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A new device for ocular surgical training on enucleated eyes1
A New Device for Ocular Surgical Training on Enucleated Eyes Giovanni Porrello, MD, Andrea Giudiceandrea, MD, Tommaso Salgarello, MD, Ciro Tamburrelli, MD, Luigi Scullica, MD Objective: To develop a reliable inexpensive device for teaching ocular surgical procedures and practicing experimental techniques on enucleated eyes. Design: Teaching device trial. Participants: Thirty enucleated porcine eyes. Methods: A Plexiglas ocular bulb holder was secured with its base support to a polyvinylchloride pillar on a modified polystyrene trial head. Main Outcome Measure: The convenience and reproducibility of both laser and surgical ocular techniques performed with this new device were evaluated. Results: This model allows curvilinear capsulorrhexis and phacoemulsification of porcine lenses through a corneal tunnel incision and insertion of a soft foldable acrylic intraocular lens into the capsular bag. Argon and neodymium:YAG laser iridotomy and retinal argon laser photocoagulation can also be performed with this model. Conclusions: This inexpensive device is useful for teaching both surgical and laser ocular procedures. Ophthalmology 1999;106:1210 –1213 Previous studies have described human autopsy ocular models for teaching not only anterior and posterior segment surgeries1– 4 but also laser applications.5,6 A synthetic tissue teaching system has also been designed to simulate phacoemulsification and small-incision intraocular lens (IOL) insertion techniques.7 However, performing surgery on living8,9 or enucleated animal eyes10,11 is a popular training method because of animal availability and economics compared with surgery in which artificial eyes or eyes from human autopsies are used. The opportunity to repeatedly perform procedures is essential for acquiring skills needed to perform delicate microsurgical maneuvers in ophthalmology. With this in mind, we developed a simple, inexpensive, and reusable Plexiglas ocular bulb holder that is connected to a polystyrene trial head, which allows the maintenance of correct hand positions for comfort and stability. This ocular device may be used to facilitate teaching a wide variety of anterior and posterior segment surgical procedures, such as corneal refractive surgery, modern cataract surgery, pars plana vitrectomy, and laser procedures, such as corneal photoablation, peripheral iridotomy, and retinal photocoagulation.
Originally received: August 4, 1998. Revision accepted: February 25, 1999. Manuscript no. 98410. From the Institute of Ophthalmology, Catholic University, Rome, Italy. No authors, including Giovanni Porrello and Andrea Giudiceandrea, who hold patent-pending rights, have a commercial interest in marketing this ocular surgical system. Address correspondence to Andrea Giudiceandrea, MD, Institute of Ophthalmology, Catholic University, Largo F. Vito 1, 00168 Rome, Italy. E-mail: [email protected] or [email protected].
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Material and Methods Figure 1 shows the principal components of our prototype. A hollow bulb holder made of transparent Plexiglas (element 1) was secured to a polyvinylchloride (PVC) base support (element 2) by two lateral screws. A red reflector plate (element 3) was inserted between these two circular elements to simulate the red ocular fundus reflex and enhance the view of the anterior lens capsule during capsulorrhexis and following cataract surgical maneuvers. After removing the peribulbar fat, an enucleated porcine eye was filled with balanced salt solution injected with a 30-gauge needle through the optic nerve stump to maintain posterior segment pressure. A transparent Plexiglas circular cover with a central annular hole (element 4) allowed adequate stabilization of the eye in the bulb holder (element 1). The assembled device was screwed to the upper face of a PVC pillar (element 5) by means of its PVC base support (element 2). This artificial ocular socket was fixed by a bolt (element 6) and a nut (element 7) to the modified polystyrene trial head (element 8). To practice laser procedures, the ocular system was taped to a slit lamp (Fig 2).
Results After securing the enucleated porcine eye inside the bulb holder, phacoemulsification, argon and neodymium:YAG laser iridotomy, and retinal argon laser photocoagulation were performed. All stages of modern cataract surgery, including corneal tunnel incision, capsulorrhexis, nucleus phacoemulsification, and implantation of a soft foldable acrylic IOL (Alcon, Fort Worth, TX) into an intact capsular bag, were performed. To protect the corneal endothelium and obtain pupil dilatation, the anterior chamber was deepened by injecting intraocular viscoelastic fluid through a stab incision made at the 10 o’clock position with a 15-degree knife (Alcon). A self-sealing corneal tunnel was created at the 12 o’clock position with a disposable crescent knife (Alcon) angled
Porrello et al 䡠 A New Device for Ocular Surgical Training on Enucleated Eyes
Figure 4. A soft, foldable acrylic intraocular lens has been inserted into the capsular bag.
