Educational stereoscopic representation of a step-by-step brain white fiber dissection according to Klingler's method.

BACKGROUND: Understanding and teaching the three-dimensional architecture of the brain remains difficult because of the intricate arrangement of grey nuclei within white matter tracts. Although cortical area functions have been well studied, educational and three-dimensional descriptions of the organization of deep nuclei and white matter tracts are still missing. OBJECTIVE: We propose herein a detailed step-by-step dissection of the lateral aspect of a left hemisphere using the Klingler method and provide high-quality stereoscopic views with the aim to help teach medical students or surgeons the three-dimensional anatomy of the brain. METHODS: Three left hemispheres were extracted and prepared. Then, according to the Klingler method, dissections were carried out from the lateral aspect. Photographs were taken at each step and were modified to provide stereoscopic three-dimensional views. RESULTS: Gray and white structures were described: cortex, claustrum, putamen, pallidum, caudate nucleus, amygdala; U-fibers, external and internal capsules, superior longitudinal fasciculus, frontal aslant fasciculus, uncinate fasciculus, inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, corticospinal fasciculus, corona radiata, anterior commissure, and optic radiations. CONCLUSION: This educational stereoscopic presentation of an expert dissection of brain white fibers and basal ganglia would be of value for theoretical or hands-on teaching of brain anatomy; labeling and stereoscopy could, moreover, improve the teaching, understanding, and memorizing of brain anatomy. In addition, this could be also used for the creation of a mental map by neurosurgeons for the preoperative planning of brain tumor surgery.

Success rates, near-response patterns, and learning trends with free-fusion stereograms.

Free-fusion stereograms are routinely used for demonstrating various stereoscopic effects. Yet, untrained observers find it challenging to perform this task. This study showed that only less than 1/3rd of sixty-one pre-presbyopic adults with normal binocular vision could successfully free-fuse random-dot image pairs and identify the stereoscopic shapes embedded in these patterns. Another one-third of participants performed the task with poor success rates, while the remaining could not perform the task. There was a clear dissociation of vergence and accommodative responses in participants who were successful with free-fusion, as recorded using a dynamic infrared eye tracker and photorefractor. Those in the unsuccessful cluster either showed strong vergence and accommodation or weak vergence and strong accommodation during the task. These response patterns, however, were specific to the free-fusion task because all these participants generated good convergence/accommodation to real-world targets and to conflicting vergence and accommodative demands stimulated with prisms or lenses. Task performance of the unsuccessful cluster also improved significantly following pharmacological paralysis of accommodation and reached the performance levels of the successful cluster. A minority of participants also appeared to progressively learn to dissociate one of the two directions of their vergence and accommodation crosslinks with repeated free-fusion trials. These results suggest that successful free-fusion might depend upon how well participants generate a combination of volitional and reflex vergence responses to large differences in disparity with conflicting static accommodative demands. Such responses would require that only one direction of the vergence-accommodation crosslinks be active at any given time. The sequence of near-responses could also be learnt through repeated trials to optimize task performance.

Projection of realistic three-dimensional photogrammetry models using stereoscopic display: A technical note.

The 3D stereoscopic technique consists in providing the illusional perception of depth of a given object using two different images mimicking how the right and left eyes capture the object. Both images are slightly different and when overlapped gives a three-dimensional (3D) experience. Considering the limitations for establishing surgical laboratories and dissections courses in some educational institutions, techniques such as stereoscopy and photogrammetry seem to play an important role in neuroanatomy and neurosurgical education. The aim of this study was to describe how to combine and set up realistic models acquired with photogrammetry scans in 3D stereoscopic projections. Three donors, one dry skull, embalmed brain and head, were scanned using photogrammetry. The software used for displaying the final realistic 3D models (Blender, Amsterdam, the Netherlands) is a free software and allows stereoscopic projection without compromising the interactivity of each model. By default, the model was exported and immediately displayed as a red cyan 3D mode. The 3D projector used in the manuscript required a side-by-side 3D mode which was set up with simple commands on the software. The final stereoscopy projection offered depth perception and a visualization in 360° of each donor; this perception was noted especially when visualizing donors with different cavities and fossae. The combination of 3D techniques is of paramount importance for neuroanatomy education. Stereoscopic projections could provide a valuable tool for neuroanatomy instruction directed at clinical trainees and could be especially useful when access to laboratory-based learning is limited.

