Ординатура / Офтальмология / Английские материалы / Modern Cataract Surgery_Kohnen_2002
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Conclusion
With the significant improvement in phacoemulsification techniques, machines and viscoelastic materials, performing phacoemulsification in the anterior chamber (phaco-out technique) proved to be comparably safe to endocapsular phacoemulsification using the stop and chop technique. In addition, it is easier to learn. Thus in cases where endocapsular phacoemulsification carries a higher risk of intraoperative complications (deep anterior chamber, miosis, weakness of the capsular zonules, and rupture of the posterior capsule), the phaco-out technique could be used. This will help the surgeon avoid the problems that can occur in such conditions, while maintaining the benefits of the small incision surgery to the patient. According to our results, we recommend the use of this technique for the previously mentioned cases after applying it to a larger group of patients.
References
1Kraff MC, Sanders DR: Planned extracapsular extraction versus phacoemulsification with IOL implantation: A comparison of current series. J Am Intraocul Implant Soc 1982;8:38–41.
2Watson A, Sunderraj P: Comparison of small incision phacoemulsification with standard extracapsular cataract surgery: Post-operative astigmatism and visual recovery. Eye 1992;6: 626–629.
3Leaming DV: Practice styles and preferences of ASCRS members 1992 survey. J Cataract Refract Surg 1993;19:600–606.
4Chakrabarti A, Singh S: Phacoemulsification in eyes with white cataract. J Cataract Refract Surg 2000;26:1041–1047.
5Metani S, Kishi H, NakaiY: Usefulness of risk score in evaluating the safety of phacoemulsificationaspiration cataract surgery. Jpn J Clin Ophthalmol 1998;52:643–646.
6Burrato L: Techniques of phacoemulsification; in Burrato L (ed): Phacoemulsification, Principles and Technique. Thorofare, Slack Inc, 1998, chapt 6, pp 150–156.
7Koch PS, Katzen LE: Stop and chop phacoemulsification. J Cataract Refract Surg 1994; 20:566–570.
8Kelman CD: Phacoemulsification and aspiration – A new technique of cataract removal. A preliminary report. Am J Ophthalmol 1967;64:23–35.
9Emery JM, Wilhelmus KA, Rosenburg S: Complications of phacoemulsification. Ophthalmology 1978;85:141–150.
10Kraff MC, Sanders DR, Lieberman HL: Total cataract extraction through a 3-mm incision. A report of 650 cases. Ophthalmic Surg 1979;10:46–540.
11Glasser DB, Kratz HR, Boyd JE: Protective effects of viscous solutions in phacoemulsification and intraocular lens implantation. Arch Ophthalmol 1989;107:1047–1051.
12Glasser DB, Osborn DC, Nordeen JF, Min YI: Endothelial protection and viscoelastic retention during phacoemulsification and intraocular lens implantation. Arch Ophthalmol 1991;109: 1438–1440.
13Gimbel HV, Neuhann T: Development advantages and methods of the continuous circular capsulorhexis technique. J Cataract Refract Surg 1990;16:31–37.
14Gimbel HV, Neuhann T: Continuous curvilinear capsulorhexis (letter). J Cataract Refract Surg 1991;17:1–10.
15Fine H: Chip and flip phacoemulsification technique. J Cataract Refract Surg 1991;17:366–371.
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16Gimbel HV: Divide and conquer nucleofractis phacoemulsification: Development and variations. J Cataract Refract Surg 1991;17:281–291.
17Allen ED: Understanding phacoemulsification. III. Principles of nucleofractis techniques. Eur J Implant Refract Surg 1995;7:347–353.
18Carlson KH, Bourne WM: The clinical measurement of endothelial permeability. Cornea 1988;7:183–189.
19Sawa M, Sakanishi Y, Shimizu H: Fluorophotometric study of anterior segment barrier functions after extracapsular cataract extraction and posterior chamber intraocular lens implantation. Am J Ophthalmol 1984;97:197–204.
20Davidson JA: Endothelial cell loss during the transition from nucleus expression to posterior chamber-iris plane phacoemulsification. J Am Intraocul Implant Soc 1984;10:40–43.
21Ravalico G, Tongnetto D, Baccara F, Lovisato A: Corneal endothelial protection by different viscoelastics during phacoemulsification. J Cataract Refract Surg 1997;23:433–439.
