February 28, 1997
IU First To Isolate Method To Track Blood Flow To Optic Disc, Nerve
INDIANAPOLIS-- Researchers at the Indiana University School of Medicine are the first to discover a consistent method to measure and quantify blood flow to the optic nerve and optic disc, information that may revolutionize the treatment of glaucoma.
Glaucoma, one of the leading causes of blindness in the U.S., was thought for l 00 years to be caused by pressure buildup in the eye. Research now shows that nearly 60 percent of individuals with glaucoma have normal eye pressure. Since that discovery considerable research has focused on circulation in the eye as a possible contributing cause for the disease. During the past 10 years researchers have developed the precision instruments necessary to measure and quantify blood flow to the retina. But, until recent research at IU, the procedures for measuring blood flow to the minute optic disc and optic nerve remained elusive.
By developing special software and customizing a laser optical system, Alon Harris, Ph.D., director of the Glaucoma Research and Diagnostic Center at IU, and his team were able to utilize an argon laser to scan the most tiny vessels in the eye, measure the blood flow and quantify the circulation to the optic nerve, disc and retina. An infrared laser and dye are used to measure deeper into the eye, penetrating the choroid which is located behind the retina and optic nerve and a major site of blood flow to the eye. Previously, researchers were unable to accurately quantify blood flow in these vessels.
Dr. Harris, who is an associate professor of ophthalmology and of physiology and biophysics at the IUSM, said the discovery could lead to the restoration or improvement of vision in some glaucoma patients. He will present the findings at the upcoming meeting of the Association for Research in Vision and Ophthalmology, May 1 1- l 6, in Ft. Lauderdale, Fla.
"Up until now, we didn't have an accurate way to quantify the blood supply to the optic nerve and, a key point is, that is a site of damage in glaucoma," Dr. Harris said. "With existing technology and other technology, we have found a way to quantify the blood flow."
The IU research will allow physicians to pinpoint the affected area of the eye and be able to prescribe the appropriate medications, such as calcium channel blockers, to stimulate blood flow to the involved vessel and tissue.
The tools used to measure ocular blood flow for glaucoma patients also may be applicable in the treatment of other eye diseases such as macular degeneration, and those caused by diabetes and AIDS, Dr. Harris said.
Dr. Harris said approximately 3 percent of the U.S. population has glaucoma; 65 percent of those are over the age of 65. Glaucoma results in the "cupping" of the optic disc which results in a loss of vision. The vision loss worsens as the "cup" becomes deeper over time eventually leading to blindness.
Dr. Harris cautioned that the "eye puff" test which is commonly administered at many eye care practitioners offices may give individuals a false sense of security. Since that test only measures pressure in the eye, over half of all glaucoma patients would not be detected since eye pressure is not a symptom for them.
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