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Supracapsular Phacoemulsification

Aamir Asrar

Introduction

Since Kelman1–8 first introduced phacoemulsification improvements have been made not only with the instruments9–11 but in the technique also.12–21 Phacoemulsification is now

the preferred choice of surgery for all types of cataracts, even the ones previously considered to be pure extracapsular cataract extraction cases (ECCE). Divide and conquer20 is still the favored technique for most of the phaco surgeons, as it is quite comfortable to perform if the cataract is straightforward, but becomes much more difficult with complicated cases as in weak zonules and small pupils. With the introduction of David Brown’s,23 Phaco Flip and Jack Kearney’s, Supracapsular Technique, phacoemulsification entered into a new era. William F Maloney’s,24–28 contribution to this technique has been remarkable.

History of Supracapsular Phacoemulsification

The procedure of phacoemulsification has undergone great deal of change since it was first introduced1,6–24 in 1967. This progress has been stepwise with the improvements

made in phaco machines, intraocular lenses (IOLs), and instrumentation, leading to change in our techniques, thus making the whole procedure much safer and predictable to a greater extent. William F Maloney has explained this whole process of evolution very well by classifying it into different generations in the phacoemulsification era.24–26

•First generation (1967–1977) Anterior chamber

•Second generation (1977–1987) Posterior chamber

•Third generation (1987–1997) Endocapsular

•Fourth generation (1997–2007) Supracapsular (?).

Changes that evolved each decade have been related with the availability of the supporting equipment. With the introduction of larger capsulorhexis the idea of Supracapsular phacoemulsification evolved. Introduction of new generation phacoemulsification machines has further helped this technique of phacoemulsification. It is still a bit early to say if this really is going to be the Supracapsular phacoemulsification decade.

What is Supracapsular Phacoemulsification?

In Supracapsular phacoemulsification, the nucleus is maneuvered out of the capsular bag through a 5 to 6 mm capsulorhexis in such a way that it finally lies in a upside down position above the anterior capsule, i.e. in the Supracapsular space, where it can be emulsified. There are many variations to this technique.

Surgical Technique

Patient Selection

As with any other surgical procedure in order to achieve good results and to gain confidence, patient selection is of importance. However, with experience any patient suitable enough to undergo phacoemulsification surgery, Supracapsular approach can be utilized. The author has used this procedure in difficult cataract cases (pseudoexfoliation, small pupil, unstable capsulorhexis, etc.) and found it safer and as effective.

Anesthesia

There is no specific preference for any type of anesthesia.29–44 The author always lets the patient decide regarding the type of anesthesia they feel comfortable with. The procedure may require less time and can easily be done under topical anesthesia.

Incisions

Site and type of incision is mainly surgeon’s preference.45–52 The author prefers a corneal incision but he alters the site and type according to the needs and requirement of the surgery.

Paracentesis incision for the side-port instrument is placed 2 O’clock hours left of the main incision (for-right-handed surgeon and reverse for the left-handed surgeons).

If placing an anterior chamber maintainer, the author prefers infratemporal position in the case of superior incision and is placed infranasally if temporal incision is made.

Viscoelastic

There is no actual indication that this procedure is effected by any specific sort of a viscoelastic.53,54 The author has used various types of viscoelastic for this procedure (mainly—Viscoat by Alcon, Healon by Pharmacia & Up John, Provisc by Alcon Fig. 25.1) but have not found any significant difference between them.

Viscoelastics are used during phacoemulsification for the following main advantages

• Keep the anterior chamber formed during capsulorhexis

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•Protection of corneal endothelium

•Stabilize the anterior capsule during capsulorhexis

•Insertion of IOL

•Flip the nucleus out of the bag.

FIGURE 25.1 Viscoelastic with cannula

FIGURE 25.2 Cystotome on a viscoelastic syringe

In addition to the one mentioned above there are many other uses, that make viscoelastic an integral part of eye surgery.

Capsulorhexis

After the introduction of the continuous curvilinear capsulorhexis (CCC)55–57 in the mid to the late 80s its advantages were soon evident to the cataract surgeons. As the capsulorhexis was 3 to 4 mm in size the nucleus could not be taken out of the bag and

had to be emulsified in it. All the techniques developed during this stage were keeping in mind the limits imposed by the capsular bag. As the surgeons enjoyed the advantages58–60 of CCC, at the same time the restrictions61–62 and the problems of doing

phacoemulsification in the bag started becoming more evident. With the introduction of a larger capsulorhexis of 5 to 6 mm in diameter it was easier to flip the nucleus out of the bag, allowing us to emulsify the nucleus in the supracapsular space away from the capsular bag restriction.

