[Pattern of Body Sway While Viewing 3D Video Clips in Various Age Groups].

OBJECTIVES: These days, developments in graphical technology have resulted in an increase in the chance to view 3D video clips. Visually induced motion sickness (VIMS) has been widely reported as a negative result of viewing these clips. The onset of VIMS is explained by some hypotheses. However, the root causes of VIMS have not been elucidated yet, whereas dizziness and nausea are regarded as symptoms of VIMS. In this study, we focus on the difference in the pattern of body sway among age groups and examine whether the consistency between the background and the viewpoint motion depends on the severity of VIMS. METHODS: This experiment was conducted with 116 subjects aged 15-89 years. They peripherally viewed a 3D video clip showing a sphere whose motion was consistent with their viewpoint (VC-I) and another 3D video clip of a sphere whose motion was inconsistent with their viewpoint (VC-II). Statokinesigrams (SKGs) were recorded with their eyes open and with their eyes closed for 60 s. The amount of sway was calculated from the SKGs. RESULTS: Results showed that for all age groups, sway values were significantly higher when viewing the 3D video clip (VC-II) than in the Pre. However, for the elderly, there was no significant difference between the sway values while viewing the VC-I and those in the Pre. CONCLUSIONS: Results suggest that VIMS might not occur in the elderly because of the deterioration of their visual function, such as visual acuity and accommodation, with advancing age.

Change in the Fusion Limit by Insertion of a Middle Image Equally Dividing the Parallactic Angle of 3D Stereoscopic Images.

OBJECTIVES: The purpose of this study was to identify and clarify the requirements for 3D stereoscopic images that do not cause viewing discomfort to the human eye even when the protrusion distance is large. METHODS: A total of 140 healthy men and women aged 14 to 79 years participated in this study. We first measured the fusion limits in these participants using two 3D stereoscopic images. We then measured the expansion of the fusion limit by inserting a middle image in a region located equally parallax from the two images. RESULTS: The results showed that the fusion limits were significantly expanded (p<0.01) after inserting the middle image. CONCLUSIONS: Insertion of middle images with parallax can extend the fusion limit. This method was shown to be an effective for viewing 3D stereoscopic images without causing discomfort.

[Limits of Cognition with Visual Parallax of Stereoscopic Images].

OBJECTIVES: Recent advances in three-dimensional (3D) display technology have contributed significantly to society, particularly in the increasing use of stereoscopic characters. For example, 3D text information is utilized in digital signage. However, research on 3D characters is limited and discussion on the safety and comfort of 3D technology is lacking. According to the 3D Consortium Safety Guidelines in Japan, a comfortable visual parallax with 3D images is less than ±1.0°. However, 3D text must be shown in front of its associated content in order for it to be displayed simultaneously with that content. METHODS: We carried out an experiments to verify the permissive limits of cognition in subjects regarding the parallax of 3D images. In the experiment, 94 subjects aged 18 to 81 viewed a 3D flat Maltess cross image having no depth and projected outward from a screen at a large parallax of 1.0° to 6.0°. RESULTS: Eighty-six percent of the subjects recognized the 3D flat image even when it protruded at a 2.0° parallax. These subjects viewed the image comfortably and without visual problems. CONCLUSIONS: This study concludes that people can cognitively recognize a 3D telop at a 2.0° parallax without feeling fatigued.

[Temporal Analysis of Body Sway during Reciprocator Motion Movie Viewing].

OBJECTIVES: We aimed to investigate the effect of stereoscopic viewing and the degree of awareness of motion sickness on posture by measuring body sway during motion movie viewing. METHODS: Nineteen students (12 men and 7 women; age range, 21-24 years) participated in this study. The movie, which showed several balls randomly positioned, was projected on a white wall 2 m in front of the subjects through a two-dimensional (2-D)/three-dimensional (3-D) convertible projector. To measure body sway during movie viewing, the subjects stood statically erect on a Wii balance board, with the toe opening at 18 degrees. The study protocol was as follows: The subjects watched (1) a nonmoving movie for 1 minute as the pretest and then (2) a round-trip sinusoidally moving-in-depth-direction movie for 3 minutes. (3) The initial static movie was shown again for 1 minute. Steps (2) and (3) were treated as one trial, after which two trials (2-D and 3-D movies) were performed in a random sequence. RESULTS: In this study, we found that posture changed according to the motion in the movie and that the longer the viewing time, the higher the synchronization accuracy. These tendencies depended on the level of awareness of motion sickness or the 3-D movie viewed. CONCLUSIONS: The mechanism of postural change in movie viewing was not vection but self-defense to resolve sensory conflict between visual information (spatial swing) and equilibrium sense (motionlessness).

