Visually induced symptoms questionnaire (VISQ): A subjective evaluation method for biomedical effects induced by stereoscopic 3D video.

The purpose of this paper is to establish an easy-to-use questionnaire for subjective evaluations of visually induced motion sickness (VIMS) and visual fatigue caused by stereoscopic 3D (s3D) images. We reviewed previously used questionnaires and extracted 51 important subjective evaluation items from them. We then recruited 251 participants to observe 3D images designed to easily induce sickness or visual fatigue, and we asked them to respond to the 51 items. As a result of exploratory factor analysis, four factors were extracted according to their factor loadings, and the number of items was reduced to 21. Further processing by confirmatory factor analysis led to the selection of 15 items. Comparing mean ratings for each factor before and after item reduction indicated that item reduction did not significantly affect the participant responses. Therefore, the 15-item Visually Induced Symptoms Questionnaire (VISQ), can be used to evaluate VIMS and s3D visual fatigue.

Pupillography of relative afferent pupillary defects in amblyopia associated with peripapillary myelinated nerve fibers and myopia.

Pupillary responses to light were recorded in three patients with unilateral extensive myelinated nerve fibers and amblyopia by means of binocular infrared video pupillography. All of the patients had an afferent pupillary defect in the eye with myelinated nerve fibers. This finding supports the notion that this type of amblyopia is a severe form of anisometropic amblyopia that is often resistant to treatment.

Pupillography of automated swinging flashlight test in amblyopia.

Relative afferent pupillary defects (RAPDs) in amblyopia have been reported, and it is widely accepted that amblyopes can have an RAPD. We investigated whether or not this could be confirmed by the use of binocular pupillography. We examined twelve patients (6 males and 6 females, aged 7-57 years) with unilateral amblyopia associated with anisometropia and/or strabismus, using binocular infrared video pupillography (Newopto, Kawasaki, Japan). Eight normal subjects were also tested in the same manner. Two patients' data had to be excluded because of poor recording quality. Only one patient with moderate anisometropic amblyopia was found to have reduced contraction amplitude in the amblyopic eye, and one patient with a borderline pupillary defect. The other amblyopes, some of whom showed even denser amblyopia, did not have a pupillary defect. This study has confirmed that only a small proportion of amblyopes have a reduced pupillary contraction amplitude in the affected eye, as established by pupillographic recordings, and even these amblyopes are not necessarily associated with dense amblyopia.

A pilot study on pupillary and cardiovascular changes induced by stereoscopic video movies.

BACKGROUND: Taking advantage of developed image technology, it is expected that image presentation would be utilized to promote health in the field of medical care and public health. To accumulate knowledge on biomedical effects induced by image presentation, an essential prerequisite for these purposes, studies on autonomic responses in more than one physiological system would be necessary. In this study, changes in parameters of the pupillary light reflex and cardiovascular reflex evoked by motion pictures were examined, which would be utilized to evaluate the effects of images, and to avoid side effects. METHODS: Three stereoscopic video movies with different properties were field-sequentially rear-projected through two LCD projectors on an 80-inch screen. Seven healthy young subjects watched movies in a dark room. Pupillary parameters were measured before and after presentation of movies by an infrared pupillometer. ECG and radial blood pressure were continuously monitored. The maximum cross-correlation coefficient between heart rate and blood pressure, rho max, was used as an index to evaluate changes in the cardiovascular reflex. RESULTS: Parameters of pupillary and cardiovascular reflexes changed differently after subjects watched three different video movies. Amplitudes of the pupillary light reflex, CR, increased when subjects watched two CG movies (movies A and D), while they did not change after watching a movie with the real scenery (movie R). The rho max was significantly larger after presentation of the movie D. Scores of the questionnaire for subjective evaluation of physical condition increased after presentation of all movies, but their relationship with changes in CR and rho max was different in three movies. Possible causes of these biomedical differences are discussed. CONCLUSION: The autonomic responses were effective to monitor biomedical effects induced by image presentation. Further accumulation of data on multiple autonomic functions would contribute to develop the tools which evaluate the effects of image presentation to select applicable procedures and to avoid side effects in the medical care and rehabilitation.

