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

to know: What are the procedures of choice when we need to remove nuclei of different consistencies?

The answer is that this is not a mathematical formula whereupon the techniques can be categorized based exclusively on how hardanucleuswearegoingtooperate. Butthe subject is sufficiently clear to allow us to present highly useful guidelines, based on the extensiveexperienceofhighlyrecognizedsurgeons. Thisiswhatweareprovidingyouhere.

In Chapter 9, you can find the guidelines and surgical principles of the techniques most surgeons use now and what consistency of cataracts do better in general with the major techniques such as D & C operations, the Stop and Chop, the Crater Chop, the Null-Phaco Chop and the Choo-Choo Chop and Flip. A variety of other procedures not described in Chapter 9 are modifications of the fundamental techniques and carry the name of the surgeon who sponsors the procedure.

Representative Experts

Confronting Nuclei of Different

Hardness

Now let us focus more specifically on the procedures of choice of some highly representative experts from different regions of the worldregardingtheoperationtheyusewhen confronting nuclei of different consistencies. These surgeons are: Richard Lindstrom, M.D., from the U.S.; Lucio Buratto, M.D., from Europe (Italy); Okihiro Nishi, M.D., from Japan, Edgardo Carreño, M.D., (Chile) and Virgilio Centurion, M.D., (Brazil) the latter two representing different regions and cultures of South America. Each one of these surgeons

has performed many thousand phacoemulsification procedures. They are highly successful and their concepts are solid. What we present in this Chapter is how each one of these five (5) prestigious surgeons perform phaco, with emphasis on nucleus removal whenfacedwiththefivetypesofcataractsthat we are all familiar with, based on different nucleus consistency.

You may observe that each one of them has a different procedure of choice. I will confirm that they are all successful. This experience may serve the ophthalmic surgeon as guidelines within which to select the technique he/she feels more comfortable with and that may serve the patients best. A great deal depends on where you practice, what equipment and facilities you have and the type of cataracts you mostly do.

LINDSTROM'S PROCEDURES OF CHOICE

1)ForSoftandMediumDensity(standard) Cataract: the supracapsular iris-plane procedure (Figs. 136-139).

The supracapsular operation is popularly known as the "tilt and tumble" technique. It is performed on the iris plane and is not endocapsular.

2)Posterior capsular cataract or the cataract in a young patient with relatively soft nucleus without much ultrasound power needed:thesupracapsularirisplanetechnique.

3)For Very Hard Nuclei: the Stop and Chop (an endocapsular technique) described in Figs. 107-111).

Lindstrom considers that a clear cornea incision is not indicated when doing the stop and chop in very hard nuclei. He uses a corneo-scleralincisionandlargeramountsof

viscoelastic. Moreultrasoundenergyisneeded to disassemble these very hard nuclei with more danger of wound burn and endothelial damage. The sclera is more resistant to the heating up of the wound than is the cornea. In addition, by moving back to the sclera you are farther away from the corneal endothelium with less risk of damage, particularly in patients with borderline corneas.

Advantages of the Supracapsular

Lindstrom notes that supracapsular techniques enjoy increasing popularity. A slightly larger anterior capsulorhexis (5.5 to 6.0 mm), is necessary. This allows the sur-

geon to bring a part of the nucleus or the whole nucleus in front of the anterior capsular ridge (Figs. 136-137).

In addition, Lindstrom considers that with the endocapsular techniques the number of posterior capsular tears with or without vitreous loss is higher for most surgeons because they are working inside the capsular bag. With a supracapsular technique the nucleus is up closer to the anterior chamber so the incidence of posterior capsule tears is reduced. It is also a very easy technique to learn. Forabeginningsurgeontheendocapsulartechniques are more difficult to teach and need a longer learning curve and more time to perform (see Chapters 7 and 9).

Disadvantages of the Supracapsular

The disadvantage of the supracapsular technique is that you are working much closer to the corneal endothelium. The surgeon must be very careful in his technique and shouldnot perform it on a very hard nucleus. With the modern technology available in the phaco machines (Chapter 8) and the adequate use of viscoelastic we have another margin of security to protect the endothelium.

