April 01, 2013
2 min read

New glaucoma screening tool may allow for earlier diagnosis

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A new screening test for glaucoma currently in development uses unique properties inherent in a recently discovered retina cell to help clinicians more accurately identify patients eligible for early intervention.

The test is designed to exploit intrinsically photoreceptive retinal ganglion cells (ipRGC), which react slowly to changes in light, according to a press release distributed by the Ohio State Center for Clinical and Translational Science.

“Tests for glaucoma, particularly those that rely on quick exposure to bright light and subjective human observation or feedback, may actually be missing the early signs of glaucoma,” Andrew Hartwick, OD, PhD, said in the release. Hartwick is an assistant professor at the College of Optometry at the Ohio State University and is leading the research to find a more sensitive screening tool.

“By the time someone has detectable symptoms of glaucoma, irreversible damage has likely already occurred,” Hartwick said in the release. “We know there’s probably a lot happening on a microscopic level in the early stages of the disease that we just can’t detect yet.”

IpRGCs represent less than 1% of ganglion cells in the retina but play a critical role in communicating the presence of light to the brain in ways that affect the sleep cycle and pupil size, according to the release.

From what researchers know about these cells, the slow response time to light indicates that these cells are unable to distinguish between flickering and continuous light, which are intrinsic factors for two glaucoma tests. That means these tests will not pick up deficits in the slower-reacting ipRGCs, the release said.

“The primary problem with the visual field test is that it relies on people to accurately report what they are seeing, and that doesn’t always happen. Secondarily, the test uses flashes of light that stimulate other cells in the retina, but doesn’t tap into the slow ipRGCs, where you might be able to sensitively detect a change in response because there are so few of them,” Hartwick said in the release.

“We’ve shown that we can isolate the ipRGC response from other photoreceptors in healthy patients and that we can quantify those responses objectively with technology that’s already used in many optometrists’ and ophthalmologists’ offices,” he said.

Hartwick has applied for and won KL2 funding from the Ohio State’s federally funded Center for Clinical and Translational Science to test his hypothesis and create an objective pupil test that could measure ipRGC function, according to the release. – by Daniel R. Morgan