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. 'Off' is defined as a 12Hr overnight washout period where participants are tested in the morning prior to their first dose. 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. 40 PwPD, 20 with suspected PD, and 40 age-matched healthy control participants will be recruited 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.