Potential hazards of viewing 3-D stereoscopic television, cinema and computer games: a review

Autostereoscopic 3D viewing can change the dimensions of the crystalline lens in myopes

PURPOSE

Autostereoscopic displays have become increasingly common, but their impact on ocular dimensions remains unknown. We sought to identify changes in the crystalline lens dimensions induced by autostereoscopic three-dimensional (3D) viewing.

METHODS

Forty young adults (age: 22.6 ± 2.0 years, male/female: 15/25) were consecutively enrolled and randomly divided into two groups (3D and two-dimensional [2D] viewing groups) to watch a 30-min movie clip displayed in 3D or 2D mode on a tablet computer. The lens thickness (LT), diameter, curvature, decentration and tilt were measured with anterior segment optical coherence tomography under both non-accommodating (static) and accommodating conditions.

RESULTS

In the static condition, the LT decreased by 0.03 ± 0.03 mm (p < 0.001) and the anterior radius of curvature (ARC) increased by 0.49 ± 0.59 mm (p = 0.001) post-3D viewing. In contrast, following 2D viewing, the ARC decreased by 0.23 ± 0.25 mm (p = 0.001). Additionally, the increase in the steep ARC post-3D viewing was greater in high-myopic eyes than low to moderate myopic eyes (p = 0.04). When comparing the accommodative with the static (non-accommodative) condition, for 3D viewing the lens decentration decreased (-0.03 ± 0.05 mm, p = 0.02); while for 2D viewing, the posterior curvature radius (-0.14 ± 0.20 mm, p = 0.006) and diameter (-0.13 ± 0.20 mm, p = 0.01) decreased.

CONCLUSIONS

Viewing with the autostereoscopic 3D tablet could temporally decrease the thickness and curvature of the lens under non-accommodating conditions. However, its long-term effect requires further exploration.

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.

3D Da Vinci robotic surgery: is it a risk to the surgeon's eye health?

Da Vinci three-dimensional (3D) system has been increasingly used in customary surgical settings, gaining fundamental relevance for abdominal, urological, and gynecological laparoscopic surgery. The aim of this research is to evaluate the degree of discomfort and potential changes in the binocular vision and ocular motility of surgical operators, who employ 3D vision systems during Da Vinci robotic surgery. Twenty-four surgeons were enrolled in the study, including twelve who typically use the 3D Da Vinci system and twelve who routinely employ 2D system. Routine general ophthalmological and orthoptic examinations were conducted at baseline (T0), the day before surgery, and 30 min after the 3D or 2D surgery (T1). In addition, surgeons were interviewed using a questionnaire of 18 symptoms, with each item containing three questions regarding the frequency, severity, and bothersomeness of the symptoms, in order to evaluate the degree of discomfort. Mean age at evaluation was 45.28 ± 8.71 years (range 33-63 years). Cover test, uncover test, and fusional amplitude showed no statistically significant difference. After surgery, no statistical difference was observed in the Da Vinci group on the TNO stereotest (p > 0.9999). However, the difference in the 2D group resulted statistically significant (p = 0.0156). Comparing participants (p 0.0001) and time (T0-T1; p = 0.0137), the difference between the two groups was statistically significant. Surgeons using 2D systems reported more discomfort than those using 3D systems. The absence of short-term consequences following surgery with the Da Vinci 3D system is a promising conclusion, considering the numerous advantages of this technology. Nonetheless, multicenter investigations and more studies are required to verify and interpret our findings.

Conditions of a Multi-View 3D Display for Accurate Reproduction of Perceived Glossiness

Visualizing objects as they are perceived in the real world is often critical in our daily experiences. We previously focused on objects' surface glossiness visualized with a 3D display and found that a multi-view 3D display reproduces perceived glossiness more accurately than a 2D display. This improvement of glossiness reproduction can be explained by the fact that a glossy surface visualized by a multi-view 3D display appropriately provides luminance differences between the two eyes and luminance changes accompanying the viewer's lateral head motion. In the present study, to determine the requirements of a multi-view 3D display for the accurate reproduction of perceived glossiness, we developed a simulator of a multi-view 3D display to independently and simultaneously manipulate the viewpoint interval and the magnitude of the optical inter-view crosstalk. Using the simulator, we conducted a psychophysical experiment and found that glossiness reproduction is most accurate when the viewpoint interval is small and there is just a small (but not too small) amount of crosstalk. We proposed a simple yet perceptually valid model that quantitatively predicts the reproduction accuracy of perceived glossiness.

Holobricks: modular coarse integral holographic displays

Here, we propose and demonstrate a modular holographic display system that allows seamless spatial tiling of multiple coarse integral holographic (CIH) displays called "holobricks". A holobrick is a self-contained CIH module enclosing a spatial light modulator (SLM), a scanner, and periscopic coarse integral optics. Modular CIH uses a coarse pitch and small area but high-bandwidth SLM in conjunction with periscopic coarse integral optics to form the angularly tiled 3D holograms with large viewing areas and fields of view. The creation of periscopic coarse integral optics prevents the optical system from being larger than the holographic image and allows the holographic fringe pattern to fill the entire face of the holobrick. Thus, multiple holobricks can be seamlessly abutted to form a scalable spatially tiled holographic image display capable of both wide field-of-view angle and arbitrary large-size area. We demonstrate an initial prototype that seamlessly tiles two holobricks each with 1024 × 768 pixels, 40° FOV, full color, 24 fps, displaying 2D, 3D holographic stereograms, and full parallax 3D CGI Fresnel holograms.

