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

This is the essence of the stop and chop, one of the most important of the advanced techniques.

Absolute Requirements to Perform the Stop and Chop

Although this technique is much less complex than the original phaco chop, in order for it to be successful, the following principles must be attained:

1)Hydrodissection: this stage of the procedure must be very well done (Figs. 46-48, 78-A). A great deal of the success of this technique depends on the ability to easily mobilize the nucleus (Figs. 108-110). We mustbesurethatthenucleuscanbecompletely rotated before beginning its phacoemulsification. The ease with which the nucleus can be rorated depends on a very well done hydrodissection. Before beginning phacoemulsification of the nucleus, the surgeon should rotate the nucleus two or three times inside the bag. If the rotation is not easy, then there was afailureinthehydrodissectionmaneuver. The surgeon must not attempt to mobilize the nucleus mechanically or by force.

2)The Initial Groove: done to create the space inside the nucleus for it to be fractured (Figs. 107 - 108). This groove must be well done to be useful. It allows the surgeon to free the two sectors easily (Fig. 106 above).

3)Fracturing the Nucleus: when the surgeon has reached a good depth with the two instruments, that is, the phaco tip and the ma-

nipulator or chopper, he should attempt to fracturethenucleus(Figs.103,104,106 above). It is easy to split the nucleus into two parts because the chopper or manipulator does a better job separating the nucleus halves than the olive tip spatula previously used for this purpose. If there are difficulties and the fracture line is not seen, the initial groove in the center of the nucleus can be deepened but the surgeon must pay great attention to the color of the red reflex to be sure he/she is not too close to the posterior capsule.

Thefractureofthenucleus intotwoparts first is the key to the success of the operation. Only after this will the surgeon be allowed to proceed making smaller free segments or wedgesbyadditionallyfracturingwiththechopper (Fig. 111).

Fracturing with the chopper depends largely on the instrument insertion depth. Normally, the phaco probe and tip as well as the chopper should be inserted at a depth about 2/3 the diameter of the phaco tip. Once the nuclear fragments have been made, the procedure is continued with the usual maneuvers (Figs. 105 - 111). At the end of nuclear removal, there is a small quantity of residual material which is then aspirated.

Importance of the Phaco

Chopper

This ancillary instrument is absolutely essential to perform the chopping technique. There is a large variety of these phaco choppers. They all look like a golf club and the most

effective ones have a somewhat sharp point 1.5 mm in length (Fig. 80). In figures 103 through 121 you may observe the chopper being used in different techniques. The chopper is inserted through the side port or ancillary incision. The hook or chopper is positioned at 6:00 o'clock underneath the anterior capsule as far peripheral and deep as possible (Figs. 105, 110, 111). The shape of the point is most important. We can chop a soft nucleus using a sharp point; a wedge shaped tip facilitates chopping of a hard nucleus.

Highlights of the Stop and Chop

Technique

1)It provides excellent stabilization of the nucleus by fixation with the phaco tip and slicing and biting with the chopper. The latter has more of an active role in the procedure than the ancillary instruments in other endocapsular techniques. The surgeon uses the two hands in harmony during the entire phaco nuclear removal.

This also means that the surgeon should pay very close attention to the chopper, which needs as much control as the ultrasound tip.

2)Throughout the entire procedure, the ultrasound energy transmitted to the nucleus is not transmitted to the epinucleus and the cortex. Therefore, it is not passed on to the posterior capsule and the zonules because it is

absorbed by the external cortex and the separation induced through hydrodissection

3)How useful is this procedure is in cataracts of different nuclear consistency depends on the ability of the surgeon to adapt his technique to the type of cataract he/she is operating. The size of the nuclear wedges created can vary based on nuclear consistency. This technique is even useful in hard nuclei usinglessultrasoundandmoreaspiration. Hard nuclei require smaller wedges while softer nuclei can yield with larger wedges.

The stop and chop technique is useful in most cataracts with different consistency: in hard nuclei, in soft and in cataracts with nuclei of standard consistency. It is a method that lends itself to wide use. There is greater ease in dealing with very hard nuclei as compared with most other techniques.

4)The advantages of this procedure over the conventional divide and conquer methods include reduced stress on the capsular bag and zonular fibers because the use of the chopper simplifies the fracture.

5)The operation decreases phaco time.

6)It creates less turbulence and consequent complications.

7)Any remaining epinucleus and cortex is removed in standard fashion.

8)By dividing the nucleus in two halves, thestopandchoptechniquefacilitatesthemore difficult maneuvering encountered by the surgeon in phaco chop.

The two main groups of techniques utilized in modern, endosacular advanced methods for managing of the nucleus in phacoemulsification are the chopping techniques and its derivativesandthecrackingtechniques(divide and conquer and its derivatives). There are fundamental differences in regards to their surgical principles.