22Burrato L: Viscoelastic substances and cataract surgery; in Burrato L (ed): Phacoemulsification, Principles and Technique. Thorofare, Slack Inc, 1998, chapt 12.
23Sanders DR, Kraff M: Steroidal and non-steroidal anti-inflammatory agents. Effects on postsurgical inflammation and blood aqueous barrier breakdown. Arch Ophthalmol 1984;102:1453–1456.
Prof. Dr. Jorge L. Alió, Instituto Oftalmológico de Alicante,
Universidad Miguel Hernández, Avenida de Denia 111, E–03015 Alicante (Spain) Tel. 34 965 150 025, Fax 34 965 151 501, E-Mail jlalio@oftalio.com
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Kohnen, T (ed): Modern Cataract Surgery.
Dev Ophthalmol. Basel, Karger, 2002, vol 34, pp 74–78
Phaco Chop: Making the Transition
Neil J. Friedman a, Thomas Kohnen b, c, Douglas D. Koch c
aStanford University Hospital, Stanford, Calif., USA;
bDepartment of Ophthalmology, Johann Wolfgang Goethe University, Frankfurt am Main, Germany;
cCullen Eye Institute, Baylor College of Medicine, Houston, Tex., USA
Remarkable innovations in cataract surgery have made phacoemulsification an extremely sophisticated procedure. Since Kelman [1, 2] first introduced phacoemulsification in 1967, advances have been made in every step of the surgery from incisional architecture to lens design. Numerous methods of dismantling the nucleus have been described. Initially, one-handed anterior chamber techniques were used, and subsequently, two-handed posterior chamber methods were developed [3–9]. Alternative approaches [10–13] continue to emerge for handling the lens nucleus, and among these, various nuclear chopping techniques have become popular. Commonly referred to as ‘phaco chop’, these methods of disassembling the nucleus are faster, more efficient, and possibly safer than traditional sculpting and cracking techniques [14–16]. However, learning any new procedure and making the transition can be difficult. From studies of residents performing different types of cataract surgery, it is evident that with proper instruction, excellent results can be achieved [17–22]. In this chapter, we share some concepts and techniques that we have found helpful in our own surgery and in assisting others with the transition to phaco chop.
Methods and Materials
Phaco chop was first described by Nagahara [10]. His method consists of impaling the lens nucleus with a 0 or 15° beveled phaco tip, holding it with high vacuum, and using a second instrument (chopper) to chop it. Koch [11] modified this technique in order to facilitate quadrant removal. He found that, after cracking the nucleus by Nagahara’s method, the quadrants were held tightly together within the capsular bag and could not be easily extracted. Thus, he
Fig. 1. In the stop and chop technique, after the central groove is created, the phaco tip and chopper are used to crack the nucleus into two halves.
developed the technique of stop and chop (fig. 1), in which a central groove is created, the nucleus is cracked in half, and then each half is chopped into smaller, more manageable pieces. The initial groove removes enough of the central nuclear mass so that subsequently chopped fragments can be mobilized from within the capsular bag. Additional variations and chopping maneuvers have been developed [12, 13].
Patient selection is an essential factor with any surgical procedure, especially when learning a new phacoemulsification technique. Therefore, it is advisable to choose routine cases, specifically eyes that have a widely dilatable pupil, a bright red reflex, and a normal axial length. Exposure is also important, so we suggest avoiding patients with narrow palpebral fissures and deep set orbits during the transition period. Lens density affects the ease of chopping, and a cataract with 3 nuclear sclerosis, not too soft and not too hard, is ideal. Helpful intraoperative elements include: (1) a large capsulorhexis ( 5 mm), which facilitates placement of the chopper and minimizes the risk of inadvertently catching the edge of the anterior capsule; (2) a complete hydrodissection, so that the nucleus rotates freely, and
(3) a good hydrodelineation, to create whenever possible a golden ring, which demarcates the inner nucleus from the outer epinuclear shell, and thus identifies the peripheral landmark at which the blade of the chopper is to be positioned.
Elaborate, high-tech, new instruments are not required for phaco chop, but having the appropriate tools is necessary. A Sinskey hook is excellent to use as the initial chopping instrument for transitioning surgeons to practice chopping smaller nuclear pieces. Many different styles of choppers exist, varying in shape, size, and cutting surface. They can be curved or straight, pointed or flat, and angled or universal; it is largely a matter of personal preference. Any phaco tip may be used, however, one should remember that the flatter the bevel, the better the occlusion. Also, enough of the tip must be exposed to permit it to be buried in the nucleus, thereby enhancing nuclear purchase. As for phaco settings, these of course will vary by machine, but a good starting point is to use typical quadrant removal parameters (i.e., high aspiration flow rate and vacuum), which can be adjusted as necessary.