The author normally starts the capsulorhexis, after injecting the viscoelastic in the anterior chamber, by making a flap in the anterior capsule with the help of a cystotome on a viscoelastic syringe (Fig. 25.2). Once the flap is lifted the whole capsulorhexis of 5

FIGURE 25.8 Direction for rotation of the nucleus

FIGURE 25.9 Direction for rotation of the nucleus following hydrodissection

that the nucleus is lying free in the bag. It can be confirmed by using the hydrodissection cannula to rotate the nucleus70 taking care not to push it towards the vitreous and not to force it in any direction (Figs 25.8 and 25.9). Another important point while carrying out nuclear rotation is to keep the tip of the cannula in view as it might pass through the lens rupturing the lens capsule.

Once the nucleus lies free in the bag supracapsular phacoemulsification can be started. There are many variations to this approach. The author has mentioned the one that he used and found safe and effective.

Phaco-hemi Flip

Phacoemulsification71 is started with the standard settings (low aspiration and ultrasound power) on the phaco machine. Nuclear sculpting is done in the area of capsulorhexis along an imaginary line extending from the site of incision vertically downwards (Fig.

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25.10). Once the sculpting is completed to half the thickness of the nucleus it is rotated by 90 degrees (Fig. 25.11). Keeping the phaco probe and the side-port instrument (nucleus rotator) in the sculpted groove of the nucleus (Fig. 25.12), it is cracked into two halves by moving the instrument in the opposite direction (Fig. 25.13).

Then the settings on the phaco machine are changed, by increasing the vacuum to 200 mmHg

FIGURE 25.10 Sculpting of the nucleus

FIGURE 25.11 Rotation of the nucleus by 90 degrees

and raising the bottle to the maximum height. The author keeps both the instruments (phaco probe and the nucleus rotator) in the eye. Now the two nuclear fragments are arranged in the bag so that the smaller one is away from the site of incision. The phaco probe is brought near the superior edge of the nucleus and the smaller piece of the

nucleus fragment is engaged in the phaco tip by only utilizing the vacuum. The nucleus rotator is taken

FIGURE 25.12 Insertion of the instruments and their placement in the nuclear groove

FIGURE 25.13 Cracking the nucleus by moving the instruments in the opposite direction

to the base of the nuclear fragment (Fig. 25.14). Now with a bimanual motion, i.e. utilizing the rotatory movement of the nucleus rotator to sweep the inferior surface of the lens fragment over the posterior capsule and at the same time helped with the vacuum of the phaco instrument the nuclear fragment is flipped out of the bag into the pupillary plane (Figs 25.15 to 25.17). The nuclear fragment being smaller than the size of the whole nucleus can easily be emulsified in the iris plane (Figs 25.18 and

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FIGURE 25.14 Placement of instruments for flipping the nucleus out of the bag

FIGURE 25.15

25.19). The other nuclear piece in the capsular bag keeps the bag formed and the posterior capsule away from the phaco probe. Flipping of the other piece and its emulsification in the iris plane follows this.

Phaco Flip

David Brown,23,25 introduced this supracapsular phacoemulsification technique, and so was the

FIGURE 25.16

FIGURE 25.17 FIGURES 25.15 TO 25.17

Maneuver of flipping the nucleus out of the bag

actual birth of the new generation supracapsular phacoemulsification. After completing the basic steps mentioned above one can proceed with this technique (Fig. 25.20). The nucleus is depressed at the superior equator. This can be done with the help of a viscoelastic cannula, spatula, hydrodissection cannula or a nucleus rotator. As the capsulorhexis is large the depression on the nucleus in such a way causes the nucleus to move out of the bag. This maneuver is continued so that the nucleus flips

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FIGURE 25.18 Final position of the nuclear segment in the pupillary plane before starting emulsification

FIGURE 25.19 Emulsification of the nucleus in the pupillary plane

completely and lies almost facing upside down. Emulsification of this nucleus can now be started by bringing the phaco probe tip at the level of the iris plane in the pupillary area. Nucleus is engaged from the posterior side and emulsification started. The phaco probe is kept static in this position and the nucleus is fed into the tip with the help of a sideport instrument.

This whole process is very fast with effective utilization of ultrasound energy. With the develop-

FIGURE 25.20 Phacoflipemulsification of the nucleus from down under

ment of new generation of phacoemulsification machines, more reliance on vacuum can achieve the end point quickly.

Tilt and Tumble Phaco

Tilt and tumble phaco has been described by Richard L Lindstrom in a recently published textbook74 “Clear Cornea Lens Surgery” by Howard Fine published by Slack Incorporated.

