Ординатура / Офтальмология / Английские материалы / The Art and the Science of Cataract Surgery_Boyd, Barraquer_2000

extend almost to the edge of the capsulorhexis (to avoid the peripheral capsule), and should be deeper in the middle than in the periphery (to respect the curve of the posterior capsule) (Figs. 103, 104). They should also be slightly thicker than the ultrasound tip (including the silicone sheath) and should be 80%-90% of the depth of the nucleus (Fig. 103). The visualization of the red reflex at the bottom of the groove indicates adequate depth to the surgeon.

Second Step:

Once the cross is formed (Fig. 67), the nucleus is divided into four quadrants. The phaco tip and the manipulator are placed at the bottom of the groove at 6 o’clock and are pushed in opposite directions (with a direct or crossed maneuver) (Fig. 104). The separation results in a fracture line, which extends from the periphery to the center of the posterior nuclear wall (Fig. 104). After the nucleus is rotated 90 degrees, fractures are performed until the nucleus is divided into four fragments (Fig. 105). The fracture should include all the nuclear material; all the fragments must be separated in order to ensure a good result. Before continuing to the next step, the surgeon should mobilize the quadrants with the spatula in the capsular bag to ensure that there are no connections between them (Fig. 105).

Third Step (“memory 2”: vacuum 300 mm Hg, aspiration flow 35 cc/min, U/S power 50%, 6 - 8 pulses/sec) (Fig. 67)

The microtip is directed toward 6 o’clock, and the phaco pedal is in position 2 (irrigation/aspiration without ultrasound).

The first quadrant is captured by placing the tip in contact with nuclear material to generate occlusion (Figs. 59, 60). For greater

safety, the surgeon may first lift the corner of the quadrant with the spatula to distance it from the posterior capsule. With harder cataracts, sometimes simple aspiration is not enough to occlude the opening of the microtip. Apply a few ultrasound bursts (phaco pedal in position 3) to grasp the nuclear material and generate occlusion (Figs. 52, 53). Once occlusion is achieved and the phaco pedal is again in position 2, the surgeon should wait until the vacuum reaches the aspiration line. This makes it possible to hold the quadrant firmly on the opening of the tip. At this precise moment, relying on good grasping force, the surgeon can pull the quadrant toward the central safe zone. The quadrant should be completely controlled by the manipulator in order to avoid turbulence and contact. Then the quadrant is emulsified with the machine in pulse mode (Fig. 86). With large and hard fragments, it is useful to use chop maneuvers (with the same chopper or secondary instrument) in order to divide the quadrant into smaller fragments, to make the surgery quicker and easier (Figs. 105, 106). The procedure described is repeated for the other quadrants until the entire nucleus is emulsified.

HARD CATARACTS (grade 3-4

nucleus)

With hard cataracts, Carreño prefers to use chopping techniques. They offer clear advantages over the divide and conquer procedures in the management of this type of nucleus (See pages 177-182). As a method of nuclear fragmentation, the chopping techniques derived from Nagahara’s original “Phaco Chop” considerably reduce

the power and total time of phacoemulsification, thereby reducing the tension on the zonules and the posterior capsule and confining the entire phacoemulsification procedure to the central 3 mm of the pupil (Fig. 183).

Three important features of the chopping techniques are important to emphasize:

original “Phaco Chop,” offers a greater advantage by confining the chop to the central region within the limits of the capsulorhexis. This means the surgeon avoids the need to reach dangerously with the chopper under the anterior capsule, toward the lens equator, to create the fracture.

The “Stop and Karate Chop” technique

ent method than nuclear fracture. It basically consists of making cuts following the natural cleavage of the lens ( similar to cutting a log with ax blows) (see page 183).

2.In order to lend itself well to the chop maneuver, the nucleus must have a firm consistency.

3.The conservation of energy gained by not carving grooves (D & C) makes chopping particularly indicated for the management of hard nuclei.

