Anatomy Visualizations Using Stereopsis: Current Methodologies in Developing Stereoscopic Virtual Models in Anatomical Education

Immersive teaching using virtual reality technology to improve ophthalmic surgical skills for medical postgraduate students

Medical education is primarily based on practical schooling and the accumulation of experience and skills, which is important for the growth and development of young ophthalmic surgeons. However, present learning and refresher methods are constrained by several factors. Nevertheless, virtual reality (VR) technology has considerably contributed to medical training worldwide, providing convenient and practical auxiliary value for the selection of students' sub-majors. Moreover, it offers previously inaccessible surgical step training, scenario simulations, and immersive evaluation exams. This paper outlines the current applications of VR immersive teaching methods for ophthalmic surgery interns.

Creating Virtual Models and 3D Movies Using DemoMaker for Anatomical Education

Three-dimensional (3D) anatomy models have been used for education in health professional schools globally. Virtual technology has become more popular for online teaching since the COVID-19 pandemic. This chapter will describe a project in which a series of virtual anatomical models of organs and structures were developed for educational purposes, and it will describe in detail how to build three-dimensional (3D) movies using DemoMaker. Although setting up the 3D system was complicated and challenging, the process of reconstructing 3D models from radiographic images and the steps of creating animations and 3D movies are exponentially simpler. These efforts require minimal training, thus allowing most people to be able to engage in this modeling process and utilize the moviemaking steps. Amira® software and computed tomographic angiography (CTA) data were used to create 3D models of the lungs, heart, liver, stomach, kidney, etc. The anatomical locations of these structures within the body can be identified and visualized by recording information from multiple CTA slices using volume and surface segmentation. Ultimately, these virtual 3D models can be displayed via dual projectors onto a specialized silver screen and visualized stereoscopically by viewers as long as they wear 3D polarized glasses. Once these 3D movies are created, they can be played automatically on a computer screen, silver screen, 3D system playback screen, and video player, and they can be embedded into PowerPoint lecture slides. Both virtual models and movies are suitable for self-directed learning, face-to-face class teaching, and virtual anatomy education. Model animations and 3D movie displays offer students the opportunities to learn about anatomy and the anatomical positions of organs in the body and their 3D relationships to one another. By observing and studying these 3D models, students have the potential to be able to compartmentalize the anatomical information and retain it at a higher level than students learning corresponding anatomy without similar resources.

Stereopsis after corneal refractive surgeries: a systematic review and meta-analysis

PURPOSE

To systematically review the published manuscripts on stereopsis after corneal refractive surgery.

METHODS

The Web of Science, PubMed, Scopus, ProQuest, Clinical Key, Embase, and Cochrane Library were searched for relevant articles published until August 2020. The fixed- or random-effects models were used to estimate the Weighted mean difference (WMD) or Relative risk (RR) and 95% Confidence interval (CI) for postoperative stereopsis changes and incidence when applicable. Meta-regression was conducted for adjusting the effects of potential confounders.

RESULTS

Seven studies (1266 eyes) in adults and ten studies in pediatrics (259 eyes) were included. In adults, stereopsis improved significantly compared to the preoperative state (WMD = - 27.4, 95% CI = - 40.0, - 14.7; I² = 97.8%; P < 0.001). In pediatrics, proportion of patients with stereoacuity postoperatively was 2.18 times compared to preoperative evaluation. (RR = 2.18, 95% CI = 1.2, 3.9; I² = 68.6%, P < 0.001).

CONCLUSIONS

Stereopsis improves after corneal refractive surgery in adults and pediatrics.

Value of the surgeon's sightline on hologram registration and targeting in mixed reality

Purpose

Mixed reality (MR) is being evaluated as a visual tool for surgical navigation. Current literature presents unclear results on intraoperative accuracy using the Microsoft HoloLens 1^®. This study aims to assess the impact of the surgeon’s sightline in an inside-out marker-based MR navigation system for open surgery.

Methods

Surgeons at Akershus University Hospital tested this system. A custom-made phantom was used, containing 18 wire target crosses within its inner walls. A CT scan was obtained in order to segment all wire targets into a single 3D-model (hologram). An in-house software application (CTrue), developed for the Microsoft HoloLens 1, uploaded 3D-models and automatically registered the 3D-model with the phantom. Based on the surgeon’s sightline while registering and targeting (free sightline /F/or a strictly perpendicular sightline /P/), 4 scenarios were developed (FF-PF-FP-PP). Target error distance (TED) was obtained in three different working axes-(XYZ).

Results

Six surgeons (5 males, age 29–62) were enrolled. A total of 864 measurements were collected in 4 scenarios, twice. Scenario PP showed the smallest TED in XYZ-axes mean = 2.98 mm ± SD 1.33; 2.28 mm ± SD 1.45; 2.78 mm ± SD 1.91, respectively. Scenario FF showed the largest TED in XYZ-axes with mean = 10.03 mm ± SD 3.19; 6.36 mm ± SD 3.36; 16.11 mm ± SD 8.91, respectively. Multiple comparison tests, grouped in scenarios and axes, showed that the majority of scenario comparisons had significantly different TED values (p < 0.05). Y-axis always presented the smallest TED regardless of scenario tested.

Conclusion

A strictly perpendicular working sightline in relation to the 3D-model achieves the best accuracy results. Shortcomings in this technology, as an intraoperative visual cue, can be overcome by sightline correction. Incidentally, this is the preferred working angle for open surgery.