Relationships between sensory stimuli and autonomic nervous regulation during real and virtual exercises.

BACKGROUND: Application of virtual environment (VE) technology to motor rehabilitation increases the number of possible rehabilitation tasks and/or exercises. However, enhancing a specific sensory stimulus sometimes causes unpleasant sensations or fatigue, which would in turn decrease motivation for continuous rehabilitation. To select appropriate tasks and/or exercises for individuals, evaluation of physical activity during recovery is necessary, particularly the changes in the relationship between autonomic nervous activity (ANA) and sensory stimuli. METHODS: We estimated the ANA from the R-R interval time series of electrocardiogram and incoming sensory stimuli that would activate the ANA. For experiments in real exercise, we measured vehicle data and electromyogram signals during cycling exercise. For experiments in virtual exercise, we measured eye movement in relation to image motion vectors while the subject was viewing a mountain-bike video image from a first-person viewpoint. RESULTS: For the real cycling exercise, the results were categorized into four groups by evaluating muscle fatigue in relation to the ANA. They suggested that fatigue should be evaluated on the basis of not only muscle activity but also autonomic nervous regulation after exercise. For the virtual exercise, the ANA-related conditions revealed a remarkable time distribution of trigger points that would change eye movement and evoke unpleasant sensations. CONCLUSION: For expanding the options of motor rehabilitation using VE technology, approaches need to be developed for simultaneously monitoring and separately evaluating the activation of autonomic nervous regulation in relation to neuromuscular and sensory systems with different time scales.

Pupillography of relative afferent pupillary defect contralateral to monocular mature cataract.

CASE REPORT: Few previous reports have documented a relative afferent pupillary defect (RAPD) in the eye contralateral to a dense unilateral cataract. We report pupillographic findings of a 55-year-old man with a mature cataract in the left eye and an RAPD in the right eye, whose RAPD disappeared after cataract surgery in his left eye. Using binocular infrared video pupillography, we recorded the pupillary responses of the two eyes simultaneously during an automated swinging flashlight test before and after the cataract surgery. The average contraction amplitude in both eyes was significantly larger when the unaffected left eye was stimulated before the cataract surgery, but this difference in contraction amplitude disappeared after surgery on the left eye. COMMENTS: An RAPD was shown quantitatively with a pupillographic technique in the eye contralateral to a mature cataract, confirming previous studies that indicate a dense cataract may produce a small but definite RAPD in the contralateral eye. Such an RAPD associated with a dense cataract must be taken into consideration when evaluating patients with unilateral visual loss.

Lack of a relationship between the pupillary light reflex response and state/trait anxiety in remitted patients with panic disorder.

OBJECTIVE: Recently, some studies have indicated that pupillary function only correlates with state/trait anxiety in healthy subjects. In the present study, we examined whether or not there were relationships between the PLR functions and state/trait anxiety in remitted (the absence of panic attack (PA) symptoms for at least 6 months) PD patients compared to normal control (NC) subjects. METHODS: Before and after audiovisual stimulation (AS) that induced mental stress through exposure to video images of high stress experiences, such as driving motor vehicles, the pupillary light reflex (PLR) was measured with an infrared pupillometer in 30 remitted PD patients and 30 age- and gender-matched NC subjects. In order to examine the relationships between the 8 PLR parameters (initial pupillary diameter in darkness, pupillary diameter at maximum constriction, constriction ratio, latency of the reflex, time to reach maximum constriction and time constant of redilation) and state/trait anxiety, we used the State-Trait Anxiety Inventory (STAI) and stepwise multiple regression analysis. RESULTS: There was no significant group difference in the STAI-T score and STAI-S scores before and after AS. We confirmed the significant relationships between pupillary function and state/trait anxiety in NC subjects, but not in PD patients. CONCLUSIONS: These findings suggest that in contrast to NCs, even remitted PD patients may have dysfunctional PLR regulation with mental loading, such as AS. Moreover, it is possible that the abnormalities of ANS exist extensively in PD, since almost all panic symptoms, including PA, are involved in cardiovascular symptoms, but not pupillary ones.

Visual cortical contribution to open-loop and feed-back control of convergence eye movements in the cat.

