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

less in size, is very unlikely to leak, there is always the possibility for this to occur. The main causes are related to making the corneal incision larger than 3.0 mm and excessive trauma to the lips of the wound during surgery particularly with the phaco probe. These factors may give rise to a continuous loss of aqueous humor. This may be detected the following day by means of a positive Seidel test in which several drops of fluorescein are instilled over the wound and examination is performed with ultraviolet light.

Because the aqueous humor escapes through the wound continuously, the wound is kept open. Unless this is corrected immediately,thesurgeonmayhavetosuturethewound.

The very comfortable and effective maneuver recommended by Professor Murube in order to close-shut a leaking wound is to place

a Honan balloon over the eye for 30 minutes at 35 mm Hg pressure. At the same time, the patient is administered orally one tablet of 250 mgofAcetazolamide(Diamox). The way this works is that the significant intraocular hypotony produced by the combined use of the Honan balloon and Diamox results in the production of a significantly reduced amount of aqueous humor that is produced with sufficient continuity to reform the anterior chamber but not in sufficient quantity to seep through the wound. After a few minutes, the walls of the wound have had a chance to adhere to each other, thereby sealing the wound. No further positiveSeidel testisobservedeventhoughthe normal intraocular pressure is reestablished. This maneuver is innocuous and simple as well as highly effective (Fig. 96).

THE ANCILLARY INCISION

This is an important step in performing phacoemulsification. Although there are techniques to perform phaco with only one hand, phacoemulsification is fundamentally a twohanded procedure.

Theancillaryorside-portincisionismade before the main incision. It serves as an entry for a second instrument which is necessary for maneuverstoremovethenucleus,eithernuclear manipulators (fig. 79) or choppers (Fig. 80). The location and technique of making the ancillary incision is shown in Fig. 41 A.

In addition to serving as the mode of entry for the essential second instrument the ancillary incision is utilized in irrigation of the anterior chamber with intracameral local anesthetic as presented in Chapter 6 and illustrated in Fig. 36. It is also the route for the insertion of viscoelastic previous to making the primary incision.

At the end of surgery, the ancillary incision is used to inject fluid into the anterior chamber to test for leaks in the wound, as shown in Fig. 73.

Making the Ancillary Incision

The steps involved in performing the ancillary incision are:

1)First, mark the corneal location where the clear corneal stepped main incision would be made, which is always between 9 and 12, as shown in Figs. 41 B and 42. This measure serves the surgeon for orientation as to exactly where to place the two incisions.

2)Maketheancillaryincisionat3o'clock. This is performed with a special 15 degrees blade designed for paracentesis (Figs. 76 and 77).

ANTERIOR

CAPSULORHEXIS

Key Role

This procedure is also presented in Chapter 7 for the transition period and illustrated in Figs. 43, 44 and 45. It is generally agreed that a well performed anterior continuous capsulorhexis is an essential step for the success of phacoemulsification. The key reasonsforbeingsoimportantisthatcapsulorhexis prevents IOL decentration. In cotrast with the extracapsularextractionand canopenercapsulotomy, even when the surgeon was sure that he/she placed the IOL within the bag during surgery, sometimes 30 to 40% of cases after two or three months would have one of the lens loops protruding out of the capsular bag and reaching to the sulcus, thereby leading to decentration. On the other hand, by performing the continuous circular capsulorhexis followed by implantation of the lens within the bag, the IOL will permanently remain well centeredwithinthecapsularbag. Thishasbeen emphasized time and again by Everardo Barojas, M.D., one of Mexico's most prestigious cataract surgeons and a good number of other experts on the subject.

The Role of Viscoelastic in CCC

One of the key steps in achieving a first class capsulorhexis is to do it with viscoelastic in the anterior chamber rather than with BSS. Thehighdensityviscoelasticisusednotonlyto protect the endothelium and other surrounding tissues but also serves as a third hand that amplifies the working space and facilitates the maneuvers of the surgeon's manuevers. It also

helps to flatten the anterior capsule. This last measure facilitates the correct performance of the procedure.

Technique for Performing a First Class CCC

Beginning surgeons should be encouragedtouseforcepsasshowninFigs.44and45. Allcasesshouldbeperformedwithinjectionof viscoelastic material in the anterior chamber. Theexperiencedsurgeonmayperformtheprocedure with a cystotome-needle which is a No. 26 needle with the tip bent into a square angle as shown in Fig. 97.