The Stop and Karate Chop

the sculpting or chiseling of the central sulcus (Fig. 107, page 185) in order to fracture the nucleus in two halves, the chopping of the two hemi-nuclei, (Fig. 106, page 182) and the mobilization and ulterior emulsification of the nuclear fragments (Fig. 111). (Editor's Note: from the practical point of view, these are the same principles of the Stop and Chop (pages. 184-188), except that the direction of the cut in the “Phaco Chop” technique goes from the equator towards the center of the nucleus, while the “Karate Chop” goes from the anterior pole to the posterior pole).

Carreño’s preferred chopping technique is the “Stop and Karate Chop”, which is a combination of Koch’s “Stop and Chop and Nagahara’s “Karate Chop.” He finds it is a very safe procedure combining the advantages of both techniques.

Without a doubt, Koch’s “Stop and Chop” noticeably simplifies Nagahara’s original “Phaco Chop” technique by creating an initial groove (Fig. 107) which, in turn, creates a space in the nucleus, making the chopping maneuvers, mobilization, and nuclear fragment emulsification much easier. This explains its great popularity as a chop technique (page 184). At the same time, “Karate Chop,” which corresponds to a modification introduced by Nagahara to his

First Step (“memory 1”: vacuum 20 mm Hg to 30 mm Hg, aspiration flow 30 cc/min, U/S power 80%):

The procedure is initiated by chiseling a central sulcus with the microtip toward 6 o’clock (as if it were nuclear fracture in four quadrants) (Fig. 107). The chiseling is completed toward the other extreme after rotating the nucleus 180 degrees aided by the chopper introduced through the side port incision (Fig. 109). Once the desired depth is obtained, the nucleus is divided into two halves. It is fractured with the phaco tip, and the chopper is placed in the bottom of the sulcus. The surgeon must ensure that the halves are completely separated (Fig. 106). From this time on, no more sculpting or cracking is

done, and the chopping maneuvers are initiated. (Hence, the “Stop and Chop” designation by Paul Koch).

Second Step (“memory 2”: vacuum 400 mm Hg, aspiration flow 40 cc/min, U/S power 60%, 6 to 8 pulses/sec):

The nucleus is rotated 90 degrees so that it is in a horizontal position to ease the grasp of the distal hemi-nucleus with the microtip. The phaco pedal is in position 2 (irrigation-aspiration), the microtip is placed against the wall of the sulcus in its central portion while ultrasonic pulses (phaco pedal in position 3) are applied, and the nuclear material is grasped. Once occlusion is reached, the pedal is returned to pedal position 2 in order to increase the vacuum and obtain good fixation at the microtip. Now the choopper is sunk into the nuclear material slightly in front of the microtip. By pulling the instruments in opposite directions (the chopper towards the left and the microtip toward the right), the surgeon fractures the distal hemi-nucleus into two halves (Fig. 111, page. 189). The nucleus is then rotated 180 degrees, and the procedure is repeated so as to fracture the other heminucleus in two halves as well. The nucleus ends up divided into four quadrants. Carreño prefers not to remove the quadrants immediately. Keeping all the pieces within the capsular bag stabilizes the second hemi-nucleus at the moment the chop is performed, making the maneuver easier. It is very important to ensure that all four quadrants are completely independent of each other. Introducing the chopper directly into the nucleus, without having to reach the periphery to carry out the fracture, as with

the “Phaco Chop,” is what prompted Nagahara to call this modification of his technique the “Karate Chop.”

Third Step (“memory 2” is maintained: vacuum 400 mm Hg, aspiration flow 40 cc/min, U/S power 60%, 6 to 8 pulses/ sec):

Once the nuclear division is complete, the quadrants are mobilized. They are captured with the microtip and pulled to the central safety zone, where they are emulsified. In order to capture the quadrants, the surgeon grasps the nuclear material by applying some ultrasonic pulses (Fig. 105) (phaco pedal in position 3). Once occlusion is achieved, the vacuum is increased (phaco pedal in position 2) to ensure grasp at the microtip. The maneuver is repeated until all fragments are removed. As with Shepherd’s “Quadrant Nuclear Fracture,” any large nuclear fragments present should be divided using chopping maneuvers to speed the procedure.