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Fig. 2. The chopper is placed around the nucleus at the golden ring.
Fig. 3. The chopper and phaco tip are separated creating a successful chop.
The actual steps involved in chopping can be summarized as follows: (1) the nucleus is impaled with the phaco needle by burying the tip into lens material (foot-pedal position 3);
(2) while holding the nucleus with the phaco probe (foot-pedal position 2), it is gently displaced towards the surgeon as the chopper is placed under the capsulorhexis rim around the outer edge of the nucleus at the golden ring (fig. 2); (3) the chopper is then pulled towards the phaco tip, and, just prior to contact, the two instruments are sufficiently separated to create the fracture (fig. 3).
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Results
Transitioning to phaco chop can be challenging, and therefore learning a progression of skills is helpful. A logical way to practice chopping is to first perform a divide and conquer technique and then chop each quadrant (either with a Sinskey hook or chopper). Once comfortable with the chopping maneuver, stop and chop can be quickly mastered. The advantage of this method is that, if chopping becomes difficult, the surgeon can readily convert to a standard cracking technique, since the nucleus has already been grooved and split into two halves. Finally, other methods of chopping can be attempted; however, if problems are encountered, it may be more difficult to revert to divide and conquer phaco, especially if too much of the central nuclear mass has been removed, and a bowling technique may be needed to complete nuclear removal. We have found this stepwise method of learning to chop to be an invaluable tool in teaching surgeons to make the transition to phaco chop.
A number of potential pitfalls exist for phaco chop. The most feared complication is damaging the capsule during the chop. This usually involves the anterior capsule by improper placement of the chopper above or peripheral to rather than under the anterior capsule. The posterior capsule can also be torn, perhaps most commonly during removal of the last quadrant when a change in fluid dynamics may suddenly bring an unprotected posterior capsule in contact with the chopper. A less worrisome occurrence is dislodging the nucleus from the phaco tip when placing the chopper, a problem that is easily solved by increasing the vacuum setting. Finally, very hard and very soft nuclei are difficult to chop and pose unique challenges. With the hard nucleus, after propagation of the crack, the posterior nucleus often contains bridging bands that prevent complete separation. The soft nucleus typically cannot withstand the requisite high vacuum levels, and therefore it fragments and emulsifies before the phaco needle can attain an adequate purchase to initiate the chop.
Comment
Learning new techniques is always challenging, but with careful attention to case selection and practicing a straightforward progression of skills, phaco chop can become a valuable tool for nucleus removal during cataract surgery. Although this method is technically more difficult than many others, it is within the grasp of any two-handed phaco surgeon. Phaco chop is fast, dramatically reducing phaco time and potentially minimizing corneal endothelial damage from ultrasound energy [14–16]. It also causes less zonular stress than standard cracking methods and can be performed without an intact capsulorhexis. Once mastered, phaco chop can be an invaluable addition to the phaco surgeon’s armamentarium.
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References
1 Kelman CD: Phaco-emulsification and aspiration: A new technique of cataract extraction: a preliminary report. Am J Ophthalmol 1967;64:23–35.
2Kelman CD: Phaco-emulsification and aspiration: A progress report. Am J Ophthalmol 1969;67: 464–477.
3Kelman CD: Phacoemulsification in the anterior chamber. Ophthalmology 1979;86:1980–1982.
4Emery JM, Little JH: Phacoemulsification and aspiration of cataracts. St Louis, Mosby, 1979, p 201.
5Little JH: Outline of Phacoemulsification for the Ophthalmic Surgeon, ed 2. Oklahoma City, Samco Color Press, 1975.
6Shepherd JR: In situ fracture. J Cataract Refract Surg 1990;16:436– 440.
7Gimbel HV: Divide and conquer – Nucleofractis phacoemulsification development and variations. J Cataract Refract Surg 1991;17:281–291.
8Fine IH: The chip and flip phacoemulsification technique. J Cataract Refract Surg 1991;17: 366–367.
9Fine IH, Maloney WF, Dillman DM: Crack and flip phacoemulsification. J Cataract Refract Surg 1993;19:797–802.
