Stereopsis and Eye Movement Abnormalities in Parkinson’s Disease and Their Clinical Implications

Abstract

BackgroundParkinson’s disease (PD) is not exclusively a motor disorder. Among non-motor features, patients with PD possess sensory visual dysfunctions. Depth perception and oculomotor deficits can significantly impact patients’ motor performance. Stereopsis and eye behavioral study using 3D stimuli may help determine their implications in disease status.ObjectiveThe objective of this study is to investigate stereopsis and eye movement abnormalities in PD with reliable tools and their correlation with indicators of PD severity. We hypothesize that patients with PD exhibit different eye behaviors and that these differences may correlate to the severity of motor symptoms and cognitive status.MethodsControl and PD participants were first evaluated for visual acuity, visual field, contrast acuity, and stereo perception with 2D and Titmus stereotests, followed by the assessment with a 3D active shutter system. Eye movement behaviors were assessed by a Tobii X2-60 eye tracker.ResultsScreening visual tests did not reveal any differences between the PD and control groups. With the 3D active shutter system, the PD group demonstrated significantly worse stereopsis. The preserved cognitive function was correlated to a more intact stereo function. Patients with PD had longer visual response times, with a higher number of fixations and bigger saccade amplitude, suggesting fixation stabilization difficulties. Such changes showed a positive correlation with the severity of motor symptoms and a negative correlation with normal cognitive status.ConclusionWe assessed stereopsis with a 3D active shutter system and oculomotor behaviors with the Tobii eye tracker. Patients with PD exhibit poorer stereopsis and impaired oculomotor behaviors during response time. These deficits were correlated with PD motor and cognitive status. The visual parameters may potentially serve as the clinical biomarkers for PD.

Vestibular dysfunction in Parkinson’s disease: a neglected topic

“…A study of eye movements in 35 patients with idiopathic PD using videonystagmography (VNG) revealed visual and vestibular motoneuron abnormalities ( 39 ). Similarly, patients with PD exhibited poorer stereopsis and impaired oculomotor behaviors, as assessed using a three-dimensional active shutter system and Tobii Eye Tracker, respectively ( 40 ). Large meta-analyses have also confirmed the occurrence of increased response latencies in pro- and anti-saccade tasks in patients with PD ( 41 , 42 ).…”

Visual Dysfunction in Parkinson’s Disease

“…Stereopsis impairment has been observed in some studies [ 117 , 118 , 119 ]. It has been explained as a result of basic visual perception alterations, such as color vision and contrast sensitivity deficits [ 118 ], and oculomotor behavior [ 120 ], which appear linked to the degree of disease deterioration and motor impairment [ 119 ].…”

Perspective: Present and Future of Virtual Reality for Neurological Disorders

“…This can help standardize multi-center research or even allow home-based tracking of patients’ cognitive abilities, which will likely promote the neurorehabilitation of life-relevant functions through repetitions of such VR tasks [ 6 , 7 ]. Additionally, VR with HMDs can be used to detect decreased stereopsis in PD patients [ 21 ], providing more standardized and controlled assessment methods.…”