Chopping tends to stabilize the nucleus between the phaco tip and the chopping instrument. Furthermore, mechanical force is directed centripetally as the chopping instrument cleaves the nucleus (Fig. 106 above). Therefore, minimal force is directed outward against the capsule periphery. This is in contrast to cracking methods, during which the nuclear periphery is pushed outward againstthecapsulebythecrackinginstruments (Figs. 104, 106 below). As a consequence, any defect in the capsulorhexis is at greater risk and may have a tendency to extend to the periphery and posteriorly with cracking as opposed to chopping.

Chopping is also a more productive method than cracking with respect to the need touseultrasoundpowerbecausechoppinguses mechanical force for nuclear segmentation as opposed to sculpting grooves which are done with ultrasound, even though modified D & C techniques do allow the use of low total ultrasound energy because it is not used continuously.

Ultrasound is used more efficiently during chopping because it is applied in the more effective occlusion mode.

Finally, chopping is a more time productive method than cracking in that a segmenting chop can be made with a single instrument movement (Figs. 104 above, 111) as opposed tomultipleultrasonicsculptingpassesrequired for a groove (Figs. 56, 67). Also, the smaller chopped fragments are more readily emulsified with less repositioning required as compared to larger quadrants.

In the chopping techniques, the chopping direction is from the equator to the center (Fig. 104 above). In the divide and conquer procedures, the cracking is from the center toward the equator (Fig. 104 below). Therefore, in the divide and conquer procedures, the surgeon must begin sculpting the center of the nucleus and debilitating the nucleus at that stage, making a trench or a crater with ultrasound to start the cracking from the center, as shown in Figs. 106 below, and 104. In the chopping techniques, the surgeon sticks the phaco tip into the nucleus and insert the phaco chopper into the space between the equator and the capsule at the 6 o'clock position (Figs. 105, 110, 111). Then the phaco chopper is drawn to the phaco tip to crack the nucleus. There is no needofsculptingduringthisstageoftheprocedure which is the reason why the phaco energy can be significantly reduced.

Sculpting with the ultrasound energy is the easiest and safest step of the operation and that is why we recommend the divide and conquer original four quadrant technique for the transition. There is no ultrasound sculpting in the stop and chop.

THE CRATER PROCEDURES

The Crater Divide and Conquer

(Mackool)

This procedure is based on Gimbel's Divide and Conquer surgical principles. It is a modification of the original four quadrant divide and conquer. Because it is used mostly for hard nuclei, the center of the nucleus is weakened in the shape of a small crater by applying ultrasound energy and proceeding to crack the nucleus in two halves. This is followed by further cracking into four pieces usingtheultrasoundenergywiththehelpofthe ancillaryinstrument. Thepiecesarethenemulsified.

The Crater Phaco Chop for Dense, Hard Nuclei

The crater phaco chop is essentially used in harder, more dense and brunescent cataracts (Fig. 2) in which a trench or trough or groove cannot be used because it does not weaken the entire lens nucleus sufficiently to easily fracturethenucleus. Theresultingsegmentswould be too large to manage safely. This is because the epinucleus of a hard nucleus is thin and a hard nucleus has a dual structure consisting of an outer soft and inner hard nucleus or core. Also, a hard nucleus is thicker than a soft nucleus and the posterior part is harder and more elastic. In these lenses, the phaco chop of Nagahara or even the stop and chop of Koch may not be sufficient.

Instead, a small, central crater is sculpted with controlled amounts of ultrasound energy, leavingadenseperipheralrim(Fig.112). After the central core of the nucleus is removed, the maneuveringoffracturingcanbeaccomplished by first placing the chopping instrument under the anterior capsule at the 6 o'clock position (Fig. 113). Keeping the phaco tip placed into the bulkhead of the nuclear rim (Fig. 113), the vacuum of the tip is used to stimulate division of the nucleus. No ultrasound is used. The chopping instrument which has been introduced through the ancillary incision pulls toward the incision (arrow), slightly away from the phaco tip and gently towards the posterior capsule. This results in a fracture through the nuclear rim and any remaining thin nuclear plate (Figs. 114). The nucleus is then rotated in order to accomplish additional fracturing of small segments (Figs. 114, 115). Fracturing is done with much less ultrasound energy than in the D & C Crater Procedure.

In the Crater Chop technique, again we initially debilitate the nuclear core with ultrasound energy. When weakened, the phaco tip isimpaledorfirmlyburiedinthecentralnucleus (Figs. 113, 114). Multiple wedges are created by the continuous process of biting tissue using the chopper. These small pieces are then emulsified (Fig. 116).

This Crater Chop technique is not to be identified as the Crater-Bowl procedure describedpreviouslyinwhichasubstantialamount of ultrasound energy was used to debilitate the central tissue.

