Smooth-pursuit eye movements without head movement disrupt the static body balance

The effects of gaze stability exercises on balance, gait ability, and fall efficacy in patients with chronic stroke: A 2-week follow-up from a randomized controlled trial

BACKGROUND

This study aimed to examine the effect of gaze stability exercises on balance, gait ability, and fall efficacy in patients with chronic stroke, as well as to investigate whether any observed effects were maintained 2 weeks later.

METHODS

In this experiment, 30 chronic stroke patients were selected. The patients were randomly divided into 3 groups (10 patients in each group). All patients in the 3 groups performed basic neurodevelopmental treatment. Group 1 performed balance exercises accompanied by gaze stability exercises. Group 2 performed gaze stability exercises, and group 3 performed balance exercises. Each exercise program for 40 minutes 3 times a week for 4 weeks. After the intervention period, the patient's balance, gait ability, and fall efficacy were measured again. In order to know whether the training effect is maintained, a 2-week follow-up test was conducted after the training.

RESULTS

The results of this study showed that there was a significant improve in balance (overall stability index, limit of stability test, and Berg Balance Scale), gait ability (gait velocity, cadence, step time and step length, Timed Up and Go [TUG] test), and fall efficacy over the different time within the 3 groups. The effect was observed to be maintained in follow-up tests after 2 weeks. In the comparison among 3 groups, the overall stability index, limit of stability test in the balance test and the gait velocity, cadence, step time, step length and Timed Up and Go test in the gait test all showed statistically significant differences, and the other items did not have significant differences. In most of the assessments, group 1 that used balance exercise combined with gaze stability exercise showed a better improvement than the other 2 groups.

CONCLUSION

As a result, for stroke patients, gaze stability exercise is an effective arbitration method to improve balance and gait ability and fall efficacy. With balance exercise combined with gaze stability exercise, a greater effect can be seen than with gaze stability exercise or balance exercise alone. Thus, this combination exercise program can be recommended as effective.

The Effects of Different Kinds of Smooth Pursuit Exercises on Center of Pressure and Muscle Activities during One Leg Standing

This study examined the effects of gaze fixation and different kinds of smooth-pursuit eye movements on the trunk and lower extremity muscle activities and center of pressure.

METHODS

Twenty-four subjects were selected for the study. The activity of trunk and lower limb muscles (tibialis anterior, lateral gastrocnemius, medial gastrocnemius, vastus midialis obliques, vastus lateralis, biceps femoris, rectus abdominis, and erector spinae) and the COP (center of pressure) (surface area ellipse, length, and average speed) were measured to observe the effects of gaze fixation and different kinds of smooth-pursuit eye movements on the center of pressure and muscle activities during one leg standing. Before the experiment, a Gaze point GP3 HD Eye Tracker (Gazept, Vancouver, BC, Canada) was used to train eye movement so that the subjects would be familiar with smooth eye movement. Repeated each exercise 3 times at random. In order to avoid the sequence deviation caused by fatigue, the movement sequence is randomly selected.

RESULT

The center of pressure and muscle activities were increased significantly when the smooth-pursuit eye movement with one leg standing compared with gaze fixation with one leg standing. In smooth-pursuit eye movements, the changes in the center of pressure and muscle activities were increased significantly with eye and head movement. When the head and eyes moved in opposite directions, the center of pressure and muscle activities were increased more than with any other exercises.

CONCLUSION

Smooth-pursuit eye movement with one leg movement affects balance. In particular, in the smooth-pursuit eye movement with one leg standing, there were higher requirements for balance when the eyes and head move in the opposite direction. Therefore, this movement can be recommended to people who need to enhance their balance ability.

Deterioration of postural control due to the increase of similarity between center of pressure and smooth-pursuit eye movements during standing on one leg

Upright postural control is regulated by afferent and efferent/reafferent visual mechanisms. There are two types of efferent and conjugate eye movements: saccades and smooth pursuits. Although postural control is improved by saccades, the effects of smooth pursuits on postural control are still debated, because the difficulties of postural and visual tasks differ in the previous research. Additionally, the mechanisms that interfere with postural control and smooth pursuit are not fully understood. To address these issues, we examined the effects of different patterns of smooth-pursuit eye movement on the path length of the center of pressure (COP) displacement under bipedal and unipedal standing conditions. The relative frequency and amplitude of the COP displacement were remarkably increased when uniform linear visual targets were presented during unipedal standing. In addition, dynamic time warping analysis demonstrated that the similarity between the displacement of the COP and eye movements was increased by the presentation of uniform linear visual targets with orientation selectivity during unipedal standing but not during bipedal standing. In contrast, the attenuation of similarity between the displacement of the COP and eye movements significantly decreased the path length, relative frequency, and amplitude of the COP displacement. Our results indicate that postural stability is deteriorated by the increase of similarity between the displacement of the COP and smooth-pursuit eye movements under unstable conditions.

Cervical Rotator Muscle Activity With Eye Movement at Different Speeds is Distorted in Whiplash

BACKGROUND

People with whiplash-associated disorders (WADs) report difficulty with quick head movements and cervicoocular dysfunction. Changes in coordination between eye movement and neck muscle activity may be involved.

OBJECTIVE

To examine whether activity of superficial and deep neck muscles increases with eye movement when the head is held in a fixed position, whether this differs between directions and speed of eye movement, and whether this is modified in WAD.

DESIGN

Convenience case series with unmatched controls.

SETTING

Research laboratory.

PARTICIPANTS

Nine individuals with chronic WAD grade II and 11 pain-free controls.

METHODS

Electromyography (EMG) was recorded from muscles that could act to rotate the neck to the right (right obliquus capitis inferior [OI], multifidus [MF], splenius capitis [SC], and left sternocleidomastoid [SCM]) with intramuscular or surface electrodes in 9 WAD participants and 11 pain-free controls. Eyes were rotated without head movement to track slow and medium-speed targets to the right or left, and as fast as possible (FP).

MAIN OUTCOME MEASUREMENTS

Amplitude of EMG.

RESULTS

In controls, SCM and SC EMG increased with right gaze (all P's < .03). EMG of the deep OI muscle increased in both directions (P < .001). WAD involved counterintuitive greater activity of SCM with left rotation across speeds of eye movement (SC with slow movement, P < .036), decreased OI EMG with gaze left (P < .019), and no change in MF EMG (P < .6) in either gaze direction. For FP tasks, EMG of all muscles was greater than slower speeds in controls (all P's < .0001), but not WAD (all P's > .33).

CONCLUSIONS

Coordination between neck muscle activity and eye movements with increasing speed is modified in WAD. Contrasting changes are present in deep and superficial neck muscles with implications for neck function that may explain some common WAD symptoms.

LEVEL OF EVIDENCE

IV.