Adaptable 2D to 3D Stereo Vision Image Conversion Based on a Deep Convolutional Neural Network and Fast Inpaint Algorithm.

Algorithms for converting 2D to 3D are gaining importance following the hiatus brought about by the discontinuation of 3D TV production; this is due to the high availability and popularity of virtual reality systems that use stereo vision. In this paper, several depth image-based rendering (DIBR) approaches using state-of-the-art single-frame depth generation neural networks and inpaint algorithms are proposed and validated, including a novel very fast inpaint (FAST). FAST significantly exceeds the speed of currently used inpaint algorithms by reducing computational complexity, without degrading the quality of the resulting image. The role of the inpaint algorithm is to fill in missing pixels in the stereo pair estimated by DIBR. Missing estimated pixels appear at the boundaries of areas that differ significantly in their estimated distance from the observer. In addition, we propose parameterizing DIBR using a singular, easy-to-interpret adaptable parameter that can be adjusted online according to the preferences of the user who views the visualization. This single parameter governs both the camera parameters and the maximum binocular disparity. The proposed solutions are also compared with a fully automatic 2D to 3D mapping solution. The algorithm proposed in this work, which features intuitive disparity steering, the foundational deep neural network MiDaS, and the FAST inpaint algorithm, received considerable acclaim from evaluators. The mean absolute error of the proposed solution does not contain statistically significant differences from state-of-the-art approaches like Deep3D and other DIBR-based approaches using different inpaint functions. Since both the source codes and the generated videos are available for download, all experiments can be reproduced, and one can apply our algorithm to any selected video or single image to convert it.

Stereopsis for rapidly moving targets.

Stereoscopic depth perception is possible with luminance-defined target velocities at least as high as 600° s-1, up to the limit of 30 Hz imposed by the high-temporal frequency cut-off of the eye. The limitation for perceiving depth from stereo disparity of moving targets is not their velocity but the temporal frequency bandwidth of the eye, which is affected by adaption state. Stereoacuity for a depth shift in a horizontally moving grating depends not on spatial disparity between corresponding luminance points in spatial units of arc min, but on the spatial shift as a fixed proportion of the period of the grating, in other words, on the phase angle difference between the two eyes, as is also the case for obliquely orientated, stationary gratings. Phase differences explain not only the classic Pulfrich stereophenomenon but its equivalent with dynamic visual noise, and a new effect in which depth results from interocular phase differences in luminance modulation. This article is part of a discussion meeting issue 'New approaches to 3D vision'.

An Experimental Assessment of Depth Estimation in Transparent and Translucent Scenes for Intel RealSense D415, SR305 and L515.

RGB-D cameras have become common in many research fields since these inexpensive devices provide dense 3D information from the observed scene. Over the past few years, the RealSense™ range from Intel® has introduced new, cost-effective RGB-D sensors with different technologies, more sophisticated in both hardware and software. Models D415, SR305, and L515 are examples of successful cameras launched by Intel® RealSense™ between 2018 and 2020. These three cameras are different since they have distinct operating principles. Then, their behavior concerning depth estimation while in the presence of many error sources will also be specific. For instance, semi-transparent and scattering media are expected error sources for an RGB-D sensor. The main new contribution of this paper is a full evaluation and comparison between the three Intel RealSense cameras in scenarios with transparency and translucency. We propose an experimental setup involving an aquarium and liquids. The evaluation, based on repeatability/precision and statistical distribution of the acquired depth, allows us to compare the three cameras and conclude that Intel RealSense D415 has overall the best behavior namely in what concerns the statistical variability (also known as precision or repeatability) and also in what concerns valid measurements.

360° 3D virtual reality operative video for the training of residents in neurosurgery.