Figure 1. The components of the microsurgical ocular device. Element 1, hollow bulb holder; 2, base support and two lateral screws; 3, red reflector plate; 4, circular cover with a central annular hole; 5, PVC pillar; 6, bolt; 7, nut; 8, polystyrene trial head.
Figure 5. Argon and neodymium:YAG laser iridotomy.
Figure 2. Side view of the assembled ocular system taped to a slit lamp for laser procedures. A porcine eye is secured inside the ocular bulb holder.
Figure 3. Phacoemulsification of the lens nucleus.
Figure 6. Argon laser photocoagulation spots on a porcine retina performed by means of a Goldmann lens.
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Ophthalmology Volume 106, Number 6, June 1999 bevel up, followed by entry into the anterior chamber with a 3.2-mm angled slit knife (Alcon). Capsulorrhexis was performed via the corneal tunnel with a 25-gauge disposable needle, the tip of which was bent 90 degrees from the lumen; hydrodissection with a characteristic fluid wave was practiced with a blunt 27-gauge cannula. During the phacoemulsification step (Fig 3), a spatula was introduced through the incision at the 10 o’clock position to rotate the nucleus and push the nuclear fragments toward the phacoemulsification tip (Diplomate, OMS, Peabody, MA). Aspiration of the residual cortical material was carried out using the automatic irrigation–aspiration hand piece with a 0.3-mm aspiration port. Before implanting a soft, foldable acrylic IOL, a viscoelastic substance was injected inside the capsular bag. The lens implant coated with viscoelastic material was inserted using Buratto forceps (J 2186.2, Janach, Como, Italy) under a clearly visible capsulorrhexis and slowly unfolded with both loops inside the capsular bag (Fig 4). Maneuvering the IOL, when necessary, was accomplished using a lens hook through the second incision, until both haptics were horizontal. Usual surgical complications, such as capsule rupture with vitreous loss and vitreous lens fragment dispersion, were resolved in a realistic manner. Argon and neodymium:YAG laser iridotomy (Fig 5) and retinal argon laser photocoagulation (Fig 6) were practiced using an appropriate lens, even though the energy required was higher than that used in a typical clinical setting.
Discussion One of the most important aims of surgical ocular models is to reproduce a red ocular fundus reflex for a better view of the anterior and posterior lens capsules, mainly during capsulorrhexis and cortex aspiration during cataract surgery.2– 4 A fiberoptic light below the scleral bulb10 or a red reflector plate below the bisected ocular bulb11 was introduced for this purpose. We observed that in our device a red reflector plate positioned under an intact ocular bulb was sufficient for performing cataract surgery, thus avoiding the expense of a fiberoptic light. Among surgical models that used artificial,7 animal,10,11 and human1– 4 enucleated eyes, only a few realistically simulated a wide range of ocular surgical techniques. In the teaching system developed by Maloney and associates,7 a replaceable and widely available synthetic cataract of varying densities was inserted into a synthetic capsular bag inside a plastic ocular globe, which was secured to a trial head. Nevertheless, the use of a cornea with a preplaced incision and the absence of adequate anatomic spaces did not allow reproduction of true intraoperative conditions while learning phacoemulsification. In the device developed by Zirm,11 an ocular bulb was bisected at the equator, after formalin fixation of the posterior segment, and positioned by means of an ocular holder into the artificial ocular socket of a plastic trial head. A red reflector plate, which was firmly fixed on the bottom of the ocular socket, provided a good red reflex during phacoemulsification. Because of the large variability of cutting sites, which was related to the dimensions of the ocular bulb, the globes were not always successfully blocked by the lateral plastic segment inside the ocular holder. Furthermore, pos-