Another measure that helps a good deal to protect the endothelium is to do the phacoemulsification with the bevel of the tip down or to the side. You have the alternative of placingthephacoinstrumentintheeyewiththe

bevel anterior, bevel to the side, bevel down or bevel close to you. There is a little spray that comes out of the phaco tip when you are doing the surgery. We want that spray to go away from the corneal endothelium so it is important to place the bevel to the side or the bevel down technique in using supracapsular technique.

Contraindications of Supracapsular

Lindstromperforms thesupracapsular techniquein allcataracts except:1)Patients who have cornea guttata, Fuchs' dystrophy or low endothelial counts. 2) Very hard cataracts.

HIGHLIGHTS OF THE SUPRACAPSULAR IRIS PLANE TECHNIQUE

The main steps are illustrated and explained in Figs. 136-139. The surgeon needs tobecomequiteadeptathydrodissectinguntil the nucleus is lifted, which is the first step

Figure 139 (right): Phacoemulsification

of the Second Half of the Nucleus -

Lindstrom’s Supracapsular (“Tilt and

Tumble”)

The remaining nuclear half is emulsified and removed with the phaco from an outside edge-in direction. Again, the nucleus is supported in the iris plane by the secondary instrument (R) during phacoemulsification.

priortotumblingthenucleusinasupracapsular approach. Rather than completing the tumbling of the entire nucleus, Lindstrom supports the nucleus in the plane of the iris and anterior capsular leaflet and then emulsifies half of it (Figs. 136-137). With a much smaller nuclearremnant,hetumblestheremainingone half upside down and completes the emulsification (Figs. 138-139).

Figure 138 (left): Tumbling the Remaining Half of the Nucleus - Lindstrom’s Supracapsular (“Tilt and Tumble”)

One half of the nucleus has been removed, the remaining half is tumbled upside down (arrow) with the secondary instrument

(R). This brings the nucleus into a position to be attacked from the opposite pole with the phaco probe (P).

In this operation, it is important to make a slightly larger anterior CCC (5.5 to 6.0 mm). If a small anterior capsulorhexis is done, the hydrodissectionstepwherethenucleusistilted can be dangerous and rupture the posterior capsule during hydrodissection could be possible. If a small anterior capsulectomy is inadvertently created, Lindstrom favors converting to an endocapsular phacoemulsification technique or enlarging the capsulorhexis. If he is unable to tilt the nucleus with either hydrodissection or manual technique, he will also convert to an endocapsular approach.

Occasionally the entire nucleus will subluxate into the anterior chamber. In this setting, if the cornea is healthy, the anterior chamber roomy, and the nucleus soft, he will often complete the phacoemulsification in the anterior chamber keeping the nucleus away from the corneal endothelium. The nucleus can also be pushed back inferiorly over the capsular bag to allow the iris plane tilt and tumble technique to be completed.

CENTURION'S TECHNIQUES RELATED TO NUCLEUS CONSISTENCY

1)For soft nucleus (+) Centurion's procedure of choice is the flip and chip (Fine

-see Figs. 122-126).

2)Forintermediatenucleus(++)(those not hard enough to be chopped), Centurion performs the classical divide and conquer

(Figs. 56, 67, 103, 104, 206 below). Because Centurion does not perform

hydrodelamination, he usually removes the epinucleus during emulsification of the nucleus. If thehydrodissectionwaswelldone, usually irrigation-aspiration (I/A) will not be necessary.

3) For hard nucleus (+ + + and above) Centurion's favorite technique is the Phaco Quick Chop, as developed by Pfeifer. The parameters he prefers are based on the different machines that he uses and are presented.

The main difference between this technique and other phaco chop procedures are: 1) The placement of the chopper is in the center of the lens, and not under the anterior capsule. 2) The movement of the chopper is vertical, instead of horizontal as in other phaco chop techniques.

Highlights of Other Steps in

Centurion's Technique

Anesthesia:Forroutinecasesherecommends topical anesthesia. Peribulbar is used for special situations, such as subluxated lens, white cataract, combined cataractglaucoma surgery and so on.

The Ancillary Incision: Usually, he sits at the head of the patient, performing first the ancillary incision and injecting a viscoelastic substance. This incision is placed 80º away from the primary incision, which is usually located between 10 and 11 o’clock (Fig. 41).

The Primary Incision: Is a one step incision between 10 and 11 o'clock performed with the 3.0 mm clear path (Asico) diamond knife (Figs. 41, 42).

Capsulorhexis: He refills the anterior chamber with more viscoelastic and performs a 5.5 mm capsulorhexis, with a cystotome.