OBJECTIVE: Training of residents is an essential but time-consuming and costly task in the surgical disciplines. During the coronavirus disease 2019 pandemic, surgical education became even more challenging because of the reduced caseload due to the increased shift to corona care. In this context, augmented 360° 3D virtual reality (VR) videos of surgical procedures enable effective off-site training through virtual participation in the surgery. The goal of this study was to establish and evaluate 360° 3D VR operative videos for neurosurgical training. METHODS: Using a 360° camera, the authors recorded three standard neurosurgical procedures: a lumbar discectomy, brain metastasis resection, and clipping of an aneurysm. Combined with the stereoscopic view of the surgical microscope, 7- to 10-minute 360° 3D VR videos augmented with annotations, overlays, and commentary were created. These videos were then presented to the neurosurgical residents at the authors' institution using a head-mounted display. Before viewing the videos, the residents were asked to fill out a questionnaire indicating their VR experience and self-assessment of surgical skills regarding the specific procedure. After watching the videos, the residents completed another questionnaire to evaluate their quality and usefulness. The parameters were scaled with a 5-point Likert scale. RESULTS: Twenty-two residents participated in this study. The mean years of experience of the participants in neurosurgery was 3.2 years, ranging from the 1st through the 7th year of training. Most participants (86.4%) had no or less than 15 minutes of VR experience. The overall quality of the videos was rated good to very good. Immersion, the feeling of being in the operating room, was high, and almost all participants (91%) stated that 360° VR videos provide a useful addition to the neurosurgical training. VR sickness was negligible in the cohort. CONCLUSIONS: In this study, the authors demonstrated the feasibility and high acceptance of augmented 360° 3D VR videos in neurosurgical training. Augmentation of 360° videos with complementary and interactive content has the potential to effectively support trainees in acquiring conceptual knowledge. Further studies are necessary to investigate the effectiveness of their use in improving surgical skills.

3D Stereoscopic View in Neurosurgical Anatomy: Compilation of Basic Methods.

BACKGROUND: Stereoscopy has been demonstrated to be a useful method of education in the field of anatomy because it allows users to see, in a simulation, the anatomical structures in their actual volume and depth. METHODS: Cadaveric specimens preserved under formaldehyde using the Thiel and Klinger techniques have been dissected and photographed in the medical school anatomy laboratory (University Miguel Hernández) for the past 10 years. The photographic material and technique required to capture and project stereoscopic photographs have been described in different fields of surgical neuroanatomy. We used the results from a survey completed by the participants of different training courses to evaluate the utility of the 3-dimensional (3D) method. RESULTS: A large database of photographs taken of different anatomical regions and approaches of neurosurgical interest was obtained. We have presented some examples in the form of pairs of photographs in 2-dimensional (2D) format, with explanatory labels, paired with the corresponding 3D photograph in anaglyph format. The survey showed that the lectures that had included 3D photographs were significantly better accepted than the lectures with conventional 2D photographs. CONCLUSIONS: The teaching of basic, academic, and clinical neuroanatomy through the projection of stereoscopic photographs can be useful. The methods of image capture and stereoscopic projection in neuroanatomy, once combined with the necessary theoretical and practical knowledge, can be reproduced at other centers of neuroanatomy teaching.

High-Performance Image Acquisition and Processing for Stereoscopic Diagnostic Systems with the Application of Graphical Processing Units.