Study of the Immediate Effects of Autostereoscopic 3D Visual Training on the Accommodative Functions of Myopes

Purpose

Stereoscopic viewing has an impact on ocular dynamics, but its effects on accommodative functions are not fully understood, especially for autostereoscopic viewing. This study aimed to investigate the changes in dynamic accommodative response, accommodative amplitude, and accommodative facility of myopes after autostereoscopic visual training.

Methods

We enrolled 46 adults (men = 22 and women = 24; age = 21.5 ± 2.5 [range = 18–25] years, spherical equivalent: −4.52 ± 1.89 [−8.88 to −1.75] diopters [D]) who visited the Eye & ENT Hospital of Fudan University. The study population was randomly divided into three-dimensional (3D) and two-dimensional (2D) viewing groups to watch an 11-minute training video displayed in 3D or 2D mode. Dynamic accommodative response, accommodative facility, and accommodative amplitude were measured before, during, and immediately after the training. Accommodative lag and the variability of accommodation were also analyzed. Visual fatigue was evaluated subjectively using a questionnaire.

Results

Accommodative lag decreased from 0.54 ± 0.29 D to 0.42 ± 0.32 D (P = 0.004), whereas accommodative facility increased from 10.83 ± 4.55 cycles per minute (cpm) to 13.15 ± 5.25 cpm (P < 0.001) in the 3D group. In the 2D group, there was no significant change in the accommodative lag (P = 0.163) or facility (P = 0.975), but a decrease in accommodative amplitude was observed (from 13.88 ± 3.17 D to 12.71 ± 2.23 D, P = 0.013). In the 3D group, the accommodative response changed with the simulated target distance. Visual fatigue was relatively mild in both groups.

Conclusions

The immediate impact of autostereoscopic training included a decrease in the accommodative lag and an increase in the accommodative facility. However, the long-term effects of autostereoscopic training require further exploration.

When virtual and real worlds coexist: Visualization and visual system affect spatial performance in augmented reality

New visualization approaches are being actively developed aiming to mitigate the effect of vergence-accommodation conflict in stereoscopic augmented reality; however, high interindividual variability in spatial performance makes it difficult to predict user gain. To address this issue, we investigated the effects of consistent and inconsistent binocular and focus cues on perceptual matching in the stereoscopic environment of augmented reality using a head-mounted display that was driven in multifocal and single focal plane modes. Participants matched the distance of a real object with images projected at three viewing distances, concordant with the display focal planes when driven in the multifocal mode. As a result, consistency of depth cues facilitated faster perceptual judgments on spatial relations. Moreover, the individuals with mild binocular and accommodative disorders benefited from the visualization of information on the focal planes corresponding to image planes more than individuals with normal vision, which was reflected in performance accuracy. Because symptoms and complaints may be absent when the functionality of the sensorimotor system is reduced, the results indicate the need for a detailed assessment of visual functions in research on spatial performance. This study highlights that the development of a visualization system that reduces visual stress and improves user performance should be a priority for the successful implementation of augmented reality displays.

Image Size and the Range of Clear and Single Binocular Vision in 3D Displays

SIGNIFICANCE

The range of clear and single binocular vision differs between 3D displays and clinical prism vergences, but this difference is unexplained. This difference prevents clinicians from predicting the range of clear and single binocular vision in 3D-viewing patients. In this study, we tested a hypothesis for this difference.

PURPOSE

The purpose of this study was to determine whether changing fixation target size in 3D viewing significantly affects the vergence ranges and, if so, then to determine whether the target size effect is driven by fusional vergence gain changes, threshold of blur changes, or both.

METHODS

Twenty-one visually normal adults aged 18 to 28 years viewed 3D images at 40 cm in an electronic stereoscopic. The fixation target, a Maltese cross, moved in depth at 2∆/s by way of changing crossed or uncrossed disparity until blur and diplopia ensued. We used four target sizes: (1) small (width × height, 0.21° × 0.63°), (2) medium (1.43° × 4.3°), (3) large (3.6° × 10.8°), and (4) 3D (size changing congruently with disparity). The effect of target size on responses was tested by mixed ANOVAs.

RESULT

Mean convergence blurs and breaks increased with target size by 40% (P < .001) and 71% (P < .001), respectively, and in divergence by 33% (P = .03) and 30% (P = .04), respectively. The increases in break magnitude with target size implicate fusional vergence gain change in the size effect. Increasing target size raised the threshold of blur from 1.06 to 1.82 D in convergence and from 0.97 to 1.48 D in divergence (P = .008).

CONCLUSIONS

Growing fixation target size in 3D viewing increases fusional vergence gain and blur thresholds, which together increase the limits of clear and single binocular vision. Therefore, the clarity of a 3D image depends not only on its disparity but also on the size of the viewed image.

VITOM 3D System in Parotid Gland Surgery: Our Experience

ABSTRACT

In this report, we present our experience with the VITOM 3D system for parotid gland surgery. A retrospective review of 9 consecutive VITOM 3D-assisted parotidectomies was carried out. All of the cases included had benign pathology. Eight of the tumors were in the superficial lobe whereas one case arose in the deep lobe. Superficial parotidectomy type II, according to the ESGS classification, was performed in 5 cases (55.6%): type I-II in 2 cases (22.2%), type I and III in 1 case respectively (11.1%). The postoperative period was uneventful for all of the patients, and no cases of postoperative temporary or definite facial nerve palsy or other complications were reported. The mean operating time was 145 minutes (range 135-165 minutes). Asthenopia never occurred, and there were no cases in which the first surgeon, the assistants, or the nurses needed to interrupt the 3D vision. VITOM 3D has been demonstrated to be safe and effective for parotid gland surgery. The main advantages of VITOM 3D are improved visualization, ergonomics, versatility, training, and education. The drawbacks are related to asthenopia and the learning curve, even though, in our experience, the impact of these factors is minimal.

