DryLabs in Virtual VitreoRetinal Surgery

mercredi 6 avril 2011

Between May 2007 and June 2010, 152 ophthalmologic residents with less surgical experience (group 1) and 62 fully trained ophthalmologists (group 2).attended one drylab and performed several virtual reality training tasks. Each participant trained basic abstract skills (like anti-tremor training) followed by a virtual operation (like ILM peeling) and evaluated their drylab experience with a questionnaire (1 = strongly disagree to 5 = strongly agree). Items on visual quality in comparison to the reality, complexity of the tasks, clinical impact, learning effect and overall impression were analyzed.
We analyzed 214 questionnaires of 309 participants of 11 drylabs (69.3% response rate). Group 1 consisted of 152 trainees (71%, mean age 28.7 +/-6.5 years) with an average time of 2.2 +/-1.3 years in training. Group 2 included 62 attendees (29%, 41.4 +/-3.2 years) with 8.5 years +/- 3.2 of work experience. Visual quality was rated with mean 4.6 points (group 1) versus 4.2 (group 2 ; p>0.05), complexity 4.5 vs. 3.2 (p>0.01), clinical impact 4.4 vs. 4.0 (p<0.01), and overall impression 4.6 vs. 4.0 (p<0.01).
The majority of the participants highly appreciated the virtual vitreoretinal training and would recommend the course in 95.2% in group 1 and 83.4% in group 2.

Since many years evidence-based training on simulators has already been standard in the aviation industry(Brown 1976). Today, flying is considered to be one of the safest means of transport. Computer-based training systems are also becoming increasingly important in medical training(Lucas et al. 2008 ; Windsor et al. 2008). We, as ophthalmologists, have learned from other fields of medicine that patient safety can thereby be increased as personnel shortages among teaching staff and not least financial and insurance constraints increasingly advocate the development of new teaching methods(Seymour et al. 2002 ; Haque & Srinivasan 2006 ; Khalifa et al. 2006 ; Solverson et al. 2009).
In the field of ophthalmology, diagnostic and therapeutic skills have so far been acquired almost exclusively through study of specialist literature, participation in meetings and then managing of various clinical scenarios and complications with conservative treatment(Scott et al. 2009). Surgical ophthalmologic education usually starts by assistance in the operating room and practical training on cadaver eyes (wetlabs). Regardless of the strength of a residency or fellowship program the education is generally non standardized in terms of objective parameters and depends on the single teaching institution that differs in size of patients, faculty, and colleagues. Transfer of knowledge to everyday clinical conditions takes place with varying quality. In addition, ophthalmosurgical training is subject to constant changes in practice due to further development of instruments and surgical techniques.
Since 2003, the virtual reality simulator Eyesi® (VRmagic, Mannheim, Germany) has offered trainee physicians the opportunity of training microsurgical procedures on the anterior and posterior eye segments. Our department has been involved in the development of the software since then and with Frank Koch being the principle medical advisor, we have conducted multiple workshops on ophthalmologic surgical training worldwide to coin these workshops dry lab. The goal of this study was to establish the acceptance and evaluation capability of simulation-based training in ophthalmosurgical training.

I.Material and Methods

The institutional review board (IRB)/ ethics committee ruled that approval was not required for this study (internal number 13/2007).


The data survey presented here is based on the evaluations of participants of 11 Vitreoretinal drylabs with Eyesi®, which took place in the period from March 2007 to June 2010 (International Congress of the German Ophthalmic Surgeons, DOC, Nuremberg ; Vitreoretinal Symposium, VRS, Frankfurt ; Congress of the German Ophthalmological Society, DOG, Berlin, figure 1a,b).

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Picture of a drylab setting at the vitreoretinal symposium in Frankfurt 8/28/2009
Picture of a drylab setting at the vitreoretinal symposium in Frankfurt 8/28/2009

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Participant during simulated ILM-peeling
Participant during simulated ILM-peeling

The participants were residents in ophthalmology with less surgical experience (if less than 10 vitrectomies had been performed) or fully trained ophthalmologists with greater surgical experience. The participants could not be split in residents, fellows and consultants, as the participants came from different medical systems (Germany 64%, 21 % other European country, USA 11%, Asia 4%). In each dry lab there were 8 simulators with two participants and one certified instructor (certification was performed by VRmagic and included handling of the soft- and hardware). The dry labs lasted for two hours and initially provided (1) an introduction to handling of the simulator and then (2) training of microsurgical skills. For this purpose, instrument handling and spatial orientation in the eye interior were first trained by means of abstract tasks (e.g. anti-tremor training, instrument coordination) followed by vitreoretinal operations (e.g. core and peripheral vitrectomy with posterior vitreous layer detachment and ILM peeling, figure 2a,b).

