This study will be conducted at Hacettepe University, Faculty of Physical Therapy and Rehabilitation. It will investigate the acute effects of virtual reality-based optokinetic stimulation (OKS) on postural sway and motion sickness symptoms in individuals with multiple sclerosis (MS). Participants will include MS patients with and without central vestibular dysfunction, as well as age- and sex-matched healthy controls. MS participants will first undergo vestibular function assessment using videonystagmography (VNG). Postural control will then be measured via a force platform under four conditions (bipodal/monopodal, eyes open/closed) before and after a 10-minute OKS session using Oculus Quest 2. Healthy participants will follow the same postural and OKS assessment protocol without VNG.Motion sickness and virtual reality effects will be evaluated using the Simulator Sickness Questionnaire. Data will be analyzed using appropriate parametric or non-parametric tests to compare postural sway and VR-related symptoms across groups, with significance set at p \< 0.05.
