This single-case study aims to evaluate the clinical effects of optokinetic stimulation (OKS) on dizziness perception and quality of life in a patient diagnosed with Mal de Débarquement Syndrome (MdDS). The intervention follows a standardized protocol in which the patient performs head roll movements synchronized with optokinetic visual stimulation at a frequency of 0.167 Hz (10 bpm). The study is conducted online using a digital application to provide full-field optokinetic stimulation. The patient's baseline motion sickness susceptibility was characterized using the Motion Sickness Susceptibility Questionnaire-Short Form (MSSQ-SF). Primary outcome measures assessed for change from baseline include the Dizziness Handicap Inventory (DHI), Visual Analog Scale (VAS), and the Istanbul MdDS Scale

Mal de Débarquement Syndrome (MdDS) is a rare neuro-otological disorder characterized by a persistent perception of self-motion, typically described as rocking, swaying, or bobbing sensations, following exposure to passive motion such as sea, air, or land travel. The syndrome can significantly impair balance, spatial orientation, and quality of life. Conventional therapeutic approaches are limited, and symptoms may persist for weeks, months, or even years. Recent studies have suggested that maladaptation of the vestibulo-ocular reflex (VOR) and velocity storage mechanisms may play a central role in the pathophysiology of MdDS.

In this single-case study, a 28-year-old female patient with a clinical diagnosis of MdDS will undergo an online OKS-based rehabilitation program. The intervention will be conducted remotely via the Smart Optometry application, using the "OKN Stripes" module to deliver full-field optokinetic visual stimulation. The participant will sit close to the screen, ensuring that the optokinetic stripes occupy approximately 85-90% of the visual field. The researcher will guide each session online, ensuring the synchronization of head roll movements with the visual stimuli using a metronome (10 bpm). The intervention will be implemented for 3-5 consecutive days, with two sessions in the morning and two in the afternoon, each lasting 4 minutes.

Assessment and Follow-up: Clinical outcomes are evaluated at multiple time points to monitor the progression and long-term sustainability of the treatment:

Baseline (T0): Pre-treatment assessment. Post-treatment (T1): Immediately following the 5-day protocol. Short-term Follow-up (T2): 1 month after treatment. Long-term Follow-up (T3): 1 year after treatment to evaluate the durability of neuroplastic changes.

Primary metrics include the Dizziness Handicap Inventory (DHI) for perceived disability, the Visual Analog Scale (VAS) for dizziness intensity, and the Istanbul MdDS Scale for syndrome-specific symptoms. To determine the patient's clinical profile and support differential diagnosis, the Motion Sickness Susceptibility Questionnaire - Short Form (MSSQ-SF) will be administered initially.

This study aims to contribute to the limited clinical evidence on non-invasive, visual-vestibular rehabilitation strategies for MdDS and to explore the feasibility of delivering optokinetic therapy in an online, remote setting.

Inclusion Criteria:

• Subjective perception of movement in the "rocking/bobbing/swaying" type, beginning after exposure to passive motion (sea/aircraft/vehicle, etc.),
• lasting ≥1 month,
• Temporary relief of symptoms upon re-exposure to passive motion,
• Findings not better explained by an alternative diagnosis.
• Head and neck health must be at a level that allows head roll movement during optokinetic stimulation (no serious cervical limitation).

Exclusion Criteria:

• Alternative vestibular/otologic diagnoses: active BPPV, Meniere's disease, acute vestibular neuronitis, significant peripheral vestibulopathy; or significant central cause (stroke, CNS lesion, etc.).
• History of photosensitizer epilepsy or uncontrolled epilepsy

Individual participant data (IPD) will not be shared because this is a single-patient case study. Sharing de-identified data could risk patient confidentiality. Summary-level data may be reported in future publications.