The CCC utilizing the cystotome needle and viscoelastic is more safely and effectively performed using the central punch technique. This makes the first incision in the center, as shown in Fig. 98 and not in the periphery, as was the tendency when the procedure was developed (shown in Fig. 43). Using the central punch technique, there are fewer possibilities that a tear will spread to the periphery. The continuation of the capsulorhexis tear, once the central punch is done, may be done clockwise or counter clockwise, as is more comfortable for the surgeon. Usually, it is continued in a circular fashion in a counter clockwise direction as shown in Fig. 99, carefullycompletingacirclefromoutwardsinward obtainingacompletelyclosesrhexis(Fig.100).

It is fundamental to advance the capsular tearinawellcontrolledmanner. Thisisachieved by placing the cystotome-needle against the surface of the anterior capsule and re-grasping the tear as many times as necessary to continue the circular teaar until completing the circle.

A very important part of the first step in CCC is to be able to obtain the flipping of the resultant capsular flap once the cystotomeneedle engages the anterior capsule centrally.

It is important for the surgeon to see the underside surface of the anterior capsular flap as shown in Fig. 98.

Some surgeons find that in order to performtheproceduremoresafely,uponfinishing each one of the circular tears with the Uttrata forceps and before completing the circle, instead of leaving the capsulorhexis folded, take it back to the way it was, that is, unfolded. This makesthenextstepeasiertoperform,thatisthe anterior capsule, easier to grasp in order to engage and disengage to provide the best control for creation of a circular opening (Figs. 99, 100).

Size of the Capsulorhexis

Forexperiencedsurgeonsmasteringphacoemulsification, it is generally advisable to use a 5.5 mm central and completely enclosed rhexis. This is close to the ideal phacoemulsification technique performed safely within the capsular bag.

The size of the capsulorhexis, however, may be better determined by the type of intraocularlensmodeltobeimplanted. Carreño emphasizes that upon using Alcon's foldable acrylic implant with a 5.5 mm optic, he prefers a 4.5 mm or 5.0 mm rhexis so that the edge of the optic is completely covered by the anterior capsule. This helps in preventing fibrosis which may be produced when both capsules come into contact. It is also helpful in reducing glare especially in younger patients who have more of a tendency for pupillary dilation at night or in the darkness.

On the other hand, upon using the silicone foldable lenses, Carreño prefers a 5.0mmto5.5mmrhexistopreventcontraction of the capsular sac, which may accompany this type of implant when the diameter of the capsulorhexis is smaller.

Another factor which influences the size of the capsulorhexis, is the degree of hardness of the cataract. In cases where the nucleus is too hard, Carreño feels that it is more prudent to perform a rhexis which is not too small, certainly no less than 5.0 mm in diameter, to ease performing the phaco chop techniques, which are the most highly recommended for treating hard nucleus.

STAINING THE ANTERIOR CAPSULEINWHITECATARACTS

As shown in Figs. 98, 99 and 100, a well performed CCC allows the coaxial light of the

microscope to provide the red reflex of the fundus. Over this red reflex the anterior capsule and the border of the progressively performed continuous circular capsulorhexis can beverywellvisualized. Thisallowsthecompletion of the circle (Fig. 100) under adequate visual control. On the other hand, when the surgeon is dealing with white, hypermature cataracts that have either been allowed to get into that advanced stage or have been produced by trauma, the details and border of the CCC cannot be well visualized because this white cataract interferes with fundus reflex . Consequently, the step by step progress in the performance of the CCC is not well visualized. Accidentally, the edge of the anterior capsule

flap could be displaced toward the periphery andthelensequator. Fromhere,uponperforming the maneuvers inherent to phacoemulsification, damage to the posterior capsule could be inflicted thereby allowing passage of the vitreoustotheanteriorchamberoraluxationof the nucleus into the vitreous or a displacement of the intraocular lens once inserted. These important considerations have led to the devel-

opment of a very effective technique to control the performance of the CCC in white cataracts. Itconsistsinstainingtheanteriorcapsuleofthe lens in order to adequately visualize the details during the performance of the CCC (Fig. 101).

Without the dye it is nearly impossible to see the anterior capsule. These cataracts are risky. It is very difficult to distinguish the anterior capsule from the underlined cortex.

StainingSubstancesandMethods

There is a variety of staining substances and methods of how to perform the staining. They have been presented by prestigious ophthalmologists since 1998: in Japan through Nagoya University School of Medicine; in Spain, OscarAsis,M.D.; in Holland, Jerritm Melles, M.D.; in the U.S., Thomas Oetting and Rick Nearhing. The most practical and effective method now being popularized is the onepresentedbyProf.JuanMurube(Madrid). The different staining substances analyzed by Murube are the following:

1)Fluorescein 2%. This is obtained by mixing1mlof10%fluoresceinforintravenous use with 2 ml of BSS.

