Evaluating Text Reading Speed in VR Scenes and 3D Particle Visualizations.

This work reports how text size and other rendering conditions affect reading speeds in a virtual reality environment and a scientific data analysis application. Displaying text legibly yet space-efficiently is a challenging problem in immersive displays. Effective text displays that enable users to read at their maximum speed must consider the variety of virtual reality (VR) display hardware and possible visual exploration tasks. We investigate how text size and display parameters affect reading speed and legibility in three state-of-the-art VR displays: two head-mounted displays and one CAVE. In our perception experiments, we establish limits where reading speed declines as the text size approaches the so-called critical print sizes (CPS) of individual displays, which can inform the design of uniform reading experiences across different VR systems. We observe an inverse correlation between display resolution and CPS. Yet, even in high-fidelity VR systems, the measured CPS was larger than in comparable physical text displays, highlighting the value of increased VR display resolutions in certain visualization scenarios. Our findings indicate that CPS can be an effective metric for evaluating VR display usability. Additionally, we evaluate the effects of text panel placement, orientation, and occlusion-reducing rendering methods on reading speeds in generic volumetric particle visualizations. Our study provides insights into the trade-off between text representation and legibility in cluttered immersive environments with specific suggestions for visualization designers and highlight areas for further research.

Improved Outcomes with Heavy Silicone Oil in Complex Primary Retinal Detachment: A Large Multicenter Matched Cohort Study.

PURPOSE: To establish whether Densiron 68, a heavier-than-water endotamponade agent, is an effective alternative to conventional light silicone oil in primary rhegmatogenous retinal detachment (RD) surgery for eyes with inferior breaks in the detached retina and severe proliferative vitreoretinopathy (PVR). DESIGN: Cohort study of routinely collected data from the European Society of Retina Specialists and British and Eire Association of Vitreoretinal Surgeons vitreoretinal database between 2015 and 2022. PARTICIPANTS: All consecutive eyes that underwent primary rhegmatogenous RD surgery using Densiron 68 or light silicone oil as an internal tamponade agent. METHODS: To minimize confounding bias, we undertook 2:1 nearest-neighbor matching on inferior breaks, large inferior rhegmatogenous RDs, PVR, and, for visual analyses, baseline visual acuity (VA) between treatment groups. We fit regression models including prognostically relevant covariates, treatment-covariate interactions, and matching weights. We used g-computation with cluster-robust methods to estimate marginal effects. For nonlinear models, we calculated confidence intervals (CIs) using bias-corrected cluster bootstrapping with 9999 replications. MAIN OUTCOME MEASURES: Presence of a fully attached retina and VA at least 2 months after oil removal. RESULTS: Of 1061 eyes enrolled, 426 and 239 were included in our matched samples for anatomic and visual outcome analyses, respectively. The primary success rate was higher in the Densiron 68 group (113 of 142; 80%) compared with the light silicone oil group (180 of 284; 63%), with an adjusted odds ratio of 1.90 (95% CI, 1.63-2.23, P < 0.001). We also observed a significant improvement favoring Densiron 68 of -0.26 logarithm of the minimum angle of resolution (logMAR) in postoperative VA between the 2 groups (95% CI, -0.43 to -0.10, P = 0.002). The anatomic benefit of using Densiron 68 in eyes with inferior retinal breaks and large detachments was more pronounced among eyes with PVR grade C. We found no evidence of visual effect moderation by anatomic outcome or foveal attachment. CONCLUSIONS: Densiron achieved higher anatomic success rates and improved visual outcomes compared with conventional light silicone oil in eyes with inferior retinal pathology and severe PVR. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Memory-efficient semantic segmentation of large microscopy images using graph-based neural networks.