In recent years, cinematography and other digital content creators have been eagerly turning to Three-Dimensional (3D) imaging technology. The creators of movies, games, and augmented reality applications are aware of this technology's advantages, possibilities, and new means of expression. The development of electronic and IT technologies enables the achievement of a better and better quality of the recorded 3D image and many possibilities for its correction and modification in post-production. However, preparing a correct 3D image that does not cause perception problems for the viewer is still a complex and demanding task. Therefore, planning and then ensuring the correct parameters and quality of the recorded 3D video is essential. Despite better post-production techniques, fixing errors in a captured image can be difficult, time consuming, and sometimes impossible. The detection of errors typical for stereo vision related to the depth of the image (e.g., depth budget violation, stereoscopic window violation) during the recording allows for their correction already on the film set, e.g., by different scene layouts and/or different camera configurations. The paper presents a prototype of an independent, non-invasive diagnostic system that supports the film crew in the process of calibrating stereoscopic cameras, as well as analysing the 3D depth while working on a film set. The system acquires full HD video streams from professional cameras using Serial Digital Interface (SDI), synchronises them, and estimates and analyses the disparity map. Objective depth analysis using computer tools while recording scenes allows stereographers to immediately spot errors in the 3D image, primarily related to the violation of the viewing comfort zone. The paper also describes an efficient method of analysing a 3D video using Graphics Processing Unit (GPU). The main steps of the proposed solution are uncalibrated rectification and disparity map estimation. The algorithms selected and implemented for the needs of this system do not require knowledge of intrinsic and extrinsic camera parameters. Thus, they can be used in non-cooperative environments, such as a film set, where the camera configuration often changes. Both of them are implemented with the use of a GPU to improve the data processing efficiency. The paper presents the evaluation results of the algorithms' accuracy, as well as the comparison of the performance of two implementations-with and without the GPU acceleration. The application of the described GPU-based method makes the system efficient and easy to use. The system can process a video stream with full HD resolution at a speed of several frames per second.

Glaucoma screening using an attention-guided stereo ensemble network.

Glaucoma is a chronic eye disease, which causes gradual vision loss and eventually blindness. Accurate glaucoma screening at early stage is critical to mitigate its aggravation. Extracting high-quality features are critical in training of classification models. In this paper, we propose a deep ensemble network with attention mechanism that detects glaucoma using optic nerve head stereo images. The network consists of two main sub-components, a deep Convolutional Neural Network that obtains global information and an Attention-Guided Network that localizes optic disc while maintaining beneficial information from other image regions. Both images in a stereo pair are fed into these sub-components, the outputs are fused together to generate the final prediction result. Abundant image features from different views and regions are being extracted, providing compensation when one of the stereo images is of poor quality. The attention-based localization method is trained in a weakly-supervised manner and only image-level annotation is required, which avoids expensive segmentation labelling. Results from real patient images show that our approach increases recall (sensitivity) from the state-of-the-art 88.89% to 95.48%, while maintaining precision and performance stability. The marked reduction in false-negative rate can significantly enhance the chance of successful early diagnosis of glaucoma.

A Benchmark Evaluation of Adaptive Image Compression for Multi Picture Object Stereoscopic Images.

A stereopair consists of two pictures related to the same subject taken by two different points of view. Since the two images contain a high amount of redundant information, new compression approaches and data formats are continuously proposed, which aim to reduce the space needed to store a stereoscopic image while preserving its quality. A standard for multi-picture image encoding is represented by the MPO format (Multi-Picture Object). The classic stereoscopic image compression approaches compute a disparity map between the two views, which is stored with one of the two views together with a residual image. An alternative approach, named adaptive stereoscopic image compression, encodes just the two views independently with different quality factors. Then, the redundancy between the two views is exploited to enhance the low quality image. In this paper, the problem of stereoscopic image compression is presented, with a focus on the adaptive stereoscopic compression approach, which allows us to obtain a standardized format of the compressed data. The paper presents a benchmark evaluation on large and standardized datasets including 60 stereopairs that differ by resolution and acquisition technique. The method is evaluated by varying the amount of compression, as well as the matching and optimization methods resulting in 16 different settings. The adaptive approach is also compared with other MPO-compliant methods. The paper also presents an Human Visual System (HVS)-based assessment experiment which involved 116 people in order to verify the perceived quality of the decoded images.

Biocompatible Nanotransfer Printing Based on Water Bridge Formation in Hyaluronic Acid and Its Application to Smart Contact Lenses.

