Critical Flicker Fusion as a Novel Measure of Remyelination in Multiple Sclerosis

Visual dysfunction is ubiquitous in multiple sclerosis (MS). Demyelination of the optic nerve is common, and visual impairment is a leading cause of disability in people with MS (pwMS). The eye provides an easily accessible window into the central nervous system, making the visual system an ideal model to evaluate remyelination therapies in MS. However, there are currently no fast, validated tests which reliably measure myelination status in the visual pathway. Visual evoked potential (VEP) is the current gold-standard measure of optic nerve function, however it is resource and time intensive, limiting its use. Critical flicker fusion (CFF) is a low-cost, efficient measure of optic nerve function. Participants view a rapidly flashing light that increases in frequency until it is perceived as a continuous light, the CFF threshold. While prior studies have demonstrated altered CFF thresholds in pwMS after optic neuritis, this is the first to establish intra-subject reliability and efficacy of CFF in pwMS with stable disease in comparison to VEP.