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A Laboratory Animal Model for Phacoemulsification Practice
VOL. 80, NO. 3, PART II
NOTES, CASES, INSTRUMENTS
that the incidence of rebleeding significantly increased w " tl Ufpirin a^tnfm'g^ratTnn REFERENCES 1. Newell, F. W.: Aspirin, bleeding and ophthal mic surgery. Am. J. Ophlhalmol. 74 :SS9, 1972. 2. Stuart, R. K.: Platelet function studies in hu man beings receiving 300 mg of aspirin per day. J. Lab. Clin. Med. 75:463, 1970. 3. Smith, J. P., Ill, and Christensen, G. R.: The effect of salicylates on aqueous fibrinolysin. Invest. Ophthalmol. 10:267, 1971. 4. Quick, A. J.: Salicylates and bleeding. The aspirin tolerance test. Am. J. Med. Sci. 252:265, 1966. 5. Evans, G., Packham, M. A., Nishizawa, E. E., Mustard, J. F., and Murphy, E. A.: The effect of acetylsalicvlic acid on platelet function. J. Exp. Med. 128:877, 1968. 6. Weiss, H. J., and Aledort, L. M.: Impaired platelet/connective-tissue reaction in man after as pirin ingestion. Lancet 2:495, 1967. 7. Zucker, M. B., and Peterson, J.: Inhibition of adenosine diphosphate-induced secondary aggrega tion and other platelet functions by acetylsalicylic acid ingestion. Proc. Soc. Exp. Biol. Med. 127:547, 1968. 8. Weiss, H. J., Aledort, L. M., and Kochwa, S.: The effect of salicylates on the hemostatic proper ties of platelets of man. J. Clin. Invest. 47:2169, 1968. 9. Mielke, C. H., Kaneshiro, M- M., Maher, I. A., Weiner, J. M., and Rapaport, S. I.: The standard ized normal Ivy bleeding time and its prolongation by aspirin. Blood 34:204, 1969. 10. Kaneshiro, M. M., Mielke, C. H., Kasper, C. K., and Rapaport, S. I.: Bleeding time after as pirin in disorders of intrinsic clotting. N. Engl. J. Med. 281:1039, 1969.
A LABORATORY ANIMAL MODEL FOR PHACOEMULSIFICATION PRACTICE FELIPE I. TOLENTINO, M.D., AND HSIAO-SU Liu, M.D. Boston, Massachusetts
Phacoemulsification of cataracts through a small corneal incision with an ultrasonic needle or a miniature mechanical cutter has aroused considerable interest in recent From the Department of Retina Research, Eye Research Institute of Retina Foundation, Boston, Massachusetts. This study was supported by Na tional Aeronautics and Space Administration re search grant NSG 3021 and Public Health Service
545
years.1"8 In the course of testing a miniature turbine-driven phacofragmentator designed for fragmenting hard nuclear cataracts, we developed a model that simulates a living eye with a cataract and can be used as a practice eye for testing of such instruments and acquiring skill in their use. MATERIAL AND METHODS
This model consisted of a human cataract removed in its capsule and implanted in the anterior or posterior aqueous chamber of a rabbit eye. The rabbit was anesthetized with sodium pentobarbital (24 mg/kg of body weight) given intravenously. The pupil of the eye chosen for implantation was maximally di lated with 2% atropine drops and 2% cyclopentate drops. An eyelid speculum was used to retract the eyelids and a superior rectus bridle suture was placed for traction and fixation. A cor neal incision was made with a keratome at 12 o'clock and was enlarged to 10 o'clock and 2 o'clock with corneal scissors. The anterior capsule of the crystalline lens was grasped and removed with an extracapsular forceps and the lens cortex and nucleus removed with a lens spoon, leaving the posterior capsule intact. Then the human cataract specimen, obtained from a hospital operating room and refrigerated in sterile saline before use, was placed in a lens loop and inserted either in the posterior or an terior aqueous chamber while the corneal flap was raised with fine forceps (Figure, top). After the cataract was positioned in the central portion of the selected chamber, the corneal incision was closed with a con tinuous interlocking 8-0 silk suture, leaving a 2- or 3-mm opening for insertion of a phacoemulsification instrument (Figure, bot tom). When this model is used with a phacoresearch grant EY-00227 from the National Eye Institute, National Institutes of Health. Reprint requests to David F. Dobies, Manuscript Editor, Eye Research Institute of Retina Founda tion, 20 Staniford St., Boston, MA 02114.
