Saccadic Eye Movements are Related to Turning Performance in Parkinson Disease

Abstract

Background Persons with Parkinson disease (PD) experience difficulty turning, leading to freezing of gait and falls. We hypothesized that saccade dysfunction may relate to turning impairments, as turns are normally initiated with a saccade. Objective Determine whether saccades are impaired during turns in PD and if characteristics of the turn-initiating saccade are predictive of ensuing turn performance. Methods 23 persons with PD off medication and 19 controls performed 90 and 180 degree in-place turns to the right and left. Body segment rotations were measured using 3-D motion capture and oculomotor data were captured using a head-mounted eye tracking system and electrooculography. Total number of saccades and the amplitude, velocity, and timing of the first saccade were determined. Results Turn performance (turn duration, number of steps to turn) was impaired in PD (p<0.05). PD performed more saccades, and the velocity and timing of the first saccade was impaired for both turn amplitudes (p<0.05). Amplitude of the first saccade was decreased in PD during 180 degree turns. Turn duration correlated with oculomotor function. Characteristics of the first saccade explained 48% and 58% of the variance in turn duration for 90 and 180 degree turns, respectively. Conclusions Turning performance is impaired in PD and may be influenced by saccade dysfunction. An association between saccade function and turning performance may be indicative of the key role of saccades in initiating proper turning kinematics. Future work should focus on improving saccade performance during functional tasks and testing the effects of therapeutic interventions on related outcomes.

Effect of subthalamic deep brain stimulation on turning kinematics and related saccadic eye movements in Parkinson disease

“…Our findings of improved turning duration and concomitant improvements in oculomotor performance during turns are novel yet anticipated based on the efficacy of DBS in improving saccade function and gait in previous studies. Previous work in our lab (Lohnes and Earhart, 2011) showed that persons with PD turn slower and with more steps than healthy, age-matched controls, and that turn performance is correlated with oculomotor function such that individuals who perform later, larger, faster, and fewer saccades turn better. Similarly, data herein suggest that improved oculomotor performance associated with DBS is correlated with improved turn performance.…”

“…Such studies have noted that persons with PD require more steps and take longer to complete a turn than healthy controls (Hong et al, 2009; Lohnes and Earhart, 2011; Morris et al, 2001; Stack and Ashburn, 2008) Additionally, individuals with PD show altered timing of segmental rotations during turn initiation, such that their turning strategy is more “en bloc” than healthy controls (Crenna et al, 2007; Hong et al, 2009; Huxham et al, 2008; Visser et al, 2007), although this finding may not be observed in early PD stages (Anastasopoulos et al, 2011). …”

“…During standing turns, Anastasopoulos et al (2011) found that patients with PD more frequently performed multiple saccades to reach a lateral target and expressed altered eye-head-trunk gaze shifts as compared with healthy controls. Lohnes and Earhart (2011) measured saccades during 180 degree turns and found that patients with PD had a longer delay between initiation of eye movement and start of the first step of the turn, and that first saccades were smaller and slower than controls. Further, measures of saccade function were correlated with turn performance.…”

Direct and indirect effects of attention and visual function on gait impairment in Parkinson's disease: influence of task and turning

“…This agrees in part with previous work which demonstrated an increase in horizontal saccade frequency during turns in PD (Galna et al ., ). Methodological differences however, limit comparison to other turning studies which report saccades when turning while standing in place rather than walking (Anastasopoulos et al ., ; Lohnes & Earhart, ). In contrast, their findings show that saccade frequency increases in PD compared to controls when turning.…”

The measurement of visual sampling during real-world activity in Parkinson's disease and healthy controls: A structured literature review

“…The majority of the studies provided no visual outcome (saccade and fixation) definitions. Five studies (Desmurget et al, 2004, Lohnes and Earhart, 2011, Marx et al, 2012, Muilwijk et al, 2013 did provide outcome definitions, but definitions varied between studies. Twelve studies specified the VS outcome variables obtained, which often involved saccade or fixation measurements (such as saccade frequency, duration, velocity, amplitude, latency, fixation frequency and duration, Table 2).…”