glucose levels, these people traditionally use a "finger stick" to draw a tiny spot of blood, an invasive process that often needs to be performed several times a day. The annual global finger-stick market has a value of around $7 billion.

"We decided very early on that the skin was not the place to make a non-invasive glucose measurement. It is simply too variable," explained Daly. "We quickly realised that the eye was the ideal place to measure glucose."

According to Daly, the three main areas in the eye where glucose measurements can be made are the anterior chamber (the part of the eye between the cornea and the lens, which is filled with aqueous humour), the tear film and the retina.

Lein's current prototype measures around 9 x 5 x 5 inches and relies on just 11 microwatts from a 785 nm laser diode in a confocal arrangement. The beam is scanned and reflections from various parts of the eye are gathered and used to calculate the glucose level. Each scan takes around 1/8 of a second.

"The meter helps the patient get into the right position and tells them how well aligned they are." added Daly. "Importantly the meter analyses the data in real time, so can reject data if the patient is misaligned."

Until now, Lein's prototype has only been tested against finger sticks but the new trial at the Royal Berkshire Hospital, Reading, UK, will see it pitted against a gold-standard venous blood meter. "We will test 30 patients over a period of 4 hours every 15 minutes to compare the performance of all the technologies," said Daly.

Assuming the trial goes well, the next step for Daly and his team is to build a hand-held unit roughly the size of a mobile phone and put that through clinical trials in both Europe and the US.

The company is now expanding its platform technology into new markets. "These are exciting times for Lein. Key players in the ophthalmic market are interested in our measurements and pharmaceutical companies have identified ways in which we can use our technology to detect levels of drugs in the body via the eye," concluded Daly.

Author
Jacqueline Hewett is editor of Optics & Laser Europe magazine.

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