Full-immersion virtual reality: Adverse effects related to static balance

The use of virtual reality (VR) is associated with several adverse effects including dizziness, headache, and motion sickness. This study investigates how full-immersion VR games cause changes in static balance with associated adverse effects, and whether a fixed or a changing game background is more likely to contribute to such problems. Static balance and adverse effects (eye fatigue and dizziness) were measured in 15 healthy adults under three conditions: baseline; after a full-immersion virtual reality game (PlayStation 4 Pro and PlayStation® VR headset) with a fixed background (15 min); and after a full-immersion virtual reality game with a unfixed background (15 min). Static balance was measured with an AMTI force plate, while eye fatigue and dizziness were measured with the Virtual Reality Symptom Questionnaire (VRSQ) and the Simulator Sickness Questionnaire (SSQ). It was determined that playing a full-immersion VR game had a negative effect on static balance and produced several adverse effects including eye fatigue and dizziness. Moreover, sway velocity and sway length increased significantly in the game with a moving background compared to both the baseline and the game with a fixed background (p < 0.05); VRSQ and SSQ were also significantly higher in this case. It is thus preferable from the perspective of reducing adverse effects that only fixed-background full-immersion VR games be used in rehabilitative interventions.

Assessment of stereo acuity levels using random dot stereo acuity chart in college students

Background and Aims:

Watching 3D images are known to induce more ocular, systemic fatigue and discomfort, which can be referred to as '3D asthenopia', than watching two-dimensional (2D) images. This study was designed to determine the stereo acuity levels among college students and compare it with the hours of use of digital technology.

Methods:

University students in the age group of 18-25 years were screened for visual acuity for distance and near. Refraction was done to find the presence of refractive errors. Those students who had no vergence or accommodation dysfunction and orthophoria were only included in the study. Stereopsis was assessed using random dot stereo acuity chart. The stereo acuity results were grouped as either normal (20 arc seconds or better), Borderline (25 arc seconds to 40 arc seconds) and reduced stereopsis (50 arc seconds to 400 arc seconds). Students were also questioned about the hours of use of digital media.

Results:

The average age of the 246 participates was 20 ± 1.9 years with 78 (32%) were males and 168 (68%) were females. 7% of the population was found to be myopic in our study. The hours of use of digital technology ranged from 0-9 hours a day. Only 13.1% of the student's population met the normal level of stereopsis (20 arc seconds). Around 44.3% of the study population was found to have borderline stereopsis. Also 42.6% of the study population, reduced stereopsis was found. Among the reduced stereo acuity levels, we found stereoacuity levels as low as 100-200 arc seconds were found in nearly 17.6% of the study population.

Conclusion:

It is very much evident from this study that a large group of college students are not enjoying the highest level of binocular vision, which in turn can have a negative impact on their academic performance.

Clear and Single Binocular Vision in Near 3D Displays

SIGNIFICANCE

Accommodation/convergence mismatch induced by 3D displays can cause discomfort symptoms such as those induced by accommodation/convergence mismatch in clinical vergence testing. We found that the limits of clear and single vision during vergence tests are very different between 3D and clinical tests. Clinical vergences should not be used as substitutes for measures of vergences in 3D displays.

PURPOSE

The purposes of this study were to determine whether the limits of clear and single binocular vision derived from phoropter prism vergence tests match the limits measured in a 3D display and to determine whether vergence mode, smooth versus jump, affected those limits in the 3D display.

METHODS

We tested the phoropter prism vergence limits of clear and single vision at 40 cm in 47 binocular young adults. In separate sessions, we tested, in a 3D display, the analogous 40-cm vergence limits for smooth vergence and jump vergence. The 3D fixation target was a Maltese cross whose visual angle changed congruently with target disparity.

RESULTS

Our mean phoropter vergence blur and break values were similar to those reported in previous studies. The mean smooth divergence limit was less in the 3D display (9.8Δ) than in the phoropter (12.8Δ). Most smooth convergence limits were much larger in the 3D display than in the phoropter, reaching the 35Δ limit of the 3D display without blur or diplopia in 24 subjects. Mean jump vergence limits were significantly smaller than smooth vergence limits in the 3D display.

CONCLUSIONS

The limits of clear and single binocular vision derived from phoropter vergence tests were not a good approximation of the analogous limits in our 3D display.

Liquid-Crystal-on-Silicon for Augmented Reality Displays

In this paper, we review liquid-crystal-on-silicon (LCoS) technology and focus on its new application in emerging augmented reality (AR) displays. In the first part, the LCoS working principles of three commonly adopted LC modes—vertical alignment and twist nematic for amplitude modulation, and homogeneous alignment for phase modulation—are introduced and their pros and cons evaluated. In the second part, the fringing field effect is analyzed, and a novel pretilt angle patterning method for suppressing the effect is presented. Moreover, we illustrate how to integrate the LCoS panel in an AR display system. Both currently available intensity modulators and under-developing holographic displays are covered, with special emphases on achieving high image quality, such as a fast response time and high-resolution. The rapidly increasing application of LCoS in AR head-mounted displays and head-up displays is foreseeable.

[3 D laparoscopy versus 2 D laparoscopy : An up to date evaluation]

BACKGROUND

The 3D laparoscopy is currently under intensive discussion. At the moment the majority of newly acquired laparoscopy systems include the 3D technique. New 4K systems, which will be offered in combination with 3D, are complicating the decision-making when buying new laparoscopic systems. The aim of the article is to show the advantages and possible limitations of 3D laparoscopy. Furthermore, the position of 3D laparoscopy in the current video market is evaluated.

