In cases of "possible MS" if the OCT changes from one scan to another, can this indicate demyelination? How many points difference are significant? It looks as if the normal range is anywhere between 70 and 99? If the average thickness of the RNFL falls below 70 into the sixties is this significant? Thank you so much for your help.
OCT changes in MS do not always reflect demyelination. OCT measures the thickness of the retina which has no myelin. The nerves from the retina go on to make up the optic nerve. So any loss of the thickness on OCT may correlate with loss of axons (nerve fibers) in the optic nerve. The loss of axons may be the result of demyelination or could be secondary to other causes.
The normal OCT range and amount of change that is considered significant may vary depending on the brand of machine being used.
I cannot comment on any individual OCT results and their significance without having examined a patient. One thing to keep in mind is that OCT is just one tool a physician can use in assessing a patient but that the clinical significance of any test result may depend on many other factors.
Benjamin Osborne, MD
Associate Professor of Neurology and Ophthalmology
Director, Neuromyelitis Optica (NMO) Clinic
Director, Neuro-Ophthalmology Clinic
Associate Director of the NIH/Georgetown Neurology Residency Program
Medstar Georgetown University Hospital
3800 Reservoir Road, NW 7PHC
Washington, DC 20007