We will ask 80 patients with Parkinson's disease, representing the full spectrum of motor and cognitive symptoms, to participate. Participation will include measurement of eye movements using two methods: the new computer-based saccade battery and the best available video-based eye-tracking equipment. The evaluation will be repeated about 30 days later. Data will be analyzed to determine whether the computer-based tasks are reliable and able to provide the same quality of information as the gold standard in eye-tracking. A comparison sample of 80 healthy older adults will also complete the behavioral saccade tests in order to establish normative data that will enable application in clinical settings.