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Allen M Y Cheong, Hiu-Yan Lam, Larry A Abel, Paul Lee, Anne Chan, Yuk Fai Cheung, Leonard Li, Richard Li, Roger Li; Saccadic eye movement abnormalities in Parkinson’s disease. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1036.
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© ARVO (1962-2015); The Authors (2016-present)
Parkinson’s disease (PD) is a common neurodegenerative disorder characterized by bradykinesia, resting tremor and muscle rigidity. Our study aimed to investigate saccadic eye movement abnormalities in Parkinson’s patients and evaluate their possible impacts on reading performance .
Fifteen adults with PD aged from 40 to 70 year-old and thirteen age-matched healthy controls were recruited. All participants had best corrected visual acuity of 0.2 logMAR or better. All had no manifest ocular diseases. A Tobii TX300 eye tracking system with a 300 Hz frame rate, with visual targets displayed on a monitor screen placed at 1 meter, was used for measuring eye movements. These included (1) fixation stability: to fixate a small 1° target for 30 sec, (2) prosaccade: to track a target moving randomly (±5° and ±10° horizontally and vertically, at 1 Hz), (3) anti-saccade: to make a saccade in the opposite direction to the side where a target was presented, (4) self-paced saccade: to make saccades between 2 targets separated by±10° for 30 sec, and (5) reading 2 short Chinese passages.
Our Parkinson’s participants had significantly reduced gain (ratio of saccadic amplitude to target amplitude) of saccadic eye movements for the prosaccade (14 – 18%, p<0.01) and self-paced saccade tasks (5%, p<0.05). They showed more hypometric primary saccades, indicating that additional saccades and effort were required in executing reflexive and repetitive eye movements. No statistically significant differences in fixation stability, latency of prosaccade, latency and accuracy of anti-saccade, and number of self-paced saccades were found between the two groups (p>0.05). There were no statistically significant differences in reading performance (including reading speed, and number of forward and backward saccades) between the two groups.
Here we show that Parkinson’s patients exhibit reduced gain and accuracy in performing saccadic eye movements. Neither reflexive or voluntary saccade initiation was impaired. Unexpectedly, the eye movement deficits did not result in a significant reduction of reading performance in our participants. Further studies are needed to evaluate the impact of eye movement disturbances on everyday life activities.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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