Computer-based training system for cataract surgery

International audienceThis paper describes a single simulation framework to perform interactive cataract surgery simulations. Contributions includes advanced bio-mechanical models and intensive use of modern graphics hard- ware to provide fast computation times. Surgical de- vices are replicated and located in a real-time thanks to infra-red tracking. Combination of a high-fidelity simulation and actual surgical tools are able to im- prove surgeon immersion while training. Preliminary tests have been performed by experienced ophthal- mologists to qualitatively assess the face-validity of the simulator and the faithfulness of the behavior of the anatomical structures as well as the interactions with the surgical tools

Biomechanical Soft Tissue Modeling - Techniques, Implementation and Application

The reaction of soft tissue to applied forces can be calculated with biomechanical simulation algorithms. Several modeling approaches exist. A scheme is suggested which allows the classification of arbitrary modeling approaches with respect to the degree of physical realism contained in the model (physical and descriptive models). Besides well known approaches like mass-spring, finite element, particle models and others the ChainMail algorithm is investigated. Where ChainMail in its original formulation lacked the capability to model inhomogeneous material, it is exceptionally stable and converges in one step to a valid configuration. In this thesis ChainMail is generalized to the Enhanced ChainMail algorithm which is capable to model inhomogeneous, volumetric objects and is fast enough for real time simulations. While now in principle being able to simulate and visualize an object in real time, a software architecture is required to team up simulation and visualization. As visualization and simulation have so far evolved independently, they work with different data structures. Multiplicity of data representations leads to the problems of data consistency and high memory consumption. A software architecture is developed which provides a universal data structure for several simulation and visualization approaches. The versatility of the developed architecture is demonstrated by two medical simulations. The first is the simulation of an intra-ocular surgery, which makes heavy use of Virtual Reality techniques. Designed as a training and educational tool the simulator EyeSi relies on descriptive real time ti me tissue simulation and visualization. The second deals with the simulation of decompressive craniotomy. The medical problem requires a physical model as the project's goal is to provide exact predictions on tissue behavior to support surgeons in surgery planning

Cataract complications study : an analysis of adverse effects among 14,520 eyes in relation to surgical experience

Background: To evaluate the learning-curve in performing cataract surgery with respect to developments in technology and different teaching strategies by comparing the incidence of capsular bag-related complications to operator experience. Methods: A review of the registry of 14,520 cataract surgeries carried out at the Ophthalmology Unit of Kymenlaakso Central Hospital, Kotka, Finland, from August 8, 2009 to July 31, 2017. Results: We identified 144 cases with posterior capsule rupture and/or loss of capsular bag support (incidence 0.99% of all surgeries). The mean age of patients was 76.99.1 years and gender distribution ratio 29:71 male:female. Pseudoexfoliation syndrome (PXF; incidence 21%) and small pupil (incidence 14%) were over-represented in complication eyes, especially at the beginning of the study. Capsular bag-related complication rates were reported in 0.36% of surgeries for senior and 7.03% for resident surgeons at the beginning of the study, compared to 0.32% and 1.32%, respectively, at the end of the study. Best-corrected visual acuity at the final post-operative visit was 0.61 +/- 0.16 decimals at the beginning of the study, and 0.81 +/- 0.19 decimals at the end of the study. The mean number of post-operative visits was 4.3 +/- 2.7 and did not show trend over the study period. Conclusions: Real-world evidence suggests PXF and small pupil as significant risk factors in cataract surgery. A gradual decline in the rate complications was noted with increasing surgical experience, also among residents over the follow-up period.Peer reviewe