Hydrodissection: The next step is the cortical cleaving hydrodissection, as described by Fine. The nucleus must be totally or completely free inside the capsular bag. At this time, he rotates the nucleus once or twice clockwise or anti-clockwise.

IOL Implantation: he injects viscoelastic. For routine cases Centurion uses foldable IOLs. He has been working with silicone IOL's for many years and is very confident with the implantation technique using the unfolder through 3.0 mm incision.

It is not necessary to enlarge the incision during the implantation. In his experience, with the acrylic lens it is necessary to enlarge to 3.5 mm to implant the Sensar (Allergan) and 3.75 mm with the AcrySof (Alcon).

CARREÑO'S NUCLEAR EMULSIFICATION TECHNIQUE OF CHOICE (PHACO SUB 3)

For the latest concepts on surgery related to density of cataracts, I also refer you to page 7. Carreño's Phaco Sub 3 is a phacoemulsification procedure performed through an incision of 3 mm or less. There are other modifications of the phaco technique also identified as "Phaco Sub 3." His goal is to make it as uninvasive as possible. He follows all the parameters appropriate for the entire spectrum of nuclear density that have proven to be efficient, safe, and replicable by other surgeons. Obviously, in order to achieve good surgical results, it is imperative that the phaco machine settings are perfectly adjusted to the needs of each type of nucleus and to the requirements of each step of the technique. Carreño uses the Legacy 20,000 equipment (Alcon).

Adjusting the Equipment Parameters to Remove Cataracts of Various Nuclear Density

It is important to keep in mind that the basic parameters of the phacoemulsifier are the ultrasound power, the vacuum, and the aspiration flow. These are amply discussed and beautifully illustrated in pages 112-114, 119-122 and Figs. 83, 84, 61-65.

Three Sets of Values

Programmed Into Memory

Carreño uses the following criteria: three sets of values programmed into the memory in the Legacy 20,000. These parameters are set according to the degree of hardness of the cataract. They are:

•Memory 1: Use high ultrasound power to enable a quick (continuous mode) nuclear sculpt or chisel and lower levels of vacuum and aspiration flow (Fig. 56). There is no need for great grasping or fixation power, or power of attraction in this stage of the technique.

•Memory 2: For capture, mobilization and emulsification of nuclear fragments (pulse mode) (Figs. 67, 68) it is necessary to have high vacuum levels and aspiration flow in order to achieve considerable grasp and fixation power. It is also necessary to have little ultrasound power so that the nuclear fragments that are free are not propelled from the phaco tip by excessive vibration.

•Memory 3: Is intended for the removal of soft material like the epinucleus, and uses much lower values in all settings, in pulse mode (Fig. 69).

Height of the bottle (infusion): 75 cm to 85 cm.

Phaco tip: Kelman type (curved) ABS Micro Tip with a 30-degree tip (Fig. 84).

If a good hydrodissection is performed with the cortical cleaving technique, it is possible to remove the epinucleus along with

the nuclear material in the majority of medium hard cataracts and in virtually all hard cataracts.

Working with well-programmed memories is a great advantage when using the Phaco Sub 3 Technique. By eliminating filtration through the surgical wound, the smaller incision directs the flow of liquid and nuclear fragments towards the micro tip for aspiration, making the phacoemulsification procedure more efficient. That is, there is no competition between the flow of liquid toward the surgical incision and the flow toward the phaco tip, which can occur with larger, leaking incisions. Also, the more hermetic incision of Phaco Sub 3 reduces the amount of liquid circulating in the eye during surgery and maintains a deeper and more stable anterior chamber. This helps preserve the integrity of the corneal endothelium and the posterior capsule, which, undoubtedly, confers greater safety to the technique. (Editor’s Note: see Chapter 7 for a very well illustrated presentation of the fluidics of phacoemulsification).

While performing Phaco Sub 3 it is very important to keep in mind that a lateral movement of the micro tip must be avoided so as not to enlarge the incision during surgery. It is therefore necessary to always keep the micro tip working from 12 o’clock to 6 o’clock without lateral movement. This explains the great importance of a second instrument (manipulator or chopper), introduced through the lateral paracentesis to facilitate rotation, mobilization maneuvers, and nuclear fracture.

