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

coemulsification successfully or he will need to use so much ultrasound energy that there may be endothelial damage. Present techniques of phacoemulsification are precisely geared to avoiding the use of large amounts of ultrasound energy.

There are different techniques for the fracture of the nucleus. In the end, the surgeon will decide which one he prefers or feels more secure with. Often, it depends on the type and maturity of the cataract. At this stage of the transition, when the surgeon is only beginning in his experience in fracturing and dividing the lens to apply the ultrasound, the most recommended procedure is to divide it into four quadrants, the well known "divide and conquer" first presented by Gimbel (Fig. 56). Later, the surgeon will be able to utilize other moderntechniqueswhichalsousehighvacuum and low phaco but which may be too difficult in the transition.

At this stage of division or fracturing of the lens in the transition, it is recommended that the surgeon use Memory 1 of the phaco machine (Fig. 56) which implies a discretely high amount of ultrasound, low or no vacuum, low aspiration and the conventional height of the bottle (65-72 cms).

The Divide and Conquer Technique

In the "divide and conquer" technique, the phacoemulsification instrument is used to create a deep tunnel in the center or the upper part of the nucleus. The nucleus is split into halves, sometimes fourths, and even occasionally into eighths. Splitting the nucleus is safer for the endothelium and easier to learn, especially for the less experienced ophthalmologist convertingfromplannedextracapsularsurgery to phacoemulsification. It is easier to keep smaller particles away from the endothelium

without having to push them against the posterior capsule than it is to emulsify a large, cumbersome nucleus.

The nuclearfracturingtechniquesdevelopedby Gimbelareinpartpossiblebecauseof theCCC(capsulorhexis)techniquethatGimbel and Neuhann originated. The mechanical fracturing of the lens causes extra physical stress within the capsule, and that cannot be done without great risks of tears extending around posteriorly unless you have a proper CCC. There is almost an interdependence of these two methods. The fracturing techniques have not only provided more efficiency in phacoemulsificationinroutinecases;theyhave also made phacoemulsification in difficult cases safer and more feasible.

Gimbel clarifies that not only are there lamellar cleavage planes corresponding to the different zones of the lens, but also there are radial fault lines corresponding to the radial orientation of the fibers, as first described by Drews. Until the development of these nuclear fracturing techniques we had not taken advantage of this construction (Figs. 55,56,67,68). The lens fractures quite readily in radial or pieshaped segments(Fig.67). Toaccomplishthis radialfracturing,thesurgeonmustsculptdeeply into the center of the nucleus and push outwards (Fig. 56). Sculpting is used to create a trench or trough in the nucleus. Then the surrounding part is divided into two hemisections. Theseparationmustoccurinthe thickest area of the lens located at the center of the nucleus (Figs. 103 and 104).

An additional consideration with these types of nuclear fractures is whether the segments should be left in place until all the fracturing is complete or whether they should bebrokenoffandemulsifiedassoonastheyare separated. With a lax capsule and particularly with a dense, or brunescent nucleus (Fig. 2),

Gimbel considers that it is safer to leave the segments in place to keep the posterior capsule protected. The segments are easier to fracture if they are held loosely in place by the rest of the already fractured segments still in the bag (Fig. 105).

Emulsification of the Nuclear

Fragments

If the surgeon has been successful in the fragmentation of the nucleus, the next step is to emulsify the pieces of segments of the divided nucleus. He may do this with the linear continuous mode or with the pulse mode. The latter done during the transition provides more security for the surgeon and allows him to use less ultrasound which is the definite tendency at present.

The surgeon may later slowly begin to utilizeothermorespecializedtechniquesknown as the different "chop" techniques which we will discuss later. These techniques facilitate much more the emulsification of the segments or pieces of the fractured nucleus than the divide and conquer but they are a little more complex. During this step of emulsification of the nuclear fragments, the surgeon may use Memory 2 in the machine which delivers low ultrasound, high vacuum, and a larger flow of aspiration, with a conventional height of the bottle of fluid (Figs. 67, 68).

FINAL STEPS

Aspiration of the Epinucleus

It is during this specific step that there is a higher incidence of rupture of the posterior capsule for the surgeon in the period of transi-

tion. This is due to his lack of familiarity with handling large fragments of epinucleus and cortex since in the planned extracapsular extraction he is accustomed to remove a large and complete nucleus that includes all the epinucleus and a significant amount of cortex. During the transition, the surgeon has to manage safely the irrigation-aspiration handpiece. Later, when he masters the technique, he may aspiratetheepinucleusandcortexbymaintaining the aspiration with the tip of the phaco handpiece. For this stage of the aspiration of the epinucleus, the surgeon will use Memory3 which means very low or no ultrasound power, a moderate to high vacuum, and high flow of aspiration,withthebottleoffluidmaintainedat the conventional height (Fig. 69).