Many conventional micropatterning and nanopatterning techniques employ toxic chemicals, rendering them nonbiocompatible and unsuited for biodevice production. Herein the formation of water bridges on the surface of hyaluronic acid (HA) films is exploited to develop a transfer-based nanopatterning method applicable to diverse structures and materials. The HA film surface, made deformable via water bridge generation, is brought into contact with a functional material and subjected to thermal treatment, which results in film shrinkage, allowing a robust pattern transfer. The proposed biocompatible method, which avoids the use of extra chemicals, enables the transfer of nanoscale, microscale, and thin-film structures as well as functional materials such as metals and metal oxides. A nanopatterned HA film is transferred onto a moisture-containing contact lens to fabricate smart contact lenses with unique optical characteristics of rationally designed optical nanopatterns. These lenses demonstrated binocular parallax-induced stereoscopy via nanoline array polarization and acted as cutoff filters, with nanodot arrays, capable of treating Irlen syndrome.

On the Origins of Terms in Binocular Vision.

Vision with two eyes has been commented upon for many centuries, and the principal concern has been with binocular single vision. The terminology we apply to binocular vision developed rapidly after the invention of the stereoscope in the early 19th century. The origins of terms such as anaglyph, binocular lustre, chromatic stereoscope, cyclopean eye, dichoptic, horopter, pseudoscope, rivalry, stereoscope, stereograph, and stereopsis are described together with portraits of those who introduced them.

Virtual Reality Bell-Ringer: The Development and Testing of a Stereoscopic Application for Human Gross Anatomy.

As post-secondary education migrates online, developing and evaluating new avenues for assessment in anatomy is paramount. Three-dimensional (3D) visualization technology is one area with the potential to augment or even replace resource-intensive cadaver use in anatomical education. This manuscript details the development of a smartphone application, entitled "Virtual Reality Bell-Ringer (VRBR)," capable of displaying monoscopic two-dimensional (2D) or stereoscopic 3D images with the use of an inexpensive cardboard headset for use in spot examinations. Cadaveric image use, creation, and pinning processes are explained, and the source code is provided. To validate this tool, this paper compares traditional laboratory-based spot examination assessment stations against those administered using the VRBR application to test anatomical knowledge. Participants (undergraduate, n = 38; graduate, n = 13) completed three spot examinations specific to their level of study, one in each of the modalities (2D, 3D, laboratory) as well as a mental rotation test (MRT), Stereo Fly stereotest, and cybersickness survey. Repeated measures ANCOVA suggested participants performed significantly better on laboratory and 3D stations compared to 2D stations. Moderate to severe cybersickness symptoms were reported by 63% of participants in at least one category while using the VRBR application. Highest reported symptoms included: eye strain, general discomfort, difficulty focusing, and difficulty concentrating. Overall, the VRBR application is a promising tool for its portability, affordability, and accessibility. Due to reported cybersickness and other technical limitations, the use of VRBR as an alternative to cadaveric specimens presents several challenges when testing anatomy knowledge that must be addressed before widespread adoption.

Learning curves, potential and speed in training of laparoscopic skills: a randomised comparative study in a box trainer.

BACKGROUND: The effectiveness of practical surgical training is characterised by an inherent learning curve. Decisive are individual initial starting capabilities, learning speed, ideal learning plateaus, and resulting learning potentials. The quantification of learning curves requires reproducible tasks with varied levels of difficulty. The hypothesis of this study is that the use of three-dimensional (3D) vision is more advantageous than two-dimensional vision (2D) for the learning curve in laparoscopic training. METHODS: Forty laparoscopy novices were recruited and randomised to a 2D Group and a 3D Group. A laparoscopy box trainer with two standardised tasks was used for training of surgical tasks. Task 1 was a positioning task, while Task 2 called for laparoscopic knotting as a more complex process. Each task was repeated at least ten times. Performance time and the number of predefined errors were recorded. 2D performance after 3D training was assessed in an additional final 2D cycle undertaken by the 3D Group. RESULTS: The calculated learning plateaus of both performance times and errors were lower for 3D. Independent of the vision mode the learning curves were smoother (exponential decay) and efficiency was learned faster than precision. The learning potentials varied widely depending on the corresponding initial values and learning plateaus. The final 2D performance time of the 3D-trained group was not significantly better than that of the 2D Group. The final 2D error numbers were similar for all groups. CONCLUSIONS: Stereoscopic vision can speed up laparoscopic training. The 3D learning curves resulted in better precision and efficiency. The 3D-trained group did not show inferior performance in the final 2D cycle. Consequently, we encourage the training of surgical competences like suturing and knotting under 3D vision, even if it is not available in clinical routine.