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terior segment procedures, such as retinal laser photocoagulation and vitrectomy, could not be performed because the retina and posterior vitreous were removed during the assembling maneuver. A similar procedure of cutting and fixing ocular globes was also used in the Miyake posterior photographic technique,2 which did not need a trial head because the ocular bulb was anchored to a glass slide. A digital video camera positioned below the table surface and beside a fiberoptic light enabled recording and real-time observations of all stages of cataract surgery by a posterior view for teaching purposes. However, because it was often preferable to remove the cornea and iris, open-sky surgery was usually practiced, and therefore many anterior and posterior segment procedures could not be performed. In the model developed by Borirak-Chanyavat and colleagues,3 a Lander wide-field keratoprosthesis was sutured to a scleral bulb wrapped with a gauze bandage inside a commonly available bottle cap, which was used as the ocular bulb holder, to practice a wide variety of anterior and posterior segment surgical procedures. By taping the ocular model to the frame of a slit lamp, laser procedures were also performed. Nevertheless, the lack of a connection to a trial head did not allow simulation of the correct hand positions under an operating microscope during surgery. The device developed by Buratto and Orciuolo,10 as well as the surgical systems of Maloney and colleagues7 and Zirm,11 allowed this kind of simulation by using a plastic trial head. In the device developed by Buratto and Orciuolo,10 the entire ocular globe was easily secured by a circular plastic cover with a central hole in a metal bulb holder with an inferior fiberoptic light; a hollow trial head, with a circular hole at the level of the orbit, was inserted on the bulb holder. Nonetheless, the high cost of the illumination source made this device too expensive for young surgeons. Regarding our new device, the absence of a fiberoptic light and eye cutting procedures, the optimal stabilization of the ocular globe, and the uncomplicated assembly make it practical for beginners and experienced surgeons. Furthermore, according to the different surgical maneuvers and ocular bulb sizes, a circular cover (element 4) with a central annular hole of varying dimensions may also be fitted. To avoid postmortem corneal opacification, Lander wide-field3 and antireflective-coated polymethyl methacrylate keratoprostheses6 and a scleral Plexiglas window1 were used as artificial corneas in human autopsy eyes. By using freshly enucleated porcine eyes, our surgical procedures were not limited by corneal opacity. The corneal epithelium was removed in only a few cases to improve the surgical view and to perform each technique. Manipulation of the surgical instruments during all surgical steps was similar to that performed in a living eye. Nevertheless, the presence of a soft-density nucleus reduced the length of the phacoemulsification. A pars plana vitrectomy could even be practiced by using a circular cover with a large central annular hole to facilitate placement of the vitrectomy instruments. Vitreous opacities could be simulated by injecting a small amount of milk solution, instead of a bolus of fluorescein solution,9 with a 30-gauge needle through the optic nerve stump.
Porrello et al 䡠 A New Device for Ocular Surgical Training on Enucleated Eyes Although we preferred to perform surgery on enucleated porcine eyes because of economics and the shortage of donor eyes, we believe that the device we describe could also be easily used with human autopsy eyes by injecting 15% hyperosmotic dextran solution into the anterior chamber to dehydrate and clarify the cornea.4 Further, this ocular surgery system could be useful not only for residency training and postgraduate courses but also for future laser procedures, such as excimer laser nucleus ablation.12 Acknowledgments. The authors thank Mr. Franco Moro for providing equipment and materials during the development of the ocular surgical system.
References 1. Grand MG, Boldrey E, Okun E. An experimental model for the evaluation of vitrectomy instruments. Ophthalmic Surg 1979;10:59 – 63. 2. Apple DJ, Lim ES, Morgan RC, et al. Preparation and study of human eyes obtained postmortem with the Miyake posterior photographic technique. Ophthalmology 1990;97:810 – 6. 3. Borirak-Chanyavat S, Lindquist TD, Kaplan HJ. A cadaveric eye model for practicing anterior and posterior segment surgeries. Ophthalmology 1995;102:1932–5.