Open-loop and closed loop controls in convergence eye movement have been reported by human psycho-physical studies. To investigate the visual cortical involvement in open-loop convergence eye movement, we trained a cat to elicit anticipatory convergence (convergence eye movement before the onset of target movement) by using an approaching visual target with a preceding alarm signal. After 1-2 weeks of training, anticipatory convergence was observed in more than half of the trials in seven cats. The frequency of occurrence of anticipatory convergence was significantly decreased after electrocoagulation in the convergence-related region of the lateral suprasylvian (LS) area, an extrastriate visual cortex of the cat. On the other hand, the localized injection of Muscimol, a GABA-A agonist, reduced visually evoked convergence, but caused no significant effects to anticipatory convergence. These differential results suggest that the LS plays a role in both open-loop and feed-back control of convergence eye movement, and a GABA-A sensitive subregion is involved in the feed-back control of convergence eye movement.

Effect of the background on the disparity-induced ramp vergence response in humans.

PURPOSE: Our purpose was to investigate the changes in the dynamic property of vergence eye movements caused by changes in the co-existing stationary background in the central visual field. METHODS: Disparity-driven target movement was presented virtually by a head-mounted liquid-crystal display. Two targets were used: a bar-shaped target that moved between 2 and 0.5 m along the mid-sagittal line at a speed of 50 cm/s (vergence target) and a background image of a cross-shaped target that stayed at a distance of 2 m (background target). Eight normal subjects participated in the experiments. The subject was asked to follow the vergence target while the configuration of the background target was randomly changed among four conditions in each experiment: the length (experiment 1) or the width (experiment 2) of the horizontal and vertical lines composing the cross of the background target was each randomly changed among four conditions. A limbus tracker was used to measure eye movements. RESULTS: In experiment 1, there was a negative correlation between the amplitude of the vergence eye movements and the lengths of the lines of the cross in each of five subjects (mean r = 0.018, n = 48 in each subject). Similarly, in experiment 2, there was a negative correlation between the amplitude of the vergence eye movements and the width of the lines of the cross in each of 8 subjects (mean r = -0.12, n = 48 in each subject). CONCLUSION: The vergence response to a target object significantly differs depending on the texture of background objects on the visual axis.

Target spatial frequency determines the response to conflicting defocus- and convergence-driven accommodative stimuli.

Asthenopia, or visual fatigue, is a frequent complaint from observers of stereoscopic three-dimensional displays. It has been proposed that asthenopia is a consequence of anomalous oculomotor responses generated by conflict between accommodative and convergence stimuli. The hypothesis was examined by measuring accommodation and convergence continuously with a Shin-Nippon SRW5000 infrared autorefractor and a limbus tracking device. Subjects viewed a high contrast Maltese Cross target at three levels of Gaussian filter target blur under conditions of relatively low- and high-conflict between accommodation and convergence stimuli, the latter inducing the sensation of stereopsis. Under the low-conflict conditions accommodation was stable, but convergence-driven accommodation was dominant when the target was extremely blurred. Under the high-conflict conditions the role of convergence-driven accommodation increased systematically with the degree of target blur. It is proposed that defocus-driven accommodation becomes weak when the target comprises low spatial frequency components. Large accommodative overshoots to step stimuli that are not blurred or only mildly blurred were consistently observed and are attributed to the initial accommodative response being convergence-driven. Whereas the possibility that high-conflict conditions are a cause of asthenopia has been previously reported, this is the first evidence that they specifically affect accommodative responses while viewing stereoscopic displays.

Dysfunctional baroreflex regulation of sympathetic nerve activity in remitted patients with panic disorder. A new methodological approach.