MATERIAL AND METHODS

This study was based on an up to date literature search in PubMed. Concerning the question whether the 3D is replacing the 2D laparoscopy, observations from the industry and a personal evaluation were included in the analysis.

RESULTS

The current studies show clear advantages of 3D laparoscopy concerning operation time, efficiency and workload. A major proportion of the studies were conducted on simulation trainers; however, some clinical trials also confirmed these results. The learning curve in laparoscopic surgery is clearly improved with the 3D technique and 3D also seems be useful for operations by experts. The limitation is that not every surgeon can see three dimensionally. Furthermore, the set-up in the operation room needs to be optimized so that a 3D system can be successfully implemented with the nursing staff and side effects, such as exhaustion, dizziness or headache can be prevented.

CONCLUSION

The choice of video system will depend on the personal interest of the surgeon and the ability to see 3D. It can be assumed that the majority of the systems will include 3D laparoscopy but 2D laparoscopy will not be completely replaced. A dynamic development of 3D in association with 4K and robotics can be expected.

Prefrontal Cortex Oxygenation Evoked by Convergence Load Under Conflicting Stimulus-to-Accommodation and Stimulus-to-Vergence Eye-Movements Measured by NIRS

Purpose: To extend our knowledge of the functional linkages between visual fatigue and regional cerebral prefrontal cortex (PFC) oxygenation, we measured time related hemodynamic changes over the right dorsolateral prefrontal cortex (dlPFC) during convergence load under conflicting stimulus-to-accommodation and stimulus-to-vergence eye movements with and without concurrent mental load.

Methods: Twenty healthy participants with a median age of 28 years (range: 18–44 years) fixated upon a vertical bar presented separately to the left and right eyes, using polarized filters, during four counterbalanced 10-min periods: (i) no accommodation/vergence conflict (Control, Ctrl); (ii) added convergence load and accommodation/vergence conflict (Conv); (iii) added cognitive load only (Cog) and; (iv) a combination of added cognitive and convergence load and accommodation/vergence conflict (Cc). Viewing distance was 65 cm. Non-invasive measurements of hemodynamic activity over the dlPFC were quantified by functional near-infrared spectroscopy (fNIRS). During the two-convergence load conditions, the horizontal disparity of the two bars varied dynamically from no disparity to a disparity set 20% below the individual threshold for diplopia. Cognitive load was induced by the n-back-2 test which required the subject to memorize and recall the changing colors of the horizontal bars and decide when a given color was the same as that occurring two colors previously. fNIRS data were averaged over 10-s windows centered at 0, 2, 4, 6, 8, and 10 min of each task, subtracted from a 20-s baseline window immediately preceding the visual task, and then represented as changes in oxygenated hemoglobin (ΔHbO₂)_, deoxygenated hemoglobin (ΔHHb) and total hemoglobin (ΔtHb).

Results: Linear mixed model analyses showed that hemodynamic activity was systematically influenced by time (p < 0.001). The group-averaged time-related level of change across the viewing conditions did not differ when compared with one another (p > 0.05). Larger convergence eye-movement responses under conflicting stimulus-to-accommodation, and stimulus-to-vergence over time, increased ΔHbO₂ and ΔtHb only in condition Cc and after 8 min of task time (p < 0.10 for min^-6 and min^-8: p < 0.05 for min^-10).

Discussion: Collectively, our data suggest that HbO₂, HHb, and tHb, recorded over the dlPFC with fNIRS, can be used to assay the degree to which supervisory oculomotor control processes are activated during visually deficient near work.

The impact on human visual performance when viewing 2-D and 3-D movies

BACKGROUND AND OBJECTIVE:

To examine the human visual performance (wavefront aberration) and subjective questionnaire (SQ) of visual fatigue when viewing 2-D and 3-D movies.

METHODS:

Thirty healthy adults observed 2-D and 3-D movies on the same television from a 3m distances during 2D, 3D-A (with better 3D glasses), and 3D-B (with poorer 3D glasses) viewing conditions. Visual quality index, including modulation transfer function index (MTFI), higher order aberration root mean square (RMS), vertical coma (VC), horizontal coma (HC) and spherical aberration (SA), were assessed before and after each viewing condition. One-way repeated measures ANOVA was performed to assess the changes of each test variable before and after movie viewing.

RESULTS:

Participants watching movies with 3D-B conditions experienced higher change of MTFI, RMS, VC and HC but smaller SQ, compared with 2D and 3D-A (P< 0.05). Additionally, higher MTFI but smaller SQ was found for 3D-A compared with 2D viewing condition (P< 0.05).

CONCLUSIONS:

While prolonged viewing 2-D and 3-D movies would lead to poorer visual performance, 3-D glasses with better quality can play the major role in reducing visual ability for users. The change of human eye wavefront aberration might be useful for the evaluation of visual fatigue in the future.

Ocular effects of virtual reality headset wear in young adults

Virtual Reality (VR) headsets create immersion by displaying images on screens placed very close to the eyes, which are viewed through high powered lenses. Here we investigate whether this viewing arrangement alters the binocular status of the eyes, and whether it is likely to provide a stimulus for myopia development. We compared binocular status after 40-minute trials in indoor and outdoor environments, in both real and virtual worlds. We also measured the change in thickness of the ocular choroid, to assess the likely presence of signals for ocular growth and myopia development. We found that changes in binocular posture at distance and near, gaze stability, amplitude of accommodation and stereopsis were not different after exposure to each of the 4 environments. Thus, we found no evidence that the VR optical arrangement had an adverse effect on the binocular status of the eyes in the short term. Choroidal thickness did not change after either real world trial, but there was a significant thickening (≈10 microns) after each VR trial (p < 0.001). The choroidal thickening which we observed suggest that a VR headset may not be a myopiagenic stimulus, despite the very close viewing distances involved.