4. Auffarth GU, Wesendahl TA, Solomon KD, et al. A modified preparation technique for closed-system ocular surgery of human eyes obtained postmortem. An improved research and teaching tool. Ophthalmology 1996;103:977– 82. 5. Minckler DS, Gaasterland D, Erickson PJ. Improved, reusable, autopsy eye model container for laser trabeculoplasty and iridectomy [letter]. Am J Ophthalmol 1992;113:341–2. 6. Oram O, Gross RL, Severin TD, et al. A human cadaver eye model for anterior and posterior segment laser applications. Ophthalmic Surg 1994;25:449 –51. 7. Maloney WF, Hall D, Parkinson DB. Synthetic cataract teaching system for phacoemulsification. J Cataract Refract Surg 1988;14:218 –21. 8. Tolentino FI, Liu HS. A laboratory animal model for phacoemulsification practice. Am J Ophthalmol 1975;80:(3 Pt 2): 545– 6. 9. Abrams GW, Topping T, Machemer R. An improved method for practice vitrectomy. Arch Ophthalmol 1978;96:521–5. 10. Buratto L, Orciuolo M. Chirurgia Della Cataratta: Strumenti e Tecniche per Chirurgia Extracapsulare. Milano: Fogliazza, 1994; 239 – 42. 11. Zirm ME. The SFVT Surgical System Manual, 3rd ed. Innsbruck: Techno-Care, 1990. 12. Martinez M, Maguen E, Bardenstein D, et al. A comparison of excimer laser (308 nm) ablation of the human lens nucleus in air and saline with a fiber optic delivery system. Refract Corneal Surg 1992;8:368 –74.
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Originally received: August 4, 1998. Revision accepted: February 25, 1999. Manuscript no. 98410. From the Institute of Ophthalmology, Catholic University, Rome, Italy. No authors, including Giovanni Porrello and Andrea Giudiceandrea, who hold patent-pending rights, have a commercial interest in marketing this ocular surgical system. Address correspondence to Andrea Giudiceandrea, MD, Institute of Ophthalmology, Catholic University, Largo F. Vito 1, 00168 Rome, Italy. E-mail: [email protected] or [email protected].
1210
Material and Methods Figure 1 shows the principal components of our prototype. A hollow bulb holder made of transparent Plexiglas (element 1) was secured to a polyvinylchloride (PVC) base support (element 2) by two lateral screws. A red reflector plate (element 3) was inserted between these two circular elements to simulate the red ocular fundus reflex and enhance the view of the anterior lens capsule during capsulorrhexis and following cataract surgical maneuvers. After removing the peribulbar fat, an enucleated porcine eye was filled with balanced salt solution injected with a 30-gauge needle through the optic nerve stump to maintain posterior segment pressure. A transparent Plexiglas circular cover with a central annular hole (element 4) allowed adequate stabilization of the eye in the bulb holder (element 1). The assembled device was screwed to the upper face of a PVC pillar (element 5) by means of its PVC base support (element 2). This artificial ocular socket was fixed by a bolt (element 6) and a nut (element 7) to the modified polystyrene trial head (element 8). To practice laser procedures, the ocular system was taped to a slit lamp (Fig 2).
Results After securing the enucleated porcine eye inside the bulb holder, phacoemulsification, argon and neodymium:YAG laser iridotomy, and retinal argon laser photocoagulation were performed. All stages of modern cataract surgery, including corneal tunnel incision, capsulorrhexis, nucleus phacoemulsification, and implantation of a soft foldable acrylic IOL (Alcon, Fort Worth, TX) into an intact capsular bag, were performed. To protect the corneal endothelium and obtain pupil dilatation, the anterior chamber was deepened by injecting intraocular viscoelastic fluid through a stab incision made at the 10 o’clock position with a 15-degree knife (Alcon). A self-sealing corneal tunnel was created at the 12 o’clock position with a disposable crescent knife (Alcon) angled
Porrello et al 䡠 A New Device for Ocular Surgical Training on Enucleated Eyes
Figure 4. A soft, foldable acrylic intraocular lens has been inserted into the capsular bag.
Figure 1. The components of the microsurgical ocular device. Element 1, hollow bulb holder; 2, base support and two lateral screws; 3, red reflector plate; 4, circular cover with a central annular hole; 5, PVC pillar; 6, bolt; 7, nut; 8, polystyrene trial head.
Figure 5. Argon and neodymium:YAG laser iridotomy.
Figure 2. Side view of the assembled ocular system taped to a slit lamp for laser procedures. A porcine eye is secured inside the ocular bulb holder.
Figure 3. Phacoemulsification of the lens nucleus.
Figure 6. Argon laser photocoagulation spots on a porcine retina performed by means of a Goldmann lens.
