A CNN-Based Wearable Assistive System for Visually Impaired People Walking Outdoors

In this study, we propose an assistive system for helping visually impaired people walk outdoors. This assistive system contains an embedded system—Jetson AGX Xavier (manufacture by Nvidia in Santa Clara, CA, USA) and a binocular depth camera—ZED 2 (manufacture by Stereolabs in San Francisco, CA, USA). Based on the CNN neural network FAST-SCNN and the depth map obtained by the ZED 2, the image of the environment in front of the visually impaired user is split into seven equal divisions. A walkability confidence value for each division is computed, and a voice prompt is played to guide the user toward the most appropriate direction such that the visually impaired user can navigate a safe path on the sidewalk, avoid any obstacles, or walk on the crosswalk safely. Furthermore, the obstacle in front of the user is identified by the network YOLOv5s proposed by Jocher, G. et al. Finally, we provided the proposed assistive system to a visually impaired person and experimented around an MRT station in Taiwan. The visually impaired person indicated that the proposed system indeed helped him feel safer when walking outdoors. The experiment also verified that the system could effectively guide the visually impaired person walking safely on the sidewalk and crosswalks.

Associations Between Binocular Depth Perception and Performance Gains in Laparoscopic Skill Acquisition

The ability to perceive differences in depth is important in many daily life situations. It is also of relevance in laparoscopic surgical procedures that require the extrapolation of three-dimensional visual information from two-dimensional planar images. Besides visual-motor coordination, laparoscopic skills and binocular depth perception are demanding visual tasks for which learning is important. This study explored potential relations between binocular depth perception and individual variations in performance gains during laparoscopic skill acquisition in medical students naïve of such procedures. Individual differences in perceptual learning of binocular depth discrimination when performing a random dot stereogram (RDS) task were measured as variations in the slope changes of the logistic disparity psychometric curves from the first to the last blocks of the experiment. The results showed that not only did the individuals differ in their depth discrimination; the extent with which this performance changed across blocks also differed substantially between individuals. Of note, individual differences in perceptual learning of depth discrimination are associated with performance gains from laparoscopic skill training, both with respect to movement speed and an efficiency score that considered both speed and precision. These results indicate that learning-related benefits for enhancing demanding visual processes are, in part, shared between these two tasks. Future studies that include a broader selection of task-varying monocular and binocular cues as well as visual-motor coordination are needed to further investigate potential mechanistic relations between depth perceptual learning and laparoscopic skill acquisition. A deeper understanding of these mechanisms would be important for applied research that aims at designing behavioral interventions for enhancing technology-assisted laparoscopic skills.

Correlated structure of neuronal firing in macaque visual cortex limits information for binocular depth discrimination

Variability in cortical neural activity potentially limits sensory discriminations. Theoretical work shows that information required to discriminate two similar stimuli is limited by the correlation structure of cortical variability. We investigated these information-limiting correlations by recording simultaneously from visual cortical areas V1 and V4 in macaque monkeys, performing a binocular, stereo-depth discrimination task. Within both areas, noise correlations on a rapid temporal scale (20-30ms) were stronger for neuron-pairs with similar selectivity for binocular depth, meaning that these correlations potentially limit information for making the discrimination. Between-area correlations (V1 to V4) were different, being weaker for neuron pairs with similar tuning, and having a slower temporal scale (100+ms). Fluctuations in these information-limiting correlations just prior to the detection event were associated with changes in behavioral accuracy. Although these correlations limit the recovery of information about sensory targets, their impact may be curtailed by integrative processing of signals across multiple brain areas.

Learning to see in 3D with two eyes: the role of experience, plasticity and neurochemistry

Humans, along with other predators, have forward-facing eyes which restrict the area of the world that can be seen when compared to animals with eyes on the side of the head. Why would we sacrifice this panoramic vision? The answer is the very precise ability that having two eyes with overlapping and slightly different viewpoints provides to determine fine differences in depth. While interpreting this type of ‘binocular depth’ appears effortless, the precise calculations necessary for perceiving binocular depth require significant computational power in the cerebral cortex and the fine tuning of neurochemical interactions. This processing occurs in the visual regions of the brain and must be honed through early experience for accurate performance. By considering each stage of binocular processing and the neurochemical interactions required for integrating signals from the two eyes, we can begin to understand how the inherent ability of the brain to learn might help us when binocular vision goes wrong.

Comparison of two extended depth of focus intraocular lenses with a monofocal lens: a multi-centre randomised trial

Purpose The AT LARA 829MP is a next-generation extended depth of focus (EDOF) intraocular lens (IOL) providing continuous vision over a range of distances. The aim of this prospective multi-centre randomised trial was to compare two EDOF IOLs and one monofocal IOL. Methods Cataract patients between 50 and 80 years were randomised for bilateral implantation with either the AT LARA 829MP (EDOF), the TECNIS Symfony (EDOF) or the CT ASPHINA 409MP (monofocal). Follow-up was at 1 to 2 weeks, 1 month and 4 to 6 months. Results A total of 211 patients were randomised and included in the final analysis. Monocular depth of focus was significantly better for AT LARA 829MP eyes compared with that for TECNIS Symfony at all thresholds (p = 0.024, 0.001 and 0.006, for 0.1, 0.2 and 0.3 logMAR respectively) with no significant difference for binocular depth of focus. LARA eyes had significantly better monocular depth of focus at all levels compared with ASPHINA eyes (all p < 0.0001), while there was no significant difference between Symfony and ASPHINA eyes at 0.1 logMAR and 0.2 logMAR. Both EDOF IOLs were significantly better than the monofocal ASPHINA at all levels for binocular depth of focus (LARA: all p < 0.0001; Symfony: all p = 0.002). Distance visual acuity was similar for all IOLs at 6 months; intermediate and near visual acuity were significantly better for the EDOF IOLs than for the monofocal (p < 0.0001). Refraction improved in all groups relative to baseline. Contrast sensitivity was higher with the CT ASPHINA 409MP but both EDOF lenses had a better spectacle independence rate. At 6 months, all IOLs were well centred with no cases of tilt. No general safety issues were raised for any of the groups. Conclusion The two EDOF intraocular lenses investigated provided good visual outcomes with comparable visual acuity at all distances. The AT LARA 829MP provided the widest monocular depth of focus at 0.1 and 0.2 logMAR, with a clear superiority compared with the monofocal IOL. TECNIS Symfony was superior to the monofocal control at 0.3 logMAR. Spectacle independence and patient satisfaction were comparable. Trial registration Trial registered on https://clinicaltrials.gov/ under the identification NCT03172351 (date of registration 1 June May 2017).

Correlated structure of neuronal firing in macaque visual cortex limits information for binocular depth discrimination

ABSTRACTVariability in cortical neural activity potentially limits sensory discriminations. Theoretical work shows that information required to discriminate two similar stimuli is limited by the correlation structure of cortical variability. We investigated these information-limiting correlations by recording simultaneously from visual cortical areas V1 and V4 in macaque monkeys, performing a binocular, stereo-depth discrimination task. Within both areas, noise correlations on a rapid temporal scale (20-30ms) were stronger for neuron-pairs with similar selectivity for binocular depth, meaning that these correlations potentially limit information for making the discrimination. Between-area correlations (V1 to V4) were different, being weaker for neuron pairs with similar tuning, and having a slower temporal scale (100+ms). Fluctuations in these information-limiting correlations just prior to the detection event were associated with changes in behavioural accuracy. Although these correlations limit the recovery of information about sensory targets, their impact may be curtailed by integrative processing of signals across multiple brain areas.