Steven L. Galetta, MD, and Laura J. Balcer, MD
PHOTO: Karsten Moran
Expanded applications of optical coherence tomography (OCT)—delivering 1,000 times the resolution of MRI—and other vision-based diagnostic tools are elucidating the markers and mechanisms behind complex neurological conditions and traumatic brain injury.
OCT Scans Show Promise for Early Diagnosis of Multiple Sclerosis
Although the optic nerve is involved in the manifestation of multiple sclerosis (MS) for most patients—in a quarter of them, acute optic neuritis is its initial manifestation—the optic nerve remains absent from the condition’s diagnostic criteria. Bolstered by new ٺƵ Health-led research with an international reach, clinicians can now turn to OCT scans of the retinal nerve fiber layer to identify how the optic nerve can add to MS diagnostic criteria.
A high-resolution, noninvasive ocular imaging method, OCT allows clinicians to spot microscopic changes in nerve fiber layer thickness that MRIs can’t detect. “With OCT scans, we have an effective structural measure for this important dimension of MS,” notes Laura J. Balcer, MD, professor of neurology, ophthalmology, and population health and vice chair of the . Furthermore, Dr. Balcer notes, OCT can identify even very subtle optic nerve damage that occurs before there is any subjective change in vision. This can be useful for early diagnosis for the large cohort of MS patients whose condition begins with acute optic neuritis.
Dr. Balcer and a team of investigators conducted an extensive analysis of OCT scan data from MS patients and from individuals without MS, and determined that a five-micron reduction in the thickness of the retinal nerve fiber layer is enough to indicate MS-related nerve damage. In conjunction with the International Multiple Sclerosis Visual System Consortium (IMSVISUAL), researchers are now using these results, published in late 2017, to lead the effort to expand studies of OCT-visualized optic nerve lesions as a potential diagnostic marker for MS. Dr. Balcer, a co-director of IMSVISUAL, and Steven L. Galetta, MD, the Philip K. Moskowitz, MD, Professor and Chair of Neurology and professor of neurology and ophthalmology, co-wrote an editorial published in 2017 in Multiple Sclerosis Journal, advocating for the inclusion of the optic nerve in the international MS diagnosis criteria.
OCT imaging technology affects the MS field beyond its use in measuring acute optic nerve damage from MS, adds Dr. Balcer. Since optic nerve thinning has been found to reflect the overall impact of MS on the central nervous system, she speculates that OCT retinal scans could one day be used as one of several measures to track overall progression of the disease, including therapeutic response.
Assessing Concussion-Related Brain Damage with Visual Screens
Researchers are also investigating the use of OCT and other vision-based testing to measure function in the setting of concussion and related neurological damage. The Division of Neuro-Ophthalmology plays a leadership role in ٺƵ’s Concussion Center, where research on the use of a rapid number-naming test and laboratory-based eye tracking is aiding in the sideline diagnosis and assessment of sports-related concussion.
The division is spearheading a study of OCT in active and retired contact-sport athletes. At the same time, ٺƵ is an enrolling site for a Boston University-led, National Institutes of Health-funded study of potential markers for chronic traumatic encephalopathy among retired football players and individuals with little or no contact sport exposure.
In a separate study, published in 2017 in the Journal of Neuro-Ophthalmology, division researchers and colleagues from the Illinois College of Optometry found that average retinal nerve thickness among collision-sport athletes was reduced relative to controls. The difference was especially pronounced among the study’s subgroup of boxers, who had an average nerve thickness reduction of almost 11 microns compared with the control group. “This study suggests that OCT may identify athletes who have had significant repetitive traumatic brain injury,” notes Dr. Galetta. A test of the same subjects’ low-contrast letter acuity also found significant differences between the athletes and controls, with boxers again showing the greatest disparity. Further investigations are under way to better determine the relationship between retinal nerve fiber loss and traumatic brain injury.
“We were fortunate to be early adopters of OCT and low-contrast visual tests in MS, over a decade ago,” says Dr. Galetta. “Now we’re taking the paradigms we learned in MS and applying them to traumatic brain injury, studying visual tests and OCT as outcome measures in other neurological conditions.”
