Capturing the Efferent Side of Vision in Multiple Sclerosis: New Data from a Digitized Rapid Number Naming Task

OBJECTIVEVisual function in multiple sclerosis (MS) has been well characterized from an afferent standpoint using low-contrast acuity, optical coherence tomography (OCT) and quality of life (QOL). We sought to determine ocular motor performance using recorded eye movements during a digitized King-Devick (K-D) test. The goal was to characterize eye movement deficits that underlie K-D reading time slowing in MS.BACKGROUNDThe K-D is a rapid number naming test that captures widely distributed aspects of efferent function, particularly saccades. Compared to controls, patients with MS demonstrate slowed K-D reading times, which are associated with neurologic dysfunction and reduced vision-specific (QOL). However, the ocular motor underpinnings of such slowing have not been determined.DESIGN/METHODSWe tested 13 patients with MS (mean age 37) and compared their results to those of our normative database of control participants without MS (n=38, mean age 31). Participants completed the digitized K-D task with simultaneous video-oculographic eye movement recording (EyeLink 1000+). Data were analyzed off-line in Matlab and Stata 14.0.RESULTSDigitized K-D completion times in the MS cohort were longer (worse) relative to controls (52.6 ± 14.1 sec vs. 43.7 ± 8.5 sec, p=0.02, t-test). Intersaccadic intervals (ISI), which represent a combination of saccadic latency and fixation duration between saccades, were prolonged in MS patients (397 ±137 msec vs. 312 ± 53 msec, p=0.02, t-test). Within the MS cohort, test times were longer for the digitized vs. spiral-bound hand-held K-D test (52.0 ± 9.2 sec vs. 43.7 ± 9.7 sec, p=0.01, linear regression).CONCLUSIONSIn this ongoing study of ocular motor performance in MS, we have demonstrated that K-D reading times are slower secondary to prolonged ISI. The K-D test captures efferent visual dysfunction in MS, and is likely to be a sensitive performance-based outcome measure for future research, practice and clinical trials. Disclosure: Dr. Hainline has nothing to disclose. Dr. Rizzo has nothing to disclose. Dr. Hudson has nothing to disclose. Dr. Dai has nothing to disclose. Dr. Joel has nothing to disclose. Dr. Nolan has nothing to disclose. Dr. Hasanaj has nothing to disclose. Dr. Balcer has received personal compensation for activities with Biogen Idec and Genzyme as a consultant. Dr. Galetta has received personal compensation for activities with Biogen Idec and Genzyme as a consultant. Dr. Kister has nothing to disclose. Dr. Rucker has received personal compensation in an editorial capacity for AAN Continuum.