For the study, researchers used DTI to image the optic nerves of 12 healthy volunteers, 12 patients who had begun to suffer from optic neuritis within the past month and 28 patients with a history of earlier outbreaks. They gave participants with optic neuritis or a history of it detailed assessments of their visual health, including tests of visual acuity and the thickness and conductivity of their optic nerves.
In the healthy subjects, DTI scans showed that the water diffusion along the length of the subjects' optic nerves, a characteristic known as axial diffusivity, averaged about 1.66 micrometers squared per millisecond. In three patients with acute optic neuritis, those levels went down as much as 0.45 micrometers squared per millisecond.
"As the inflammation breaks down the structure of the axons or branches of the optic nerves, the normal water diffusion in this direction is impeded," Naismith explains. "After several months, though, the debris is cleared away, and this value and another characteristic known as radial diffusivity then start to increase."
In acute patients, the initial decrease in axial diffusivity brought on by optic neuritis correlated with decreased sensitivity to visual contrast one month and three months later. In patients with a history of optic neuritis, the increase in radial diffusivity was a good predictor of lower scor
|Contact: Michael C. Purdy|
Washington University School of Medicine