A team of researchers scanned the eyes of a group of people with MS over nearly two years, and also did MRI scans and regular clinical exams. The researchers, from Johns Hopkins University and other institutions across the country, found that thinning of the back layer of the eye may represent a window to global damage occurring in the nervous system, and suggest that this tool may be useful for tracking nerve protection in clinical trials involving people with MS. The study, by John Ratchford, MD, Peter Calabresi, MD, and colleagues, was funded in part by the National MS Society’s Promise: 2010 Nervous System Repair and Protection
initiative. It was published
in the January 2013 issue of Neurology.
In MS, the immune system damages the brain and spinal cord. However, damage to nerve fibers and cells, which send messages and allow normal nervous system function, also occurs even when inflammation is controlled. Finding better ways to more quickly measure nervous system damage and progression would speed clinical trials focusing on trying to protect the nervous system and stop MS progression
The back part of the eye, called the retina, is affected in MS and is damaged even in people with MS who do not have visual symptoms. The use of a simple, non-invasive technique called optical coherence tomography (OCT) has been shown by members of the study team and several other groups to be an effective way to examine the retina to track MS damage. The new study uses a more powerful technique called OCT segmentation, which allows a finer quantification of the thickness of various layers of the retina. For this study, the team set out to see how thinning of another layer of the retina, called the ganglion cell and inner plexiform layer (GCIP), may link to MS disease activity such as relapses and lesions seen on MRI scans. They also wanted to track changes to the GCIP over time to determine whether it would be a sensitive measure of nerve protection in clinical trials.
Dr. Ratchford and colleagues examined a link between changes in the retina and changes in the brain and nervous system function in people with MS. Over a period of 21.1 months, they studied 164 people with relapsing or progressive disease, as well as 59 healthy control participants. They used OCT scans every six months to measure the thickness of the GCIP layer, which contains cells whose nerve fibers are damaged in MS. GCIP thinning is known to occur in the eyes of people with MS, regardless of vision problems. Participants also underwent traditional brain MRI imaging and neurological assessments to see how changes in the retina seen with OCT correlated with other manifestations of disease activity.
Results showed that the GCIP layer was thinner in people with MS than in healthy controls. Faster rates of GCIP thinning occurred in people with MS who experienced non-visual relapses, who had new brains lesions (as seen with other types of imaging), who showed disability progression, and who had an MS disease duration of less than 5 years compared to people with MS who did not show these types of progression. Thus, changes in the retina in MS were linked to global changes in the brain.
An unmet need for finding therapies for progressive forms of MS revolves around finding better tools to quickly measure the ability of treatments to protect or repair the nervous system. Until now, researchers have had to rely on more expensive and more difficult MRI to look at progression of MS damage. This study, funded in part through the National MS Society’s Nervous System Repair and Protection initiative, provides the first longer-term evidence that tracking a specific portion of the retina offers a window to global nervous system damage. If further research verifies these findings, OCT may provide a way to indirectly measure nervous system damage or protection and speed clinical trials in progressive MS.