THE NUCLEAR PRE-SLICE OR NULL PHACO CHOP TECHNIQUE

This technique has been devised by Jack Dodick, M.D., from New York, one of the world's experts in cataract surgery. Almost everycontemporarycataractsurgeonusessome form of chopping, and all surgeons who perform chopping use some form of ultrasound to facilitatethechop. Whetheritbeagroove-and- chop, divide and conquer, or a technique like HowardFine'squickchop(thechoo-choochop and flip technique presented later in this chapter), some form of ultrasound is used for chopping.

Disassembling the Nucleus

ImportanceinModernTechniques

All modern techniques are oriented toward breaking up or disassembling the nucleus to facilitate its removal from the eye. These techniques, which rely on mechanical energy, have been developed to reduce the amount of ultrasound energy necessary to break up the hard part of the lens nucleus. In addition, disassembling the nucleus removes it from the capsular recesses of the bag, thereby facilitating its removal with the phaco probe.

Nuclear disassembling techniques use some ultrasound at the beginning of the procedure to create multiple troughs or grooves. A second instrument such as a spatula or chopper can then be used to crack or break the nucleus. Dodick now routinely uses the nuclear preslice or null-phaco chop technique except in hardened, black cataracts. This procedure reduces the amount of ultrasound needed to remove cataracts by phacoemulsification. The

actual breaking up of the lens uses no ultrasound at all.

In this technique, Dodick sections the nucleus into four parts with no ultrasound using two specially designed hooks (Figs. 117 - 121). It is as safe as any phaco chop, and takes an equal amount of time.

How Is the Null-Phaco Chop Done

The procedure uses two elongated Sinskey hooks, which have a 2 mm bend with a round polished ball at the end neatly shown in Figs. 119 and 120. The anterior cortex is vacuumed, and viscoelastic is placed in the eye. The first hook is introduced through the paracentesis incision parallel to the lens until it is in the capsular bag. Dodick always does the phacoemulsification at the 11:00 position, which means the paracentesis incision is at about 2:30 (Fig. 117). The hook enters the capsular bag and is rotated 90 degrees so that it engages the equator of the nucleus. The first hook is now in place and is pointing toward the optic nerve.

Then the second hook is introduced through the phacoemulsification incision, again parallel to the lens (Fig. 117). It engages the capsular bag and enters it. The surgeon then rotates the hook 90 degrees so that the tip faces the optic nerve and engages the equator of the nucleus below. The hooks should be about 180 degrees apart. Taking great care, the surgeon moves the hooks to bring the tips together (Fig. 118). This process will not tear the posterior capsule, but it is important not to place the hooks in the sulcus. As the two hooks are brought together, they bisect the nucleus (Fig. 118).

Figure 119 (above): Dodick’s NullPhaco Chop Technique - Stage 3 - Fracturing the Inferior Half of the Cataract

The 11 o’clock hook is moved toward 6 o’clock and placed in the capsular bag. The second hook is left in the groove. The two hooks are brought together resulting in a trisection (this part of lens is cut into three parts).

T H E A R T A N D THE S C I E N C E OF C ATA R A C T S U R G E R Y

After the first crack a second crack of each half is easily made. The 11:00 hook is moved toward 6:00, and placed in the capsular bag while the second hook is left in the trough or groove (Fig. 119). The two hooks are brought together resulting in a trisection. At this point the lens has been cut into three parts (Fig. 119). The procedure can be repeated by splitting the next half in a similar fashion (Fig. 120). Upto this point no ultrasound has been used.

Once the quadrants are each broken up into three or four parts, they are removed with bevel down phaco, with high vacuum of 300 mm Hg to 500 mm Hg. This is in a peristaltic system, with a high flow rate of 30cc to 40 cc per minute. The amount of energy needed is extremely low.

Dodick disassembles some 1+ 2+ lenses with little or no ultrasound, because this maneuver not only sections the nucleus into four parts, it actually dislodges these parts quite well from the recesses of the capsular bag (Figs. 120, 121). He brings the last two quadrants into the pupillary plane and is able to break them up further with the aid of a Sinskey hook through the paracentesis incision. When he needs ultrasound in 3+ or 4+ cataracts, he rarely goes above 30 % ultrasound because the lens is already broken into four parts (Fig. 121).

Learning and Adjustment

Performing this technique does require some learning and adjustment. The learning curve required for this technique is to master the placement of the two hooks nd to prevent rotation of the nucleus while it is being divided. Great care must be exercised in the placement of the hooks into the capsular bag. There is a tendency for the nucleus to rotate, but you soon develop a proprioceptive-like sense of placing those hooks. If you see or feel internal rotation of the nucleus about to begin, you simply adjust the hooks.