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.
Highlights
Along with the cardinal motor symptoms of Parkinson’s disease (PD), patients with PD possess sensory visual and oculomotor dysfunctions
Among the 20 patients with PD recruited (Table 1), 45% had a moderate disease with an Hoehn and Yahr (H&Y) ≥III
Our current study demonstrated significant stereo deficits in PD, a longer response time with eye gazing, and less accurate saccades and fixations when evaluating these visual functions with easy to use, non-invasive methods, namely the 3D active shuttered system and Tobii eye tracker
Summary
Along with the cardinal motor symptoms of Parkinson’s disease (PD), patients with PD possess sensory visual and oculomotor dysfunctions. Visual signs and symptoms of PD may include defects in extraocular movement (Pinkhardt and Kassubek, 2011), pupillary function (Micieli et al, 1991; Wang et al, 2016), and higher-level complex visual tasks (Armstrong, 2017). Among these dysfunctions, impairment in depth perception– namely the ability to judge distance, the shape of an object, and the speed of movements–can significantly impact patients’ motor performance when impaired. Stereopsis and eye behavioral study using 3D stimuli may help determine their implications in disease status
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