Vergence-Accommodation Conflict: Increased Presbyopia in Virtual Reality.

BACKGROUND: Performance and symptoms in completing a visual search task on a PC monitor and using a head-mounted display (HMD) were compared for different viewing conditions and between users of different ages. PATIENTS AND METHODS: Twenty-three young (M = 30 y, SD = 7 y) and 23 older (M = 52 y, SD = 5 y) participants performed a visual search task presented on a PC monitor. The task was repeated using an HMD for a near and a far virtual viewing distance. Reaction times (RT), detection sensitivity (d'), and symptoms were recorded for the three different viewing conditions. RESULTS: RT and d' were not affected by the viewing condition (p > 0.05). In contrast, symptoms significantly depended on the viewing condition but were, in part, not significantly affected by age. It is interesting to note that although not significant, young participants reported more ocular symptoms than older participants in the near vision task carried out using the HMD. DISCUSSION: HMD increases visual symptoms. However, HMD could be, in part, a remedy to problems when using visual aids for near work, in particular for presbyopes.

Head-mounted display versus computer monitor for visual attention screening: A comparative study.

Visual attention is crucial to many tasks during working. When it is impaired, the risk of occupational accidents is increased. A potential accident prevention would be the tracking of employees' attentional states to construct break regimes. There is a promising visual attention test administered on a computer monitor (CM) that has several advantages over widely used continuous performance tests in detecting inattentiveness in occupational environments. However, as the setup with a CM is impractical for the use in particular working environments (e.g., lack of space or disturbing exposure to light), the test was implemented into a head-mounted display (HMD). This study aimed to investigate whether the HMD version of the test is a suitable alternative to the CM version. For this purpose, participants (N = 30; 20-29 y) performed both tests. The performance on the HMD was significantly lower than on the CM. Moreover, the performances were compared with normative data recorded with a CM in a previous study. These data significantly differ from the data recorded with the CM in the present study. This emphasizes the importance of a standardized test environment, which could be provided by an HMD. Conclusively, this study revealed that the new VR tool, based on a previous test designed to assess visual skills in a complex visual environment, exhibited good psychometric property regarding the reliability. In additional, no problems were revealed regarding the functionality and usability of the HMD.

Effects of viewing distance and age on the performance and symptoms in a visual search task in augmented reality.

In augmented reality (AR), virtual information is optically combined with the physical environment. In the most frequently used combination technique, optical settings in AR depart from the settings in natural viewing. Depending on the combination of viewing distances of the virtual task and its physical background, this deviation may lower visual performance and cause visual disturbance symptoms. The so-called vergence-accommodation conflict (VAC) has been identified as a cause for the visual disturbance symptoms in AR. In this study, for various distance combinations, the performance and symptoms when performing a search task displayed in a see-through head-mounted display (AR HMD, HoloLens 1st generation, Microsoft, USA) was investigated. The search task was displayed at a virtual distance of either 200 cm or 30 cm, and the real background was viewed either at a distance of 200 cm or 30 cm. Three combinations of viewing distances for the background and the virtual task were studied: 200 cm/200 cm, 200 cm/30 cm, and 30 cm/30 cm. Results revealed that both performance and visual disturbance symptoms depend on the combination of the viewing distances of the physical background and the virtual task. When the physical background was viewed at a distance of 200 cm, younger participants showed a significantly better search performance and reported stronger symptoms compared with older participants, no matter whether the virtual task was performed at 30 cm or at 200 cm. However, with the physical background at a distance of 30 cm, the performance of the younger group dropped to the level of the performance of the older group, and younger participants tended to report a stronger increase in visual disturbance symptoms compared with the older participants. From the AR HMD technology used in this study, it can be concluded that a near viewing distance of the virtual task does not cause a negative impact on performance and visual disturbance symptoms, provided any physical background seen through the AR HMD is not at a near viewing distance. The findings indicate that the VAC, which persists in augmented and virtual reality, depends, in addition to the physical component evaluating the optical distance, on a cognitive component evaluating the perceived distance. AR settings should therefore also be evaluated in terms of possible effects on perceived distance.