546
AMERICAN JOURNAL OF OPHTHALMOLOGY
Figure (Tolentino and Liu). Top, Hard nuclear cataract placed in a wire loop was inserted into the anterior chamber of an animal eye. Bottom, Corneal incision was closed with a continuous inter locking 8-0 silk suture, leaving a 2- or 3-mm open ing for insertion of instrument tip. emulsification instrument that infuses and aspirates, the sutures must be pulled tight to minimize leakage of fluid from the an terior chamber. When it is used with an instrument that infuses but does not aspi rate,4 the sutures should be tied loosely to allow irrigation of lens material through the corneal opening. DISCUSSION
An increasing interest in phacoemulsification stresses the need for a laboratory animal that can be used for practicing the tech nique. Moreover, improvement of phacoemulsification instruments and techniques requires the use of an animal model that simulates conditions in the human eye. Al though some domestic animals may develop a naturally occurring cataract, they are not always available. Also, a traumatic cataract in a laboratory animal is unsatisfactory be cause it is soft and does not resemble a human senile cataract, which often has a hard nucleus. Therefore, such models can not be used to gauge the fragmentation or cutting efficiency of an instrument.
SEPTEMBER, 1975
Our laboratory model is easy to produce and can be used either for practice surgery or for evaluation of an instrument designed to remove a cataract through a small incision. The ready availability of rabbits, whose eyes have large anterior segments, and of human cataract specimens provides surgeons with the elements of a practical animal model simulating a clinical case of human senile cataract. We have used replications of this model more than 100 times to test cutting effective ness and other functions of several phacoemulsification and fragmentation instru ments. The model has been especially helpful in evaluating the infusion and suction sys tem of the cataract instruments because of the way it simulates the conditions during phacoemulsification or phacofragmentation. SUMMARY
A human cataract, removed in its capsule, and implanted in either the anterior or pos terior aqueous chamber of a rabbit eye, pro vided a model system that simulated a clini cal case of human senile cataract. Such a model can be used for practice surgery or for evaluation of an instrument designed to remove a cataract through a small incision. REFERENCES
1. Kelman, C. D.: Phaco-emulsification and aspiration. A new technique of cataract removal. A preliminary report. Am. J. Ophthalmol. 64:23, 1967. 2. : Phaco-emulsification and aspiration. A report of 500 consecutive cases. Am. J. Ophthalmol. 75:764, 1973. 3. Girard, L. J., and Hawkins, R. S.: Cataract extraction by ultrasonic aspiration, vitrectomy by ultrasonic aspiration Trans. Am. Acad. Ophthalmol. Otolaryngol. 78:50, 1974. 4. Shock, J. P.: Phacocryolysis combined with phacofragmentation and irrigation for removal of cataracts. Am. J. Ophthalmol. 77:860, 1974. 5. Kelman, C. D.: Phako-emulsification. High lights Ophthalmol. 13:38, 1970-1971. 6. Spector, A.: Report on the National Eye In stitute cataract workshop. Invest. Ophthalmol. 13: 325, 1974. 7. Cohen, S. W., Banko, A., and Lasky, M.: Phakotomy and aspiration. A new technique for lens removal through a small incision. Arch. Ophthal mol. 87:206, 1972. 8. Douvas, N. G.: The cataract roto-extractor. A preliminary report. Trans. Am. Acad. Ophthal mol. Otolaryngol. 77:792, 1973.