We present a graph neural network (GNN)-based framework applied to large-scale microscopy image segmentation tasks. While deep learning models, like convolutional neural networks (CNNs), have become common for automating image segmentation tasks, they are limited by the image size that can fit in the memory of computational hardware. In a GNN framework, large-scale images are converted into graphs using superpixels (regions of pixels with similar color/intensity values), allowing us to input information from the entire image into the model. By converting images with hundreds of millions of pixels to graphs with thousands of nodes, we can segment large images using memory-limited computational resources. We compare the performance of GNN- and CNN-based segmentation in terms of accuracy, training time and required graphics processing unit memory. Based on our experiments with microscopy images of biological cells and cell colonies, GNN-based segmentation used one to three orders-of-magnitude fewer computational resources with only a change in accuracy of $-2\;%$ to $+0.3\;%$. Furthermore, errors due to superpixel generation can be reduced by either using better superpixel generation algorithms or increasing the number of superpixels, thereby allowing for improvement in the GNN framework's accuracy. This trade-off between accuracy and computational cost over CNN models makes the GNN framework attractive for many large-scale microscopy image segmentation tasks in biology.

Visual Cue Effects on a Classification Accuracy Estimation Task in Immersive Scatterplots.

Immersive visualization in virtual reality (VR) allows us to exploit visual cues for perception in 3D space, yet few existing studies have measured the effects of visual cues. Across a desktop monitor and a head-mounted display (HMD), we assessed scatterplot designs which vary their use of visual cues-motion, shading, perspective (graphical projection), and dimensionality-on two sets of data. We conducted a user study with a summary task in which 32 participants estimated the classification accuracy of an artificial neural network from the scatterplots. With Bayesian multilevel modeling, we capture the intricate visual effects and find that no cue alone explains all the variance in estimation error. Visual motion cues generally reduce participants' estimation error; besides this motion, using other cues may increase participants' estimation error. Using an HMD, adding visual motion cues, providing a third data dimension, or showing a more complicated dataset leads to longer response times. We speculate that most visual cues may not strongly affect perception in immersive analytics unless they change people's mental model about data. In summary, by studying participants as they interpret the output from a complicated machine learning model, we advance our understanding of how to use the visual cues in immersive analytics.

Safety and effectiveness of pre-emptive diabetic vitrectomy in patients with severe, non-fibrotic retinal neovascularisation despite panretinal photocoagulation.

OBJECTIVES: To investigate the safety and effectiveness of pre-emptive vitrectomy in eyes with severe non-fibrotic proliferative diabetic retinopathy. METHODS: A multi-centre, retrospective, observational study. Pre-emptive vitrectomy was performed in non-fibrotic diabetic eyes with a visual acuity (VA) of 20/50 or better, where there was extensive persistent neovascularisation despite prior panretinal photocoagulation, and where the fellow eye had established sight loss despite vitrectomy for tractional complications. The primary outcome measure was the VA at last visit. RESULTS: Twenty patients were included. The mean age was 39 ± 14 years. Fifteen patients were Type 1 diabetic. The median baseline VA was 20/30 and remained stable at 20/28 at last visit (median follow-up period: 24 months). Eight eyes (40.0%) developed post-operative vitreous cavity haemorrhage; 4 of which required a vitreous cavity washout procedure. There were no post-operative retinal detachments. The index eye remained the significantly better eye at all time points bar one month post-surgery. Regression of retinopathy grading was observed in all eyes. CONCLUSION: In this pilot study, we found no sight loss with pre-emptive diabetic vitrectomy. Better eye status was maintained in this high-risk group. Further study with larger number of patients and longer-term follow-up is indicated.

Virtual and augmented reality: New tools for visualizing, analyzing, and communicating complex morphology.

Virtual and augmented reality (VR/AR) are new technologies with the power to revolutionize the study of morphology. Modern imaging approaches such as computed tomography, laser scanning, and photogrammetry have opened up a new digital world, enabling researchers to share and analyze morphological data electronically and in great detail. Because this digital data exists on a computer screen, however, it can remain difficult to understand and unintuitive to interact with. VR/AR technologies bridge the analog-to-digital divide by presenting 3D data to users in a very similar way to how they would interact with actual anatomy, while also providing a more immersive experience and greater possibilities for exploration. This manuscript describes VR/AR hardware, software, and techniques, and is designed to give practicing morphologists and educators a primer on using these technologies in their research, pedagogy, and communication to a wide variety of audiences. We also include a series of case studies from the presentations and workshop given at the 2019 International Congress of Vertebrate Morphology, and suggest best practices for the use of VR/AR in comparative morphology.