10Nagahara K: Video of phacochop. Presented at the American Society of Cataract and Refractive Surgery, Seattle, May 1993.
11Koch PS, Katzen LE: Stop and chop phacoemulsification. J Cataract Refract Surg 1994; 20:566–570.
12Vasavada AR, Desai JP: Stop, chop, chop, and stuff. J Cataract Refract Surg 1996;22:526–529.
13Zirm ME, Salchow DJ: Double phaco chop. J Cataract Refract Surg 1999;25:732–735.
14Ram J, Wesendahl TA, Auffarth GU, Apple DJ: Evaluation of in situ fracture versus phaco chop techniques. J Cataract Refract Surg 1998;24:1464–1468.
15DeBry P, Olson RJ, Crandall AS: Comparison of energy required for phaco-chop and divide and conquer phacoemulsification. J Cataract Refract Surg 1998;24:689–692.
16Pirazzoli G, D’Eliseo D, Ziosi M, Acciarri R: Effects of phacoemulsification time on the corneal endothelium using phacofracture and phaco chop techniques. J Cataract Refract Surg 1996;22: 967–969.
17Badoza DA, Jure T, Zunino LA, Argento CJ: State-of-the-art phacoemulsification performed by residents in Buenos Aires, Argentina. J Cataract Refract Surg 1999;25:1651–1655.
18Noecker RJ, Allinson RW, Snyder RW: Resident phacoemulsification experience using the in situ nuclear fracture technique. Ophthalmic Surg 1994;25:216–221.
19Tarbet KJ, Mamalis N, Theurer J, Jones BD, Olson RJ: Complications and results of phacoemulsification performed by residents. J Cataract Refract Surg 1995;21:661–665.
20Corey RP, Olson RJ: Surgical outcomes of cataract extractions performed by residents using phacoemulsification. J Cataract Refract Surg 1998;24:66–72.
21Albanis CV, Dwyer MA, Ernest JT: Outcomes of extracapsular cataract extraction and phacoemulsification performed in a university training program. Ophthalmic Surg Lasers 1998;29:643–648.
22Pingree MF, Crandall AS, Olson RJ: Cataract surgery complications in 1 year at an academic institution. J Cataract Refract Surg 1999;25:705–708.
Priv.-Doz. Dr. med. Thomas Kohnen, Department of Ophthalmology, Johann Wolfgang Goethe University, Theodor-Stern-Kai 7, D–60590 Frankfurt am Main (Germany)
Tel. 49 69 6301 6739, Fax 49 69 6301 3893, E-Mail Kohnen@em.uni-frankfurt.de
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Ultrasound-Assisted Phaco Aspiration
Randall J. Olson
University of Utah Health Sciences Center, Salt Lake City, Utah, USA
When I first had teenage children and our car insurance went up dramatically, I realized that the car insurance industry is interested in how many miles are driven and what the risk is per mile. This analogy holds for cataract surgery in that the most dangerous thing we do is the use of ultrasound with phacoemulsification. We can aspirate the iris, the capsule or be near the cornea with no or minimal damage; however, if we perform exactly the same maneuver and ultrasound is used, damage is usually immediate and significant. It would seem logical, therefore, that all maneuvers we use that decrease our ultrasound reliance will decrease our complication risk during cataract surgery.
It is often stated that we usually break the capsule during the irrigation and aspiration phase of cataract surgery. In order to verify whether or not that was our experience, we reviewed all complications at the John Moran Eye Center for one academic year both to determine the incidence of complications and to better understand when these complications occurred [1]. What we found is that over 70% of the capsular breaks occurred during the use of ultrasound energy. This confirms our concern that it is during the use of ultrasound that we are at our greatest risk as surgeons. Dr. Bill Fishkind [pers. commun.] has also reviewed his complication rate and has come to a similar conclusion.
So what alternatives do we have? Laser has been proposed as a safer modality as has phacoptemesis. While both may be a safer energy modality than ultrasound, they have had difficulty with very hard nuclei. In fact, it is our thesis that neither have much to add to the use of mechanical forces which change the nature of the disassembly of the nucleus from an ultrasound-based procedure to a mechanical-based one.
