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Researcher takes glaucoma detection personally

BioPhotonics
May 2010
Krista D. Zanolli, krista.zanolli@photonics.com

AMES, Iowa – A new test is being developed that could revolutionize the diagnosis of glaucoma by detecting the disease years earlier than is currently possible. And for Chenxu Yu, an assistant professor at Iowa State University who headed the study, this development hits particularly close to home.

“Roughly a year ago I visited an eye specialist who told me I was at high risk for glaucoma, but due to the limitations of current detection methods, he couldn’t tell me whether or not I actually had the disease,” Yu said. “Of course, this sparked my interest. The doctor [Nicholas Hamouche] and I began to talk about working together to explore new methods for early detection.”

Glaucoma is a disease that attacks the optic nerve, leading to a gradual loss of vision over a long period of time. Glaucoma usually occurs as a result of fluid pressure inside the eye slowly increasing over time, but unfortunately there are no obvious warning symptoms that would prompt a patient to see a doctor. Once lost, this damaged visual field can never be recovered. And, with 70 million people worldwide (2.2 million in the US) affected by this disease that has no cure, early detection is king.


A person with advanced glaucoma could have this view of the world, a risk that might be reduced by a new early diagnostic test for the common eye disease. Image courtesy of National Institutes of Health.


Scientists at Iowa State University are among the first to explore the potential of using Raman spectroscopy for early detection and characterization of this common eye disease.

“We are confident that we’re moving toward a breakthrough that will allow us to detect glaucoma at its earliest stage,” Yu said. “We hope it will benefit millions of glaucoma patients and individuals at risk for this devastating eye disease worldwide.”

Currently there are two main techniques used for detection – tonometry and ophthalmoscopy. Tonometry measures eye pressure by gently touching an instrument to the outer surface of the eye, while ophthalmoscopy uses an ophthalmoscope to look directly through the pupil at the optic nerve.

“All too often, these tests detect glaucoma after the disease has been silently causing damage to the optic nerve,” Yu explained. “We need ways of diagnosing glaucoma earlier, before permanent damage has occurred, so that patients can begin taking medication to control it.”

Along with Yu and Hamouche, who is a glaucoma specialist at the McFarland Clinic, the research team included Dr. Sinisa Grozdanic, a glaucoma researcher and director of animal research for the Iowa City Veterans Administration Center for Prevention and Treatment of Vision Loss (VACPTVL); Qi Wang, a doctoral student at the university; and Drs. Matthew Harper and Helga Kecova, research scientists at VACPTVL.

The team chose to use Raman spectroscopy because it provides rapid in vivo biochemical characterization of tissue and bodily fluids in a nondestructive and noninvasive fashion. In this study, the method involved shining a beam of infrared laser light (invisible to the human eye) through the pupil of the eye. The optic nerve cells inside the eye scatter the light, producing a spectrum pattern that reveals the chemical composition of the cells, allowing scientists to identify biochemical changes in the cells that indicate glaucoma.

According to Yu, the technique detected glaucomatous changes in the retinal tissue of dogs with 90 percent accuracy. The next step will be in vivo study of dogs and, if all goes well, they can begin looking at potential clinical trials in humans. According to the team, this new technique could be ready to be used in eye doctors’ offices within five years.

“This is a very promising technique,” Yu said. “We are very excited about the results so far and look forward to additional studies.”


GLOSSARY
light
Electromagnetic radiation detectable by the eye, ranging in wavelength from about 400 to 750 nm. In photonic applications light can be considered to cover the nonvisible portion of the spectrum which includes the ultraviolet and the infrared.
ophthalmoscope
Also referred to as a funduscope, an ophthalmoscope is a specialized instrument used by ophthalmologists for observing and photographing the fundus (interior) of the eye which includes the retina, macula, fovea, optic disc, macula, and posterior pole. The ophthalmoscope consists of a concave mirror with an orifice at the center through which the viewer examines the eye. A light source is then reflected to the eye from the mirror. A set of lenses are then rotated in front of the hole in the...
ophthalmoscopy
Also referred to as fundus photography, ophthalmoscopy is the dioptrical study of the various interior components of the eye such as the macula, fovea, and opticdisk,  and is overall essential in determining the health of the retina and vitreous humor.
pupil
1. In the eye, the opening in the iris that permits light to pass and be focused on the retina. 2. In a lens, the image of the aperture stop as seen from object and image space.
raman spectroscopy
That branch of spectroscopy concerned with Raman spectra and used to provide a means of studying pure rotational, pure vibrational and rotation-vibration energy changes in the ground level of molecules. Raman spectroscopy is dependent on the collision of incident light quanta with the molecule, inducing the molecule to undergo the change.  
vision
The processes in which luminous energy incident on the eye is perceived and evaluated.
visual field
The angular field of view that is seen by the eyes when fixed on a point straight ahead. The normal binocular visual field is approximately 130° in diameter.
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