Visual Fatigue Induced by Viewing a Tablet Computer with a High-resolution Display

Purpose

In the present study, the visual discomfort induced by smart mobile devices was assessed in normal and healthy adults.

Methods

Fifty-nine volunteers (age, 38.16 ± 10.23 years; male : female = 19 : 40) were exposed to tablet computer screen stimuli (iPad Air, Apple Inc.) for 1 hour. Participants watched a movie or played a computer game on the tablet computer. Visual fatigue and discomfort were assessed using an asthenopia questionnaire, tear film break-up time, and total ocular wavefront aberration before and after viewing smart mobile devices.

Results

Based on the questionnaire, viewing smart mobile devices for 1 hour significantly increased mean total asthenopia score from 19.59 ± 8.58 to 22.68 ± 9.39 (p < 0.001). Specifically, the scores for five items (tired eyes, sore/aching eyes, irritated eyes, watery eyes, and hot/burning eye) were significantly increased by viewing smart mobile devices. Tear film break-up time significantly decreased from 5.09 ± 1.52 seconds to 4.63 ± 1.34 seconds (p = 0.003). However, total ocular wavefront aberration was unchanged.

Conclusions

Visual fatigue and discomfort were significantly induced by viewing smart mobile devices, even though the devices were equipped with state-of-the-art display technology.

Visual fatigue while watching 3D stimuli from different positions

PURPOSE

When observers focus their stereoscopic visual system for a long time (e.g., watching a 3D movie) they may experience visual discomfort or asthenopia. We tested two types of models for predicting visual fatigue in a task in which subjects were instructed to discriminate between 3D characters. One model was based on viewing distance (focal distance, vergence distance) and another in visual direction (oculomotor imbalance).

METHOD

A 3D test was designed to assess binocular visual fatigue while looking at 3D stimuli located in different visual directions and viewed from two distances from the screen. The observers were tested under three conditions: (a) normal vision; (b) wearing a lens (-2 diop.); (c) wearing a base-out prism (2▿) over each eye. Sensitivity and specificity were calculated (as Signal Detection Theory parameters: SDT).

RESULTS

An ANOVA and SDT analyses revealed that impaired visual performance were directly related to short distance and larger deviation in visual direction, particularly when the stimuli were located nearer and at more than 24° to the centre of the screen in dextroversion and beyond.

CONCLUSION

This results support a mixed model, combining a model based on the visual angle (related to viewing distance) and another based on the oculomotor imbalance (related to visual direction). This mixed model could help to predict the distribution of seats in the cinema room ranging from those that produce greater visual comfort to those that produce more visual discomfort. Also could be a first step to pre-diagnosis of binocular vision disorders.

Effect of Illumination on Ocular Status Modifications Induced by Short-Term 3D TV Viewing

Objectives. This study aimed to compare changes in ocular status after 3D TV viewing under three modes of illumination and thereby identify optimal illumination for 3D TV viewing. Methods. The following measures of ocular status were assessed: the accommodative response, accommodative microfluctuation, accommodative facility, relative accommodation, gradient accommodative convergence/accommodation (AC/A) ratio, phoria, and fusional vergence. The observers watched 3D television for 90 minutes through 3D shutter glasses under three illumination modes: A, complete darkness; B, back illumination (50 lx); and C, front illumination (130 lx). The ocular status of the observers was assessed both before and after the viewing. Results. After 3D TV viewing, the accommodative response and accommodative microfluctuation were significantly changed under illumination Modes A and B. The near positive fusional vergence decreased significantly after the 90-minute 3D viewing session under each illumination mode, and this effect was not significantly different among the three modes. Conclusions. Short-term 3D viewing modified the ocular status of adults. The least amount of such change occurred with front illumination, suggesting that this type of illumination is an appropriate mode for 3D shutter TV viewing.

The viewpoint-specific failure of modern 3D displays in laparoscopic surgery

PURPOSE

Surgeons conventionally assume the optimal viewing position during 3D laparoscopic surgery and may not be aware of the potential hazards to team members positioned across different suboptimal viewing positions. The first aim of this study was to map the viewing positions within a standard operating theatre where individuals may experience visual ghosting (i.e. double vision images) from crosstalk. The second aim was to characterize the standard viewing positions adopted by instrument nurses and surgical assistants during laparoscopic pelvic surgery and report the associated levels of visual ghosting and discomfort.

METHODS

In experiment 1, 15 participants viewed a laparoscopic 3D display from 176 different viewing positions around the screen. In experiment 2, 12 participants (randomly assigned to four clinically relevant viewing positions) viewed laparoscopic suturing in a simulation laboratory. In both experiments, we measured the intensity of visual ghosting. In experiment 2, participants also completed the Simulator Sickness Questionnaire.

RESULTS

We mapped locations within the dimensions of a standard operating theatre at which visual ghosting may result during 3D laparoscopy. Head height relative to the bottom of the image and large horizontal eccentricities away from the surface normal were important contributors to high levels of visual ghosting. Conventional viewing positions adopted by instrument nurses yielded high levels of visual ghosting and severe discomfort.