Aspiration of the Cortex

This step is closely related to the previous one (Figs. 70, 71). There can also be a larger incidence of posterior capsule rupture during this stage since the surgeon does not have the epinucleus as a barrier which up to a few seconds before was protecting the posterior capsule. The surgeon should use a larger quantityofviscoelasticwheneverrequiredwith the purpose of protecting the posterior capsule. During the transition period, he may help his maneuvers by using the Simcoe cannula with which the planned extracapsular surgeon usuallyfeelssafe. Thiscannula maybeintroduced through the ancillary incision. The Simcoe cannula has the disadvantage, though, that the aspiration hole or aperture is smaller than that of the irrigation-aspiration handpiece of the phaco machine. Consequently, the aspiration of the masses of cortex may become more difficult and slow. During this stage, the sur-

geon should use Memory 4 in the setting of the machinewhichmeanszerophacopower,maximum vacuum and the highest flow of aspiration as compared with all the previously mentioned memories. The fluid bottle is maintained at the conventional height.

Intraocular Lens Implantation

For the surgeon in the stage of transition, it is advisable to begin by implanting PMMA IOLs either of the ovoid shape (Fig. 72-A) or with round optics of a fairly small diameter. The ovoid 5 x 6 lens shown in Fig. 72-A is just right.

Enlarging the Incision and Implanting the Lens

Inordertoaccomplishthisthesurgeonneedsto extendthesmallincisionwithwhichhestarted,

to 5.2 mm. A 5.2 mm knife blade will do this most accurately. In extending the arc of the incision, the surgeon must maintain the valvelike, auto-sealingcharacteristics presentinthe original small incision. The PMMA IOL implantation is performed as shown in Fig. 72-B. Afterthisstagehasbeenmastered, thesurgeon may then change to implantation of the foldable lenses but this must be done only after the surgeon is completely satisfied with his phaco technique.

Removal of Viscoelastic

Throughout the different stages of this procedure, the presence of viscoelastic in the anterior chamber is always a measure to keep inmindinordertopreventorminimizedamage to the surrounding structures during surgical maneuvers, particularly the corneal endothelium. When removing viscoelastic from the anterior chamber, the phaco machine must be

in zero phaco or ultrasound, high vacuum, very low aspiration and the bottle of fluid should be significantly lower. After all the surgical steps have been accomplished, it is important, as we all know, to remove the viscoelastic in order to avoid a high intraocular pressure postoperatively, with subsequent corneal edema, blurred vision and pain during the first postoperative days.

Even though this measure of removing all the viscoelastic has been emphasized over and over again in lectures and published papers, there are still surgeons who are not fully aware of the importance of taking this step and the consequent complications.

Closure of the Wound

If a good incision has been made, valvelike, auto-sealing and waterproof, no suture will be absolutely necessary even in those caseswhere thewoundhasbeenextendedtoan arc of 5.2 mm for the PMMA IOL implantation as shown in Figs. 72-A and B. As long as these two requisites are met, that is, extending the incision to 5.2 mm with a special knife blade of that size and maintaining a valve-like, autosealing incision, there is little danger of complications without sutures. Nevertheless, if thesurgeonisnotsurehehasmadeavalvulated

incision from the beginning (3 steps - Fig. 40-A and 42 A-B), even a 3 mm incision with no sutures will leak. If so, to leave the patient without any sutures would be to take an unnecessary risk. It is more prudent to place two or three 10-0 nylon sutures in the wound and they may be removed early in the postoperative stage. This decision really depends on the ability of the surgeon to create a valve-like, self sealing incision.

What to Do if Necessary to Convert

When the surgeon decides to convert from phaco to extracapsular,, viscoelastic is placed in the anterior chamber. The incision is

enlarged to one side and 2 or 3 sutures are placed (pre or post placed). The incision is completed to the other side and 2 or 3 more sutures are put in place (pre or post placed ). The two superior sutures are placed at either end of the "valve incision", so that irrigationaspiration (I + A) can be performed unhindered at that site. These two sutures are tied with a slip knot prior to I & A, and then loosened to place the IOL. The other sutures are tied and knots buried before I & A. At the end of the operation an additional suture can be placed if the incision is not secure. To reduce risks, the surgeon may preplace the 3 10-0 nylon sutures across a grove on each side first, before enlarging the incision.

Testing the Wound for Leakage

Before considering that the surgery is over, it is important to be sure that no leakage exists either through the main incision or through an ancillary incision, under the microscope. This is done by cleaning and drying the incision with a Weck-cell sponge, removing the viscoelastic and slightly overfilling the anteriorchamberwithBSS aftertheviscoelasticisremovedand exertingmild pressureover the cornea with the sponge (Fig. 73) or using fine forceps to lightly "dance on" the cornea. At this time one can observe if there is any wound leak (Fig. 73). If the surgeon finds that there is a leak, the best way to solve it is by injecting BSS into the lips of the incision to hydratethetissuesandforcetheincisionclosed. This works even better for the small ancillary

incision. The small conjunctival flap is then advanced over the incision.

Immediate Postoperative

Management

After instilling antibiotic ointment and topicalantiinflammatorydrops,theeyemaybe patched if local anesthesia such as retrobulbar, peribulbar or sub-Tenon's were used. If only topical anesthesia or topical combined with intracameral irrigation anesthesia was used (Figs, 35, 36), you may leave the patient without any patch. This facilitates the postoperative use of antiinflammatory drops by the patient.

The use of subconjunctival or parabulbar injection of antibiotics and steroids immediatelyfollowingsurgery,isnolongeraccepted as necessary, as was outlined in Chapter 4.