Pilot study using structured VR exposure in 11 people with Parkinson's disease or dementia with Lewy bodies to elicit and characterize abnormal visual perceptual events, finding more misperceptions and hallucination-like events in visually degraded VR conditions but no clear separation between…

Demonstrates a feasible, tolerable, and potentially objective VR-based phenotyping approach that could be developed as a biomarker or outcome measure for trials targeting visual hallucinations, though the small sample size and technical limitations limit immediate therapeutic translation.

Visual hallucinations (VH), defined a visual perception without a corresponding object in the visual environment, are characteristic of Lewy body disorders and associated with adverse outcomes. Clinical management remains limited by reliance on retrospective self-report and challenges distinguishing between various visual experiences. We piloted a structured virtual reality (VR) environmental exposure protocol to systematically characterize abnormal visual perceptual events. Participants were exposed to four environments under varying visual conditions and narrated their experience. Narratives were independently reviewed by two clinicians for abnormal visual perceptive events. Eleven participants with Parkinson's disease or dementia with Lewy bodies (6 VH+, 5 VH - by questionnaire) completed the protocol. Across participants, 23 abnormal perceptual events were identified (6 hallucinations, 17 misperceptions). Event phenomenology aligned with clinical descriptions and occurred more frequently during visually degraded conditions. Perceptual error events were observed more frequently in VR than typically captured through retrospective interview (2.09 vs. 0.016 per participant). However, event rates did not differ significantly between VH + and VH- groups and did not replicate participants' typical spontaneous hallucinations. Technical and methodological constraints further limit interpretation. These findings demonstrate the feasibility and tolerability of structured VR-based assessment of perceptual vulnerability in Lewy body disorders and support further development and validation of this approach.