The presence of a central sulcus plays a fundamental part in the development of the “Stop and Karate Chop” technique, as space is created within the nucleus (Fig. 107). With the occlusion of the tip, it is easier to perform the chop, to move the nucleus posteriorly, and to remove the fragments.

VERY HARD CATARACTS

(4-5 grade nucleus):

In these extremely hard nuclei (rubra and nigra cataracts), that represent a great challenge for the phaco surgeon, Carreño’s technique of choice is “Crater and Karate Chop,” which is a combination of Gimbel’s

“Crater Divide and Conquer” with Nagahara’s previously mentioned “Karate Chop.” The key to success with these very hard nuclei lies in reducing the nuclear volume as much as possible while maintaining a peripheral nuclear ring firm enough to perform chopping maneuvers geared to creating the fractures (See pages. 191-193 for reference of the very similar Crater Phaco Chop Technique - Editor).

The basic steps for the “Crater and Karate Chop” technique are the sculpting of a very deep central crater, the chopping of the peripheral nuclear ring to create multiple fragments, and finally, the mobilization and emulsification of these fragments (Fig. 112116 for reference).

First Step (“memory 1”: vacuum 20 mm to 30 mm Hg, aspiration flow 30 cc/min, U/S power 90%):

Directing the microtip always towards 6 o’clock, the surgeon sculpts a crater in the central nuclear zone, using rotation maneuvers to facilitate and deepen it. (The use of ultrasound for a prolonged amount of time during this step of the technique is not risky because the nuclear sculpting is performed inside the capsular sac, far away from the corneal endothelium.) In order to fracture, it is necessary to centrally sculpt very deeply (until the red reflex appears in the bottom) while maintaining enough dense material in the nuclear periphery.

Second Step (“memory 2”: vacuum 400 mm Hg, aspiration flow 40 cc/min, U/S power 70%, 6 to 8 pulses/sec):

The microtip is placed against the wall of the central crater at 6 o’clock, and ultrasound pulses are applied (phaco pedal in

position 3). The nuclear material is impaled. Once occlusion is reached, the pedal is placed in position 2 to increase the vacuum in the aspiration line and firmly attach the nucleus to the opening of the microtip. The chopper is then introduced into the nuclear edge in front of the microtip (“Karate Chop” technique, without taking the chopper to the equator underneath the anterior capsule.) The instruments are pulled apart to complete the first fracture. The nucleus is rotated, and the maneuver is repeated in order to make the second fracture, creating the first fragment. The process continues until the nucleus is divided into multiple fragments (five or more). The surgeon must ensure that there are no connections between them. The harder the nucleus, the smaller and more numerous the fragments must be in order to make them more manageable. While making subsequent chopping maneuvers, it is useful to leave the fragments in place to keep the capsular bag well-distended. This reduces the possibility of an inadvertent cut into the posterior capsule with the phaco tip.

Third Step (uses “memory 2”: vacuum 400 mm Hg, aspiration flow 40 cc/min, U/S power 70%, 6 to 8 pulses/ sec):

Once the nucleus is fragmented, Carreño proceeds to move each individual fragment toward the center to emulsify it. (Because very hard fragments are involved, it is advisable to inject viscoelastic to protect the corneal endothelium). The tip is placed against the nuclear fragment at 6 o’clock, and ultrasonic pulses are applied (phaco pedal in position 3) to capture the fragment. Then the vacuum is allowed to increase

(phaco pedal in position 2) to reach a firm grasp at the microtip opening. The fragment is then pulled toward the center, into the safety zone, to be emulsified. The nucleus

is then rotated in order to place another fragment at 6 o’clock. The procedure is repeated until all the fragments are completely removed.

NISHI'S TECHNIQUES OF CHOICE FOR NUCLEI OF DIFFERENT CONSISTENCIES

Nishi uses two different techniques depending on nucleus consistency.