Mechanical forces are something we have used for a long time and, therefore, greater utilization of these should be no surprise. Irrigation as a force maintains our anterior chamber and moves things freely around. It has been well
known that increasing the irrigation flow will make things happen much faster. Aspiration is another important mechanical force, which in the past when it was increased above very low levels would result in a surge or flattening of the anterior chamber as the pent up energy in the system resulted in a rapid efflux of fluid from the anterior chamber. The latest in phacoemulsification platforms, however, have powerful fluidic capabilities that monitor the aspiration levels and occlusion as well as decrease the kinetic energy of the system such that surge is tamed at levels of aspiration previously unheard of. Chunks of nucleus that would require significant ultrasound energy can often be aspirated without any ultrasound use. Certainly this is an important mechanical modality to help the efficiency of our surgery.
Beyond irrigation and aspiration, for a long time we have used second instruments to crack the nucleus into multiple small pieces. This has usually occurred after scoring furrows in the nucleus to make the crack a simple step. Having bite-size pieces allows a safer procedure with ease of maneuverability but also clearly decreases the phacoemulsification time because as the pieces are brought down to ever smaller and smaller bite-size chunks, they often aspirate without ultrasound. Newer approaches using mechanical forces almost exclusively chop the nucleus into bite-size pieces eliminating or dramatically decreasing reliance upon ultrasound energy [2, 3]. This has been called by various names such as chop or snap or quick chop; however, the common theme for all of these approaches is mechanically splitting the nucleus without ultrasound into multiple bite-size pieces. When the pieces are small enough, ultrasound is only necessary to assist aspiration and the ultimate in mechanical energy use is to chop the nucleus into pieces so small that they can be aspirated without any ultrasound whatsoever.
A new mechanical force that decreases even the small amount of ultrasound needed to assist in aspiration is with phaco chop using the second instrument to mash the pieces onto the ultrasound tip. By using slight mechanical pressure and high aspiration levels even larger pieces are often aspirated without difficulty. Mashing onto the tip with a little patience will eliminate all residual fragments without any ultrasound need (or laser or sonic energy). Ultrasound, therefore, is used minimally and only for some efficiency and is not necessary for elimination of even the hardest of the cataract pieces.
Such reasoning for me has resulted in a technique with a specially-designed chopper (fig. 1) for horizontal chop with very hard nuclei with a 0° ultrasound tip used to impale the nucleus near the wound and the chopper used to cleave the nucleus cleanly in half. The first bite-size piece is removed with the chopper, usually less than 1/8 th of the total nucleus, and then mashed into the ultrasound tip with only brief bursts of ultrasound energy used only if necessary. The remaining smaller piece is then chopped into multiple small fragments usually
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Fig. 1. A 21-gauge experimental irrigating chopper, especially designed by the author for hard cataracts, that can be placed through a 0.8-mm incision (available from ASICO).
never less than four or five such that only brief bursts or often no ultrasound is necessary when both chopping and mashing are used in combination.
With the first half finished, the second half can either be rotated to 180° or simply pushed so that both sides are exposed such that the chopper is placed on one side of the heminucleus and the ultrasound tip on the other side. Again, a combination of chopping and mashing, cutting the second half into at least five pieces and usually more, results in an extremely efficient procedure with minimal or no ultrasound energy used.
The evolution of this technique clearly eliminates or substantially decreases ultrasound reliance such that the increased risk in association with ultrasound is virtually eliminated. The efficiency and utility is so obvious that the use of phacoptemesis or of laser would seem to add little or nothing to the overall efficiency or safety profile. Furthermore, in cases with very hard mature cataracts, the corneas with minimal ultrasound time are impressively clear suggesting minimal damage to the cornea. This prompted a new approach to cataract surgery in the face of corneal decompensation (Fuchs’ corneal dystrophy or old trauma).
There has been controversy about such corneas, in particular in cases of Fuchs’ dystrophy, about whether or not cataract extraction alone should occur when the cataracts are clinically significant and the corneas are still quite clear or a combination of cataract extraction with corneal transplantation should occur. It has been well known that cataract surgery will often tip these corneas into bullous keratopathy requiring secondary penetrating keratoplasty. Most cataract surgeons have had cases of Fuchs’dystrophy in which the cornea seemed quite clear before surgery and yet failed after surgery. At issue, therefore, was whether or not this new approach to cataract surgery could result in minimal corneal endothelial damage in cases of Fuchs’ dystrophy.
We have had 2 cases with this new approach and both have had impressive results.
Case 1: A 73-year-old retired general surgeon with Fuchs’ dystrophy and cataract had progressive loss of vision with difficulty functioning. He had sought three consults who had
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