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I. Gottlob, H. Shekhar, Y. Rajabally, F.A. Proudlock; OKN and Smooth Pursuit in Parkinson's Disease . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2399.
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Purpose:In Parkinson’s disease (PD) hypometric saccades, reduced smooth pursuit and defects in the vestibulo–ocular reflex have been described. We also have reported changed reading patterns. In the current study we investigated optokinetic nystagmus (OKN) compared to smooth pursuit (SP) in PD. Methods: Eye movements of 22 PD patients without clinical frontal lobe involvement (mean age 65.3 years, SD 11 years, 15 males, 8 females, mean Hoehn & Yahr stage 2.1, SD 0.7) were compared to 23 healthy control subjects (mean age 65.2 years, SD 11.8 years, 11 males, 12 females) during horizontal binocular OKN and smooth pursuit at a stimulation velocity of 20 and 40 °/sec. OKN was elicited using high contrast vertical linear stripes back projected onto a screen measuring 65°horizontally and 50° vertically. Linear SP was elicited by a black dot moving linearly ±30° to the right and left of the screen. Eye movements were performed using head–free conditions with a high–resolution infrared eye tracker (Eyelink, Sensomotoric Instruments). For OKN the mean slow phase velocity (MSPV) and the beat frequency (BF) were evaluated, for SP the mean velocity (MSV) and numbers of saccades per ramp (SPR) were calculated Results: For OKN, PD patients had significant reduce of MSPV (at 20 °/sec mean 10.6 °/sec, SE 0.7 °/sec; at 40 °/sec mean 6.41 °/sec, SE 2.18 °/sec) than controls (at 20 °/sec mean 13.9 °/sec, SE 0.7 °/sec (p=0.005)); at 40 °/sec mean 17.2 °/sec, SE 2.18°/sec (p=0.0001)). OKN BF was reduced in PD patients (mean 2.9 Hz, SE 0.14 for 20 °/sec stimulation; mean 2.53 Hz, SE 0.16 for 40 °/sec stimulation) when compared to control subjects (mean 3.4 Hz, SE 0.11 (p=0.138) for 20 °/sec stimulation; mean 3.01 Hz, SE 0.13 (p=0.05) for 40 °/sec stimulation). However, we did not find a difference in SP between PD patients and controls for MSPV and SPR. Conclusions: While there was no difference in smooth pursuit in PD patients and controls even at higher stimulus velocities, OKN was very poor in PD patients, especially at 40°/sec. Normal SP in PD could be attributed to the head–free recordings performed in this study. Differences in PD patients between OKN and SP support changes in different cortical pathways.
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