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Ophthalmology Volume 106, Number 6, June 1999 bevel up, followed by entry into the anterior chamber with a 3.2-mm angled slit knife (Alcon). Capsulorrhexis was performed via the corneal tunnel with a 25-gauge disposable needle, the tip of which was bent 90 degrees from the lumen; hydrodissection with a characteristic fluid wave was practiced with a blunt 27-gauge cannula. During the phacoemulsification step (Fig 3), a spatula was introduced through the incision at the 10 o’clock position to rotate the nucleus and push the nuclear fragments toward the phacoemulsification tip (Diplomate, OMS, Peabody, MA). Aspiration of the residual cortical material was carried out using the automatic irrigation–aspiration hand piece with a 0.3-mm aspiration port. Before implanting a soft, foldable acrylic IOL, a viscoelastic substance was injected inside the capsular bag. The lens implant coated with viscoelastic material was inserted using Buratto forceps (J 2186.2, Janach, Como, Italy) under a clearly visible capsulorrhexis and slowly unfolded with both loops inside the capsular bag (Fig 4). Maneuvering the IOL, when necessary, was accomplished using a lens hook through the second incision, until both haptics were horizontal. Usual surgical complications, such as capsule rupture with vitreous loss and vitreous lens fragment dispersion, were resolved in a realistic manner. Argon and neodymium:YAG laser iridotomy (Fig 5) and retinal argon laser photocoagulation (Fig 6) were practiced using an appropriate lens, even though the energy required was higher than that used in a typical clinical setting.
Discussion One of the most important aims of surgical ocular models is to reproduce a red ocular fundus reflex for a better view of the anterior and posterior lens capsules, mainly during capsulorrhexis and cortex aspiration during cataract surgery.2– 4 A fiberoptic light below the scleral bulb10 or a red reflector plate below the bisected ocular bulb11 was introduced for this purpose. We observed that in our device a red reflector plate positioned under an intact ocular bulb was sufficient for performing cataract surgery, thus avoiding the expense of a fiberoptic light. Among surgical models that used artificial,7 animal,10,11 and human1– 4 enucleated eyes, only a few realistically simulated a wide range of ocular surgical techniques. In the teaching system developed by Maloney and associates,7 a replaceable and widely available synthetic cataract of varying densities was inserted into a synthetic capsular bag inside a plastic ocular globe, which was secured to a trial head. Nevertheless, the use of a cornea with a preplaced incision and the absence of adequate anatomic spaces did not allow reproduction of true intraoperative conditions while learning phacoemulsification. In the device developed by Zirm,11 an ocular bulb was bisected at the equator, after formalin fixation of the posterior segment, and positioned by means of an ocular holder into the artificial ocular socket of a plastic trial head. A red reflector plate, which was firmly fixed on the bottom of the ocular socket, provided a good red reflex during phacoemulsification. Because of the large variability of cutting sites, which was related to the dimensions of the ocular bulb, the globes were not always successfully blocked by the lateral plastic segment inside the ocular holder. Furthermore, pos-
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terior segment procedures, such as retinal laser photocoagulation and vitrectomy, could not be performed because the retina and posterior vitreous were removed during the assembling maneuver. A similar procedure of cutting and fixing ocular globes was also used in the Miyake posterior photographic technique,2 which did not need a trial head because the ocular bulb was anchored to a glass slide. A digital video camera positioned below the table surface and beside a fiberoptic light enabled recording and real-time observations of all stages of cataract surgery by a posterior view for teaching purposes. However, because it was often preferable to remove the cornea and iris, open-sky surgery was usually practiced, and therefore many anterior and posterior segment procedures could not be performed. In the model developed by Borirak-Chanyavat and colleagues,3 a Lander wide-field keratoprosthesis was sutured to a scleral bulb wrapped with a gauze bandage inside a commonly available bottle cap, which was used as the ocular bulb holder, to practice a wide variety of anterior and posterior segment surgical procedures. By taping the ocular model to the frame of a slit lamp, laser procedures were also performed. Nevertheless, the lack