Abstract
Demyelination, the pathological hallmark of optic neuritis (ON) is identified by prolonged Visual Evoked Potentials (VEP) latency. Yet, no behavioral correlate to this prolongation was previously described. We hypothesized that dynamic visual processes, such as motion perception, may be more vulnerable to slowed conduction in the optic nerve. To that end, we performed a longitudinal study on patients with unilateral, first-ever ON. Static and dynamic visual functions, VEPs, functional MRI (fMRI) and diffusion tensor imaging (DTI) examinations were repeatedly assessed in patients and age-matched controls over the course of a year. We found a sustained motion perception deficit, via the affected eye, long after the recovery of static visual functions. fMRI studies showed recovery in cortical activation during static object recognition, as opposed to sustained deficit in tasks that require motion perception. Moreover, motion perception deficit was highly correlated with prolonged VEP latencies. Interestingly, the patients' fellow eyes, which also demonstrated prolonged VEP latencies, exhibit intact dynamic visual functions. We suggested that these delayed latencies evolved due to prolonged cortical processing of the fellow eyes' input. We found that these changes offered a functional advantage; synchronization of inputs resulted in improved dynamic 3-dimentional perception. Thus, while results in the affected eyes, highlight the need for rapid transmission of visual input to perceive motion, the results in the fellow eyes reflect an adaptive process aimed at binocular integration in time, to adjust the damage incurred. Our results emphasize the importance of the temporal domain when assessing demyelinative diseases.
Meeting abstract presented at OSA Fall Vision 2012