Before beginning nuclear emulsification, regardless of the technique used, the surgeon should always inject viscoelastic in the anterior chamber to ease the penetration

of the phaco tip and to provide protection to the corneal endothelium.

Technique of Choice and

Consistency of Cataract

SOFT CATARACTS (grade 1 - 2

nucleus)

Carreño recommends Fine’s Chip and Flip because the nuclei are not very hard and generally cannot be fractured (Figs. 122-126). With this technique, it is important to use hydrodissection and hydrodelamination maneuvers. Hydrodissection makes free nuclear rotation within the capsular sac easier, and hydrodelamination clearly outlines the separation between the harder inner nucleus and the softer epinucleus that surrounds it. The gold hydrodelamination ring denotes the limit to which it is possible to emulsify the nucleus without risking capsular damage (Fig. 48).

First Step (“memory 1”: vacuum 0 to 10 mm Hg, aspiration flow 18 cc/min, U/S power 60%).

With a manipulator introduced through the lateral paracentesis, the nucleus is gently moved toward 12 o’clock to allow the micro tip, maintained in a central position, to emulsify the inner nucleus ring at 6 o’clock without the risk of reaching the capsular fornix. Then, with the manipulator, the nucleus is rotated in order to place other nuclear fragments in position to be emulsified. The microtip must not be advanced past the gold hydrodelamination ring. This maneuver is repeated until the entire inner nuclear ring is completely removed.

Second Step (“memory 2”: vacuum 200 mm Hg, aspiration flow 25 cc/min, U/S power 40%, 6 - 8 pulses/sec).

The manipulator is inserted into the cleavage plane obtained through hydrodelamination and is passed behind the residual nuclear fragment (chip). The chip is lifted and taken to the center of the capsular sac. It is here that the chip may be emulsified with greater safety.

Third Step (“memory 3”: vacuum 100 mm Hg, aspiration flow 20 cc/min, U/S power 30%, 6 - 8 pulses/sec).

The center of the epinucleus is pushed toward 6 o’clock with the manipulator. Sliding the epinucleus out of the upper capsular fornix, the microtip can pull the epinucleus up toward the main incision using aspiration only (phaco pedal in position 2). The epinucleus is then folded over itself top-down (flip), using the spatula and the microtip. This moves the nucleus away from the posterior capsule. Once the flip maneuver is completed, the epinucleus is removed safely by simple aspiration or using low power ultrasound (Figs. 122 – 126).

MEDIUM DENSITY CATARACTS (grade 2 - 3 nucleus)

For cataracts with a medium-hard nucleus, Carreño prefers to use Shepherd’s

Quadrant Nuclear Fracture technique,

which is a variation of Gimbel’s original “Divide and Conquer” procedure (Fig. 67) which is a grooving and cracking method. Carreño considers that Shepherd’s technique has become the nuclear fracture technique most widely used by phaco surgeons because of its simplicity and the high

level of safety it provides. The nucleus is soft enough to allow quick sculpting with low ultrasound. At the same time it is hard enough for the surgeon to create fractures without difficulty (keep in mind that soft grade 1 (+) cataracts cannot be fractured). Furthermore, with grade 2-3 nuclei, no excessive pull is exerted on the zonule while the fragments are sculpted, which can occur with harder nuclei.

In general, all of the nuclear fracture techniques (Fig. 106) aim to divide the nucleus in multiple fragments to allow their removal through the small circular aperture of the capsulorhexis and also to make phacoemulsification more efficient inside the capsular bag (Fig. 105). Phacoemulsification of small fragments of nuclear material is faster than emulsification of an entire nucleus. The procedure is therefore quicker, and the ultrasound time is reduced. The fragments are mobilized more easily within the capsular bag and it is possible to take them to the center without much difficulty (Fig.111). This allows them to be removed in a safe zone, eliminating the risk of injury to the posterior capsule or the corneal endothelium.

In Quadrant Nuclear Fracture, the nucleus is divided into four parts, which are then moved individually toward the central safe zone to be emulsified (Fig. 105).

First Step (“memory 1”: vacuum 10 to 20 mm Hg, aspiration flow 25 cc/min, U/S power 70%):

A manipulator is introduced through the side port incision to rotate the nucleus (Figs. 56 and 67). Moving the microtip from 12 o’clock to 6 o’clock, thin and deep grooves are carved until a cross is formed (Fig. 67). Ideally, these grooves should