After completing the CCC, hydrodissection is performed by placing the hydrodissection cannula under the anterior capsule approximately 180° from the site of incision. BSS is injected until a fluid wave is seen. The hydrodissection is continued which causes the nucleus to tilt out of the bag. The nucleus can also be tilted out of the bag by retracting the anterior capsule at 7:30 O’clock position. If the nucleus does not tilt out of the bag at the superior edge then it can always be rotated to face the site of incision. Otherwise the inferior half of the nucleus is depressed which causes the superior edge of the nucleus to tilt out of the bag. Viscoelastic is injected anterior and posterior to the nucleus to protect the cornea, iris and posterior capsule. Nucleus is kept in this position supported by the nucleus rotator and can be emulsified using high vacuum (Fig. 25.21). Once half of the nucleus is emulsified the half left can be tumbled upside down

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FIGURE 25.21 Tilt and tumble phaco

and can now be emulsified by a direct approach on to the posterior surface of this fragment. The whole nucleus can also be emulsified without tumbling the last fragment. This has also been described as a transitional step from endocapsular to supracapsular phacoemulsification procedure.

Supracapsular Quick Chop Phaco

William F Maloney introduced supracapsular quick chop phacoemulsification.24–28 In this procedure he tilts the lens early during hydrodissection by continuing it even after the fluid wave is seen (Fig. 25.21). If not successful, one can repeat hydrodissection after nuclear rotation. He advises to convert it into an endocapsular approach if the lens fails to tilt. Once a lens tilt is achieved the process to flip the nucleus can be carried out further, by depressing the posterior half of the tilted nucleus with a hydrodissection cannula (Fig. 25.22) and then gently sweeping the posterior equator of the nucleus over the posterior capsule, till the superior equator lies just pass the midline (Fig. 25.23). Now viscoelastic is injected as needed (Fig. 25.24) and at the same time the viscoelastic cannula continues to flip the nucleus so that it finally lies in a horizontal position but only upside down (Fig. 25.25). With the help of the same cannula the nucleus is moved into the posterior chamber, i.e. between the iris and the anterior capsule outside the capsular bag (Fig. 25.26).

The tip of the phaco probe is extended 1.5 to 2.00 mm beyond the irrigation sleeve (Fig. 25.27) as this will act as safeguard to deeper penetration. He also advises to use 100 percent linear phaco power with slow pulse mode of 2 to 4 pulse/second. Introduce the phaco tip (Fig. 25.28) and the quick chopper into the anterior chamber.

The phaco probe is buried deep into the central nucleus up to its sleeve and then maintaining the

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FIGURE 25.25 Viscoelastic used to complete the flipping of the nucleus

aspiration to stabilize the nucleus till the nuclear chop is completed. Quick chopper is buried into the nucleus just above the phaco tip (Fig. 25.29). Now the nucleus is separated vertically by briskly depressing the nucleus straight down accounting for 80 percent displacement and elevating the embedded phaco tip accounting for the remaining 20 percent of the vertical displacement (Fig. 25.30). This causes the division to appear in the center of the nucleus (Fig. 25.31). Now the phaco tip and the quick chopper are separated laterally causing a complete break in the nucleus. Nucleus is rotated by 90 degrees. The separation can now be confirmed

FIGURE 25.26 Nucleus being placed in the posterior chamber above the anterior capsule

FIGURE 25.31 Appearance of division in the center of the nucleus

tion18,22,69,70 can also be used like cracking, chopping, sculpting or manual prechopping, etc (Figs 25.35 to 25.40).

Other Variations

Bruce Wallace

Dr Wallace begins sculpting the nucleus in the bag. Completes a classic criss-cross pattern. Then flips the nucleus outside the bag so that it lies in an upside down position. The criss-cross pattern is still visible from the inverted side. This can be used as a landmark for chopping and completing the sculpting and emulsification.

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FIGURES 25.32A AND B

Completion of second chop

Irrigation, Aspiration and IOL Insertion

Once all the nuclear fragments are emulsified irrigation and aspiration can be started. It is important to remove all the soft lens matter and then to clean the capsule properly. This should not only be done in the obvious visible areas of the capsule but the author prefers to clean the cells from the remaining anterior capsule and the equator. Polishing of the posterior capsule is also essential. Once convinced that no more polishing is required the lens can be introduced in the bag.

FIGURE 25.33 Division of nucleus in four and start of their emulsification

FIGURE 25.34 Emulsification of each fragment independently

Advantages

Emulsifying the nuclear fragments in the supracapsular space protects the posterior capsule from rupture. The author found that phaco hemiflip could be performed easily in small pupils without the need of stretching the iris, using iris clips, sphincterotomy or any other damaging procedures to the iris. At the same time the zonules are not damaged to the same extent as if the phacoemulsification is done in the bag.

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FIGURE 25.35 Splitting of the nucleus

FIGURE 25.36 Separating the nucleus pieces further by lateral movement of the instruments

Protection of posterior capsule Once the nucleus is flipped out of the bag it can be emulsified in the iris plane or in the posterior chamber above the capsular bag, away from its restrictions. This leads to less pressure and danger to rupture of the posterior capsule.75–79 Emulsification is helped by the use of higher vacuum, which normally is not used in the bag, as chances of catching the capsule in the phaco tip are minimal.