NOTES, CASES, INSTRUMENTS
that the incidence of rebleeding significantly increased w " tl Ufpirin a^tnfm'g^ratTnn REFERENCES 1. Newell, F. W.: Aspirin, bleeding and ophthal mic surgery. Am. J. Ophlhalmol. 74 :SS9, 1972. 2. Stuart, R. K.: Platelet function studies in hu man beings receiving 300 mg of aspirin per day. J. Lab. Clin. Med. 75:463, 1970. 3. Smith, J. P., Ill, and Christensen, G. R.: The effect of salicylates on aqueous fibrinolysin. Invest. Ophthalmol. 10:267, 1971. 4. Quick, A. J.: Salicylates and bleeding. The aspirin tolerance test. Am. J. Med. Sci. 252:265, 1966. 5. Evans, G., Packham, M. A., Nishizawa, E. E., Mustard, J. F., and Murphy, E. A.: The effect of acetylsalicvlic acid on platelet function. J. Exp. Med. 128:877, 1968. 6. Weiss, H. J., and Aledort, L. M.: Impaired platelet/connective-tissue reaction in man after as pirin ingestion. Lancet 2:495, 1967. 7. Zucker, M. B., and Peterson, J.: Inhibition of adenosine diphosphate-induced secondary aggrega tion and other platelet functions by acetylsalicylic acid ingestion. Proc. Soc. Exp. Biol. Med. 127:547, 1968. 8. Weiss, H. J., Aledort, L. M., and Kochwa, S.: The effect of salicylates on the hemostatic proper ties of platelets of man. J. Clin. Invest. 47:2169, 1968. 9. Mielke, C. H., Kaneshiro, M- M., Maher, I. A., Weiner, J. M., and Rapaport, S. I.: The standard ized normal Ivy bleeding time and its prolongation by aspirin. Blood 34:204, 1969. 10. Kaneshiro, M. M., Mielke, C. H., Kasper, C. K., and Rapaport, S. I.: Bleeding time after as pirin in disorders of intrinsic clotting. N. Engl. J. Med. 281:1039, 1969.
A LABORATORY ANIMAL MODEL FOR PHACOEMULSIFICATION PRACTICE FELIPE I. TOLENTINO, M.D., AND HSIAO-SU Liu, M.D. Boston, Massachusetts
Phacoemulsification of cataracts through a small corneal incision with an ultrasonic needle or a miniature mechanical cutter has aroused considerable interest in recent From the Department of Retina Research, Eye Research Institute of Retina Foundation, Boston, Massachusetts. This study was supported by Na tional Aeronautics and Space Administration re search grant NSG 3021 and Public Health Service
545
years.1"8 In the course of testing a miniature turbine-driven phacofragmentator designed for fragmenting hard nuclear cataracts, we developed a model that simulates a living eye with a cataract and can be used as a practice eye for testing of such instruments and acquiring skill in their use. MATERIAL AND METHODS
This model consisted of a human cataract removed in its capsule and implanted in the anterior or posterior aqueous chamber of a rabbit eye. The rabbit was anesthetized with sodium pentobarbital (24 mg/kg of body weight) given intravenously. The pupil of the eye chosen for implantation was maximally di lated with 2% atropine drops and 2% cyclopentate drops. An eyelid speculum was used to retract the eyelids and a superior rectus bridle suture was placed for traction and fixation. A cor neal incision was made with a keratome at 12 o'clock and was enlarged to 10 o'clock and 2 o'clock with corneal scissors. The anterior capsule of the crystalline lens was grasped and removed with an extracapsular forceps and the lens cortex and nucleus removed with a lens spoon, leaving the posterior capsule intact. Then the human cataract specimen, obtained from a hospital operating room and refrigerated in sterile saline before use, was placed in a lens loop and inserted either in the posterior or an terior aqueous chamber while the corneal flap was raised with fine forceps (Figure, top). After the cataract was positioned in the central portion of the selected chamber, the corneal incision was closed with a con tinuous interlocking 8-0 silk suture, leaving a 2- or 3-mm opening for insertion of a phacoemulsification instrument (Figure, bot tom). When this model is used with a phacoresearch grant EY-00227 from the National Eye Institute, National Institutes of Health. Reprint requests to David F. Dobies, Manuscript Editor, Eye Research Institute of Retina Founda tion, 20 Staniford St., Boston, MA 02114.
