The analyses were performed on data from the AFFIRM and SENTINEL studies, which involved 2,138 men and women with relapsing multiple sclerosis from clinics in Europe, North American, Australia, and New Zealand. More than half of the people received the drug natalizumab every four weeks for two years. The rest of the group received placebo. Researchers used eye charts of low contrast letters to test the vision of the participants every 12 weeks.

The study found vision loss, defined as a worsening in score by two rows of letters on the eye chart, was reduced by as much as 47 percent among people taking natalizumab compared to those taking placebo.

"Not only does natalizumab prevent the worsening of vision loss in people with relapsing MS, we also found the drug was associated with significant reductions in the likelihood of sustained vision loss," said study author Laura J. Balcer, MD, MSCE, with the University of Pennsylvania School of Medicine in Philadelphia, PA, and member of the American Academy of Neurology. "Specifically, this drug may have implications for preventing further sustained vision loss due to inflammatory demyelination of nerve fibers that connect to the eye, which is common in MS."

However, Balcer said the potential benefits of natalizumab treatment must be weighed with the drug's potential risks or complications, including the rare, often lethal brain disease progressive multifocal leukoencephalopathy (PML), of which three confirmed cases have been reported.

In addition, data from AFFIRM and SENTINEL studies showed that low-contrast letter acuity eye chart testing is effective for assessing visual outcomes in future MS clinical trials, which have not typically included visual testing components despite vision loss being a main disability of MS.

http://www.eurekalert.org/pub_releases/2007-04/aaon-mdh041007.php