2)Indocyanine Green (ICG): This is obtained by mixing 25 mg of ICG in 0.5 ml of an aqueous solvent which might be obtained from Akorn in Buffalo Grove, Illinois. This mixture is then diluted in 4.5 ml of BSS.

3)Trypan Blue: Preparedbymixing1ml of trypan blue 0.4% (obtained from Life Technology, Grand Island, New York) in 3 ml of BSS.

4)Gentian Violet: solution at 0.01 concentration diluted with BSS.

5)MethyleneBlue:solutionat0.01mixed with BSS.

Murube's research has led him to select TrypanBlueasthestainingsolutionofchoice. This has been confirmed through the clinical research of Carlos Nicoli, M.D., in Argentina, one of South America's top phacoemulsification surgeons. Nicoli emphasizes that Methylene Blue and Gentian Violet are very difficult to prepare because they must have very specific concentrations. It is fundamental that the stain used not be toxic to the corneal endothelium. Therefore, it should be prepared at exactly the right concentration. For instance,

Methylene Blue, if used, should be a 1% solution while Gentian Violet should be at one part per thousand. The new research by the Japanese in Nagoya refers to the use of 0.05% Indocyanine Green solution. The problem with the latter is that it is very costly. The Trypan Blue solution is being currently marketed as a nontoxic stain.

Technique for Injection of Staining Solutions

Murube first irrigates a viscoelastic into the anterior chamber. This is immediately and partially displaced by an air bubble in the anterior chamber in order to leave the corneal endothelium slightly lubricated and protected by the viscoelastic. A cannula is inserted through the corneal incision as shown in Fig. 101 and two drops of Trypan Blue are deposited over the anterior capsule. The surgeon waits ten seconds. This is followed by injection again of viscoelastic in order to eliminate the air bubble from the anterior chamber, the so-called "air exchange". At this time tinting is not yet detected until the first flap of the rhexis is done because the tissue absorbing the tint is not the capsular epithelium but the internal face of the capsule, visible enough for the surgeon to see the capsule very clearly and to proceed to perform the capsulorhexis adequately. Utilizing this technique, when performing the capsulorhexis (Figs. 98, 99, 100) the surgeon can see that the epithelium behind the anterior capsule is selectively stained. It is important to keep in mind that the epithelium is behind the anterior capsule. When the surgeon lifts the flap gently, he/she can see the epithelium perfectly stained so he/she may safely proceed to complete the capsulorhexis.

This technique is considered of great value,abreakthroughinthisstepofphacoemulsification.

HYDRODISSECTION - HYDRODELAMINATION

This next step is of great importance. Its objective is to separate the capsule from the cortex and the cortex from the nucleus (Figs. 46, 47, 48). Its significance is related to the liberation of the adherences which attach the nucleus to the cortex or the cortex to the capsule,facilitatingaspiration(Figs.1,46,47,48). The hydric chamber created with hydrodissection also plays a role in the protection of the posterior chamber and the posterior capsule during the phacoemulsification maneuvers.

Technique of Hydrodissection

Using a 3 ml syringe with a maximum of 1.5 ml infusion fluid, a 25 G flat tip cannula is introduced underneath the capsulorhexis (Fig. 78-A). Following Fine and Centurion's recommendations, the anterior capsule is raised and BSS is infused with light pressure. The fluid will distribute itself along the posterior capsule and will drain through the opposite side. The liquid wave can be seen in the center of the red reflex (Fig. 46, 47). This process is repeated at 6, 3 and 9 o'clock keeping in mind that after infusing, we should press the cataract against the capsule to avoid elevation of pressure within the capsular bag.

After the liquid wave reaches the area of the pupillary opening, the syringe is withdrawn and the center of the nucleus is compressed in an attempt to release the adherences of the cortex to the capsule on the side opposite

towherehydrodissectionwasbegun. Afterthis maneuver, the surgeon attempts to rotate the nucleus. If the nucleus was released by complete hydrodissection, it will rotate freely. If there is no rotation, try a new hydrodissection located opposite the site of the initial one. Centurion recommendsthatafter thenucleus is released, it be rotated four or five times 360º. This releases possible cortex or epinucleus or capsule adherence. Thus, at the end of nucleus emulsification there is practically no need to aspirate cortical remains.

Followinghydrodissection,itisessential to confirm that the nucleus is completely separated from the cortex before proceeding with the next step, which is management of the nucleus with the different phaco techniques. (For the do's and particularly don'ts related to hydrodissection, it is important to read the text onthissubjectinChapter7,nexttoFigs.46,47, 48).

Hydrodelamination

Hydrodelamination is the separation of the nucleus from the soft epinucleus (Fig. 48). This technique is done after completing hydrodissection. The same needle (Fig. 78-A) is introduced beneath the cortex and into the lens stroma while infusing BSS, which will delaminate sheets of cataracts, isolating the nucleusfromtheepinucleus,formingthegolden ring (Fig. 48 GR).