Validity and usability of a virtual reality intraocular surgical simulator

Cataract surgery is one of the most common surgical procedures in Sweden and around 90 000 operations are made each year. An aging population with increased demands on quality of life and good visual acuity, has led to an increased rate of surgery and more surgeons needs to be trained. Training of new cataract surgeons is done on scarce wet-lab training but mainly on patients. Training is costly and complications are higher for new surgeons compared to experienced ones. In the airline industry simulators are used for training. Pilots have to prove competent before flying a new airplane. No such standards exist for new cataract surgeons. Surgical simulators have been used in other surgical fields for training and reports have shown that training has improved performance on real operations. The purpose of this work was to validate Eyesi, a surgical simulator for cataract surgery training, and analyze learning curves. Furthermore we set out to investigate whether factors like stereoacuity and sex would be important for performance in the simulator. Evidence for construct validity was found for cataract specific modules capsulorhexis, hydromaneuvers and phaco divide and conquer and for manipulating modules cataract navigation training, cataract forceps training and cataract cracking and chopping training. Analysis of learning curves showed significant improvement throughout training. Evidence for concurrent validity was established for the capsulorhexis module. For the hydromaneuvers and phaco modules, the innate simulator scoring could not distinguish surgical skill but discrimination was dependent on video based human scoring. Stereoacuity was found to correlate with performance on the simulator but there were large individual variations. An individual’s sex had no influence on performance. We have shown that Eyesi can differentiate cataract surgical skill and that naïve can train in the simulator and improve. Stereoacuity has an effect on performance but there were large individual variations. Simulation-based training has the potential to move the early learning curve out of the operating room

Cataract complications study: an analysis of adverse effects among 14,520 eyes in relation to surgical experience

Background: To evaluate the learning-curve in performing cataract surgery with respect to developments in technology and different teaching strategies by comparing the incidence of capsular bag-related complications to operator experience.Methods: A review of the registry of 14,520 cataract surgeries carried out at the Ophthalmology Unit of Kymenlaakso Central Hospital, Kotka, Finland, from August 8, 2009 to July 31, 2017.Results: We identified 144 cases with posterior capsule rupture and/or loss of capsular bag support (incidence 0.99% of all surgeries). The mean age of patients was 76.99.1 years and gender distribution ratio 29:71 male:female. Pseudoexfoliation syndrome (PXF; incidence 21%) and small pupil (incidence 14%) were over-represented in complication eyes, especially at the beginning of the study. Capsular bag-related complication rates were reported in 0.36% of surgeries for senior and 7.03% for resident surgeons at the beginning of the study, compared to 0.32% and 1.32%, respectively, at the end of the study. Best-corrected visual acuity at the final post-operative visit was 0.61 +/- 0.16 decimals at the beginning of the study, and 0.81 +/- 0.19 decimals at the end of the study. The mean number of post-operative visits was 4.3 +/- 2.7 and did not show trend over the study period.Conclusions: Real-world evidence suggests PXF and small pupil as significant risk factors in cataract surgery. A gradual decline in the rate complications was noted with increasing surgical experience, also among residents over the follow-up period

The simulated ocular surgery (SOS) trials: randomised-controlled trials comparing intense simulation-based surgical edication for cataract and glaucoma surgery to conventional training alone in East and Southern Africa