Less zonular damage Small amount of manipulation is done in the bag, which prevents any

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FIGURE 25.40 Final outcome

damage to the zonules.80,81,86 Emulsification performed outside the bag in the supracapsular space prevents damage to the zonules.

Effective utilization of ultrasound energy Since the nucleus is easily approachable in the supracapsular space and in the upside down position the use of ultrasound energy is utilized very effectively. At the same time it is helped by the added high aspiration flow rate, which keeps the nucleus near the phaco tip.

High volume surgery For high volume phaco surgeons this is an effective way of doing surgery, as the average time required for supracapsular phaco is less than that of the endocapsular approach.

Advantages of larger capsulorhexis Larger capsulorhexis is the key for a supracapsular phacoemulsification. Other than allowing one to flip the nucleus out of the bag it has following main advantages.

•Prevents IOL decentration.

•Prevents capsular phimosis.82,83

•Good retinal view following phacoemulsification.

•Easy access to the equator of the capsule for removal of cells thus preventing posterior capsule opacification.

Supracapsular Phacoemulsification in Difficult Cases

Difficult cases are the test of endurance for any procedure. The credibility and efficiency of a procedure can be honored by its effectiveness in difficult cases. The author has used these techniques in cases like small pupil, pseudoexfoliation, vitrectomized eyes, hard nucleus, white cataracts and others and found these procedures very effective with excellent results.

Pseudoexfoliation

In a pseudoexfoliation84–87 case, the surgeon is always concerned about the status of the zonules. Excessive manipulation of the lens in the bag can lead to damage of the zonules.

This damage can be significant enough to cause a dislocated or dropped nucleus or unstable bag at the end of surgery not suitable enough to support an IOL. Capsule tension rings are a good option but they also have their limits. With supracapsular phacoemulsification there is little amount of manipulation in the bag and once the nucleus is removed out of the bag no further pressure is exerted on the zonules.

Small Pupil

Phacoemulsification in small size pupils88–93 is always a challenge. Mainly because it is difficult to achieve a good size capsulorhexis and then it is difficult to do sculpting and aspiration of soft lens matter under the iris. One can use iris hooks, stretching of the iris, or sphincterotomy for such eyes to increase the pupillary diameter. The author always does phaco hemiflip procedure for such cases.

To have good pupillary aperture the author tries to dilate the iris by stretching but if this does not work then he does the following procedure.

Lifting the flap of anterior capsule towards the paracentesis incision with the help of a cystotome starts the capsulorhexis. Then introduce a Sinskey hook from the paracentesis incision and Utrata forceps through the main incision. Pull the iris to the paracentesis side with the help of a Sinskey hook exposing 5 to 6 mm zone of the capsule. Once this area is exposed hold the flap of the capsule with the help of Utrata forceps held in the other hand. Now start rotating the flap to attain capsulorhexis in 5 to 6 mm zone of the anterior capsule, exposing that area of capsule by dragging iris toward the periphery. Once pass the 6 O’clock position when it is required to push the iris then to pull it away the author uses the Y-shaped instrument as he finds Sinskey hook to be a sharp instrument for this purpose. The capsulorhexis continues in the same fashion as to expose with the side-port instrument and tearing of the flap with Utrata forceps. Once the capsulorhexis is completed phaco hemiflip can be started by just burring the phaco tip in the center of the nucleus to create groove almost two-third of the thickness of the nucleus then it is divided and flipped out of the bag as discussed before. As it is half the size of the whole nucleus it can fit in the pupillary plane where it can be emulsified easily. Aspiration of the lens cortex can also be done with the same exposure technique as used for doing capsulorhexis.

Vitrectomized Eyes94–97

As there is no support of the vitreous the posterior capsule is quite flabby and the dynamics in the anterior and posterior segment are very different than in the normal eye. With this technique the lens is out of the bag in the early stages and the posterior capsule does not come in the way of the phaco probe. On occasions, the author has used an anterior chamber maintainer in these eyes which makes phacoemulsification very easy. It is important to note that the pressure in the anterior segment should not be increased to an extent that the bag ruptures. The author has seen people using posterior segment infusion but he thinks this is really not required.

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Hard Nucleus

These types of nuclei are not difficult with supracapsular approach as a high aspiration flow rate can be used to help the emulsification of the nucleus.

Low Endothelial Cell Count Cornea

The author prefers to use a phaco flip technique in these cases. As his average percentage of endothelial cell loss with this technique is 7.00 percent.98–112 The main reason for less

endothelial cell loss (ECL) is that

•The pieces are smaller than the whole nucleus and can be emulsified in the pupillary plane.