Visualization of 3D Stress Tensor Fields Using Superquadric Glyphs on Displacement Streamlines.

Stress tensor fields play a central role in solid mechanics studies, but their visualization in 3D space remains challenging as the information-dense multi-variate tensor needs to be sampled in 3D space while avoiding clutter. Taking cues from current tensor visualizations, we adapted glyph-based visualization for stress tensors in 3D space. We also developed a testing framework and performed user studies to evaluate the various glyph-based tensor visualizations for objective accuracy measures, and subjective user feedback for each visualization method. To represent the stress tensor, we color encoded the original superquadric glyph, and in the user study, we compared it to superquadric glyphs developed for second-order symmetric tensors. We found that color encoding improved the user accuracy measures, while the users also rated our method the highest. We compared our method of placing stress tensor glyphs on displacement streamlines to the glyph placement on a 3D grid. In the visualization, we modified the glyph to show both the stress tensor and the displacement vector at each sample point. The participants preferred our method of glyph placement on displacement streamlines as it highlighted the underlying continuous structure in the tensor field.

Tractography Processing with the Sparse Closest Point Transform.

We propose a novel approach for processing diffusion MRI tractography datasets using the sparse closest point transform (SCPT). Tractography enables the 3D geometry of white matter pathways to be reconstructed; however, algorithms for processing them are often highly customized, and thus, do not leverage the existing wealth of machine learning (ML) algorithms. We investigated a vector-space tractography representation that aims to bridge this gap by using the SCPT, which consists of two steps: first, extracting sparse and representative landmarks from a tractography dataset, and second transforming curves relative to these landmarks with a closest point transform. We explore its use in three typical tasks: fiber bundle clustering, simplification, and selection across a population. The clustering algorithm groups fibers from single whole-brain datasets using a non-parametric k-means clustering algorithm, with performance compared with three alternative methods and across four datasets. The simplification algorithm removes redundant curves to improve interactive visualization, with performance gauged relative to random subsampling. The selection algorithm extracts bundles across a population using a one-class Gaussian classifier derived from an atlas prototype, with performance gauged by scan-rescan reliability and sensitivity to normal aging, as compared to manual mask-based selection. Our results demonstrate how the SCPT enables the novel application of existing vector-space ML algorithms to create effective and efficient tools for tractography processing. Our experimental data is available online, and our software implementation is available in the Quantitative Imaging Toolkit.

A Virtual Reality Memory Palace Variant Aids Knowledge Retrieval from Scholarly Articles.

We present exploratory research of virtual reality techniques and mnemonic devices to assist in retrieving knowledge from scholarly articles. We used abstracts of scientific publications to represent knowledge in scholarly articles; participants were asked to read, remember, and retrieve knowledge from a set of abstracts. We conducted an experiment to compare participants' recall and recognition performance in three different conditions: a control condition without a pre-specified strategy to test baseline individual memory ability, a condition using an image-based variant of a mnemonic called a "memory palace," and a condition using a virtual reality-based variant of a memory palace. Our analyses show that using a virtual reality-based memory palace variant greatly increased the amount of knowledge retrieved and retained over the baseline, and it shows a moderate improvement over the other image-based memory palace variant. Anecdotal feedback from participants suggested that personalizing a memory palace variant would be appreciated. Our results support the value of virtual reality for some high-level cognitive tasks and help improve future applications of virtual reality and visualization.

Rate of Postoperative Autofluorescent Macular Shift with Expanding Gas Bubble Tamponade and No Prone Posture Ambulatory Care in Patients with Macula-Involved Retinal Detachment.

