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Theodore Jacques, Anqi Lyu, Larry A Abel, Anne Chan, Yuk-fai Cheung, Paul H Lee, Richard Li, Allen M Y Cheong; Vergence eye movements in patients with Parkinson's Disease. Invest. Ophthalmol. Vis. Sci. 2022;63(7):2574 – F0528.
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© ARVO (1962-2015); The Authors (2016-present)
Parkinson’s Disease (PD) is associated with a variety of abnormalities in eye movements, and there is ample evidence for specific deficits in convergent eye movements. Often self-report or subjective judgements by clinicians, or objective eye-tracking measures are reported in the literature; but seldom both. Here we used both methods to describe the vergence deficits in PD patients.
13 PD and 6 age-matched older adults (OA) were recruited to complete a smooth vergence task. A target mounted on a rod moved steadily closer and farther away (between 48 cm and 0 cm) at 3 different speeds (1, 2 and 4 cm/sec). Subjects fixated at the moving target and pressed a button when they perceived the approaching target as two (i.e. subjective break point). They also pressed the button when the retreating target became one (i.e. subjective recovery point). In addition to subjective reporting, subjects’ eye movements were captured using a binocular eye-tracking headset (Pupil Core 200Hz). The target positions at the time where convergence broke (i.e. objective break point) and at the time when the eyes recovered the binocular tracking (i.e. objective recovery point) were recorded. Each speed was measured twice and each trial comprised 3 cycles.
Based on the objective measure, OA subjects maintained vergence until the target moved significantly closer (OA: 3.31 cm; PD:10.31 cm; F(1,50) = 18.8, p<0.001) and recovered vergence earlier (OA: 5.24 cm; PD:11.01 cm; F(1,48) = 9.4, p<0.004). We calculated the differences in target position between these objective points and the corresponding self-reported subjective points. PD subjects delayed in reporting the break point relative to OA (OA: 0.32 cm; PD: 2.22 cm; F(1,51) = 4.65, p = 0.036), but the groups did not differ in their reporting on the recovery point (OA: 1.70 cm; PD: 3.48 cm; F(1,48) = 1.14, p = 0.29).
Our PD patients showed expected deficits in objective measures of convergence and recovery. However, we found that PD subjects delayed in reporting a break in vergence but not for recovery. PD patients appear delayed in perceiving a loss of fusion but detect normally its restoration.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.
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