[Effect of Viewing a Long Stereoscopic Film on Equilibrium Function and Autonomic Nervous System].

OBJECTIVES: Owing to the recent rapid advancements in image processing and three-dimensional (3-D) technologies, stereoscopic images can now be viewed on television as well as in theaters and on gaming consoles among others. However, with these advancements, there have also been reports on motion sickness and asthenopia induced by viewing stereoscopic films. Human equilibrium function deteriorates when viewing stereoscopic films, which may lead to motion sickness; however, the exact cause of such motion sickness remains unknown. Therefore, as part of hygiene research that contributes to society, it is important to consider the safety of viewing virtual 3D contents. METHODS: In this study, we investigated the effects of viewing 2-D/3-D video clips on the human body by stabilometry, electrogastrography (EGG), and subjective assessments. Seven subjects aged 22 to 24 viewed 2-D/3-D video clips for 60 min. RESULTS: A comparison of time series data obtained at rest shows a significant change in the EGG patterns 20 min after the start of viewing the video clips. Furthermore, sway values while viewing the 3-D video clips were considerably higher than those while viewing the 2-D video clips 60 min after the start of viewing. CONCLUSIONS: These findings show that the autonomic nervous system is affected first by long-term viewing of stereoscopic films, and the equilibrium function deteriorates gradually over the course of the exposure.

The Effect of 3D Visual Simulator on Children's Visual Acuity - A Pilot Study Comparing Two Different Modalities.

PURPOSE: To evaluate the efficacy of two non-surgical interventions of vision improvement in children. METHODS: A prospective, randomized, pilot study to compare fogging method and the use of head mounted 3D display. Subjects were children, between 5 to 15 years old, with normal best corrected visual acuity (BCVA) and up to -3D myopia. Subjects played a video game as near point work, and received one of the two methods of treatments. Measurements of uncorrected far visual acuity (UCVA), refraction with autorefractometer, and subjective accommodative amplitude were taken 3 times, at the baseline, after the near work, and after the treatment. RESULTS: Both methods applied after near work, improved UCVA. Head mounted 3D display group showed significant improvement in UCVA and resulted in better UCVA than baseline. Fogging group showed improvement in subjective accommodative amplitude. While 3D display group did not show change in the refraction, fogging group's myopic refraction showed significant increase indicating the eyes showed myopic change of eyes after near work and treatment. DISCUSSION: Despite our lack of clear knowledge in the mechanisms, both methods improved UCVA after the treatments. The improvement in UCVA was not correlated to measured refraction values. CONCLUSION: UCVA after near work can be improved by repeating near and distant accommodation by fogging and 3D image viewing, although at the different degrees. Further investigation on mechanisms of improvements and their clinical significance are warranted.

Multilingual medical dialog system developed as smartphone/tablet application.

Along with the concomitant rise in foreign residents in Japan has come the need to improve understanding at several social levels. The need for clear communication is most immediate in the area of the emergency or health care fields. Several types of apps exist that can be used to assist with communication between Japanese medical staff and foreign patients. However, there are problems with ease of use. This study asked 34 subjects to evaluate three types of touch designs with the "ExLanguage Nurse" to improve the usability of such multilingual apps. Results indicate that touch designs on the apps are related to ease of usability.

Accommodation training in foreign workers.

By relaxing the contracted focus-adjustment muscles around the eyeball, known as the ciliary and extraocular muscles, the degree of pseudomyopia can be reduced. This understanding has led to accommodation training in which a visual target is presented in stereoscopic video clips. However, it has been pointed out that motion sickness can be induced by viewing stereoscopic video clips. In Measurement 1 of the present study, we verified whether the new 3D technology reduced the severity of motion sickness in accordance with stabilometry. We then evaluated the short-term effects of accommodation training using new stereoscopic video clips on foreign workers (11 females) suffering from eye fatigue in Measurement 2. The foreign workers were trained for three days. As a result, visual acuity was statistically improved by continuous accommodation training, which will help promote ciliary muscle stretching.

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.