of a connection to a trial head did not allow simulation of the correct hand positions under an operating microscope during surgery. The device developed by Buratto and Orciuolo,10 as well as the surgical systems of Maloney and colleagues7 and Zirm,11 allowed this kind of simulation by using a plastic trial head. In the device developed by Buratto and Orciuolo,10 the entire ocular globe was easily secured by a circular plastic cover with a central hole in a metal bulb holder with an inferior fiberoptic light; a hollow trial head, with a circular hole at the level of the orbit, was inserted on the bulb holder. Nonetheless, the high cost of the illumination source made this device too expensive for young surgeons. Regarding our new device, the absence of a fiberoptic light and eye cutting procedures, the optimal stabilization of the ocular globe, and the uncomplicated assembly make it practical for beginners and experienced surgeons. Furthermore, according to the different surgical maneuvers and ocular bulb sizes, a circular cover (element 4) with a central annular hole of varying dimensions may also be fitted. To avoid postmortem corneal opacification, Lander wide-field3 and antireflective-coated polymethyl methacrylate keratoprostheses6 and a scleral Plexiglas window1 were used as artificial corneas in human autopsy eyes. By using freshly enucleated porcine eyes, our surgical procedures were not limited by corneal opacity. The corneal epithelium was removed in only a few cases to improve the surgical view and to perform each technique. Manipulation of the surgical instruments during all surgical steps was similar to that performed in a living eye. Nevertheless, the presence of a soft-density nucleus reduced the length of the phacoemulsification. A pars plana vitrectomy could even be practiced by using a circular cover with a large central annular hole to facilitate placement of the vitrectomy instruments. Vitreous opacities could be simulated by injecting a small amount of milk solution, instead of a bolus of fluorescein solution,9 with a 30-gauge needle through the optic nerve stump.
Porrello et al 䡠 A New Device for Ocular Surgical Training on Enucleated Eyes Although we preferred to perform surgery on enucleated porcine eyes because of economics and the shortage of donor eyes, we believe that the device we describe could also be easily used with human autopsy eyes by injecting 15% hyperosmotic dextran solution into the anterior chamber to dehydrate and clarify the cornea.4 Further, this ocular surgery system could be useful not only for residency training and postgraduate courses but also for future laser procedures, such as excimer laser nucleus ablation.12 Acknowledgments. The authors thank Mr. Franco Moro for providing equipment and materials during the development of the ocular surgical system.
References 1. Grand MG, Boldrey E, Okun E. An experimental model for the evaluation of vitrectomy instruments. Ophthalmic Surg 1979;10:59 – 63. 2. Apple DJ, Lim ES, Morgan RC, et al. Preparation and study of human eyes obtained postmortem with the Miyake posterior photographic technique. Ophthalmology 1990;97:810 – 6. 3. Borirak-Chanyavat S, Lindquist TD, Kaplan HJ. A cadaveric eye model for practicing anterior and posterior segment surgeries. Ophthalmology 1995;102:1932–5.
4. Auffarth GU, Wesendahl TA, Solomon KD, et al. A modified preparation technique for closed-system ocular surgery of human eyes obtained postmortem. An improved research and teaching tool. Ophthalmology 1996;103:977– 82. 5. Minckler DS, Gaasterland D, Erickson PJ. Improved, reusable, autopsy eye model container for laser trabeculoplasty and iridectomy [letter]. Am J Ophthalmol 1992;113:341–2. 6. Oram O, Gross RL, Severin TD, et al. A human cadaver eye model for anterior and posterior segment laser applications. Ophthalmic Surg 1994;25:449 –51. 7. Maloney WF, Hall D, Parkinson DB. Synthetic cataract teaching system for phacoemulsification. J Cataract Refract Surg 1988;14:218 –21. 8. Tolentino FI, Liu HS. A laboratory animal model for phacoemulsification practice. Am J Ophthalmol 1975;80:(3 Pt 2): 545– 6. 9. Abrams GW, Topping T, Machemer R. An improved method for practice vitrectomy. Arch Ophthalmol 1978;96:521–5. 10. Buratto L, Orciuolo M. Chirurgia Della Cataratta: Strumenti e Tecniche per Chirurgia Extracapsulare. Milano: Fogliazza, 1994; 239 – 42. 11. Zirm ME. The SFVT Surgical System Manual, 3rd ed. Innsbruck: Techno-Care, 1990. 12. Martinez M, Maguen E, Bardenstein D, et al. A comparison of excimer laser (308 nm) ablation of the human lens nucleus in air and saline with a fiber optic delivery system. Refract Corneal Surg 1992;8:368 –74.
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