PURPOSE: Chronically distorted vision is an important adverse outcome in patients with otherwise successfully treated macula-involved retinal detachment (RD). Symptomatic distortion is associated with macular vessel shift on fundus autofluorescence (FAF) imaging. Immediate prone posture has to date been the only mechanism adopted to reduce postoperative FAF shift. The aim of this study was to establish the rates of primary anatomical success and (FAF) macular shift in 67 eyes with macula-involved RD and superior breaks treated with vitrectomy, retinopexy, 0.7-1 mL 100% gas tamponade, and no prone posture. METHODS: Single-center, retrospective series. RESULTS: Rates of primary anatomical success and fundus autofluorescent imaging macular shift were 89 and 26%, respectively. CONCLUSION: Vitrectomy with a 0.7-1 mL expanding gas bubble tamponade and no prone posture were associated with an acceptable rate of primary anatomical success. We found the lowest yet reported rate of FAF shift in patients with macula-involved RD. If confirmed, this simple technique modification could improve the visual outcome of RD surgery whilst facilitating postoperative ambulatory care.

Measuring the Effects of Scalar and Spherical Colormaps on Ensembles of DMRI Tubes.

We report empirical study results on the color encoding of ensemble scalar and orientation to visualize diffusion magnetic resonance imaging (DMRI) tubes. The experiment tested six scalar colormaps for average fractional anisotropy (FA) tasks (grayscale, blackbody, diverging, isoluminant-rainbow, extended-blackbody, and coolwarm) and four three-dimensional (3D) spherical colormaps for tract tracing tasks (uniform gray, absolute, eigenmaps, and Boy's surface embedding). We found that extended-blackbody, coolwarm, and blackbody remain the best three approaches for identifying ensemble average in 3D. Isoluminant-rainbow colormap led to the same ensemble mean accuracy as other colormaps. However, more than 50 percent of the answers consistently had higher estimates of the ensemble average, independent of the mean values. The number of hues, not luminance, influences ensemble estimates of mean values. For ensemble orientation-tracing tasks, we found that both Boy's surface embedding (greatest spatial resolution and contrast) and absolute colormaps (lowest spatial resolution and contrast) led to more accurate answers than the eigenmaps scheme (medium resolution and contrast), acting as the uncanny-valley phenomenon of visualization design in terms of accuracy. Absolute colormap broadly used in brain science is a good default spherical colormap. We could conclude from our study that human visual processing of a chunk of colors differs from that of single colors.

Topic-Based Exploration and Embedded Visualizations for Research Idea Generation.

This work analyzes sensemaking frameworks and experiments with an iteratively designed visual analysis tool to identify design implications for facilitating research idea generation using visualizations. Our tool, ThoughtFlow, structures and visualizes literature collections using topic models to bridge the information gap between core activities during research ideation. To help users stay focused on a topic while discovering relevant documents, we designed and analyzed usage patterns for two types of embedded visualization that help determine document relevance while minimizing distraction. We analyzed how research ideation outcomes and processes differ when using ThoughtFlow and conventional search engines by augmenting insight-based evaluation with concept-map analysis. Our results suggest that operations afforded by topic models match well with later ideation stages when coherent topics have emerged, but not with early stages when users are still relying heavily on individual keywords to gather background knowledge. We also present qualitative evidence that citation sparklines encourage more exploration of recommended references, and that a preference for paper thumbnails may depend on the consistency between the evidence and the current mental frame.

Towards Placental Surface Vasculature Exploration in Virtual Reality.

We present a case study evaluating the potential for interactively identifying placental surface blood vessels using magnetic resonance imaging (MRI) scans in virtual reality (VR) environments. We visualized the MRI data using direct volume rendering in a high-fidelity CAVE-like VR system, allowing medical professionals to identify relevant placental vessels directly from volume visualizations in the VR system, without prior vessel segmentation. Participants were able to trace most of the observable vascular structure, and consistently identified blood vessels down to diameters of 1 mm, an important requirement in diagnosing vascular diseases. Qualitative feedback from our participants suggests that our VR visualization is easy to understand and allows intuitive data exploration, but complex user interactions remained a challenge. Using these observations, we discuss implications and requirements for spatial tracing user interaction methods in VR environments. We believe that VR MRI visualizations are the next step towards effective surgery planning for prenatal diseases.