CONCLUSIONS

The conventional viewing positions adopted by surgical team members during laparoscopic pelvic operations are suboptimal for viewing 3D laparoscopic displays, and even short periods of viewing can yield high levels of discomfort.

3D Displays

Creating realistic three-dimensional (3D) experiences has been a very active area of research and development, and this article describes progress and what remains to be solved. A very active area of technical development has been to build displays that create the correct relationship between viewing parameters and triangulation depth cues: stereo, motion, and focus. Several disciplines are involved in the design, construction, evaluation, and use of 3D displays, but an understanding of human vision is crucial to this enterprise because in the end, the goal is to provide the desired perceptual experience for the viewer. In this article, we review research and development concerning displays that create 3D experiences. And we highlight areas in which further research and development is needed.

The Conflicting Evidence of Three-dimensional Displays in Laparoscopy: A Review of Systems Old and New

OBJECTIVE

To describe studies evaluating 3 generations of three-dimensional (3D) displays over the course of 20 years.

SUMMARY BACKGROUND DATA

Most previous studies have analyzed performance differences during 3D and two-dimensional (2D) laparoscopy without using appropriate controls that equated conditions in all respects except for 3D or 2D viewing.

METHODS

Databases search consisted of MEDLINE and PubMed. The reference lists for all relevant articles were also reviewed for additional articles. The search strategy employed the use of keywords "3D," "Laparoscopic," "Laparoscopy," "Performance," "Education," "Learning," and "Surgery" in appropriate combinations.

RESULTS

Our current understanding of the performance metrics between 3D and 2D laparoscopy is mostly from the research with flawed study designs. This review has been written in a qualitative style to explain in detail how prior research has underestimated the potential benefit of 3D displays and the improvements that must be made in future experiments comparing 3D and 2D displays to better determine any advantage of using one display or the other.

CONCLUSIONS

Individual laparoscopic performance in 3D may be affected by a multitude of factors. It is crucial for studies to measure participant stereoscopic ability, control for system crosstalk, and use validated measures of performance.

The Influence of Monocular Spatial Cues on Vergence Eye Movements in Monocular and Binocular Viewing of 3-D and 2-D Stimuli

The influence of monocular spatial cues on the vergence eye movements was studied in two series of experiments: (I) the subjects were viewing a 3-D video and also its 2-D version-binocularly and monocularly; and (II) in binocular and monocular viewing conditions, the subjects were presented with stationary 2-D stimuli containing or not containing some monocular indications of spatial arrangement. The results of the series (I) showed that, in binocular viewing conditions, the vergence eye movements were only present in the case of 3-D but not 2-D video, while in the course of monocular viewing of 2-D video, some regular vergence eye movements could be revealed, suggesting that the occluded eye position could be influenced by the spatial organization of the scene reconstructed on the basis of the monocular depth information provided by the viewing eye. The data obtained in series (II), in general, seem to support this hypothesis.

Depth-of-Focus Affects 3D Perception in Stereoscopic Displays

Stereoscopic systems present binocular images on planar surface at a fixed distance. They induce cues to flatness, indicating that images are presented on a unique surface and specifying the relative depth of that surface. The center of interest of this study is on a second problem, arising when a 3D object distance differs from the display distance. As binocular disparity must be scaled using an estimate of viewing distance, object depth can thus be affected through disparity scaling. Two previous experiments revealed that stereoscopic displays can affect depth perception due to conflicting accommodation and vergence cues at near distances. In this study, depth perception is evaluated for farther accommodation and vergence distances using a commercially available 3D TV. In Experiment I, we evaluated depth perception of 3D stimuli at different vergence distances for a large pool of participants. We observed a strong effect of vergence distance that was bigger for younger than for older participants, suggesting that the effect of accommodation was reduced in participants with emerging presbyopia. In Experiment 2, we extended 3D estimations by varying both the accommodation and vergence distances. We also tested the hypothesis that setting accommodation open loop by constricting pupil size could decrease the contribution of focus cues to perceived distance. We found that the depth constancy was affected by accommodation and vergence distances and that the accommodation distance effect was reduced with a larger depth-of-focus. We discuss these results with regard to the effectiveness of focus cues as a distance signal. Overall, these results highlight the importance of appropriate focus cues in stereoscopic displays at intermediate viewing distances.

Balance and coordination after viewing stereoscopic 3D television

Manufacturers and the media have raised the possibility that viewing stereoscopic 3D television (S3D TV) may cause temporary disruption to balance and visuomotor coordination. We looked for evidence of such effects in a laboratory-based study. Four hundred and thirty-three people aged 4-82 years old carried out tests of balance and coordination before and after viewing an 80 min movie in either conventional 2D or stereoscopic 3D, while wearing two triaxial accelerometers. Accelerometry produced little evidence of any change in body motion associated with S3D TV. We found no evidence that viewing the movie in S3D causes a detectable impairment in balance or in visuomotor coordination.

The impact of 3D and 2D TV watching on neurophysiological responses and cognitive functioning in adults

BACKGROUND

Watching three-dimensional television (3D TV) may strain the eyes. However, other potential harmful effects of 3D TV watching have been rarely investigated. The current study examined the impact of 3D TV watching on neurophysiological responses and cognitive functioning as compared with two-dimensional TV (2D TV) watching.

METHODS

A total of 72 individuals were randomly assigned to either a 3D TV watching group or a 2D TV watching group. Electroencephalography (EEG) was used to measure neurophysiological responses, and computerized neurocognitive tests were conducted immediately before and after TV watching. The Simulator Sickness Questionnaire (SSQ) was used to assess visual discomfort.