1) Soft (+), Standard (++):

In these groups, Nishi uses a modification of the Divide and Conquer procedure (Figs. 56 and 67) and sometimes Fine's Choo-Choo Chop and Flip technique (Figs. 122-126) using high vacuum and low ultrasound energy from the very beginning

(vacuum 170 mm Hg, energy up to 60% using Allergan's Diplomax phaco machine). High energy is not necessary for those nuclei, and it is cumbersome for the surgeon to switch on from high vacuum-low energy to low vacuum-high energy.

2) Moderately Hard to Hard Nucleus (+++):

In cases with moderately hard and hard nucleus, higher energy up to 80% (even 100%) is used for rock-hard nucleus, taking care not to burn the wound. This high energy is combined with low vacuum for making a groove or a cross. For making a groove, the tip is never occluded and high vacuum is not needed. After the nucleus is divided into 2 or 4 parts, the next step is emulsification. The machine is switched to high vacuum low energy, unless higher energy is needed for emulsifying the fractured quadrants. High vacuum is now needed, because the nucleus fragments must be pulled towards the center by occluding the tip opening.

3) Hard (++++) or Very Hard Nuclei (+++++):

Nishi uses a chopping technique (Figs. 103, 106, 107-111). Care is taken to stay away from the corneal endothelium.

BIBLIOGRAPHY

Buratto, L: Buratto's elective techniques for phacoemulsification according to grades of hardness of nuclei. Phacoemulsification: Principles and Techniques by Lucio Buratto, 1998; 6:166-170.

Carreño,E.:Nuclearemulsificationtechniqueofchoice

(Phaco Sub 3). Guest Expert The Art and the Science of

Cataract Surgery of HIGHLIGHTS, 2001.

Centurion,V.:Centurion'stechniquerelatedtonucleus consistency. Guest Expert The Art and the Science of Cataract Surgery of HIGHLIGHTS, 2001.

Lindstrom,R.:Lindstrom'sproceduresofchoice.Guest

Expert The Art and the Science of Cataract Surgery of

HIGHLIGHTS, 2001.

Lindstrom, R: Tilt and tumble phacoemulsification.

Clear Cornea Lens Surgery, edited by I. Howard Fine, Slack, 1999;9:99-119.

Lindstrom, R: Tilt and tumble phacoemulsification.

Operative Techniques in Cataract and Refractive Surgery. Vol. 1, Nº 2 (June), 1998: pp. 95-102.

Nishi,O:Nishi'stechnique ofchoicerelatedtonucleus of different consistency. Guest Expert The Art and the Science of Cataract Surgery of HIGHLIGHTS, 2001.

General Considerations

Eveninthemostexperiencedhandscomplications occur. The best management of complications is to avoid them. When unpreventable, a well thought out, carefully executed plan can give very good visual results.

When using topical anesthesia, the patient is an active participant in the procedure. Complications can occur when patients move theirhead,body,oreye,cough,orsqueezetheir eyelids. Consequently, they should be fully educated and carefully selected. We should provide proper education in advance about what will be experienced so that the level of anxiety will be low. When speaking with the patient, the surgeon should sound calm and in control. If patients sense the surgeon's anxiety they may become more anxious, further limiting their ability to cooperate. When patients become over sedated they may fall asleep and might awake disoriented. The best way to keep patients from waking up suddenly is to keep them from falling asleep.

In cases under topical anesthesia, excessive globe movement can impair the safe completion of the operation. If the patient is unable to hold the eye steady, or if they are perceiving discomfort from the surgery, augmentingtheanesthesiawithasubtenon,peribulbar, or retrobulbar block may be helpful. This can be accomplished quite safely when a selfsealing wound is done.

Main Intraoperative

Complications

The main complications are related to the following phases of the operation: 1) complications related to the incision.

2)Thoseassociatedwithanteriorcapsulorhexis.

3)Complications consequent upon rupture of the posterior capsule. 4) Complications related to emulsification and removal of the nucleus through different techniques. We also need to confront the complications related to hydrodissectionand/orhydrodelineation, those that occur during the process of aspiration of the cortex, intraocular lens implantation and the difficulties of the operation when the pupil is small.

