Posts Tagged saccade
Background. Humans use voluntary eye movements to actively gather visual information during many activities of daily living, such as driving, walking, and preparing meals. Most stroke survivors have difficulties performing these functional motor tasks, and we recently demonstrated that stroke survivors who require many saccades (rapid eye movements) to plan reaching movements exhibit poor motor performance. However, the nature of this relationship remains unclear.
Objective. Here we investigate if saccades interfere with speed and smoothness of reaching movements in stroke survivors, and if excessive saccades are associated with difficulties performing functional tasks.
Methods. We used a robotic device and eye tracking to examine reaching and saccades in stroke survivors and age-matched controls who performed the Trail Making Test, a visuomotor task that uses organized patterns of saccades to plan reaching movements. We also used the Stroke Impact Scale to examine difficulties performing functional tasks.
Results. Compared with controls, stroke survivors made many saccades during ongoing reaching movements, and most of these saccades closely preceded transient decreases in reaching speed. We also found that the number of saccades that stroke survivors made during ongoing reaching movements was strongly associated with slower reaching speed, decreased reaching smoothness, and greater difficulty performing functional tasks.
Conclusions. Our findings indicate that poststroke interference between eye and limb movements may contribute to difficulties performing functional tasks. This suggests that interventions aimed at treating impaired organization of eye movements may improve functional recovery after stroke.
[ARTICLE] Compensatory eye and head movements of patients with homonymous hemianopia in the naturalistic setting of a driving simulation.
Homonymous hemianopia (HH) is a frequent deficit resulting from lesions to post-chiasmal brain structures with a significant negative impact on activities of daily living.
To address the question how patients with HH may compensate their visual field defect in a naturalistic environment, we performed a driving simulation experiment and quantitatively analyzed both eye and head movements using a head-mounted pupil camera. 14 patients with HH and 14 matched healthy control subjects participated in the study.
Based on the detection performance of dynamically moving obstacles, which appeared unexpectedly along the sides of the road track, we divided the patient group into a high- and a low-performance group. Then, we compared parameters of eye and head movements between the two patient groups and the matched healthy control group to identify those which mediate successful detection of potentially hazardous objects. Differences in detection rates could not be explained by demographic variables or the extent of the visual field defect.
Instead, high performance of patients with HH in the naturalistic setting of our driving simulation depended on an adapted visual exploratory behavior characterized by a relative increase in the amplitude and a corresponding increase in the peak velocity of saccades, widening horizontally the distribution of eye movements, and by a shift of the overall distribution of saccades into the blind hemifield.
The result of the group comparison analyses was confirmed by a subsequent stepwise regression analysis which identified the horizontal spread of eye movements as single factor predicting the detection of hazardous objects.
…As brain injury vision rehabilitation becomes more commonplace, the need for optometrists trained in this area is increasing. This article discusses inpatient vs. outpatient delivery of care, diagnoses, assessment and treatment for patients who have acquired brain injuries…