•Less instrumentation required as compared to the cracking technique as one does not need to insert and reinsert different instruments.

•Less operation time is required.

•Less ultrasound time, as most of the time high vacuum is assisting.

New Generation Phaco Machines and Supracapsular

Phacoemulsification

The new generation phaco machines have provided us with a new dimension of phacoemulsification. With the availability of high aspiration flow rate supracapsular phacoemulsification is much simpler, more effective and safer. This is especially important for the high volume phaco surgeons.

Supracapsular phacoemulsification is a step forward in the phacoemulsification technique. Flipping the nucleus out of the bag not only allows easy approach to the nucleus but as it is in the supracapsular plane there is less chance of rupturing the posterior capsule and damaging the zonules. At the same time, the posterior surface is directly approachable which allows effective utilization of ultrasound energy. All these factors help to make it not only a safer and effective technique but quicker too.

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60.Luck J, Brahma AK, Noble BA: A comparative study of the elastic properties of continuous tear curvilinear capsulorhexis versus capsulorhexis produced by radio-frequency endodiathermy. Br J Ophthalmol 78(5):392–96, 1994.

61.Assia EI, Apple DJ, Tsai JC et al: The elastic properties of the lens capsule in capsulorhexis.

Am J Ophthalmol 111(5):628–32, 1991.

62.Cochener B, Jacq PL, Colin J: Capsule contraction after continuous curvilinear capsulorhexis— poly(methyl methacrylate) versus silicone intraocular lenses. J Cataract Refract Surg 25(10):1362–69, 1999.

63.Gimbel HV: Hydrodissection and hydrodelineation. Int Ophthalmol Clin 34(2):73–90, 1994.

64.Anis AY: Understanding hydrodelineation—the term and the procedure. Doc Ophthalmol 87(2):123–37, 1994.

65.Beyer RW: Distinguishing hydrodissection and hydrodelineation. Ophthalmic Surg 24(2):135, 1993.

66.Brierley L: Hydroexpression of the nucleus. J Cataract Refract Surg 19(5):666–67, 1993.

67.Allarakhia L, Pearce JL: A new cannula for nucleus hydrodissection. Ophthalmic Surg

20(4):296–97, 1989.

68.Ayaki M, Ohde H, Yokoyama N: Size of the lens nucleus separated by hydrodissection.

Ophthalmic Surg 24(7):492–93, 1993.

69.Shephered JR: In situ fracture. J Cataract Refract Surg 16:436–40, 1990.

70.Maloney WF, Grindle L: Textbook of phacoemulsification. Fallbrook, CA, Lasenda, 1988.

71.Fine IH: Cortical cleaving hydrodissection. J Cataract Refract Surg 18(5):508–12, 1992.

72.Braverman SD: Braverman-Bechert nucleus rotator. J Cataract Refract Surg 18(4):410–11, 1992.

73.Asrar A, Flitcroft I, Tormey P: Phaco-Hemiflip—a suitable technique for small pupil and weak zonules. Ocular Surgery News 17(11):28, 1999

74.Lindstrom RL: Tilt and tumble phacoemulsification technique. In Fine HI (Ed): Textbook of Clear Corneal Lens Surgery. Slack Inc, 1999.

75.Meng YA, Wang YF, Liu XM: Management of posterior capsule rupture and vitreous loss during IOL implantation. Chung Hua Yen Ko Tsa Chih 30(3):174–76, 1994.

76.Mulhern M, Kelly G, Barry P: Effects of posterior capsular disruption on the outcome of phacoemulsification surgery. Br J Ophthalmol 79(12):1133–37, 1995.

77.Koch PS: Managing the torn posterior capsule and vitreous loss. Int Ophthalmol Clin

34(2):113–30, 1994.

78.Traianidis P, Sakkias G, Avramides S: Prevention and management of posterior capsule rupture. Eur J Ophthalmol 6(4):379–82, 1996.

79.Osher RH, Cionni RJ: The torn posterior capsule—its intraoperative behavior, surgical management, and long-term consequences. J Cataract Refract Surg 16(4):490–94, 1990.

80.Saber HR, Butler TJ, Cottrell DG: Resistance of the human posterior lens capsule and zonules to disruption. J Cataract Refract Surg 24(4):536–42, 1998.

81.Mackool RJ, Sirota MA: Intracapsular foldable posterior chamber lens implantation in eyes with posterior capsule tears or zonular fiber instability. J Cataract Refract Surg 24(6):739–40, 1998.

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82.Hayashi H, Hayashi K, Nakao F et al: Anterior capsule contraction and intraocular lens dislocation in eyes with pseudoexfoliation syndrome. Br J Ophthalmol 82(12):1429–32, 1998.

