Participants in this arm will receive rehabilitation through a Collaborative Virtual Reality Environment (CVE), where both the patient and therapist interact simultaneously within a shared virtual space. The intervention is delivered using a head-mounted display-based system that enables real-time communication, guidance, and feedback.

The rehabilitation program consists of task-specific, goal-oriented exercises targeting upper limb function, gait, balance, and functional mobility. Activities are designed to simulate real-world movements and include object manipulation, reaching tasks, and controlled walking scenarios. The therapist actively supervises and adapts the exercises during each session, ensuring appropriate progression based on patient performance.

The collaborative nature of the environment facilitates increased engagement, motor learning, and adherence by incorporating interactive elements and immediate corrective feedback. The intervention follows structured progressio

Participants in this arm will undergo rehabilitation using a Non-Immersive Virtual Reality (NIVR) system delivered through a standard screen-based interface. The intervention without the use of head-mounted displays or real-time collaborative features.

The rehabilitation program includes task-oriented exercises focusing on upper limb function, balance, gait-related activities, and overall functional mobility. These exercises are designed to replicate real-world movements and are performed in a structured and repetitive manner to promote motor learning.

Participants will perform the activities independently with periodic supervision from a therapist. Feedback is primarily system-generated, and progression is based on predefined levels of difficulty within the software. The intervention emphasizes consistency, task specificity, and gradual progression throughout the study

Collaborative Virtual Reality Environment (CVE), participants perform exercises within a shared virtual space alongside a therapist, enabling real-time interaction, guidance, and adaptive feedback.

The MDS-UPDRS-III is a clinician-administered scale used to assess motor impairment in individuals with Parkinson's disease. It evaluates key domains including bradykinesia, rigidity, tremor, postural stability, and gait through a series of standardized physical examination items.

Each item is scored on a 5-point ordinal scale ranging from 0 (normal) to 4 (severe impairment), with higher total scores indicating greater motor dysfunction. The scale provides a comprehensive measure of motor severity and is widely used in both clinical and research settings due to its strong reliability and validity.

Changes in MDS-UPDRS-III scores over time will be used to determine the effectiveness of the intervention in improving motor function.

The Timed Up and Go (TUG) Test is a standardized clinical measure used to assess functional mobility, balance, and risk of falls in individuals with Parkinson's disease. The test requires the participant to stand up from a seated position, walk a distance of approximately 3 meters, turn around, walk back to the chair, and sit down.

The total time taken to complete the task is recorded in seconds. Shorter completion times indicate better functional mobility and balance performance, whereas longer times may reflect impaired mobility and increased fall risk. The TUG test is widely recognized for its simplicity, reliability, and sensitivity to changes following rehabilitation interventions.

The Falls Efficacy Scale-International (FES-I) is a standardized, self-reported questionnaire used to assess concern about falling during a range of daily activities in individuals with movement disorders, including Parkinson's disease. It evaluates both basic and more demanding physical and social activities, providing a comprehensive measure of fall-related self-efficacy.

The scale consists of 16 items, each scored on a 4-point Likert scale ranging from 1 (not at all concerned) to 4 (very concerned). The total score ranges from 16 to 64, with higher scores indicating greater fear of falling and lower confidence in performing daily activities safely. The FES-I has demonstrated strong reliability, validity, and cross-cultural applicability in clinical and research settings.