Incidence

As pointed out by Howard Gimbel, M.D., the incidence of intraoperative complications will vary to some degree with the surgeon’s experience and the type of procedure performed as, for instance, when a sclero corneal tunnel is performed versus a clear corneal incision. It will also vary depending on the anatomic characteristics of the individual eye as in small pupils and hypermature cataracts. Intraoperative complications are also related to the type of anesthesia utilized but this has been significantly diminished by combining topical and intracameral local anesthesia which is used in most cases, or using this combination with sub-Tenon’s anesthe-

sia when desired (Chapter 5). Since retrobulbar or peribulbar anesthesia are practically no longer used in phacoemulsification, even by those who are starting in the transition period, the risks of globe perforation or retrobulbar hemorrhage have practically disappeared.

Facing the Challenges

Virgilio Centurion, M.D. from Sao Paulo, Brazil, one of Latin America’s most experienced and didactic anterior segment surgeons, has dedicated years of research and teaching on how to master phacoemulsification. This includes being prepared for the challenges of the intraoperative complications, which are different than those we were accustomed to face with planned extracapsular. Centurion emphasizes that each cataract operation presents its own challenges, and that even though we have reached a very advanced level of safety and predictability with phacoemulsification, it is important that we keep in mind the complications that may arise so as to minimize situations that may bring the level of stress to a peak in the operating room.

COMPLICATIONS WITH THE INCISION

Too Short and Shallow or Too Large

Lindstrom points out that the most frequent complication he has with the clear corneal incision is that he either makes the width of the incision a little bit too short, or the dissection too shallow or too beveled

(Fig. 140). Or else, he makes the incision a little bit too large. If it is too shallow or beveled, it will become a non self-sealing, nonvalvulated wound. If it is too large, a persistent iris prolapse may occur. You may try to ignore it but it keeps coming back.

With a superficial, shallow incision, you may manage it as shown in Fig. 140. Simply abort the superficial tunnel, go back to the first or initial vertical groove of the incision (300 microns depth) corresponding to 1/2 the corneal thickness and place the blade deeper, forming a second tunnel with the correct depth located below the first or superficial tunnel (Fig. 140).

If you are having a very difficult time with an incision, the best thing to do is to close that incision with one or two vicryl sutures which will eventually dissolve and move over to another nearby spot and start over. With a clear corneal incision, starting over only takes a short additional time (Fig. 141).

Problems from Incorrect Placement and Performance of Incision

In Fig. 142 you may see a summary of the problems in creating the sclero corneal, limbal and corneal tunnel incisions. The correct placement and structure of each incision is presented in Fig. 40. A key element in the success of phacoemulsification is to obtain a good internal valve incision.

As Centurion has emphasized, it is only by experience and extreme care that we develop a sense of «feeling» of the ideal depth, that is, the one which will not endanger the intraocular tissues and will ensure a good tunnel protection.

Figure 141 (right): Problems From Incorrect Placement of Tunnel Incisions

The correct placement and performance of the sclero corneal tunnel, limbal or corneal incision is extremely important. In case of the sclero-corneal, a 5 mm external incision (E) is made 1-3 mm from the limbus to a depth corresponding to 1/2 to 2/3 thickness of the sclera. A scleral tunnel (T) between 2 to 3 mm in length is made. With blade directed toward and in a parallelpathtothepupil,theinternalvalve(V)opening is created. Common placement errors are shown by blue lines. Also shown is a detachment of Descemet’s membrane (D), another common error that can be avoided by use of abundant viscoelastic. (Original illustration by HIGHLIGHTS, based on principles from Virgilio Centurion's book titled "Complicações Durante a Facoemulsificação".)

Figure140(left): ComplicationswhileMaking a Clear Corneal Incision - Too Shallow and Short

The corneal tunnel incision should be self-sealing and valvulated, at about 300 microns depth. That is approximately half the corneal thickness. Here we observe that the first incision was too superficial (red) not permittingapropervalvetofunction. Thereby, the wound is not self-sealing. One solution for this is to abort this tunnel and start again from the initial incision, go deeper forming a second tunnel (arrows) below the first superficial tunnel.