Cataract remains the most common cause of blindness globally, and glaucoma is the third after uncorrected refractive error. Surgical management remains a priority, yet surgical training of ophthalmologists continues in the outdated apprentice model. Simulation-based surgical education is yet to be tested to the level of a randomised-controlled trial in ophthalmology. We designed two separate and independent multi-centre multi-country investigator-masked randomised controlled educational-intervention parallel group efficacy trials. Post-graduate doctors in ophthalmology training programmes at collaborating institutions in five East and Southern African countries were assessed for eligibility for inclusion (not having performed the procedure as primary surgeon) into either the OLIMPICS (ophthalmic learning and improvement initiative in cataract surgery) or GLASS (glaucoma simulated surgery) trials. Fifty-one surgical trainees were recruited into the GLASS trial, and 50 into the OLIMPICS trial. Surgical competency was assessed by video recordings, which were double marked by independent experts who were masked to group assignment and timing of the assessment. The intervention was an intense simulation-based cataract or glaucoma surgical training course over 5 days. Primary outcome measure was surgical competency at three-months assessed with validated simulated surgical competency assessment rubrics, the Sim-OSSCARs (ophthalmic simulation surgical competency assessment rubric), for both trials. The trials were registered in March 2017 on the Pan-African Clinical Trial Registry (PACTR201803002159198) and are currently closed to recruitment. Baseline characteristics of age, sex, year of training, baseline knowledge and competency scores were balanced between both arms, for both trials. In total 1,361 surgical videos from across different time-points were independently graded by two separate graders in both trials. In the OLIMPICS trial, 50 participants were recruited between November 2017 and May 2018 and 49 included in the final intention-to-treat analysis with one dropout from the control group. Intervention group participants increased mean simulated surgical competence scores from a baseline of 10.8 of 40 points (27.0%) to 33.7 (84.2%) at 3-months after the training intervention, an increase of 212%. Control group participants’ mean baseline scores were 12.8 (31.9%) and 3-month scores 17.9 (44.7%). We found strong evidence (linear regression p<0.0001) that those in the intervention arm were estimated to have higher scores at three months than those in the control arm, after adjusting for baseline score. Among individuals with the same baseline score, those who received the training were estimated to have scores 16.6 points higher (95%CI 14.5 to 18.8) at three months, compared to those who had not received the training. Intervention participants performed a mean of 22 cataract surgeries as primary surgeon in the one year following the training intervention, compared to 9 by control participants (Poisson regression p<0.0001). Surgical complications were reported for the one year period, and posterior capsule rupture (PCR) rates were 7.4% for the intervention group compared to 26.2% for controls (p<0.0001). Confidence rating scores were assessed using a ten-point Likert scale anchored at 1=’not confident at all’, and 10=’very confident’. Confidence as cataract surgeons increased from 2.2 (of 10) to 6.3 at three-months in the intervention group, compared to 3.4 at baseline to 4.2 for the control group. Among individuals with the same baseline confidence score, those receiving the training were estimated to have scores 2.7 points higher (95%CI 1.6 to 3.7) (p<0.001). In the GLASS trial, 53 trainee ophthalmologists were assessed for eligibility, and 51 were enrolled and randomised. Forty-nine participants were included in the final intention-to-treat analysis: 23 intervention and 26 control, following two drop outs from the intervention group. Baseline surgical competency scores for intervention were a mean of 9.1/40 (22.6%) [median 7.3, IQR 5.4-12.1]; and for control: 8.7/40 (21.8%) [median 8.2, IQR 6.3-12.0] participants. Mean Sim-OSSCAR scores at three-months were 30.4 (76.1%) [median 30.3 IQR 27.8-33.5] and 9.8 (24.4%) [median 9.2 IQR 7.5-11.7] for intervention and control groups respectively. We found strong evidence (linear regression p<0.0001) that those in the intervention arm were estimated to have higher scores at three months than those in the control arm, after adjusting for baseline score as a fixed effect. Among individuals with the same baseline score, those who received the training were estimated to have scores 20.5 points (of 40) higher (95%CI 18.4 to 22.6) at three months, compared to those who had not received the training (linear regression p<0.0001). Baseline mean self-reported confidence in glaucoma surgical skills was 3.0/10 for intervention and 3.2 for control participants. This increased to mean 6.4 and 3.7 at three months respectively (p=0.002). Trainee participants in the intervention group performed a mean of 3.1 live surgical trabeculectomies as primary surgeon over one year following training (median 2, range 0-15, IQR 0-4). Over the same period (and before their simulation training) the control group performed a mean of 0.15 (only one of the 26 control participants performed any glaucoma surgery, compared to 14 of the 23 intervention participants). These are the first multi-centre ophthalmic simulation surgery educational-intervention randomised controlled trials ever conducted. Intense simulation training affords a rapid and sustained increase in surgical competence, confidence as a surgeon, and impacts the number of live surgeries performed. Simulation education in cataract surgery affords a striking benefit in terms of patient safety

Structured proficiency based progression phacoemulsification training curriculum using virtual reality simulator technology

The current method of surgical training is based on the Halstedian model where novice surgeons learn by observing and performing surgery under supervision. Cataract extraction by phacoemulsification is a type of minimally invasive surgery where direct observation is inadequate in revealing how things are done. Operating under the microscope takes away the direct hand-eye coordination. During the operation, a novice surgeon has to pay disproportionate amount of attention to psychomotor performance, depth and spatial judgment, operative judgment and decision-making, comprehending instruction, and gaining additional knowledge. The attentional capacity quickly becomes saturated, leaving very little to spot dangers ahead or to get out of difficulty situation. Consequently, patients are at higher risk when novice surgeons perform the operation. The solution to improve novice surgeon\u27s attentional capacity is to pre-trained pertinent operative skills in a controlled setting using simulator technology. EYESi phacoemulsification simulator offers high fidelity rendition of intra-ocular microsurgical environment. Novice surgeons can practice on the simulator until proficiency level is achieved. The aim of this project is to design and validate didactic and skill training curriculum for cataract surgery. The didactic curriculum employs 3-dimentional animations in order to explain complex surgical procedures. The proficiency level for skill training is set based on the simulator performance of ten expert cataract surgeons. A structured proficiency based simulator curriculum is designed and validated with randomized control trialin this study