83.Sugimoto Y, Takayanagi K, Tsuzuki S et al: Postoperative changes over time in size of anterior capsulorhexis in phacoemulsification/aspiration. Jpn J Ophthalmol 42(6): 495–98, 1998.

84.Breyer DR, Hermeking H, Gerke E: Late dislocation of the capsular bag after phacoemulsification with endocapsular IOL in pseudoexfoliation syndrome. Ophthalmology 96(4):248–51, 1999.

85.Fine IH, Hoffman RS: Phacoemulsification in the presence of pseudoexfoliation: challenges and options. J Cataract Refract Surg 23(2):160–65:1997.

86.Gimbel HV, Sun R, Heston JP: Management of zonular dialysis in phacoemulsification and IOL implantation using the capsular tension ring. Ophthalmic Surg Lasers 28(4):273–81, 1997.

87.Dosso AA, Bonvin ER, Leuenberger PM: Exfoliation syndrome and phacoemulsification. J Cataract Refract Surg 23(1):122–25, 1997.

88.Kadonosono K, Ohno S: New iris retractor for pupil dilatation during anterior vitrectomy: double-hook iris retractor. Ophthalmic Surg Lasers 30(3):241–43, 1999.

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26

New Non-laser Phacoemulsification

Technologies

I Howard Fine, Mark Packer

Richard S Hoffman

Introduction

New technology brings challenges and opportunities to the anterior segment surgeon. The drive towards less traumatic surgery and more rapid visual rehabilitation after cataract surgery has spawned various modalities for reducing incision size and decreasing energy utilization.

Although ultrasonic phacoemulsification allows for relatively safe removal of cataractous lenses through astigmatically neutral small incisions, current technology still has its drawbacks. In ultrasonic phacoemulsification piezoelectric crystals convert electrical energy into mechanical energy which emulsifies the lens material by means of tip vibration. Ultrasonic tips create both heat and cavitational energy. A conventional phaco tip moves at ultrasonic frequencies of between 25 KHz and 62 KHz. The amount of heat generated is directly proportional to the operating frequency. In addition, cavitational effects from the high frequency ultrasonic waves generate even more heat.

Because of the liberation of heat, phacoemulsification needles have required an irrigation sleeve for cooling. This irrigation sleeve carries heat away from the tip and necessitates an incision size larger than the tip alone would require. Nevertheless, standard ultrasonic phacoemulsification with an irrigation sleeve still carries with it the potential for thermal injury to the cornea in case of diminished flow. Flow and aspiration problems may be caused by compression of the irrigation sleeve at the incision site, kinking of the sleeve during manipulation of the handpiece, tip clogging by nuclear or viscoelastic material and inadequate flow rate or vacuum settings.1 Heating of the tip can create corneal incision burns.2 When incisional burns develop in clear corneal incisions, there may be a loss of self-sealability, corneal edema, and severe induced astigmatism.3

Cavitational energy results from pressure waves emanating from the tip in all directions. Although increased cavitational energy can allow for phacoemulsification of dense nuclei, it can also damage the corneal endothelium and produce irreversible corneal edema in compromised corneas with pre-existing endothelial dystrophies. Reduction in average phaco power and effective phaco time has been correlated with improved patient outcomes after cataract surgery.4 Low power phaco technology will have an important advantage in minimizing intraoperative damage to ocular structures and maximizing the level and rapidity of visual rehabilitation of the patient.

The last decade has given rise to some of the most profound advances in both phacoemulsification technique and technology. Techniques for cataract removal have

moved from those that use mainly ultrasound energy to emulsify nuclear material for aspiration to those that utilize greater levels of vacuum and small quantities of energy for lens disassembly and removal. Advances in phacoemulsification technology and fluidics have allowed for this ongoing change in technique by allowing for greater amounts of vacuum to be safely utilized, while power modulations that have allowed for more efficient utilization of ultrasound energy with greater safety for the delicate intraocular environment.5

Elimination of the frictional heat produced during ultrasound phacoemulsification and reduction of the power required for cataract extraction represent important steps towards the goal of atraumatic surgery. The sonic phacoemulsification system (Staar Wave, Staar Surgical) demonstrates another new approach to elimination of heat and the danger of thermal injury to the cornea. Modification of ultrasound energy through refinement of power modulation offers yet another route leading to elimination of heat and reduction of incision size (White Star, Allergan). The introduction of innovative oscillatory tip motion in coordination with power modulation permits further reduction of average phaco power and effective phaco time (NeoSonix, Alcon). Other new modalities under investigation, which promise low-energy, non-thermal cataract extraction, include vortex phacoemulsification (Avantix, Bausch and Lomb) and Aqualase (Alcon), a fluid-based cataract extraction system.

