Yasuyuki Matsuura

Effect of Accommodation Training on Visual Function of Visual Inspection Workers and Middle-Aged People

By relaxing the contracted focus-adjustment muscles around the eyeball, such as the ciliary and extraocular muscles, improvement of the pseudo-myopia is expected. This understanding has led to the accommodation training in which the visual target is given by stereoscopic video clips. In this study, we verify short-term effects of the apparatus on eyesight of visual inspection workers (22 females) suffering from eye fatigue and 12 middle-aged persons. In the Measurement 1, the workers were trained in 3 days. Moreover, the middle-aged were investigated on several trials of the eyesight recovering apparatus in the Measurement 2. As a result, the visual acuity was statistically improved by continuous accommodation training which will promote a ciliary muscle-stretching effect.

Comparison in degree of the motion sickness induced by a 3-D movie on an LCD and an HMD

Three-dimensional (3D) television sets are already on the market and are becoming increasingly popular among consumers. Watching stereoscopic 3D movies, though, can produce certain adverse affects such as asthenopia and motion sickness. Visually induced motion sickness (VIMS) is considered to be caused by an increase in visual-vestibular sensory conflict while viewing stereoscopic images. VIMS can be analyzed both psychologically and physiologically. According to our findings reported at the last HCI International conference, VIMS could be detected with the total locus length and sparse density, which were used as analytical indices of stabilograms. In the present study, we aim to analyze the severity of motion sickness induced by viewing conventional 3D movies on a liquid crystal display (LCD) compared to that induced by viewing these movies on a head-mounted display (HMD). We quantitatively measured the body sway in a resting state and during exposure to a conventional 3D movie on an LCD and HMD. Subjects maintained the Romberg posture during the recording of stabilograms at a sampling frequency of 20 Hz. The simulator sickness questionnaire (SSQ) was completed before and immediately after exposure. Statistical analyses were applied to the SSQ subscores and to the abovementioned indices (total locus length and sparse density) for the stabilograms. Friedman tests showed the main effects in the indices for the stabilograms. Multiple comparisons revealed that viewing the 3D movie on the HMD significantly affected the body sway, despite a large visual distance.

Consideration of Indices to Evaluate Age-Related Muscle Performance by Using Surface Electromyography

Recently, there has been an increasing focus on the rapid reduction of muscles that are required for the bending of the hip joint during walking (flexor muscles around the hip joint) with age. The flexor muscles around the hip joint include femoral rectus and abdominal muscles. These muscles have been implicated in falling in the elderly people. In this study, we examined the smoothed surface electromyography (sEMG) of femoral rectus muscles during biofeedback training (BFT) of the dominant leg. To this end, we developed parameters for the measurement of shapes in the smoothed sEMG, and evaluated the changes in these parameters in the muscles with age. Reduction of the muscular regulation capacity due to aging can be detected by performing sEMG during BFT by using a parameter in the muscles.

Changes of Potential Functions While Maintaining Upright Postures After Exposure to Stereoscopic Video Clips

Asthenopia and visually induced motion sickness (VIMS) is a well-known phenomenon in viewing video, playing video games and others. In previous studies, we pointed out peripherally viewing as a pathogenesis of the VIMS whose evidence was also shown and described the anomalous sway by using mathematical models. Stochastic differential equations are known to be a mathematical model of the body sway. We herein discuss the metamorphism in the potential functions to control the standing posture during/after the exposure to stereoscopic video clips.

Comparison by Simultaneous Measurement of Lens Accommodation and Convergence in 3D Vision and Their Distributions

—In general, disagreement between accommodation and convergence is considered to be a main reason for the visual fatigue and the visually induced motion sickness (VIMS). In this study, we devised a method to simultaneously measure lens accommodation and convergence, and used it to characterize 3D vision. Time courses of these fixation distances and their distributions are compared while they viewed 2D and 3D video clips. As a result, the convergence almost agreed with the distance between a subject and a 3D image. Therefore, we succeeded in measuring convergence while the distance of the accommodation focal length shifted.

Effect of LCDs displaying blurred images on the postural control system

In order to evaluate display devices, a geostationary image and the character were generally used in previous studies. We have proposed a new method for comparing the standing posture when a subject views a liquid crystal display (LCD) displaying a movie scrolling from the left to the right. In this study, we mathematically measured the degree of determinism in the dynamics of the sway of center-of-gravity. The Double-Wayland algorithm was used as a novel method. As a result, the dynamics of the sway when subjects viewed the movie as well that of the sway in the resting state was considered to be stochastic. The moving map task would not change it into a deterministic one.