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Simulated induction of a posterior vitreous detachment
Simulated induction of a posterior vitreous detachment

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Training history of posterior hyaloid training ; objective parameter of simulated vitrectomy in percentages
Training history of posterior hyaloid training ; objective parameter of simulated vitrectomy in percentages

The teaching language was German or English depending on the attendee´s preferred language.

Soft- and Hardware

The simulation environment of Eyesi® offers the most important aspects of the situation in a ophthalmology surgery room. The surgeon is seated in the usual position at a stereo microscope and inserts vitreoretinal instruments into a mechanical, rotatable artificial eye made of plastic via the pars plana. The artificial eye is suspended in the model head of the simulator so that movements can be performed in the same way as in a human eye during the operation. The eye can be rotated up and down and cyclorotated, can be pressed into the orbit and can also be pulled forward slightly. The instruments can be moved like in a bimanual pars plana vitrectomy. An optical tracking system in the model head follows the movement of the instruments with three cameras and transmits information on their position to a computer. The system calculates in real time how tissue reacts that comes into contact with the surgical instrument in the simulation. The physician sees the computer-generated scenario in the usual three dimensions through the stereo microscope. An additional monitor is used to show the instruments in the operating area, the settings of the operating machine (e.g. vacuum, cutting rate). The training system records the virtual operations and permits objective evaluation and statistical assessment of the surgical performance.


All 309 physicians who participated in the survey first performed abstract and clinical virtual tasks on Eyesi®.
Participants were asked anonymously about the following items in standardized questionnaires (see Figure 2) : Visual quality and comparison to the reality (aspect 1), difficulty (aspect 2), clinical impact (aspect 3), significance for ophthalmological training (aspect 4), learning effect of simulator-based training (aspect 5) as well as the overall impression (aspect 6) on a scale from 1 (= strongly disagree ; very easy ; poor) to 5 (= strongly agree ; very difficult ; excellent). The question “Would you recommend the course to your colleague ?” could be answered with Yes or No. None of the items weighed.


The data obtained were recorded as mean values plus standard deviation in an Excel table and initially subjected to descriptive analysis using the statistical program SPSS, Version 12.0.1. The David test was performed to check for normal distribution. Therefore comparisons of the two groups (I and II) were performed with the non-parametric Wilcoxon test to establish significant differences in the evaluation results between the two groups.


Of the 309 evaluation surveys collected, it was possible to analyze 214 (69.3 %). Inclusion criteria were participation in the dry lab and employment as residents/specialists in ophthalmology. Exclusion criteria for the questionnaires were incomplete forms, multiple answer selection and illegibility. The participants in the study were divided into two groups on the basis of the details they provided about their surgical experience : Group 1 included all participants who stated that they had no or little (fewer than 10 operations) surgical experience – this was stated by 152 participants (71 %). In contrast, 62 participants (29 %) declared that they had already performed ten or more vitreoretinal operations. These participants were assigned to group 2. Group 1 consisted of 79 women (51.9 %) and 73 men (48.1%) ; the average age was 28.7 (+/-3.2) years. Group 2 consisted of 8 women (12.9 %) and 54 men (87.1 %) with a mean age of 41.4 (+/- 6.4) years. The average clinical experience was 2.2 years (+/- 1.3) in group 1 compared with 8.5 (+/- 3.2) years in group 2 (table 1).

Group 1 Group 2 P values
Participants (% of total = 214) 152 (71%) 62 (29%)
Gender (male /female) 73 (48.1%) / 79 (51.9%) 54 (87.1 %) / 8 (12.9%)
Age 28.7 +/- 3.2 41.4 +/- 6.5 P < 0.001
Working experience 2.2 +/- 1.3 8.5 +/- 3.2 P < 0.001
Table 1. Epidemics of participants ;
age and working experience in years ;
p values were calculated with the Wilcoxon matched pairs test

The evaluations submitted by the participants were evaluated and compared separately on the basis of this grouping (table 2).

