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Implant Developed to Measure Pressure Causing Glaucoma

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26 August 2014. Biomedical engineers at Stanford University in California and Bar-Ilan University in Israel designed an implanted device for people with glaucoma to take frequent and accurate measures of high pressure inside their eyes, a factor closely associated with glaucoma. The team led by Stanford bioengineering professor Stephen Quake and Bar-Ilan ophthalmologist Yossi Mandel published its proof-of-concept findings this week in the journal Nature Medicine (paid subscription required).

Glaucoma is the name given to a collection of eye conditions that result in damage to the optic nerve that in advanced stages can lead to vision loss. In most cases of glaucoma, abnormally high intraocular pressure results in the optic nerve damage. According to statistics cited by Glaucoma Research Foundation, glaucoma affects some 2.2 million people in the U.S., accounting for 9 to 12 percent of all cases of blindness. Blindness from glaucoma is 6 to 8 times more common among people of African descent in the U.S. than Caucasians. It is also the second leading cause of blindness in the world, according to World Health Organization.

The device in development by the Stanford/Bar-Ilan team aims to offer people with glaucoma a convenient way of measuring intraocular pressure, which can provide clinicians with important data for prescribing treatments to reduce that pressure. Measuring intraocular pressure, however, is tricky since pressure readings can vary from over the course of a day and be affected by factors such as other medications, and even the individual’s posture.

The device developed by Quake, Mandel, and colleagues aims to make it possible for people with glaucoma to take their own measurements of pressure inside the eye, which in turn enables closer monitoring of this key factor. The authors cite a previous study showing close monitoring of pressure readings by people with glaucoma led to changes in treatments in up to 80 percent of those cases.

The device is primarily an ultra-fine microfluidic channel that allows fluid from the eye to enter on one end, with a tiny bulb of gas on the other end. Pressure inside the eye pushes the fluid through the channel against the force of the gas, with the length of the fluid in the channel serving as a gauge of pressure inside the eye.

The researchers designed the device to be implanted with an intraocular lens, a synthetic eye lens that replaces an individual’s natural lens to correct astigmatism or as part of cataract surgery. Once implanted, people with glaucoma could use their smartphone cameras or wearable devices — e.g., Google Glass — to take intraocular pressure readings. Tests with a U.S. Air Force vision test, say the authors, show no optical distortions.

Stanford University applied for a patent on the pressure-sensor technology. But the researchers want to reconfigure the device as a stand-alone implant, rather than rely on an intraocular lens.

“For me,” says Quake in a university statement, “the charm of this is the simplicity of the device.” Its simplicity, note the authors, should help make it ready for clinical trials in a few years.

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