Feasibility of virtual reality to induce and measure optokinetic after-nystagmus (OKAN): a pilot study.

Optokinetic nystagmus (OKN) is a reflexive eye movement triggered by repetitive motion in the visual field, characterized by a slow phase tracking the motion and a fast phase resetting the eye position. Following OKN, optokinetic after-nystagmus (OKAN) occurs in darkness, decaying over time and reflecting vestibular function. While OKAN provides valuable insights into vestibular disorders such as uni- or bilateral vestibulopathy and persistent postural perceptual dizziness (PPPD), traditional assessments require large and complex setups, limiting clinical application. This pilot study explores the feasibility of using a commercially available virtual reality (VR) headset with integrated eye-tracking to induce and measure OKAN. Twenty-two healthy participants (median age: 42 years, 54% female) with normal audiological and vestibular function were exposed to 60s of horizontal optokinetic stimulation. OKN was observed in 13 participants, with OKAN detected in 69% of these cases, consistent with traditional methods (55-90%). The median time constant (TC) of 18.75 ± 6.84s also aligns well with values reported for traditional methods (13.95-23.4s). This pilot study demonstrates that VR-based OKAN measurement is feasible and comparable to traditional methods, offering a promising tool for clinical applications in diagnosing vestibular disorders.