Comparison of Form in Potential Functions While Maintaining Upright Postures during Exposure to Stereoscopic Video Clips

Visually induced motion sickness (VIMS) is a well-known phenomenon in viewing video, playing video games and others. The VIMS is caused by sensory conflict, the disagreement between convergence and visual accommodation while viewing 3-dimensional (3D) video clips. The VIMS can be measured by psychological and physiological methods. We propose a mathematical methodology to measure the effect of 3D video clips on the equilibrium function. In this study, body sway in rest is compared with that during exposure to 3D video clips on a liquid crystal display and on a head mounted display. In addition, the Simulator Sickness Questioner (SSQ) was completed immediately afterward. Based on the statistical analysis of the SSQ sub-scores and each index for stabilograms, we succeeded in evaluating the quantity of the VIMS during exposure to the stereoscopic video clips. Moreover, we discuss the metamorphism in the potential functions to control the postures including the Romberg posture and a wide stance with the middle line of heels 20 cm apart while viewing 3Dvideo clips.

Multi-evaluation method of visual fatigue and motion sickness while viewing 2d/3d video clips on a liquid crystal display

It is physiologically known that the vestibular system and the autonomic nervous system interact with each other. The motion sickness can affect both these systems, and severity of the motion sickness is expected to be measured by dysfunction of the equilibrium system. We have proposed a new index, sparse density (SPD), of stationary stabilograms for detecting the metamorphism in the (temporally averaged) potential function of stochastic differential equations, which occurs when a human attempts to maintain an upright posture. It is known that a mathematical model of the body sway can be developed by a stochastic process. The authors have succeeded in finding the nonlinearity in the potential function. Subjects in a standing position were stimulated by a movie scrolling from left to right on a liquid crystal display (LCD) in measurement 1 and a stereoscopic video clip on an LCD in measurement 2. As a result, the dynamics of the body sway in the presence of the stimulus as well as in its absence were considered to be stochastic. The metamorphism in the potential function during exposure to blurred images and a stereoscopic video clip could be detected by using the SPD.

Comparison of form in potential functions while maintaining upright posture during exposure to stereoscopic video clips

Visually induced motion sickness (VIMS) is caused by sensory conflict, the disagreement between vergence and visual accommodation while observing stereoscopic images. VIMS can be measured by psychological and physiological methods. We propose a mathematical methodology to measure the effect of three-dimensional (3D) images on the equilibrium function. In this study, body sway in the resting state is compared with that during exposure to 3D video clips on a liquid crystal display (LCD) and on a head mounted display (HMD). In addition, the Simulator Sickness Questionnaire (SSQ) was completed immediately afterward. Based on the statistical analysis of the SSQ subscores and each index for stabilograms, we succeeded in determining the quantity of the VIMS during exposure to the stereoscopic images. Moreover, we discuss the metamorphism in the potential functions to control the standing posture during the exposure to stereoscopic video clips.

Nonlinear Analysis for Evaluation of Age-Related Muscle Performance Using Surface Electromyography

Several electromyographic methods are currently used, but needle electromyography (nEMG) and surface electromyography (sEMG) are most often applied. To physiologically evaluate electromyographic wave patterns for the detection of abnormalities, the wave patterns obtained with nEMG or sEMG have been macroscopically examined, and subjectively judged by physicians.  nEMG findings are used for the evaluation of whether a disorder is neurogenic or myogenic, and if it is both neurogenic and myogenic, they provide important information about whether it is acute, subacute, or chronic (KIMURA, 1989). However, the probe is a needle electrode, which is percutaneously inserted into muscular tissues.  sEMG findings are used for various evaluations, such as the classification of trembling for the diagnosis of involuntary motion, the diagnosis or differential diagnosis of dystonia and spasm, and the identification of involuntary constrictor muscles (KIZUKA et al., 2006).  sEMG is further used for the determination of the electric potential through a nerve conduction examination (evoked EMG). In evoked EMG, the electrostimulation of peripheral nerves is percutaneously performed (KIMURA, 1989). The examination methods described, except for method B), are invasive and cause severe pain in patients. Generally, “smoothing” and “integration” refer to two ways of quantifying EMG energy over time; smoothing refers to continuously averaging out the peaks and valleys of a changing electrical signal. On the other hand, integration refers to measuring the area under a curve over a period of time. These methods are used to examine the relative degree of muscular contraction, and are also employed to provide a parameter for the evaluation of muscular training conditions (Aukee, 2002). However, the results obtained are affected by the location of the measuring electrodes and the shape and size of the probes. That is, EMG findings are macroscopically and subjectively evaluated, as described above, and no algorithm for the quantification of the degree of muscular abnormalities or recovery