Inability to align and refocus the eyes on the objects at different depths, i.e., vergence impairment and strabismus, frequently affects the quality of life in patients with Parkinson's disease. The investigators study aims to understand the location-specific effects of subthalamic region deep brain stimulation on vergence and strabismus by integrating the patient-specific deep brain stimulation models and high-resolution eye-tracking measures. The knowledge gained will allow the investigators to find the most beneficial stimulation location and parameters for improving binocular coordination, strabismus, and vergence while preserving the ability to treat motor symptoms in Parkinson's disease.
Parkinson's disease with bilateral STN DBS
Availability of pre-operative MR images (with a T1-weighted, gradient-echo sequence) and ability to get post-operative MRI or CT scans
Hoehn and Yahr stage 2-4 when off medication, and a stable antiparkinsonian medication regimen and DBS parameter settings
Previous surgical therapy for Parkinson's disease (other than DBS)
Dementia
Clinically significant untreated depression or anxiety
Clinical features suggestive of atypical parkinsonism