In an unprecedented animal research study, researchers at the Yerkes National Primate Research Center, Emory University, and the Atlanta VA Hospital have used magnetic resonance imaging (MRI) to produce images of the eyeÕs retinal layers. The research, which will publish in an online Early Edition of the Proceedings of the National Academy of Sciences, has the potential to revolutionize the way retinal degenerative diseases, such as retinitis pigmentosa, glaucoma, age-related macular degeneration and diabetic retinopathy, are diagnosed and treated. Accelerating detection and treatment of such diseases ultimately could help prevent vision loss.
"Currently available technologies for capturing images of the retina, such as fundus photography, allow doctors to view only surface vessels and structures," said lead researcher Timothy Q. Duong, PhD, director of magnetic resonance research at Yerkes and associate professor of neurology and radiology at Emory. "The most serious retinal diseases that cause vision loss, however, attack various cellular levels within the retina. Consequently, these diseases often are diagnosed only in the late stages, after irreversible damage has occurred," he continued.
To penetrate the deep layers of the retina and produce clear images, Dr. Duong and his research team made significant improvements in spatial resolution and sensitivity using YerkesÕ state-of-the-art MRI technology. These improvements enabled them to non-invasively image structural oxygenation and functional changes in the rodent retinas and detect layer-specific changes in an animal model of retinitis pigmentosa, a degenerative disease that affects approximately 1.5 million people worldwide.
This technology also is applicable to other retinal diseases, which affect approximately 10 million Americans. For example, glaucoma causes gradual degeneration of cells of the optic nerve layer, which carries visual information from the eye to the brain. Also, age-related macular degeneration affects the part of the eye responsible for sharp central vision, and diabetic retinopathy is a common complication of uncontrolled diabetes and is the leading cause of blindness in people under 70.
"Because MRI technology is noninvasive and currently is used on people worldwide, extending this technology to imaging the retina should advance rapidly. Moreover, MRI has the unique advantage that it can provide useful physiological information, including structure, blood flow, oxygenation and function in a single setting," Dr. Duong noted. "The long-term goal is to bring this technology from the laboratory to the clinic where it may help prevent disease progression and vision loss through early diagnosis and intervention, and better monitoring of treatment." The next step is to test MRI retinal imaging in people. One of the challenges will be to find a way to reduce eye movements that can distort the MRI image. "We need to develop imaging protocols that capture information faster than the human eye can blink and co-register the time-series images in real time for diagnostic purposes," Dr. Duong concluded.
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