Group 1 Group 2 P values
Comparison to the reality (1= strongly disagree ; 5= strongly agree) 4.6 (+/- 0.7) 4.2 (+/- 0.5) P < 0.05
Complexity of the tasks (1 = very easy ; 5 = very difficult) 4.5 (+/- 0.6) 3.2 (+/- 1.6) P < 0.01
Clinical impact (1= strongly disagree ; 5= strongly agree) 4.4 +/- 0.7 4.0 +/- 0.8 P < 0.001
Learning effect 4.8 +/- 0.5 3.7 +/- 1.3 P < 0.001
Overall impression 4.6 +/- 0.9 4.0 +/- 0.7 P < 0.001
Would you recommend the course to a colleague ? Yes 95.2% Yes 83.4 %
Table 2. Results of the questionnaire displayed in mean points with +/- standard deviation ;
p values were calculated with the Wilcoxon matched pairs test

The comparison of the visual quality in to the reality yielded a p-value of <0.05 between group 1 (mean 4.6 standard deviation +/- 0.7 points) and group 2 (4.2 +/- 0.5). The comparison of all other items demonstrated a p-value of <0.01. Group 1, awarded 4.5 +/- 0.6 points on average in assessment of the degree of difficulty (1 = very easy ; 5 = very difficult) or complexity of the given task in contrast to 3.2 +/- 1.6. 62% of the participants in group 1 and 16.7 % in group 2 were of the opinion that the simulated operation was very difficult to perform, whereas 0.9% from group 1 and 20.8% of the participants in group 2 stated that the tasks were very easy. Group 1 awarded 4.4 +/- 0.7 points versus 4.0 +/- 0.8 points (p<0.01) to assess the impact of the simulation for the clinical routine. 57.4% of the participants from group 1 and 31.25 % from group 2 declared that the knowledge acquired on the simulator was very relevant for everyday clinical practice. The learning effect of the simulator training was rated with 4.8 +/-0.5 (group 1) versus 3.7 +/- (1.3). Additionally as high to very high by 93.5 % of the participants in group 1 and 57.1 % in group 2. Grades were awarded in the overall impression of the simulator-assisted ophthalmosurgical course (1 = poor ; 5 = excellent). Group 1 stated 4.6 +/- 0.9 and group 2 in average 4.0 +/- 0.7 points. 95.2 % of the participants in group 1 and 83.4 % from group 2 would recommend the course for medical training and further training to a colleague. There was no statistical difference in the evaluation of the single items between the attendees distributed by land of origin (e.g. German versus US participants).


Simulation technology has already been successfully used in medical training programs for a number of years, particularly in the fields of laparoscopic surgery and endoscopy. The studies published on this subject were able to prove that surgery simulation is suitable for improving surgical skills and associated patient safety (e.g. due to reduced tissue damage) and can also be used for assessment of surgical performance(Seymour et al. 2002 ; Haque & Srinivasan 2006 ; Lucas et al. 2008 ; Windsor et al. 2008).
The use of simulation technology has been increasing in importance in ophthalmology since the turn of the century, even though there is still enormous optimization potential in this field. The surgical simulator Eyesi® was initially presented in 2001 as a training unit for vitreoretinal procedures and has since been increasingly used for ophthalmosurgical training and further training. Rossi et al. already demonstrated the validity of the Eyesi® simulator for ILM peeling in 2004(Rossi et al. 2004). Their data showed that experienced ophthalmic surgeons had a significantly lower error rate than inexperienced surgeons. After the simulation platform had been extended to include training modules for surgical procedures in the anterior eye segment in 2005, Mahr et al. demonstrated the validity and effectiveness of the Eyesi® simulator for the motor learning curve on the basis of the newly developed “anterior segment forceps” and “anti-tremor” modules(Mahr & Hodge 2008). On the basis of the findings in their study, the authors propose that the lower variability in the surgical scores achieved by experienced ophthalmic surgeons compared with their less experienced colleagues be used as a benchmark criterion in surgical training.
Feudner et al. were able to demonstrate the effectiveness of training with the Eyesi® surgical simulator by means of the capsulorhexis module. After two weeks of training on Eyesi®, the study participants performed this procedure significantly better than the control group without simulator training(Feudner et al. 2009).
Hitherto there is until now a paucity of data on the role of virtual operating simulators in ophthalmology. The present study demonstrates the potential importance of simulation technology in ophthalmological training and further training from the ophthalmologists perspectives with differing levels of surgical experience. Analysis of the standardized evaluation data shows a consistently positive assessment of the dry lab by the participants. Nevertheless, it was possible to establish significant differences in the verdict of experienced ophthalmic surgeons compared with their less experienced colleagues : the simulation-based training was well received particularly by physicians who have little practical experience. This group assessed the difficulty of the tasks as more difficult on average and also as being more relevant for everyday clinical practice. This result correlates with the constantly discussed problem of the relatively long learning curves in ophthalmosurgical training. Integration of training simulators in the ophthalmological training curriculum can therefore significantly extend the range of available training and at the same time relieve the strain on everyday clinic operation. The main goal should be to structure and standardize training programs in order to shorten individual learning curves and generate uniform quality standards. A further challenge is reliable assessment and evaluation of aquired (residency, fellowship) or existing specialist knowledge. In Germany for example, the board certification is an oral exam, that depends on the subjective assessment of the examiner, while other countries expect written exams, that are more objective. Surgical skills are not tested in either situations. The success statistics (so called benchmarks, or failure figures) of hospitals and clinics are normally restricted to use for internal purposes. Computer-based training systems could improve the quality of medical training and give an objective assessment.
This study has several limitations. The questionnaire response rate of 69.3% may restrict the generalizability of the results, although it exceeds the mean 32 % response rate of a recent US program director survey(Scott et al. 2009). The fact that most of the participants experienced their education in the German medical system might have biased the results, however comparisons of the single items between the different lands of origins yielded no difference. The multiple choice nature of the questions might also have biased the survey, as open-ended questions might have given a more thorough understanding. Multiple choice results are on the other hand easier to analyze and to compare.