Study Protocol: The Simulated Ocular Surgery (SOS) Trials: Randomised-Controlled Trials Comparing Intense Simulation-Based Surgical Education for Cataract and Glaucoma Surgery to Conventional Training Alone in East and Southern Africa

There is a huge need to perform high volumes of surgery in sub-Saharan Africa, to tackle the backlog of avoidable blindness. There is a great need to train many eye surgeons safely, efficiently, effectively, and to an acceptable level of competence. There is also a need to maintain and improve the quality and outcomes of surgery. Currently, surgical training is often conducted using the traditional "apprentice model", where a trainee observes a qualified surgeon and learns from them, and then the surgeon supervises the trainee performing surgery on a patient. We believe that this conventional model has substantial limitations and drawbacks, making surgical training less efficient and less safe. We will test the hypothesis that intense modular simulation-based ophthalmic surgical education is superior to conventional training for the initial acquisition of competence. Pilot studies have been conducted in Malawi, Uganda, and South Africa to develop, test and refine aspects of modular simulation-based ophthalmic surgical training in cataract and glaucoma surgery. Assessment tools have been developed and validated for use in this simulation-based training (see Appendices 3a and 3b). Subsequent to these pilot and validation studies, we are now able to test the efficacy of focussed modular simulation-based ophthalmic surgical training in two separate parallel-group randomised controlled trials. We will conduct two independent trials of intense simulation-based ophthalmic surgical education for training ophthalmologists in the procedures for cataract, and separately for glaucoma: the two leading causes of blindness in sub-Saharan Africa. Trainee eye surgeons will be randomised to the 'intervention' of focussed simulation-based surgical training (in addition to, and as an enhancement to conventional training), or to the 'control' group of current conventional training alone. The 'control' group participants will receive the same simulation training, only after a period of one year. Follow-up assessments will measure whether the trainees have gained in surgical competence (objectively assessed using a specific and validated grading score), knowledge, their perceived confidence as a surgeon, and in terms of the benefit to their patients (the quality and quantity of surgery performed). All the training within the 'educational intervention' of this study will be performed using simulation. There is no testing or surgical training on patients within the study educational-intervention of both training trials. The only times when patients are indirectly involved is entirely as part of standard, regulated, and supervised clinical training within a Nationally accredited and registered ophthalmology training programme. When three anonymised and non-identifiable recordings of cataract surgical procedures are video-recorded (at three months, year one, and then another three at fifteen months), patients will be informed of the planned recording, and invited to sign a standardised informed consent as for any clinical image recording within standard clinical practice. Live surgery recordings or assessments for the GLASS trial intervention and control groups will be conducted in individual circumstances where the local Consultant Ophthalmologist deems the participant competent to perform (and record) SUPERVISED live surgery during the year post-intervention

Virtuelle Realitäten für die chirurgische Ausbildung: Strukturen, Algorithmen und ihre Anwendung