Sonic Phacoemulsification

Sonic technology offers an innovative means of removing cataractous material without the generation of heat or cavitational energy by means of sonic rather than ultrasonic technology. Its operating frequency is in the sonic rather than the ultrasonic range, between 40 Hz and 400 Hz. In contrast to ultrasonic tip motion, the sonic tip moves back and forth without changing its dimensional length. The tip of an ultrasonic handpiece can exceed 500 degrees Celsius, while the tip of the Wave handpiece in sonic mode barely generates any frictional heat. In addition, the Sonic tip does not generate cavitational effects and thus fragmentation, rather than emulsification or vaporization, material takes place.

The same handpiece and tip can be utilized for both sonic and ultrasonic modes. The surgeon can alternate between the two modes using a toggle switch on the foot pedal when more or less energy is required. The modes can also be used simultaneously with varying percentages of both sonic and ultrasonic energy. We have found that we can use our same chopping cataract extraction technique in sonic mode as we utilized in ultrasonic mode with no discernable difference in efficiency.

The Staar Wave also allows improved stability of the anterior chamber with coiled SuperVac tubing, which increases vacuum capability to upto 650 mmHg (Fig. 26.1). The key to chamber maintenance is a positive fluid balance between infusion flow and aspiration flow. When occlusion is broken, vacuum previously built in the aspiration line generates a high aspiration flow that can be higher than the infusion flow. This results in anterior chamber instability. The coiled SuperVac tubing limits surge flow resulting from occlusion breakage in a dynamic way. The continuous change in

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FIGURE 26.1

FIGURE 26.2 Postocclusion surge comparison chart

FIGURE 26.3 Postocclusion surge comparison chart

direction of flow through the coiled tubing increases resistance through the tubing at high flow rates such as upon clearance of occlusion of the tip (Figs 26.2 and 26.3). This effect only takes place at high flow rates (greater than 50 cc/minute). The fluid resistance of the Super Vac tubing increases as

FIGURE 26.4 NeoSonix™ handpiece

a function of flow and unoccluded flow is not restricted (personal communication, Alex Urich, Staar Surgical).6

The Staar Wave combines important innovations in phacoemulsification technology, which satisfy the demands of non-thermal, low power cataract extraction.

Neo Sonix Phacoemulsification

NeoSonix technology (Alcon) represents a hybrid modality involving low frequency oscillatory movement that may be used alone or in combination with standard high frequency ultrasonic phacoemulsification (Fig. 26.4). Softer grades of nuclear sclerosis may be completely addressed with the low frequency modality, while denser grades will likely require the addition of ultrasound.

In the NeoSonix mode, the phaco tip has a variable rotational oscillation upto two degrees, at 120 Hz. As with sonic phacoemulsification, this lower frequency does not produce significant thermal energy and so minimizes the risk of thermal injury.

The Legacy may be programed to initiate NeoSonix at any desired level of ultrasound energy. Thus, the surgeon may utilize the low frequency mode to burrow into the nucleus for stabilization prior to chopping by setting the lower limit of NeoSonix to zero percent phaco power. This approach works best with a straight tip, which acts like an apple corer to impale the nucleus. Alternatively, NeoSonix may be initiated as an adjunct to ultrasound at the 10 or 20 percent power level.

We have found NeoSonix most efficacious at 50 percent amplitude with a horizontal chopping technique in the AdvanTec burst mode at 50 percent power, 45 ml/minute linear flow and 450 mmHg vacuum. A 0.9 mm microflare straight ABS tip rapidly impales and holds nuclear material for chopping. During evacuation of nuclear segments the material flows easily into the tip, with very little tendency for chatter and scatter of nuclear fragments. With refinement of our parameters, we have found a 57 percent reduction in average phaco power, and an 87 percent reduction in effective phaco time, compared with the data we previously published with the Legacy system.7

NeoSonix has permitted further reduction in the application of ultrasonic energy to the eye when used in conjunction with ultrasound, and allowed nonthermal cataract extraction when used alone. It represents an important new modality in phacoemulsification technology.

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White Star Technology

White Star (Sovereign, Allergan) represents a new power modulation within ultrasonic phacoemulsification that virtually eliminates the production of thermal energy. Analogous to the ultrapulse mode familiar to users of carbon dioxide lasers, White Star extrapolates pulse mode phacoemulsification to its logical limit. As the duration of the energy pulse is reduced it eventually becomes less than the thermal relaxation time of ocular tissue. Thus, it is theoretically impossible to produce a corneal wound burn.

White Star technology sets the stage for bimanual cataract extraction with the Sovereign phacoemulsification machine. The absence of thermal energy obviates the need for an irrigation sleeve on the phaco tip, thus permitting reduction of incision size and allowing irrigation through a second instrument, such as an irrigating chopper, placed through the side-port. With an incision size for cataract extraction less than 1 mm, the challenge becomes production of intraocular lenses capable of insertion through such microphaco incisions.

