IC-52: Learning phacoemulsification cataract surgery in virtual reality
Training phacoemulsification cataract surgery in ophthalmology residents with a VR simulator.
Sanchez MJ, Kretz F, Limberger IL, Auffarth GU
Introduction
Intraocular surgeries are one of the biggest challenges of the microsurgery. Until now there were only a few possibilities for young residents to practice their surgical skills: wet labs on pig eyes or directly on patients. World wide increases the importance of computer based training programs in the medical field has increased world widely. High technology and improvement on the simulation of virtual reality allows the new generations to access to a whole new word of educational tools. The advantages of such a technology are: the possibility to practice real situations without the risks of complication on real patients, the time independency and access to the simulator any time you want the reduced human and monetary costs and the possibility to create a personalized training system depending on the needs of the resident.
Different studies have shown that the rate of complications is significant higher in groups of young surgeons.1, 2, 3 (see Table 1).
The virtual simulation has been an important tool in many other medical areas. Since 1996 a German company called VRmagic started the development of a simulator (Eyesi) for ophthalmic surgery in the anterior and posterior segment.
Bahgat et al.Br J Ophthalmol 2007 / 755 patients:
- posterior capsule rupture 6.7%
- vitreous loss 5.4%
- dislocated lenticular fragments 1.0%
Lee JS et al.
Eye 2009 / 101 surgeries:
- intraoperative complications in 27.4%
- vitreous loss 4.9%
Unal M et al.
J Cat Ref Surg 2007 / 150 procedures:
- capsulorhexis complications 9.3%
- anterior capsule tears 5.3%
- vitreous loss 6.6%
- posterior capsule rupture 2.0%
- loss of lens fragments in vitreous 2.0%
Table 1
The simulation program of Eyesi was developed to fulfil two main concepts: general skills training and the individual surgical preparation.
The surgeon sits in the normal position in front of the microscope, just like in a real OR, the surgeon has different surgical instruments available which can be inserted into the artificial eye. The main difference to a real operation is that the image seen on the microscope has been developed with a computer program. With a little time delay, which is not detectable for the human eye, the system simulates how the different tissues interact with the surgical instruments.
Material and Methods
In this study we used the Eyesi platform as a Op-simulator (VRmagic, Mannheim, Germany).
The Eyesi-Simulator allows practicing and learning ophthalmic surgeries in steps. Individual aspects of the cataract surgery can be trained during the different modules, such as the orientation inside the anterior chamber, the manipulation of different structures, the accurate use of the instruments and phaco machine.
Der VR Simulator was conceived for surgeries of the anterior and posterior segment (cataract module and vitreoretinal module). There are 2 Interface heads and two different sets of instruments. In this study we decided to work with the cataract module, so it will be described deeply in the next paragraphs.
The interface consists of a Head with a model eye, surgical instruments (3 pieces), two foot pedals (Phaco and Microscope pedal) and the software itself. The model eye is adjustable for frontal and temporal incisions, depending on the surgeon’s request. Around the artificial eye, there are several small apertures which simulate paracentesis, the surgeon is free to choose which one to use. The Interface head, as well as the instruments have got different sensors for movement, pressure and proprioception, which send signals to the computer allowing the creation of a virtual image that can be projected on the microscope. At the beginning of every test a microscope must be adjusted. The depth of field is simulated with 3D images which are useful for the user in order to interact with the different structures in the eye.
During the completion of task different parts of the performance are to be evaluated: goal achievement, time of execution, quality of the performance, instrument handling and microscope adjustment 4.
The simulator also offers the possibility to practice how to deal with complications, for example during a posterior capsule rupture (Image 2) or during an anterior chamber collapse after removing the irrigation’s cannula during I/A (Image 3).
For this prospective clinical trial we worked with residents and young anterior chamber surgeons of the Ophthalmology Department at the University of Heidelberg, Germany. The subjects were divided depending on surgical experience and year of residency in groups: A (experienced residents n=3); B (middle experienced residents n=3); C (beginner residents n=3) and D (young surgeons n=3). 8 female and 4 male colleagues were evaluated, all of them were right handed and the median age was 32 years.
Every subject had his own account and they were asked to perform a training program for 2 months for at least 2 hours per week.
In addition, a small group of first year residents without any surgical experience was encouraged to perform capsulorhexis and irrigation aspiration on pig eyes, after a normal training program with Eyesi the wet lab was repeated and the results were analyzed. A standardized questionnaire was used to analyze the comparability of the real situation versus. the virtual simulation, the complexity of the tasks, the clinical impact, the learning curve and the personal skill assessment before and after the training.