With present techniques, many surgeons do not used to perform hydrodelamination following a very well done hydrodissectgion. They remove the epinucleus usually during the emulsification of the nucleus.

General Considerations

At this stage, we proceed with the culminating phase of the operation. The previous methods of emulsification of the nucleus first within the anterior chamber and later in the iris plane are somewhat outmoded with the exception of the supracapsular otherwise known as the“tiltandtumble”irisplanetechnique,which is still Lindstrom’s first choice. It is less demanding. At present, though, the most often used phacoemulsification techniques in handlingthenucleusareperformedintheposterior chamber within the capsular bag. These are all identified as endocapsular techniques.

They have the advantage of reduced risk of damaging the endothelium. They also enable thesurgeontoworkwithalargeropeninginthe capsulorhexis which is definitely useful in patients whose pupillary dilatation is not adequate. Thesemethods havethedisadvantage that nucleus manipulation is done closer to the posterior capsule and more stress is placed on the zonular fibers, to their consequent risk.

The almost universal use of endocapsular phacoemulsification has been made possible because of innovations in technique and equipment.

Concepts Fundamental to All Techniques

Surgical Principles

Almosteverycontemporarycataractsurgeon uses some form of chopping, and all surgeonswhoperformchoppingusesomeform of ultrasound to facilitate the chop. Whether it be a groove-and-chop, divide and conquer, or a technique like Fine's quick chop (the choo-

choo chop and flip technique presented in Figs. 122126), some form of ultrasound is used for chopping.

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.

Inthischapterwepresentthethreegroups of techniques mostly used in advanced phacoemulsificationmethodsfornucleusremoval. You will find the fundamental concepts which are applicable to all methods and a description of the principles that make these methods highly successful, all of which have been developed by highly prestigious cataract surgeons. It is by understanding these concepts that the surgeon will be able to develop one or two essential techniques and use them as the methods of choice adapting his/her chosen procedure to virtually any situation and the different types of cataract encountered, either soft, standard or medium-density and the very hard cataract.

The surgeon will find in this Volume precisely what he needs to understand and to adoptthemethodwhichhefeelsmorecomfortable with and most suitable for his patients. If a more complete description of the techniques

available is desired, we suggest that you refer to the carefully selected, short list of recommended books and bibliography presented at the end of the chapter for the method's originators and proponents.

The Essential Principles

1) A general principle for all techniques to remove the nucleus in phacoemulsification, either the original four quadrants divide and conquer and its derivative divide and conquer (D & C) methods, and the relatively recent choppingtechniquesisthatitisfirstessentialto debilitate the core of the nucleus so that the nucleus can be split into halves, sometimes fourths (Figs. 67, 103 through 106) and occasionally into eighths. This allows emulsification and aspiration of nucleus segments (Fig. 105) instead of attempting to carve the entire nucleus without a planned strategy. This splitting of the nucleus is safer for the endothelium because it is easier to keep smaller par-

ticles away from the endothelium without having to push them against the posterior capsule. These essential principles are illustrated in Fig. 103 (The Cracking Effect), Fig. 104 (The Dividing Effect through Opposing Forces), Fig. 105 (The Slicing Process) and Fig. 106 (the Dividing Process).

2) Smooth sculpting which avoids nuclearmovementandzonularstressiscritical to all methods. Well-controlled deep and central sculpting facilitates cracking in segmentation methods and rim removal in one and two-handed methods. By using just enough ultrasound power to embed the phaco tip and then backing off to the I/A position (standard pedal position 2), the nucleus can be positively engaged for rotation and manipulation. This versatility of the phaco tip is especially impor- tantforone-handedtechniquesaswellaschop- ping techniques.

The principles of mechanical advantage apply to all methods; safety is maximized by using the minimum force and movement required to accomplish a given task.

THEGROOVINGANDCRACKING METHODS

The Divide and Conquer Four

Quadrant Nucleofractis

Technique

The first group of endocapsular operations was based on the principle of utilizing largeamountsofphacoenergyandlowvacuum.

The classical and less complicated technique of this first group is the Four Quadrants "Divide and Conquer" described in 1987 by HowardGimbel. Theprinciplesofthismethod are presented and described in figures 56 and 67 in Chapter 7. In order to debilitate and remove the nucleus, a linear vertical sulcus or groove is done in the nucleus from 6:00 to 12:00 o'clock and a second groove perpendicular to the first is done, both using the phacoemulsifier probe. The carving of these furrows results in the nucleus being seen with a cross as shown in Figs. 56 and 67. A second