Ocular Microtremor in Parkinson's Disease.

Ocular microtremor (OMT) is a fixational eye movement that cannot be seen with the naked eye but is always present, even when the eye appears motionless/still. The link between OMT and brain function generates a strong rationale for investigation as there lies potential for its use as a biomarker in populations of neurological impairments. OMT frequency is typically 70-80Hz in healthy adults and research suggests that this will be reduced in those with neurological disease such as Parkinson's Disease (PD). This study aims to examine OMT in people with PD (PwPD) compared to healthy older adults. Identifying OMT as a PD biomarker could better support clinical assessment, enabling improved provision of care to patients with advanced disease monitoring. This is an exploratory, observational study that will use a novel handheld device - The iTremor ONE, which has been developed to rapidly, non-invasively assess and evaluate OMT frequency. This device uses incident laser technology directed at the sclera. PwPD who meet the inclusion criteria will participate in a home-based assessment involving cognitive, motor (using the UPDRS-III) and OMT measures. With OMT as the primary outcome, assessment with the iTremor is incredibly quick, taking just three seconds to obtain a reading. PwPD will be assessed both off and on their anti-parkinsonian medication. PwPD will also be invited into the laboratory to perform extensive cognitive assessments along with an assessment of balance, gait, and turning using wearable sensors. The Investigators will recruit 40 PwPD, 20 suspected PD, and 30 age-matched healthy control participants for assessment of OMT. Ten PwPD will complete a test-retest reliability assessment at the same approx. time, exactly one week after their initial visit. This will be the first study of its kind to non-invasively investigate OMT frequency as a marker/monitor for PD with advanced technology that could be used within the clinic, laboratory, or home.