Predicting Carpal Bone Kinematics Using an Expanded Digital Database of Wrist Carpal Bone Anatomy and Kinematics.

The wrist can be considered a 2 degrees-of-freedom joint with all movements reflecting the combination of flexion-extension and radial-ulnar deviation. Wrist motions are accomplished by the kinematic reduction of the 42 degrees-of-freedom of the individual carpal bones. While previous studies have demonstrated the minimal motion of the scaphoid and lunate as the wrist moves along the dart-thrower's path or small relative motion between hamate-capitate-trapezoid, an understanding of the kinematics of the complete carpus across all wrist motions remains lacking. To address this, we assembled an open-source database of in vivo carpal motions and developed mathematical models of the carpal kinematics as a function of wrist motion. Quadratic surfaces were trained for each of the 42-carpal bone degrees-of-freedom and the goodness of fits were evaluated. Using the models, paths of wrist motion that generated minimal carpal rotations or translations were determined. Model predictions were best for flexion-extension, radial-ulnar deviation, and volar-dorsal translations for all carpal bones with R 2 > 0.8, while the estimates were least effective for supination-pronation with R 2 < 0.6. The wrist path of motion's analysis indicated that the distal row of carpal bones moves rigidly together (<3° motion), along the anatomical axis of wrist motion, while the bones in the proximal row undergo minimal motion when the wrist moves in a path oblique to the main axes. The open-source dataset along with its graphical user interface and mathematical models should facilitate clinical visualization and enable new studies of carpal kinematics and function. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2661-2670, 2019.

Behavioral inhibition corresponds to white matter fiber bundle integrity in older adults.

Little is known about the contribution of white matter integrity to inhibitory cognitive control, particularly in healthy aging. The present study examines the correspondence between white matter fiber bundle length and behavioral inhibition in 37 community-dwelling older adults (aged 51-78 years). Participants underwent neuroimaging with 3 Tesla MRI, and completed a behavioral test of inhibition (i.e., Go/NoGo task). Quantitative tractography derived from diffusion tensor imaging (qtDTI) was used to measure white matter fiber bundle lengths (FBLs) in tracts known to innervate frontal brain regions, including the anterior corpus callosum (AntCC), the cingulate gyrus segment of the cingulum bundle (CING), uncinate fasciculus (UNC), and the superior longitudinal fasciculus (SLF). Performance on the Go/NoGo task was measured by the number of commission errors standardized to reaction time. Hierarchical regression models revealed that shorter FBLs in the CING (p < 0.05) and the bilateral UNC (p < 0.01) were associated with lower inhibitory performance after adjusting for multiple comparisons, supporting a disconnection model of response inhibition in older adults. Prospective longitudinal studies are needed to examine the evolution of inhibitory errors in older adult populations and potential for therapeutic intervention.

Developing Virtual Reality Visualizations for Unsteady Flow Analysis of Dinosaur Track Formation using Scientific Sketching.

We present the results of a two-year design study to developing virtual reality (VR) flow visualization tools for the analysis of dinosaur track creation in a malleable substrate. Using Scientific Sketching methodology, we combined input from illustration artists, visualization experts, and domain scientists to create novel visualization methods. By iteratively improving visualization concepts at multiple levels of abstraction we helped domain scientists to gain insights into the relationship between dinosaur foot movements and substrate deformations. We involved over 20 art and computer science students from a VR design course in a rapid visualization sketching cycle, guided by our paleontologist collaborators through multiple critique sessions. This allowed us to explore a wide range of potential visualization methods and select the most promising methods for actual implementation. Our resulting visualization methods provide paleontologists with effective tools to analyze their data through particle, pathline and time surface visualizations. We also introduce a set of visual metaphors to compare foot motion in relation to substrate deformation by using pathsurfaces. This is one of the first large-scale projects using Scientific Sketching as a development methodology. We discuss how the research questions of our collaborators have evolved during the sketching and prototyping phases. Finally, we provide lessons learned and usage considerations for Scientific Sketching based on the experiences gathered during this project.