Distribution of and factors contributing to chronic kidney disease in a middle-aged working population.

OBJECTIVES: To clarify the distribution of chronic kidney disease (CKD) and the factors contributing to its development and progression in middle-aged Japanese workers/employees. METHODS: This was a retrospective study involving 3,964 men and 2,698 women aged 35-64 years in 2009 who had been followed-up until 2003. Data on proteinuria determined with a dipstick and glomerular filtration rate estimated from serum creatinine concentration (eGFR) were collected in the annual health check-ups. RESULTS: Proteinuria was detected in 2.9 and 1.1 % of the men and women, respectively, and total CKD was detected in 16.0 and 16.1 % of the men and women respectively. Moderate or severe CKD associated a high risk of cardiovascular diseases and end-stage kidney disease was found mostly in the male subjects [2.0 (men) vs. 0.6 % (women)]. High-risk CKD was found in 3.3 % of the men aged 55-64 years. A body mass index (BMI) of ≥30, hypertension, diabetes mellitus (DM), current smoking and some job types were independently related to the development of proteinuria, while age, BMI, hypertriglyceridemia, and job types were related to total CKD. The development of high-risk CKD was related to preceding mild CKD signs of reduced eGFR and proteinuria as well as to hypertension, DM, smoking, and job type. CONCLUSIONS: Chronic kidney disease was found in 16 % of middle-aged workers with an equal prevalence in both sexes, while high-risk CKD was found mostly in men, of whom 3.3 % were aged 55-64 years. Obesity, hypertension, DM, smoking and some job types were related to the development and progression of CKD.

The effects of continuing and discontinuing smoking on the development of chronic kidney disease (CKD) in the healthy middle-aged working population in Japan.

OBJECTIVES: The strength of the association between smoking and the development of chronic kidney disease (CKD) in the healthy middle-aged working age population has not been established. METHODS: This was a retrospective 6-year observational study involving 4,121 male and 2,877 female workers who were free of primary kidney disease, diabetes mellitus, severe hypertension, and the signs and symptoms of CKD. Proteinuria was detected by a dipstick method, and glomerular filtration rate (GFR) was estimated by the equation of the Japan Society of Nephrology. RESULTS: Sixty men (1.5 %) and 21 women (0.7 %) developed proteinuria over the 6 years of the study. Irrespective of sex, in comparison with non-smokers, those who continued smoking showed an odds ratio (OR) of 2.52 with a 95 % confidence interval (CI) of 1.50-4.25 for developing proteinuria while those who quit smoking showed an OR of 1.29 (95 % CI 0.48-3.42), following adjustment for confounders. Among the study population, 443 men (10.7 %) and 356 women (12.4 %) developed a GFR of <60 mL/min/1.73 m(2), corresponding to stage III CKD. Continuing smokers had a low OR (0.74, 95 % CI 0.60-0.90) for developing a low GFR, as well as a higher mean GFR than non-smokers. The reduction in GFR during the 6-year study period was not different between smokers and non-smokers, but it was larger in those who developed proteinuria than in those who did not, irrespective of smoking. CONCLUSIONS: Continuing smokers showed a twofold or more higher risk of developing proteinuria. Discontinuation of smoking substantially reduced the risk. A longer observational period may be required to detect the smoking-induced risk of developing stage III CKD in the middle-aged working population.

Cigarette smoking, proteinuria, and renal function in middle-aged Japanese men from an occupational population.

OBJECTIVES: To clarify the renal effects of cigarette smoking in a middle-aged occupational population because the effects have previously been demonstrated mainly in community populations that included many elderly people who are thought to be vulnerable to such effects. METHODS: In 990 middle-aged men recruited from a chemical plant, proteinuria was measured by a dipstick method and the glomerular filtration rate was estimated (eGFR) using a formula proposed by the Japanese Society of Nephrology. RESULTS: Proteinuria was found in 4.6% of the current smokers and 1.5% of the never-smokers. It was found in 4.8% of the subjects having a Brinkman index (BI) of 400-599 and 6.3% of those having a BI of 600 or above. The odds ratio for proteinuria in them was 2.94 (CI: 1.01-8.55) and 3.61 (CI: 1.29-10.1), respectively, adjusting for possible confounders. The mean eGFR was higher in smokers than in nonsmokers throughout middle age up to 64 years. Normal but high eGFR was found in 6.7% of the current heavy smokers and subnormal eGFR in 5.7% of the largest cumulative cigarette consumers in contrast to 3.0% or less of the never-smokers. Proteinuria was found in 13.3% of the subjects showing subnormal eGFR, specifically in 16.7% of the smokers and 8.3% of the nonsmokers. CONCLUSIONS: Smoking causes proteinuria in working middle-aged men. Smokers tend to have a high eGFR, but those with subnormal eGFR showed proteinuria most frequently. Whether the high eGFR in smokers will eventually decrease and cause proteinuria remains an important focus for further studies.