Stereoscopic three-dimensional visualization: interest for neuroanatomy teaching in medical school.

PURPOSE: The anatomy of both the brain and the skull is particularly difficult to learn and to teach. Since their anatomical structures are numerous and gathered in a complex tridimensional (3D) architecture, classic schematical drawing or photography in two dimensions (2D) has difficulties in providing a clear, simple, and accurate message. Advances in photography and computer sciences have led to develop stereoscopic 3D visualization, firstly for entertainment then for education. In the present study, we report our experience of stereoscopic 3D lecture for neuroanatomy teaching to early medical school students. METHODS: High-resolution specific pictures were taken on various specimen dissections in the Anatomy Laboratory of the University of Lyon, France. Selected stereoscopic 3D views were displayed on a large dedicated screen using a doubled video projector. A 2-h stereoscopic neuroanatomy lecture was given by two neuroanatomists to third-year medicine students who wore passive 3D glasses. Setting up lasted 30 min and involved four people. The feedback from students was collected and analyzed. RESULTS: Among the 483 students who have attended the stereoscopic 3D lecture, 195 gave feedback, and all (100%) were satisfied. Among these, 190 (97.5%) reported a better knowledge transfer of brain anatomy and its 3D architecture. Furthermore, 167 (86.1%) students felt it could change their further clinical practice, 179 (91.8%) thought it could enhance their results in forthcoming anatomy examinations, and 150 (76.9%) believed such a 3D lecture might allow them to become better physicians. This 3D anatomy lecture was graded 8.9/10 a mean against 5.9/10 for previous classical 2D lectures. DISCUSSION-CONCLUSION: The stereoscopic 3D teaching of neuroanatomy made medical students enthusiastic involving digital technologies. It could improve their anatomical knowledge and test scores, as well as their clinical competences. Depending on university means and the commitment of teachers, this new tool should be extended to other anatomical fields. However, its setting up requires resources from faculties and its impact on clinical competencies needs to be objectively assessed.

Empirical Analysis of Safe Distance Calculation by the Stereoscopic Capturing and Processing of Images Through the Tailigator System.

Driver disregard for the minimum safety distance increases the probability of rear-end collisions. In order to contribute to active safety on the road, we propose in this work a low-cost Forward Collision Warning system that captures and processes images. Using cameras located in the rear section of a leading vehicle, this system serves the purpose of discouraging tailgating behavior from the vehicle driving behind. We perform in this paper the pertinent field tests to assess system performance, focusing on the calculated distance from the processing of images and the error margins in a straight line, as well as in a curve. Based on the evaluation results, the current version of the Tailigator can be used at speeds up to 50 km per hour without any restrictions. The measurements showed similar characteristics both on the straight line and in the curve. At close distances, between 3 and 5 m, the values deviated from the real value. At average distances, around 10 to 15 m, the Tailigator achieved the best results. From distances higher than 20 m, the deviations increased steadily with the distance. We contribute to the state of the art with an innovative low-cost system to identify tailgating behavior and raise awareness, which works independently of the rear vehicle's communication capabilities or equipment.

Dynamic Cancellation of Perceived Rotation from the Venetian Blind Effect.