The Eyesi® platform is currently used for surgical procedures in the anterior/posterior chamber, in the vitreous chamber and from here on the retina. Surface procedures such as 23/25 gauge vitrectomy or mini-incision cataract surgery must still be trained on artificial or cadaver eyes with table microscope control. Development of new simulation concepts is therefore necessary for surgical procedures on surfaces.


Since the winter term 2009/10, the training program with the Eyesi® surgical simulator at the University Eye Clinic Frankfurt am Main has been supplemented by a training system for diagnosis : in cooperation with the Department of Computer Science V at the University of Heidelberg and the company VRmagic GmbH, Mannheim, a training simulator for indirect ophthalmoscopy has been undergoing development since 2007. Even at the prototype stage, this system was already incorporated in the ophthalmoscopy course at the Eye Clinic in Frankfurt (figure 3a,b).

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Setting of a simulated funduscopy
Setting of a simulated funduscopy

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Simulated postinflammatory chorioretinal scarring
Simulated postinflammatory chorioretinal scarring

Clinically relevant clinical pictures that manifest themselves on the retina were systematically prepared and integrated in the case database of the training system. Initial evaluations show that the simulator represents a more than adequate substitute for previous teaching methods with artificial eyes, patients or mutual examination between students thanks to a comprehensive case database and objective evaluation of procedural and diagnostic skills. In addition, the simulator provides a platform for systematic preparation of clinical cases with interdisciplinary relevance and can thus contribute to future standardization of teaching content.


Further development of surgical and ophthalmoscopic simulation will create a comprehensive training station for students and physicians that is continuously evaluated and also integrated in training programs. Further research is needed to especially demonstrate the benefit of a virtual-reality-to-real-surgery outcome compared to the traditional method of surgical education (see-do-teach).


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_*Scott IU, AD Smalley & AR Kunselman (2009) : Ophthalmology residency program leadership expectations of resident competency in retinal procedures and resident experience with retinal procedures. Retina 29 : 251-6.
_*Seymour NE, AG Gallagher, SA Roman, MK O’Brien, VK Bansal, DK Andersen & RM Satava (2002) : Virtual reality training improves operating room performance : results of a randomized, double-blinded study. Ann Surg 236 : 458-63 ; discussion 463-4.
_*Solverson DJ, RA Mazzoli, WR Raymond, ML Nelson, EA Hansen, MF Torres, A Bhandari & CD Hartranft (2009) : Virtual reality simulation in acquiring and differentiating basic ophthalmic microsurgical skills. Simul Healthc 4 : 98-103.
_*Windsor JA, S Diener & F Zoha (2008) : Learning style and laparoscopic experience in psychomotor skill performance using a virtual reality surgical simulator. Am J Surg 195 : 837-42.


Picture of a drylab setting at the vitreoretinal symposium in Frankfurt (...) Participant during simulated ILM-peeling Simulated induction of a posterior vitreous detachment Training history of posterior hyaloid training ; objective parameter of (...) Setting of a simulated funduscopy Simulated postinflammatory chorioretinal scarring

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