The cataract beginners’ course (Cat-A) contains 4 modules and in every task a score of at least 30% muss be achieved in order to move on to the next task. All subjects executed the course 3 times in a roll in order to also evaluate the reliability of the program and analyze the intra- and interindividual performances.
Figure. 1a. Figure. 1b.
Image.1 Eyesi Platform. a) Microscope and control panel of the foot pedal. b) Interface head and instruments for anterior and posterior segment.
Figure. 2a. Figure. 2b.
Figure 2. Example of simulated complications. a) Posterior capsule rupture during phacoemulsification with loss of lens-nucleus in the vitreous. b) Anterior chamber collapse after removing the irrigation’s cannula during I/A
Figure. 3a. Figure. 3b.
Figure.3 Example of the module instrument Handling. a) Handling with forceps. b) Cataract Navigation
Figure. 4
Figure 4. Example of a simulated cataract surgery: Hydrodissection, Capsulorhexis, Phacoemulsification and I/A.
Results
The group of young surgeons showed a better performance compared to all resident’s groups. Group A showed better results in all tasks, but due to the small number of subjects, no statistical significance was found (P > 0.05 Kruskal-Wallis Test) (Figure 5).
In figure 6 we can see a graph showing the number of attempts in the resident’s group, group A needed less attempts per task compared to groups B and C.
The intra- and interindividual analysis showed an improvement on the performance of all groups.
The simulator showed a good reliability, in figure 7 we can see that group B showed a higher statistical spread, but this was no significant (P > 0.05 Kruskal-Wallis Test) (Figure 7).
In figure 8 we can see two examples of two different learning curves. The first one from group C (beginners group) showed less total score, but an improvement of the first results with time. The second learning curve is from a subject in group A (experienced group) where we can see a better performance from the beginning. Also in this case there is an improvement of the performance with the time.
The experiment with the first year residents showed an improvement of the skills during capsulorhexis and I/A after the Eyesi Training and the subjective questionnaire revealed a high acceptance of the simulated training among the young residents.
Figure. 5
Figure.5 Total score in all 3 resident groups. (A, B und C) for instrument handling, capsulorhexis and phaco concepts.
Figure. 6.
Figure.6 Number of attempts per group, at least 30 % of the score was required to move to the next task.
Figure. 7.
Figure.7 Reliability in all 3 resident groups after repeating the Cat-A course 3 times
Figure. 8a.
Figure. 8b.
Figure.8. Example of the learning curves a) Group C b) Group A
Conclusions
Other clinical trials have already analyzed and demonstrated a significant construct validity of the Eyesi Op-Simulator 5,6,7. Based on these studies we developed training’s programs for our residents.
In order to generate an individual training program bigger groups and a longer period of training will be necessary; however the advantages from a VR System as an educational tool are evident. This equipment is time independent and gives us the possibility to practice under different conditions and to simulate complications without having the risk of a real operation. Not only could we see a relation between results and surgical experience, but we could also see the improvement of the performances in all groups after a defined period of time. Also the subjects (first residents group) express a subjective improvement of their skills on pig eye wet-labs after going through a training program with Eyesi.
With the release of the new 2.7 Software we expect to be able to evaluate the performance of more experienced cataract surgeons in difficult cases such as during surgical complications (e.g. cases of weak zonula, difficult capsulorhexis and hard cataracts) as well as continuing to evaluate the individual Training program with our residents. Further analysis with a bigger number of subjects would be necessary for the establishment of individual training programs of young ophthalmologists.
References:
1. Bahgat et al. „complication in resident-performance Phacoemulsification Cataract surgery“ Br J Ophthalmol 2007.
2. Lee JS et al. „Complications after cataract surgery“ Eye 2009.
3 Unal M et al. “Cataract surgery complications”. J Cat Ref Surg 2007.
4. User Guide für Eyesi Surgery Simulator Version 2.6.
5. Brian Privett et al. “Construst validity of a surgical simulator as a valid model for capsulorhexis training”. J Cataract Refract Surg 2010; 36:1835-1838.
6. M. Selvander et al. “Virtual reality cataract surgery training: learning curves and concurrent validity”. Acta Ophthalmol. 2010 j.1755-37687.
7. M. A. Mahr et al. “Construct validity of anterior segment anti-tremor and forceps surgical simulator training modules”. J Cataract Refract Surg 2008;34:980-985.