RESULTS

There was a significant change in visual discomfort between the two groups (SSQ score at baseline: 2.28 ± 3.05 for the 3D TV group and 3.69 ± 3.49 for the 2D TV group; SSQ score after watching TV: 4.6 ± 3.35 for the 3D TV group and 4.03 ± 3.47 for the 2D TV group), and this change was greater for the 3D TV watching group (P = 0.025). However, 3D TV watching did not have a differential impact on EEG responses. Furthermore, there were no significant differences between the groups in terms of changes in cognitive performance, except for a subtle difference in backward digit span performance.

CONCLUSION

Our findings suggest that 3D TV watching is as safe as 2D TV watching in terms of neurophysiological responses and cognitive functioning. Potential harmful effects of TV viewing might be similar regardless of whether 3D or 2D TV is viewed.

The rate of change of vergence-accommodation conflict affects visual discomfort

Stereoscopic (S3D) displays create conflicts between the distance to which the eyes must converge and the distance to which the eyes must accommodate. Such conflicts require the viewer to overcome the normal coupling between vergence and accommodation, and this effort appears to cause viewer discomfort. Vergence-accommodation coupling is driven by the phasic components of the underlying control systems, and those components respond to relatively fast changes in vergence and accommodative stimuli. Given the relationship between phasic changes and vergence-accommodation coupling, we examined how the rate of change in the vergence-accommodation conflict affects viewer discomfort. We used a stereoscopic display that allows independent manipulation of the stimuli to vergence and accommodation. We presented stimuli that simulate natural viewing (i.e., vergence and accommodative stimuli changed together) and stimuli that simulate S3D viewing (i.e., vergence stimulus changes but accommodative stimulus remains fixed). The changes occurred at 0.01, 0.05, or 0.25 Hz. The lowest rate is too slow to stimulate the phasic components while the highest rate is well within the phasic range. The results were consistent with our expectation: somewhat greater discomfort was experienced when stimulus distance changed rapidly, particularly in S3D viewing when the vergence stimulus changed but the accommodative stimulus did not. These results may help in the generation of guidelines for the creation and viewing of stereo content with acceptable viewer comfort.

Instability of the perceived world while watching 3D stereoscopic imagery: A likely source of motion sickness symptoms

Watching 3D content using a stereoscopic display may cause various discomforting symptoms, including eye strain, blurred vision, double vision, and motion sickness. Numerous studies have reported motion-sickness-like symptoms during stereoscopic viewing, but no causal linkage between specific aspects of the presentation and the induced discomfort has been explicitly proposed. Here, we describe several causes, in which stereoscopic capture, display, and viewing differ from natural viewing resulting in static and, importantly, dynamic distortions that conflict with the expected stability and rigidity of the real world. This analysis provides a basis for suggested changes to display systems that may alleviate the symptoms, and suggestions for future studies to determine the relative contribution of the various effects to the unpleasant symptoms.

Vergence facility with stereoscopic and nonstereoscopic targets

PURPOSE

To compare vergence facility with nonstereo and stereo targets in binocular symptomatic and asymptomatic subjects.

METHODS

Sixty-six students were divided into symptomatic and asymptomatic groups according to the Convergence Insufficiency Symptom Survey Questionnaire score. Vergence facility was tested at 40 cm by flipper prism 3Δ BI/12Δ BO (BI, base-in; BO, base-out). The targets used were a nonstereo target (a vertical column of small letter "E" of ~20/30 size), a stereo-local target (fifth set of circles of the Titmus test with stereoacuity of 100 arcsec), and a stereo-global target (page 6 of the TNO test with stereoacuity of 120 arcsec).

RESULTS

Repeated-measures analysis of variance showed differences in the mean vergence facility with different targets in all subjects and separately in two symptom groups (p < 0.001). In all subjects and separately in the symptomatic subjects, this difference was statistically significant among the three different targets (p < 0.05). In the asymptomatic subjects, this difference was not significant between the measured values with nonstereo and stereo-local targets (p > 0.05) but significant for the comparison of stereo-global targets with the other two targets. The receiver operating characteristic curve analysis showed the cutoff points 10.5, 10.5, and 9.75 cycles per minute with nonstereo, stereo-local, and stereo-global targets, respectively. The sensitivity of the three targets used was the same (97%). Specificity was 0.93 or higher with all three targets, with the highest specificity obtained with the stereo-global target (100%).

CONCLUSIONS

The highest vergence facility was obtained with a nonstereo target and the lowest was obtained with a stereo-global target. High sensitivity with all three targets means that there are few false-negative results with them, and the high specificity is indicative of low false-positive results. Hence, the vergence facility predictive value would be high in diagnosing binocular symptomatic patients using a 3Δ BI/12Δ BO prism flipper at near and a response cutoff of about 10 cycles per minute or less.

User experience while viewing stereoscopic 3D television

3D display technologies have been linked to visual discomfort and fatigue. In a lab-based study with a between-subjects design, 433 viewers aged from 4 to 82 years watched the same movie in either 2D or stereo 3D (S3D), and subjectively reported on a range of aspects of their viewing experience. Our results suggest that a minority of viewers, around 14%, experience adverse effects due to viewing S3D, mainly headache and eyestrain. A control experiment where participants viewed 2D content through 3D glasses suggests that around 8% may report adverse effects which are not due directly to viewing S3D, but instead are due to the glasses or to negative preconceptions about S3D (the 'nocebo effect'). Women were slightly more likely than men to report adverse effects with S3D. We could not detect any link between pre-existing eye conditions or low stereoacuity and the likelihood of experiencing adverse effects with S3D.

