ObjectiveTo reduce the surgical risks to patients and expose surgeons to surgical experience and complications, we have developed a practical system of vitreous surgery using virtual-reality technology.MethodsThe system is composed of high-resolution color stereo binoculars, haptic devices, foot switches, and a high-speed graphics computer. To simulate vitreous surgery, we created several virtual patient eyes with retinal diseases such as preretinal membranes and subretinal neovascular tissue at the fovea.ResultsThe simulator provided the trainees with an operating environment similar to an actual one, and allowed them to learn to maneuver surgical instruments and remove proliferative tissue on the retina, under the retina, or both. This system allowed surgeons to avoid iatrogenic complications through visual signs such as retinal hemorrhage when the instrument contacted the retinal surface.ConclusionsThis simulator may not only be suitable for residents to learn ocular surgical techniques but may also allow veteran surgeons to develop new surgical methods and skills.VITREOUS SURGERY is an established treatment for many eye diseases that can cause blindness, such as proliferative diabetic retinopathy, macular disorders, and complicated retinal detachment. The surgery involves removing the vitreous gel and proliferative tissue on the retina, under the retina, or both.Intraoperative complications such as iatrogenic retinal breaks, lens contact, or retinal contusive injury from instruments can occur, especially if the surgeon is a novice. Although such complications usually do not result in severe visual damage, they impose some burdens on patients. The surgery is performed under microscopic observation, and the surgical maneuvers are minute. Unfortunately, there are no suitable models on which to practice vitreous surgery,and surgical experience is generally gained during actual ocular procedures. Thus, surgical education is one of the problems in the field of ophthalmology. Learning new surgical procedures and maintaining skills requires practice. There is a need for a practice eye system that closely mimics the feel of a living human eye and yet does not put patients at risk. To reduce the risk to patients and allow surgeons to gain surgical experience, we have now developed a practical system of vitreous surgery using virtual-reality technology.MATERIALS AND METHODSThe practical system of vitreous surgery using virtual-reality technology is composed of 4 major parts (Figure 1): high-resolution color stereo binoculars, haptic devices, foot switches, and a high-speed graphics computer.Figure 1.Vitreous surgery using virtual-reality technology. A, Diagram of the system of vitreous surgery using virtual-reality technology. B, Schema of the system. This practical system of surgery is composed of 4 major parts: high-resolution color stereo binoculars, haptic devices, foot switches, and a high-speed graphics computer. LAN indicates local area network; PC, personal computer; TV, televison; VCR, videocassette recorder; and WS, work station.The high-resolution color stereo binoculars simulate the surgical microscope that ophthalmologists use during actual ocular surgery. It has 1280 × 1024-pixel resolution and simultaneously displays 16.7 million colors. It also provides 2 images that can be seen by the surgeon's right and left eyes, thus providing a stereo image of the surgery. The haptic devices simulate operating instruments such as intraocular forceps or scissors, which can be controlled with the switch of haptic devices. The devices have 6 degrees of freedom for input so that it makes a matrix, which defines the position of the virtual operating instrument. They also have 3 degrees of freedom for output so that the surgeon can feel the force of feedback. Two virtual operating instruments enable the surgeon to practice 2-handed virtual surgery. The system has 2 foot switches, 1 to control the vitreous surgical instrument and the other to control the microscope. Pushing the foot switch of the microscope changes the virtual-surgery image. For example, the foot switch moves the microscope position, expands and shrinks the image, adjusts the microscope focus, and turns the major light on and off. With the foot switch that controls the vitreous surgery instrument, the surgeon can control vitreous aspiration. The 2 foot switches are controlled by a personal computer and the foot-switch status information is sent to a high-speed graphics computer through a local area network. The high-speed graphics computer generates the virtual-surgery image based on the haptic device and foot-switch information, and provides the surgeon with stereo visual feedback. At present, the virtual-surgery image achieves more than 20 Hz, which is sufficiently fast for real-time surgical simulation. In addition, the virtual-surgery image can be recorded through a down-converter and a VCR, which allow surgeons to review their own training.RESULTSTo simulate vitreous surgery, we created several virtual patient eyes with retinal diseases, such as preretinal membranes and subretinal neovascular membranes at the macula. Figure 2shows a computer-generated image of a virtual patient