BACKGROUND: Many researchers have studied the abnormalities of autonomic nervous system (ANS) such as decreased heart rate variability, which is a risk factor for sudden cardiac death, in patients with panic disorder (PD). However, no consistent abnormality has been uncovered to date. One of the reasons for this controversy may be due to the fact that most of these conventional studies have analyzed each physiological variable independent of other indices. We examined the ANS in PD patients using a new method which can more directly investigate the function of the baroreflex by examining the relation between the blood pressure (BP) and heart rate (HR). METHODS: During rest and audiovisual stimulation (AS) as mental stress such as being exposed to video imaginary of experiences such as driving motor vehicles, cardiovascular parameters, HR and BP were consecutively measured in 13 remitted PD patients and twenty aged and gender-matched normal controls (NC). In this study, to assess the cardiovascular ANS function (baroreflex) in PD we used the power spectrum analysis as usual and the mean of lag time (tau) between the Mayer wave components, which was closely related to sympathetic nerve activity of vasomotor, of HR and BP variability as a new trial. RESULTS: The PD patients and NC did not differ with regard to the power spectrum analysis of the heart rate. We found that tau in the PD group was significantly shorter than that in the NC both before and after AS, especially before. CONCLUSIONS: These findings suggest that remitted PD patients may have a dysfunctional baroreflex regulation of sympathetic nerve activity.

Relationships between Sensory Stimuli and Autonomic Regulation During Real and Virtual Exercises.

For expanding application of virtual reality, such as rehabilitation engineering, concerns of cybersicknes should be cleared. We have investigated changes in autonomic regulations under real cycling and virtual mountain biking video with the first-person viewpoint. The results showed that the dominant sensory stimuli affected autonomic regulation with different process. The different process will lead to the hints for preventing cybersickness.

Momentary changes in the cardiovascular autonomic system during mental loading in patients with panic disorder: a new physiological index "rho(max)".

BACKGROUND: Although panic disorder (PD) is suggestive of autonomic nervous system dysfunction, especially in the cardiovascular autonomic system (CAS), the results in many previous studies are still controversial. Using a new physiological index which could well reflect emotional reaction to visual stimuli (Yoshizawa, M., Sugita, N., Tanaka, A., Abe, K., Yambe, T., Nitta, S., 2001. Quantiatative Physioligical Evaluation of Three Dimensional Images. The Seventh International Conference on Virtual Systems and Multumedia, 25-27.), we studied momentary changes in the CAS in patients with PD during audiovisual stimulation (AS) as mental loading. METHODS: During AS, exposed to a video of imaginary experiences such as driving a motor vehicle or diving into the sea, blood pressure (BP) and heart rate (HR) were measured in 12 remitted patients with PD and 19 age- and sex-matched normal controls (NC). We used the maximum cross-correlation coefficient (rho(max)) from the BP to the HR, whose frequency components were limited to around 0.1 Hz. RESULTS: The rho(max) was an available index which could detect the momentary changes in the CAS during AS in both groups. The two-way ANOVA disclosed significant group and time effects on the rho(max). The momentary response to emotional stimuli in the PD patients was slower than that in the NC subjects. LIMITATIONS: Antidepressants have a potential impact on the autonomic variables in this study. CONCLUSIONS: These findings suggest that there may be a dysfunction of the CAS in remitted PD patients and that the dysfunction may be one of the trait markers of PD. To confirm these findings, however, further studies with a large sample size are required.

Pupillary light reflex in panic disorder. A trial using audiovisual stimulation.

BACKGROUND: Although many previous studies reported abnormalities of autonomic function in patients with panic disorder (PD), almost all targets in those studies primarily focused on cardiovascular autonomic functions. In the present study, we determined whether PD patients exhibited abnormalities in the pupillary autonomic nervous system (ANS). METHODS: Before and after audiovisual stimulation (AS), which induced mental stress through exposure to video images of high stress experiences, such as driving motor vehicles, the pupillary light reflex (PLR) was measured by infrared pupillometer in 13 remitted PD patients and twenty age- and gender-matched normal controls (NC). RESULTS: Before and after AS, there were no significant differences in initial pupillary diameters in dark conditions (D1), pupillary diameters at maximum constriction (D2) or constriction ratios (CR: (D1-D2)/D1) between PD and NC subjects. However, the CR ratio (CR before/CR after) was significantly higher in the PD group than in the NC. CONCLUSIONS: These findings suggest that even remitted PD patients may have a dysfunctional PLR regulation with experimental stressors such as AS.

Central and peripheral visual interactions in disparity-induced vergence eye movements: I. Spatial interaction.