Olson8 and Packard9 have reported exciting results using a 21-gauge irrigating chopper and a 21-gauge bare phaco needle with the bimanual technique. Olson’s study of cadaver eyes has demonstrated that thermal injury does not occur even in the absence of aspiration with 100 percent power for three minutes. Packard reported an absence of wound burns with excellent surgical ease and efficiency via sub-2 mm incisions.

The White Star technology demonstrates important advantages in improved safety and efficiency of cataract extraction, whether used in standard fashion or with the microphaco technique.

Avantix

Vortex phacoemulsification involves placement of a tiny rotary impeller inside the capsular bag through a 1 mm capsulorhexis. The impeller rotates at 60 kHz and causes expansion of the capsular bag with rotation of the nuclear complex, thus allowing extraction of the cataract from a nearly intact lens capsule. Expansion of the capsular bag minimizes risk of capsular rupture.

The tiny circular capsulorhexis is constructed with a round diathermy instrument, thus reducing the technical demands of such a surgical feat. The irrigation/aspiration tube containing the rotary impeller is placed over the capsulorhexis while hydrodissection is performed with gentle irrigation. The tube is then inserted into the capsular bag through the 1 mm capsulorhexis prior to initiation of rotation, thus completely isolating the anterior chamber from the activity of cataract extraction. Nuclear material is effectively removed from the capsular bag with vortex action, after which cortex is actually stripped away and extracted.

The advantages of leaving nearly the entire capsular bag in situ following cataract extraction will not be realized until an injectable artificial crystalline lens becomes available and the problem of capsular opacification is eliminated. Okahiro Nishi and others are currently investigating these devices, and may soon have a prototype available.10

Aqualase

Research at Alcon has led to the development of a fluid-based cataract extraction system. Another nonthermal modality, Aqualase employs pulses of balanced salt solution at 50 to 100 Hz to dissolve the cataract. This modality may potentially demonstrate advantages in terms of safety and prevention of secondary posterior capsular opacification. Still early in its development, Aqualase represents an innovative and potentially advantageous modality for cataract extraction.

Conclusion

Since the time of Charles Kelman’s inspiration in the dentist’s chair (while having his teeth ultrasonically cleaned), incremental advances in phacoemulsification technology have produced ever-increasing benefits for patients with cataract. The modern procedure simply was not possible even a few years ago, and until recently prolonged hospital stays were common after cataract surgery. The competitive business environment and the wellspring of human ingenuity continue to demonstrate synergistic activity in the improvement of surgical technique and technology. Future advances in cataract surgery will continue to benefit our patients as we develop new phacoemulsification technology.

References

1.Sugar A, Schertzer RIO: Clinical course of phacoemulsification wound burns. J Cataract Refract Surg 25:688–92, 1999.

2.Majid MA, Sharma MK, Harding SP: Corneoscleral burn during phacoemulsification surgery. J Cataract Refract Surg 24:1413–15, 1998.

3.Sugar A, Schertzer RM: Clinical course of phacoemulsification wound burns. J Cataract Refract Surg 25:688–92, 1999.

4.Fine IH, Packer M, Hoffman RS: Use of power modulations in phacoemulsification. J Cataract Refract Surg 27: 188–97, 2001.

5.Fine IH: The choo choo chop and flip phacoemulsification technique. Operative Techniques in Cataract and Refractive Surgery 1:61–65, 1998.

6.Fine IH, Hoffman RS, Packer M: The Staar Wave in Kohnen T (Ed). Modern Cataract Surgery Update. Dev Ophthalmol. Basel, Karger, 2002, vol 34 (in press).

7.Fine IH, Packer M, Hoffman RS: Use of power modulations in phacoemulsification. J Cataract Refract Surg 27: 188–97, 2001.

8.Olson RJ, Soscia WL: Safety and efficacy of bimanual phaco chop through two stab incisions with the Sovereign. XIII Congress of the European Society of Ophthalmology, Istanbul, 3–7, 2001.

9.Packard R: Evaluation of a new approach to phacoemulsification: bimanual phaco with the Sovereign system rapid pulse software. XIII Congress of the European Society of Ophthalmology, Istanbul, 3–7, 2001.

10.Nishi O, Nishi K: Accommodation amplitude after lens refilling with injectable silicone by sealing the capsule with a plug in primates. Arch Ophthalmol 116(10):1358–61, 1998.

Section V

No Anesthesia Cataract

Surgery

27.No Anesthesia Cataract Surgery with the Karate Chop Technique

28.No Anesthesia Cataract Surgery

29.No Anesthesia Cataract Surgery: Comparision Between Topical, Intracameral and No Anesthesia

30.Ocular Anesthesia for Small Incision Cataract Surgery