with a preretinal membrane and the trainee simulating the surgery using this system. The arrow indicates a light guide on the trainee's left-hand side that illuminates the retina, and the arrowhead indicates a forceps that is used to grasp the membrane and dissect it from the retinal surface. When the trainee accidentally keeps the instrument in contact with the retina, bleeding occurs. When the amount of bleeding exceeds a safe threshold, the trainee receives a warning message.Figure 2.Computer-generated image of a virtual patient with a preretinal membrane and a trainee using the system. The arrow indicates a light guide on the trainee's left-hand side that illuminates the retina; the arrowhead indicates a forceps, which grasps the membrane and dissects it from the retinal surface.Using this simulator, trainees can learn to maneuver the surgical instruments and remove the proliferative tissues on the retina, under the retina, or both. This simulator can provide trainees with the same operating environment as a real one, since the binocular color stereo display provides trainees with the same color stereo image they see in a microscope during an actual operation; the 2 foot pedals can simulate an ocular surgery foot switch, and by operating the foot pedals, the color stereo images change in the same manner as during an actual operation; the simulation image can be monitored on the computer screen so that other ophthalmologists can see the same image being viewed by the trainee; and the simulation image can be recorded with a VCR so that trainees can review their own virtual ocular procedures.COMMENTThis simulator has been developed with virtual-reality technology, and procedures are performed in a virtual world rather than a real one; that is, the simulator does not use an animal eye to provide training, but rather a virtual eye model generated by computer. The simulator uses new devices, called haptic devices, that can simulate real operating tools such as a light guide, a vitreous cutter, and a membrane peeler. In addition, the trainees can feel friction when a tool is being inserted into the virtual eye.The benefits of this surgical simulation are as follows: first, surgeons can avoid causing any iatrogenic complications in real patients; second, simulation allows physicians to experience more complications; third, the current training method, the master-apprentice method, can be a burden to mentors and this simulator can reduce the time and monetary costs of training; and fourth, simulation can be used for credentialing standards and will allow longitudinal assessment of physician competence.There are other surgical simulators, some of which use virtual-reality technology, currently available in fields other than ophthalmology, and the usefulness of these products has been reported.Also, in fields other than ophthalmology, surgical experience is generally gained during actual operations, and surgical education is a problem. The surgical simulators are not only useful for ophthalmologists to learn operating techniques, but also for physicians in other fields.This simulator is a prototype. Since a lowering of cost is necessary for many physicians to have a chance to use this simulator, we are now trying to replace the high-speed graphics computer with a standard personal computer, and are adding more simulated cases that demonstrate different abnormalities. In our department, vitreoretinal residents use this simulator to learn and practice vitrectomy techniques. We believe that this simulator is not only useful for residents to learn ocular operating techniques but that it is also practical for veteran surgeons to develop new operating techniques.SCharlesVitreous Microsurgery.Baltimore, Md: Williams & Wilkins; 1981.SBoriak-ChanyavatTDLindquistHJKaplanA cadaveric eye model for practicing anterior and posterior segment surgeries.Ophthalmology.1995;102:1932-1935.GUAuffarthTAWesendahlKDSolomonSJBrownDJAppleA modified preparation technique for closed-system ocular surgery of human eyes obtained postmortem: an improved research and teaching tool.Ophthalmology.1996;104:977-982.GPorrelloAGiudiceandreaTSalgarelloCTamburrelliLScullicaA new device for ocular surgical training on enucleated eyes.Ophthalmology.1999;106:1210-1213.DTRudmanDStredneyDSessannaFunctional endoscopic sinus surgery training simulator.Laryngoscope.1998;108:1643-1647.AMDerossisJBothwellHHSigmanGMFriedThe effect of practice on performance in a laparoscopic simulator.Surg Endosc.1998;12:1117-1120.RVO'TooleRRPlayterTMKrummelMeasuring and developing suturing technique with a virtual reality surgical simulator.J Am Coll Surg.1999;189:114-127.PWirzRPJakobKnee joint simulator: an anatomical reconstruction of the joint surfaces and of the ligamentous structures of the knee joint for teaching purposes.Knee Surg Sports Traumatol Arthrosc.1999;7:59-62.Accepted for publication May 12, 2000.Reprints: Taiichi Hikichi, MD, Department of Ophthalmology, Asahikawa Medical College, 2-1 Midorigaoka-higashi, Asahikawa 078-8307, Japan (e-mail: firstname.lastname@example.org).
JAMA Ophthalmology – American Medical Association
Published: Dec 1, 2000
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