Effect of the accommodation-vergence conflict on vergence eye movements

With the broader use of stereoscopic displays, a flurry of research activity about the accommodation-vergence conflict has emerged to highlight the implications for the human visual system. In stereoscopic displays, the introduction of binocular disparities requires the eyes to make vergence movements. In this study, we examined vergence dynamics with regard to the conflict between the stimulus-to-accommodation and the stimulus-to-vergence. In a first experiment, we evaluated the immediate effect of the conflict on vergence responses by presenting stimuli with conflicting disparity and focus on a stereoscopic display (i.e. increasing the stereoscopic demand) or by presenting stimuli with matched disparity and focus using an arrangement of displays and a beam splitter (i.e. focus and disparity specifying the same locations). We found that the dynamics of vergence responses were slower overall in the first case due to the conflict between accommodation and vergence. In a second experiment, we examined the effect of a prolonged exposure to the accommodation-vergence conflict on vergence responses, in which participants judged whether an oscillating depth pattern was in front or behind the fixation plane. An increase in peak velocity was observed, thereby suggesting that the vergence system has adapted to the stereoscopic demand. A slight increase in vergence latency was also observed, thus indicating a small decline of vergence performance. These findings offer a better understanding and document how the vergence system behaves in stereoscopic displays. We describe what stimuli in stereo-movies might produce these oculomotor effects, and discuss potential applications perspectives.

Microbiological safety of glasses dispensed at 3D movie theatres

Recent popularity of three-dimensional movies raised some concern about microbiological safety of glasses dispensed into movie theatres. In this study, we analysed the level of microbiological contamination on them before and after use and between theatres adopting manual and automatic sanitation systems. The manual sanitation system was more effective in reducing the total mesophilic count levels compared with the automatic system (P < 0.05), but no differences were found for coagulase-positive staphylococci levels (P = 0.22). No differences were found for mould and yeast between before and after levels (P = 0.21) and between sanitation systems (P = 0.44). We conclude that more evidences are needed to support microbiological risk evaluation.

Utility of stereoscopic displays for indirect-vision driving and robot teleoperation

The effectiveness of an active shutter-glasses stereoscopic display (SD) and a passive polarised SD was evaluated in a live robot-teleoperation task and a simulated indirect-vision driving task in various terrains. Overall, participants completed their tasks significantly faster with the SDs in three-dimensional (3D) mode than with the SDs in the baseline 2D mode. They also navigated more accurately with the SDs in 3D mode. When the effectiveness of the two types of SDs was examined separately, results showed that the active shutter-glasses SD resulted in faster responses and task completion times than the passive polarised SD, though most of the differences failed to reach statistical significance. Perceived workload when interacting with the two SD systems did not differ significantly between the active versus passive display types or between the 3D and 2D modes of operation; however, participants reported more severe discomfort after interacting with the passive polarised SD.

Dichoptic Viewing Methods for Binocular Rivalry Research: Prospects for Large-Scale Clinical and Genetic Studies

Binocular rivalry (BR) is an intriguing phenomenon that occurs when two different images are presented, one to each eye, resulting in alternation orrivalrybetween the percepts. The phenomenon has been studied for nearly 200 years, with renewed and intensive investigation over recent decades. Therateof perceptual switching has long been known to vary widely between individuals but to be relatively stable within individuals. A recent twin study demonstrated that individual variation in BR rate is under substantial genetic control, a finding that also represented the first report, using a large study, of genetic contribution for any post-retinal visual processing phenomenon. The twin study had been prompted by earlier work showing BR rate was slow in the heritable psychiatric condition, bipolar disorder (BD). Together, these studies suggested that slow BR may represent an endophenotype for BD, and heralded the advent of modern clinical and genetic studies of rivalry. This new focus has coincided with rapid advances in 3D display technology, but despite such progress, specific development of technology for rivalry research has been lacking. This review therefore compares different display methods for BR research across several factors, including viewing parameters, image quality, equipment cost, compatibility with other investigative methods, subject group, and sample size, with a focus on requirements specific to large-scale clinical and genetic studies. It is intended to be a resource for investigators new to BR research, such as clinicians and geneticists, and to stimulate the development of 3D display technology for advancing interdisciplinary studies of rivalry.

Visual fatigue effects on vergence dynamics in asymptomatic individuals

PURPOSE

To evaluate objectively changes in vergence dynamics following intentional visual fatiguing tasks using congruent (C) and non-congruent (NC) vergence stimulus demands.

METHODS

Pre- and post-task vergence dynamics to a 10.3° disparity stimulus were recorded objectively in 12 adult, asymptomatic individuals for both convergence and divergence. There were two fatigue-inducing tasks: Congruent or C-task: Subjects altered bifixation (50 cycles) between reduced Snellen charts at 2 m and at 20 cm every 3 s. Non-congruent or NC task: Subjects performed 50 cycles of vergence flipper (7Δ BO/BI), while bifixating a reduced Snellen chart at 40 cm. Pre- and post-task mean amplitude, time constant, peak velocity, and steady-state response variability were compared.

RESULTS

There was a significant increase in mean post-task, steady-state response variability for both the C and NC tasks. However, there were no significant group differences for either convergence or divergence between the pre- and post-mean amplitude, time constant, and peak velocity parameters for both the C and NC tasks, although post-task peak velocity was consistently reduced.

CONCLUSIONS

Steady-state vergence response variability was found to be the critical objective parameter to demonstrate significant fatigue effects in the group. Peak velocity was also consistently reduced to a small extent in the NC task. We speculate that these fatigue effects are of a central, and not of peripheral, origin.