PURPOSE: To evaluate the interaction between central and peripheral disparities in the initiation of vergence eye movements. METHODS: Eye movements were recorded in eight normal subjects using an infrared limbus tracker. Three-dimensional visual stimuli were back projected onto a tangent screen by using two liquid crystal display (LCD) projectors through crossed polarizers. The central target was a vertical bar, which always jumped from 2 to 1 m. The peripheral target was a random-dot pattern that jumped from 2 to 0.75, 1, or 1.5 m (near planes), 2 m (no change), or 3 m (far plane) simultaneously with the central target jump. Latency, amplitude at 150 ms, and average amplitude over 1 to 2 seconds after vergence onset; peak velocity; and the main-sequence relationship of the initial vergence response were calculated. How far the central target appeared to jump was scored subjectively. RESULTS: In half of the subjects, there was a clear effect of the peripheral disparity on the dynamics of the vergence response to the central disparity. The amplitude of vergence at 150 ms, as an index of open-loop gain, was significantly greater when the peripheral target moved closer, but steady state amplitude (average during 1-2 seconds) did not change, and the vergence latency was significantly greater when the peripheral target jumped away. There was no obvious relationship between the perceived amount of movement of the central target and the parameters of the dynamic properties of the vergence response. CONCLUSIONS: Peripheral disparity can modulate the dynamics of the initial vergence response to a central disparity and is probably independent of the perception of motion in depth.

Time-varying behavior of motion vectors in vection-induced images in relation to autonomic regulation.

Virtual reality (VR) is a promising technology in biomedical engineering, but at the same time enlarges another problem called cybersickness. Aiming at suppression of cybersicknes, we are investigating the influences of vection-induced images on the autonomic regulation quantitatively. We used the motion vectors to quantify image scenes and measured electrocardiogram, blood pressure, and respiration for evaluating the autonomic regulation. Using the estimated motion vectors, we further synthesized random-dot pattern images to survey which component of the global motion vectors seriously affected the autonomic regulation. The results showed that the zoom component with a specific frequency band (0.1-3.0 Hz) would induce sickness.

Blink rate variability in patients with panic disorder: new trial using audiovisual stimulation.

Several lines of evidence have implicated central dopaminergic pathways in the modulation of spontaneous blink rate (BR). Furthermore, previous studies have indicated a relationship between spontaneous BR and anxiety and/or depression. However, to our knowledge, there is no report on the examination of BR in a group of patients with panic disorder (PD). During the conditions of rest and with audiovisual stimulation, exposed to a video of imaginary experiences, such as driving a motor vehicle or diving into the sea, BR was examined in 11 male patients with PD and compared with the BR of 16 age-matched normal controls. The BR was significantly higher in PD patients relative to normal controls under both conditions. In particular, the PD group had a higher BR score during the sea scene as relaxation compared with the normal controls. In conclusion, although the sample size was small the present preliminary study, these findings suggest that BR may have potential for application in the assessment of anxiety state, which is consistent with previous studies.

Pupillary and cardiovascular responses to a video movie in senior human subjects.

The effects of watching video movies on autonomic functions were estimated by measuring changes in pupillary and cardiovascular parameters in 10 senior subjects. The subjects looked at a series of video images (with accompanied sounds) taken during the execution of motor vehicles. The images were rear-projected on a large screen for 15 min. Pupil diameter and parameters of the light reflex were measured by an infrared pupillometer before and after the video presentation. Their electrocardiograms (ECG) and blood pressure were measured continuously. Subjects were divided into two groups depending on their values of blood pressure and fasting plasma glucose level. Subjects in Group A had blood pressures of less than 140 mm Hg and a fasting plasma glucose level of less than 7 mmol/dl (normal group). Other subjects were included in Group B (mild hypertension or diabetes mellitus group). While changes in pupillary light reflex after video viewing were minimal in the members of Group A, amplitudes of the pupillary reflex in the members of Group B varied over a significantly wide range. By the spectral analysis of cardiovascular rhythm, %LF and %HF components of blood pressure rhythm were significantly different between the two groups before video viewing. However, the ratios of frequency components before and after video viewing were not significantly different between the two groups. Our findings suggest that pupillary light reflex was less precisely controlled in subjects with mild autonomic dysfunction after prolonged audiovisual stimulation.