A sudden variation in the visual field reduces driver's accuracy in estimation of the speed of the car ahead.

We offer the hypothesis that a variation in the visual environment of a driver affects their performance in estimating the speed of a car in front. The hypothesis was tested in a driving simulator with 18 drivers by recording their ability to estimate the relative speed of a car ahead when exposed to sudden variations in the visual environment. The sudden variation was produced by briefly (200 ms) masking the driving environment with a grey frame. The results of our study confirm the hypothesis, as the flashed mask significantly lowered the drivers' accuracy in estimating the speed of a car ahead. The results also show that it is possible to cope with variations in the visual environment and to partially recover from the loss of accuracy. The findings are relevant to the layout of driving environments, such as the placement of dynamic advertisements along the side of the road or the entrance zones of tunnels, and to the training of drivers. Practitioner summary: In our driving simulator study, we showed that sudden transitions in the visual environment reduce a driver's performance in evaluating the speed of the car ahead and are therefore a factor in accidents and traffic jams. Transitions should be limited, and drivers should be prepared for the effect of transitions. Abbreviation: ANOVA: analysis of variance.

Development of Ophthalmic Microsurgery Training in Augmented Reality.

BACKGROUND: Using a group of 23 physician trainees, we investigated whether microsurgery training in an augmented reality (AR) training simulator improves motor skills and whether an intelligent tutoring system (ITS) improves training efficiency. METHODS: Characteristic motor skill steps involved in the peeling of an internal limiting membrane (ILM) were identified and implemented in the AR simulation. For training, implemented steps were either presented in the natural sequence, as in a real ILM surgery, or administered according to the ITS. Participants underwent the training over 5 days for 10 minutes per day. A subgroup of 11 participants performed the 5 microsurgical steps in a natural sequence. The other 12 participants used the ITS method. Motor skill performance was recorded before and after each training session with the AR simulator, and before the first and after the last training session using a method that did not rely on AR. RESULTS: Five steps of the ILM peeling procedure were identified and implemented: insertion of the instrument, flap creation, clockwise peeling, counterclockwise peeling, and retraction of the instrument. Both training methods significantly improved the motor skills of the participants. In both methods, steep learning progress was found within the first three training sessions. In both methods, motor skills continued to improve on days 4 and 5, but at a slower rate. After the 5 training days, performance was significantly improved, but improvement did not depend significantly on the training method. However, within the first 3 days of training, ITS led to steeper training progress than the natural sequence method. CONCLUSION: It is possible to improve microsurgical motor skills using the implemented AR simulation. Some technical limitations, such as system lag, deserve further improvements. However, the proposed AR solution was highly appreciated by the participants and could help overcome constraints of practice in microsurgical training, such as limited availability of training opportunities or a standardized assessment of motor skill performance.

Training visual attention in a naturalistic visual environment.

The efficiency of training visual attention in the central and peripheral visual field was investigated by means of a visual detection task that was performed in a naturalistic visual environment including numerous, time-varying visual distractors. We investigated the minimum number of repetitions of the training required to obtain the top performance and whether intra-day training improved performance as efficiently as inter-day training. Additionally, our research aimed to find out whether exposure to a demanding task such as a microsurgical intervention may cancel out the effects of training. Results showed that performance in visual attention peaked within three (for tasks in the central visual field) to seven (for tasks in the periphery) days subsequent to training. Intra-day training had no significant effect on performance. When attention training was administered after exposure to stress, improvement of attentional performance was more pronounced than when training was completed before the exposure. Our findings support the implementation of training in situ at work for more efficient results. Practitioner Summary: Visual attention is important in an increasing number of workplaces, such as with surveillance, inspection, or driving. This study shows that it is possible to train visual attention efficiently within three to seven days. Because our study was executed in a naturalistic environment, training results are more likely to reflect the effects in the real workplace.