546
AMERICAN JOURNAL OF OPHTHALMOLOGY
Figure (Tolentino and Liu). Top, Hard nuclear cataract placed in a wire loop was inserted into the anterior chamber of an animal eye. Bottom, Corneal incision was closed with a continuous inter locking 8-0 silk suture, leaving a 2- or 3-mm open ing for insertion of instrument tip. emulsification instrument that infuses and aspirates, the sutures must be pulled tight to minimize leakage of fluid from the an terior chamber. When it is used with an instrument that infuses but does not aspi rate,4 the sutures should be tied loosely to allow irrigation of lens material through the corneal opening. DISCUSSION
An increasing interest in phacoemulsification stresses the need for a laboratory animal that can be used for practicing the tech nique. Moreover, improvement of phacoemulsification instruments and techniques requires the use of an animal model that simulates conditions in the human eye. Al though some domestic animals may develop a naturally occurring cataract, they are not always available. Also, a traumatic cataract in a laboratory animal is unsatisfactory be cause it is soft and does not resemble a human senile cataract, which often has a hard nucleus. Therefore, such models can not be used to gauge the fragmentation or cutting efficiency of an instrument.
SEPTEMBER, 1975
Our laboratory model is easy to produce and can be used either for practice surgery or for evaluation of an instrument designed to remove a cataract through a small incision. The ready availability of rabbits, whose eyes have large anterior segments, and of human cataract specimens provides surgeons with the elements of a practical animal model simulating a clinical case of human senile cataract. We have used replications of this model more than 100 times to test cutting effective ness and other functions of several phacoemulsification and fragmentation instru ments. The model has been especially helpful in evaluating the infusion and suction sys tem of the cataract instruments because of the way it simulates the conditions during phacoemulsification or phacofragmentation. SUMMARY
A human cataract, removed in its capsule, and implanted in either the anterior or pos terior aqueous chamber of a rabbit eye, pro vided a model system that simulated a clini cal case of human senile cataract. Such a model can be used for practice surgery or for evaluation of an instrument designed to remove a cataract through a small incision. REFERENCES
1. Kelman, C. D.: Phaco-emulsification and aspiration. A new technique of cataract removal. A preliminary report. Am. J. Ophthalmol. 64:23, 1967. 2. : Phaco-emulsification and aspiration. A report of 500 consecutive cases. Am. J. Ophthalmol. 75:764, 1973. 3. Girard, L. J., and Hawkins, R. S.: Cataract extraction by ultrasonic aspiration, vitrectomy by ultrasonic aspiration Trans. Am. Acad. Ophthalmol. Otolaryngol. 78:50, 1974. 4. Shock, J. P.: Phacocryolysis combined with phacofragmentation and irrigation for removal of cataracts. Am. J. Ophthalmol. 77:860, 1974. 5. Kelman, C. D.: Phako-emulsification. High lights Ophthalmol. 13:38, 1970-1971. 6. Spector, A.: Report on the National Eye In stitute cataract workshop. Invest. Ophthalmol. 13: 325, 1974. 7. Cohen, S. W., Banko, A., and Lasky, M.: Phakotomy and aspiration. A new technique for lens removal through a small incision. Arch. Ophthal mol. 87:206, 1972. 8. Douvas, N. G.: The cataract roto-extractor. A preliminary report. Trans. Am. Acad. Ophthal mol. Otolaryngol. 77:792, 1973.