Vitreoretinal surgery on the fellow eye: A retrospective analysis of 18 years of surgical data from a tertiary center in England.

Purpose: To determine the long-term incidence of fellow-eye surgical involvement in patients who have undergone first-eye vitreoretinal (VR) surgery for a variety of indications. This was a single-institution retrospective, consecutive series. Methods: Eighteen years of electronic surgical data were reviewed at our institution. All patients having surgery for the following indications were included: rhegmatogenous retinal detachment (RRD), macular hole (MH), epiretinal membrane (ERM), proliferative diabetic retinopathy (PDR), vitritis, and dropped nucleus. Primary outcome was the cumulative incidence of fellow-eye surgery at 10 years by Kaplan-Meier analysis. Results: Total follow-up was 29,629 patient-years. Cumulative incidence (± standard error) of fellow-eye surgery at 10 years was 7.2% ± 0.6% for RRD, 9.1% ± 1.3% for ERM, 7.5% ± 1.8% for MH, 30.6% ± 1.9% for PDR, 13.7% ± 2.9% for vitritis, and 2.8% ± 1.6% for dropped nuclei. The hazard for second-eye surgery was greatest in the early postoperative period after first-eye surgery for all indications. For RRD, the hazard was 2.7% ± 0.3% at year 1, 1.1% ± 0.2% at year 2, and 0.5% ± 0.2% at year 5. Risk factors for fellow-eye involvement for RRD were younger age (P < 0.001) and male gender (P < 0.01). Conclusion: We report the long-term risk of fellow-eye involvement in various VR pathologies, which is important in counseling patients regarding their risks as well as planning service provision.

INTRAOPERATIVE AND POSTOPERATIVE COMPLICATIONS IN PHACOVITRECTOMY FOR EPIRETINAL MEMBRANE AND MACULAR HOLE: A Clinical Audit of 1,000 Consecutive Eyes.

PURPOSE: The aim of this study was to report the intraoperative and postoperative complications of phacovitrectomy for epiretinal membrane (ERM) and macular hole (MH). METHODS: This was a retrospective audit of 1,052 phacovitrectomy operations (410 for ERM and 642 for MH) by the same surgical team between 1998 and 2017. Outcome measures included rates of intraoperative anterior segment and posterior segment complications such as posterior capsule rupture and retinal breaks. A subgroup analysis of 189 procedures in which postoperative complications were rigorously recorded was also undertaken. RESULTS: The rate of posterior capsule rupture was 2.2%, with no difference between ERM and MH (1.7 vs. 2.5%; P = 0.40). Iatrogenic retinal tears were more common in MH than in ERM surgery (15.6 vs. 6.8%; P < 0.001). The chance of one or more anterior segment or posterior segment intraoperative complications occurring (excluding iatrogenic retinal breaks) was not associated with: indication for surgery, grade of surgeon, gauge of surgery, surgical machine, diabetic status, patient sex, or patient age. Subgroup analysis showed postoperative events as follows: posterior capsular opacification 10.6% (20/189), posterior synechiae 4.2% (8/189), uveitis 2.1% (4/189), angle closure glaucoma 1.6% (3/189), and rhegmatogenous retinal detachment 1.1% (2/189). CONCLUSION: Phacovitrectomy seems to be safe in phakic patients with ERM or MH, performed either by fellows or consultants. It avoids the requirement for repeat surgery and is more cost and resource efficient.

Acute retinal detachment induced by the Valsalva manoeuvre in morning glory disc anomaly.

We present a case in which a large, bullous, predominantly inferior, serous retinal detachment developed acutely after the Valsalva manoeuvre (from a coughing fit) in an eye with morning glory disc anomaly. We postulate that a rapid alteration in intracranial pressure was transmitted through the cavitary disc defect. This allowed a sudden influx of cerebrospinal fluid and/or liquefied vitreous into the subretinal space. This previously unreported case provides important evidence for the role of intracranial pressure fluctuations in the pathogenesis of macular schisis and neurosensory detachment secondary to optic disc cavitations.