Geometric differences between the images seen by each eye enable the perception of depth. Additionally, depth is produced in the absence of geometric disparities with binocular disparities in either the average luminance or contrast, which is known as the Venetian blind effect. The temporal dynamics of the Venetian blind effect are much slower (1.3 Hz) than those for geometric binocular disparities (4-5 Hz). Sine-wave modulations of luminance and contrast disparity, however, can be discriminated from square-wave modulations at 1 Hz, which suggests a non-linearity. To measure this non-linearity, a luminance or contrast disparity modulation was presented at a particular frequency and paired with a geometric disparity modulation that cancelled the perceived rotation induced by the luminance or contrast modulation. Phases between the luminance or contrast and the geometric modulation varied in 50 ms increments from -200 and 200 ms. When phases were aligned, observers perceived little or no rotation. When not aligned, a perceived rotation was induced by a contrast or luminance disparity that was then cancelled by the geometric disparity. This causes the perception of a slight jump. The Generalized Difference Model, which is linear in time, predicted a minimal probability in cases when luminance or contrast disparities occurred before the geometric disparities due to the slower dynamics of the Venetian blind effect. The Gated Generalized Difference Model, which is non-linear in time, predicted a minimal probability for offsets of 0 ms. Results followed the Gated model, which further suggests a non-linearity in time for the Venetian blind effect.

tDCS recovers depth perception in adult amblyopic rats and reorganizes visual cortex activity.

Amblyopia or lazy eye is a neurodevelopmental disorder that arises during the infancy and is caused by the interruption of binocular sensory activity before maturation of the nervous system. This impairment causes long-term deterioration of visual skills, particularly visual acuity and depth perception. Although visual function recovery has been supposed to be decreased with age as consequence of reduced neuronal plasticity, recent studies have shown that it is possible to promote plasticity and neurorestoration in the adult brain. Thus, transcranial direct current stimulation (tDCS) has been shown effective to treat amblyopia in the adulthood. In the present work we used postnatal monocular deprivation in Long Evans rats as an experimental model of amblyopia and the cliff test task to assess depth perception. Functional brain imaging PET was used to assess the effect of tDCS on cortical and subcortical activity. Visually deprived animals ability to perceive depth in the cliff test was significantly reduced in comparison to their controls. However, after 8 sessions of tDCS applied through 8 consecutive days, depth perception of amblyopic treated animals improved reaching control level. PET data showed 18F-FDG uptake asymmetries in the visual cortex of amblyopic animals, which disappeared after tDCS treatment. The possibility of cortical reorganization and stereoscopy recovery following brain stimulation points at tDCS as a useful strategy for treating amblyopia in adulthood. Furthermore, monocular deprivation in Long Evans rats is a valuable research model to study visual cortex mechanisms involved in depth perception and neural restoration after brain stimulation.

3D Exoscope System in Neurosurgery-Comparison of a Standard Operating Microscope With a New 3D Exoscope in the Cadaver Lab.

BACKGROUND: For decades, the operating microscope has been the "gold standard" visualization device in neurosurgery. The development of endoscopy revolutionized different surgical disciplines, whereas in neurosurgery, the endoscope is commonly used as an additional device more than as single visualization tool. Invention of a 3D exoscope system opens new possibilities in visualization and ergonomics in neurosurgery. OBJECTIVE: To assess the prototype of a 3D exoscope (3D exoscope, year of manufacture 2015, FA Aesculap, Tüttlingen, Germany) as neurosurgical visualization device in comparison to a standard operating microscope. METHODS: A pterional approach was performed in 3 ETOH-fixed specimens (6 sides). A standard operating microscope was compared to a 3D exoscope prototype. Dimensions like visual field, magnification, illumination, ergonomics, depth effect, and 3D impression were compared. RESULTS: In all approaches, the structures of interest could be clearly visualized with both devices. Magnification showed similar results. The exoscope had more magnification potential, whereas the visual quality got worse in higher magnification levels. The illumination showed better results in the microscope. Surgeons felt more comfortable with the 3D exoscope, concerning ergonomic considerations. Depth effect and 3D impression showed similar results. None of the surgeons felt uncomfortable using the exoscope. CONCLUSION: The operating microscope is the gold standard visualization tool in neurosurgery because of its illumination, stereoscopy, and magnification. Nevertheless, it causes ergonomic problems. The prototype of a 3D exoscope showed comparable features in visual field, stereoscopic impression, and magnification, with a clear benefit concerning the ergonomic possibilities.