Cancer mortality among atomic bomb survivors exposed as children.

OBJECTIVES: To compare cancer mortality among A-bomb survivors exposed as children with cancer mortality among an unexposed control group (the entire population of Japan, JPCG). METHODS: The subjects were the Hiroshima and Nagasaki A-bomb survivor groups (0-14 years of age in 1945) reported in life span study report 12 (follow-up years were from 1950 to 1990), and a control group consisting of the JPCG. We estimated the expected number of deaths due to all causes and cancers of various causes among the exposed survivors who died in the follow-up interval, if they had died with the same mortality as the JPCG (0-14 years of age in 1945). We calculated the standardized mortality ratio (SMR) of A-bomb survivors in comparison with the JPCG. RESULTS: SMRs were significantly higher in exposed boys overall for all deaths, all cancers, leukemia, and liver cancer, and for exposed girls overall for all cancers, solid cancers, liver cancer, and breast cancer. In boys, SMRs were significantly higher for all deaths and liver cancer even in those exposed to very low doses, and for all cancers, solid cancers, and liver cancer in those exposed to low doses. In girls, SMRs were significantly higher for liver cancer and uterine cancer in those exposed to low doses, and for leukemia, solid cancers, stomach cancer, and breast cancer in those exposed to high doses. CONCLUSIONS: We calculated the SMRs for the A-bomb survivors versus JPCG in childhood and compared them with a true non-exposed group. A notable result was that SMRs in boys exposed to low doses were significantly higher for solid cancer.

[Analysis of electrogastrography in gastrectomized subjects].

OBJECTIVES: To establish a method for the development of a mathematical model of autonomic activity in gastrointestinal movements and to basically evaluate of the application of the nonlinear analysis method to electrogastrography, we performed feature extraction of electrogastrographic changes in healthy elderly and gastrectomized subjects. METHODS: The subjects consisted of 9 healthy elderly males and 3 elderly males without constipation who had undergone resection of 2/3 of the stomach. Electrogastrograms were obtained in a sitting position for 30 minutes and in a supine position for 90 minutes. Spectrum analyses of electrographic time series, the maximum Lyapunov exponent for the evaluation of the chaos of dynamic systems forming time series, and translation error for the evaluation of the smoothness of the attractor orbit were performed. RESULTS: The maximum Lyapunov exponent was a positive number in all analysis intervals in all subjects. This suggests the irregularity of electrogastrograms in gastrectomized subjects. The translation error in the gastrectomized subjects was higher than that in the healthy elderly subjects, showing irregularity. However, as a result of spectrum analysis, gastric electric activity was predominant on electrogastrograms of the healthy elderly subjects, but intestinal electric activity was predominant in the gastrectomized subjects. CONCLUSIONS: Differentiation between healthy and gastrectomized elderly people is difficult using only one of the spectrum analysis methods, the maximum Lyapunov exponent, or the translation error. However, since the extracted features differed among the 3 analysis methods, differentiation and diagnosis may be possible using a combination of these methods.

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.

Metamorphism in potential function while maintaining upright posture during exposure to a three-dimensional movie on an head-mounted display.

We propose 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. In this study, subjects in a standing position were stimulated by three-dimensional (3-D) movies on an head-mounted display (HMD). We also measured the degree of determinism in the dynamics of the sway of the center of gravity of the subjects. The Double-Wayland algorithm was used as a novel method. 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 the conventional 3-D images could be detected by using the SPD.

Evaluating indices of 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. 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. Statistical analysis indicated that it was necessary to include the time constant of the exponential decay curve fit to maximal points during prolonged muscular contraction, to evaluate the changes with age by using the smoothed sEMG during BFT. Reduction of the muscular regulation capacity due to aging can be detected by performing sEMG during BFT by using the time constant.