The inexpensive test could lead to new drugs, researchers add
MONDAY, Oct. 15 (HealthDay News) -- A short and simple eye scan not only appears capable of spotting multiple sclerosis earlier in the course of the disease, but might also provide a way to track progression of the illness, as well as the effectiveness new drugs in development, researchers say.
"We're in the process of validating this [eye exam] for clinical utility," said Dr. Peter Calabresi, lead author of the study and director of the Johns Hopkins Multiple Sclerosis Center. "But the data we've seen are so compelling that I do predict that every MS center will be using this in three to five years."
Patricia O'Looney, vice president of biomedical research programs at the National Multiple Sclerosis Society, called the new study "small" but the "results are certainly encouraging that would indicate that [this test], in conjunction with an MRI [magnetic resonance imaging] would provide key information to go forward in developing new drugs."
The findings, which involve a technology called optical coherence tomography (OCT), are published in the October issue of the journal Neurology.
Multiple sclerosis is a disease of the central nervous system in which myelin -- the protective covering of nerves -- is damaged. Much research into the disease has focused on the damage to the myelin. But it is becoming increasingly evident that the axon, or nerve fiber, is also damaged in individuals with MS.
"Better technology has shown that the axons are damaged earlier in the disease than originally thought," O'Looney explained. "If you remove the protective covering then you're going to impact what's underneath, in this case, the axon. That makes sense."
In fact, according to the study authors, axon degeneration resulting from "demyelination" and from inflammation is thought to be responsible for much of the permanent disability that comes with MS.
Conventional MRIs have long been used to measure decreases in the brain's volume, an indication of how many neurons are dying. But MRI technology is expensive and uncomfortable. It is also often misleading because it doesn't take into account the brain inflammation that is also a characteristic of the disease. And brain shrinkage happens relatively late in the disease, when treatments are less effective.
Optical coherence tomography, a new technology, gauges the thickness of retinal nerve fiber, which becomes the optic nerve and is affected early in the course of MS. This is also the only part of the brain where nerve cells, even in healthy people, are not coated in myelin. The OCT test would specifically pick up on nerve damage, as opposed to more general brain changes, the researchers said.
"This allows you to measure the thickness of the axon itself," O'Looney explained.
The cost of the eye exam is only a fraction (10 percent to 15 percent) of a conventional MRI and, O'Looney noted, "it's user-friendly, it's inexpensive and it's less time-consuming for the patient."
For the study, the Hopkins researchers used the eye exam to scan the layers of nerve fibers of the retina in 40 people with either relapsing-remitting MS, secondary progressive MS, or primary progressive MS. Fifteen healthy volunteers served as control participants.
There appeared to be a strong association between retinal fiber thickness and how much the brain had atrophied.
But optical nerve damage could be used to indicate of other ailments, usually glaucoma, which would need to be ruled out. "If the ophthalmologist says there is no other obvious explanation in a young, healthy person who's tired and has some tingling sensations, I think it could be used as another way of helping to figure out if they have MS," Calabresi said.
Calabresi's team is now doing further studies involving the technology. If those studies pan out, OCT could be a way to deliver effective treatments to patients much earlier, he said.
"The longer MS goes undiagnosed the more damage is done," Calabresi stated. "Having a better test is extremely helpful."
The technology could end up paving the way for more effective drugs as well.
"As we move forward in developing new drugs to protect the axon from damage, we need a way to measure that. And OCT is certainly a strong potential technology that could be used," O'Looney said.
For more on multiple sclerosis, visit the National Multiple Sclerosis Society.
SOURCES: Peter A. Calabresi, M.D., associate professor of neurology, Johns Hopkins School of Medicine, and director, the Johns Hopkins Multiple Sclerosis Center, Baltimore; Patricia O'Looney, vice president of biomedical research programs, National Multiple Sclerosis Society, New York City; October 2007, Neurology
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