Die vorliegende Arbeit beschreibt Strukturen und Algorithmen zum Bau virtueller Realitäten für die chirurgische Ausbildung. Anwendungsbeispiel ist die Software des Augenoperationssimulators EyeSi; alle Verfahren wurden aber in größerer Allgemeinheit für die Softwarebibliothek VRM (Virtuelle Realität in der Medizin) implementiert. (1) Datenrepräsentation: Zu Repräsentation der Daten einer virtuellen Welt wird ein gerichteter Multigraph mit attributierten Knoten und gefärbten Kanten vorgeschlagen. Die strukturelle Information wird in knotenzentrierten Adjazenzlisten gespeichert. Um schnellen sequentiellen Zugriff zu ermöglichen, können einzelne Attribute in zusammenhängenden Speicherbereichen abgelegt werden. Mit Hilfe einer dünnen Zugriffsschicht werden Sichten auf Subgraphen definiert, innerhalb derer Typsicherheit und Zugriffsschutz gewährleistet sind. Ausdrucksmächtigkeit und Zugriffsgeschwindigkeit des Datenformats ermöglichen es, alle Informationen über die virtuelle Welt auf einheitliche Weise zu repräsentieren -- die inneren Strukturen der Objekte genauso wie szenegraphähnliche Beziehungen der Objekte untereinander. (2) Softwarearchitektur: Die Software für einen VR-Simulator wird in die Komponenten I/O (VR-Interfaces), Simulation (Berechnung der physikalischen Vorgänge) und Systemsteuerung (GUI, Benutzerverwaltung, Multimedia-Ausgabe) aufgeteilt. Die Komponenten werden auf logische und softwaretechnische Weise getrennt, so dass die Softwareentwicklung in unabhängigen Teilprojekten erfolgen kann. Die Datenströme zwischen den Komponenten können umgeleitet werden. Dies ermöglicht es beispielsweise, Trainingssitzungen aufzuzeichnen und wiederzugeben, mehrere Simulatoren miteinander zu koppeln oder den grafischen Renderer auszutauschen. Anhand bestehender psychologischer Untersuchungen wird eine VR-Echtzeitbedingung definiert. Auf der Basis von Laufzeitmessungen wird diskutiert, unter welchen Bedingungen die VR-Echtzeitbedingung auch auf Standard-PCs erfüllt werden kann. Es wird vorgeschlagen, zeitintensive Vorgänge auf unabhängige, aber synchron arbeitende Subsysteme auszulagern. EyeSi setzt diesen Vorschlag bei der Kollisionserkennung mit Grafikoperationen sowie bei der FPGA-basierten Bildverarbeitung des Trackingsystems um. (3) Gewebeinteraktion: Der erste Schritt bei der Berechnung einer Gewebeinteraktion ist die Erkennung der Kollision zwischen einem Instrument und einem Gewebestück. Standard-Verfahren sind häufig ungeeignet, da sie die möglichen Objektformen zu sehr einschränken oder eine zeitaufwändige Vorberechnung benötigen. Es wurde daher ein bildbasiertes Verfahren entwickelt, das auf einem Vorschlag von Myszkowski et al. (1995) basiert. Es wird gezeigt, dass unter bestimmten Bedingungen ein lokales Konvexitätskriterium gilt, mit dessen Hilfe ein Rendering-Schritt eingespart werden kann. Durch Berücksichtigung der vorgegebenen Interaktions- und Deformationsrichtungen entfällt ein weiterer Rendering-Schritt. Für die Berechnung von Deformationsvektoren werden die z-Buffer-Einträge genutzt, kollidierende Polygone werden über eine eindeutige Färbung im Color-Buffer identifiziert. Es wird gezeigt, dass mit diesem Ansatz Kollisionserkennung und -antwort in EyeSi schnell genug berechnet werden können. Es wird diskutiert, wie bei der Kollisionsantwort Oszillationen und daraus resultierende numerische Instabilitäten vermieden werden können. Für die Gewebedeformation stellt die VRM-Bibliothek FEM-Verfahren, ChainMail- und Feder-Masse-Modelle zur Verfügung. Es werden verschiedene Integrationsmethoden für Feder-Masse-Modelle diskutiert. Um bei expliziter Integration den Stabilitätsbereich zu vergrößern, wird die Dehnungskorrektor von Provot (1995) mit einer Feder-Sortierung verbunden. Zur lokalen Gitterverfeinerung wird ein einfaches Verfahren vorgestellt. (4) EyeSi: EyeSi ist eine virtuelle Realität zum Training von Augenoperationen. Es werden alle wesentlichen Aspekte einer realen Operation nachgebildet: ein stereoskopisches Display ersetzt das Stereomikroskop. Originalgetreue Instrumente werden in einem Metallauge bewegt; die Positionen der Objekte werden mit einem optischen Trackingsystem gemessen. Ein PC übernimmt die Verwaltungsaufgaben des Systems: Benutzerverwaltung, GUI-Steuerung über einen Touchscreen, Kontrolle, Auswertung und Aufzeichnung von Trainingsläufen, realistische 3D-Visualisierung über einen eigenen Renderer sowie generische Routinen für die Instrument-Gewebe-Interaktion. Innerhalb dieses Rahmens sind verschiedene Trainingsmodule implementiert, die dem angehenenden Chirurgen nicht nur grundlegende manuelle Fähigkeiten vermitteln, sondern die Durchführung vollständiger Operationen gestatten. Durch die realistische Gewebesimulation und das aufwändige VR-Interface ist eine überzeugende virtuelle Realität entstanden, die bereits in der ophthalmochirurgischen Ausbildung im Einsatz ist