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

Guidelines for Insertion of Different Types of Lenses

Surgical Technique with Array Lens

Fine and Hoffman consider it very important that incision construction be appropriatewithrespecttosizeandlocationbecausethe multifocal Array works best when the final postoperative refraction has less than 1 D of astigmatism. They favor a clear corneal incision at the temporal periphery that is 3 mm or less in width and 2 mm long (Fig. 91). Each surgeon should be aware of his or her usual amount of surgically induced astigmatism by vector analysis. The surgeon must also considerthebestmeridianinthecorneatoplacethe incision considering the existing preoperative astigmatism in order to end up with minimum postop astigmatism. We discuss this subject under "Refractive Cataract Surgery" in Chapter 12 (Complex Cases).

In preparation for phacoemulsifiction, the capsulorhexis must be round (Figs. 44, 45) and its size should be sufficient so that there is a small margin of anterior capsule overlapping the optic circumferentially. This is important in order to guarantee in-the-bag placement of the IOL and prevent anteroposterior alterations in location that would affect the final refractive status. Hydrodelineation and cor- tical-cleaving hydrodissection are crucial in all patients because they facilitatelens disassembly and complete cortical cleanup.

Taking the time and care to perform a careful and effective cortical cleanup as shown in Figs. 127 and 128, without being aggressive, may reduce the incidence of posterior capsule opacification, the presence of which, even in very small amounts, will inordi-

nately degrade visual acuity in Array patients. Because of these phenomena, patients implanted with Array lenses will require YAG laser posterior capsulotomies earlier than will patients with monofocal IOLs.

Minimally invasive surgery is key.

Techniques that utilize effective phacoemulsification powers of 10% or less are highly advantageous and can best be achieved with power modulations (burst mode or two pulses persecond)ratherthancontinuousphacoemulsification modes (Figs. 86-89, Chapter 8). The Management of Complications with the Array Lens is discussed in Chapter 11 (Complications).

Carreño's Technique of Acrylic IOL Implantation Through a 2.75 mm Incision

Because it is generally considered that acrylic lenses require a somewhat larger incision (3.4 mm) to be introduced into the anterior chamberwithoutharmingthelipsofthewound, we present Carreño's technique by which he implants the AcrySof lens (acrylic, Alcon) through a 2.75 mm incision. This is one stage ofthePhacoSub3methodwhichheadvocates. Carreño from Chile, is a highly skilled cataract surgeon.

Carreño emphasizes that in order to introduce the acrylic intraocular lens through verysmallincisions,asisthecaseinPhacoSub 3, using adequate technique and equipment is imperative. Otherwise, the implantation could cause severe trauma to the corneal margins of the wound and the endothelium as well as leading to an undesired increase in the size of the incision. Before implantation, a generous amount of viscoelastic should be injected into the capsular bag and the anterior chamber.

Foldable Acrylic Lens of Choice

Carreño'sexperienceisbasedontheuse of Alcon's AcrySof lens model MA30BA (5.5mm optic, total length 12.5mm, PMMA haptics).

Implantation Technique

Thelensisfoldedwithforceps(paddle),placed parallel to the haptics (longitudinal implantation technique). The implantation forceps (Buratto) are used to grasp the lens so that the haptics are perfectly parallel to the fold, going through the center line of the optic, and reaching the edge.

Correctly grasping the Buratto forceps is critical to penetration with the AcrySof through a 2.75mm incision. If the lens fold is not completely symmetrically, an edge is produced that impedes its introduction. If the jaws of the forceps are at an angle to the lens fold, a separation is created between the faces, which may make the lens impossible to introduce through a small incision.

The surgeon proceeds with the Buratto forceps placed in such a way that the lens fold stays on the left. It is very important that the first haptic enters the anterior chamber before the optic. Otherwise, the lens may be damaged if the haptic is trapped with the optic inside the corneal tunnel. Then the surgeon inserts the optic by exerting pressure and using slight lateral movements along the corneal tunnel. The spatula, introduced through the lateral paracentesis, exerts firm and constant counterpressure. (In order to exert adequate counterpressure, the lateral paracentesis must be placed 60 degrees from the main incision.) This pressure and counterpressure maneuver is another key aspect of successful implantation

of the AcrySof MA30BA through a 2.75mm corneal incision without complications.

Before completing the insertion of the optic,whichshouldbeverycontrolledsoasnot to penetrate abruptly into the anterior chamber and risking the integrity of the posterior capsule, the surgeon puts the haptic under the edge of the capsulorhexis so it can be placed in the capsular bag.

Once the optic is in the anterior chamber, the Buratto forceps are rotated 90 degrees in this position, and they are released so the lens unfolds (Fig. 133). Due to the thin incision, the lens tends to be trapped in the claws of the forceps. To release it, the surgeon pushes gently downward with the spatula. Now the forceps may be withdrawn, and the lens continues to gradually unfold (Fig. 133). The second haptic is immediately grasped with KelmanMcPherson forceps to introduce it into the anterior chamber. Aided by the spatula, using a bimanual maneuver, the implantation is completed by placing the lens optic first and then the second haptic into the capsular bag (Fig. 134).

Implantation of the AcrySof MA30BA lens through a 2.75mm corneal incision is not easy, but Carreño emphasizes that if the described technique is followed step by step, the surgeon can perform it without injuring corneal tissues. However, when dealing with AcrySof MA30BA lenses stronger than 24 diopters, Dr. Carreño prefers to use a slightly larger incision (3.0mm) because the greater thickness of these lenses may make them difficultorimpossibletoimplantthrougha2.75mm incision. (Editor's Note: as pointed out at the beginning when describing the acrylic IOL's implantation, most expert surgeons find it very difficultorunfeasibletoimplantanacryliclens through a 3.0 mm incision using forceps without harming the lips of the wound - Fig. 132).

Once the implantation is complete, the viscoelastic is carefully removed from the anterior chamber and from the capsular bag. The surgeonmusttakecarenottoleaveviscoelastic material behind the intraocular lens. (It is necessary to push the implant optic gently backward with the cannula to force the evacuation of the viscoelastic through the capsulorhexis opening.)

Finally, balanced saline solution is injected through the lateral paracentesis to ensure that the incision is perfectly self-sealing.

Dodick'sAcrySof'sImplantation

Technique

Special Features About

AcrySof´s Implantation

When handling the lens, it is important to keep in mind that especially in high powers up to 30 diopters, this is a thick lens. This makes folding more difficult. Jack Dodick, M.D., has found that pre-warming the lens dramatically facilitates the ease of the fold. This is done at his institution (Manhattan Eye and Ear Hospital) by placing it in a warm environment such as on top of a sterilizer that has an ambient temperature between 100 and 105 degrees. This seems to soften the material and facilitates the gentle folding of the lens, making it much easier to implant especially for high diopter lenses which are more difficult to fold.

It is also important to keep in mind that if the surgeon performs rapid folding of a cold lens, this may leave striae in the lens that

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

could conceivably interfere with visual acuity.

A second measure taken by Dodick to facilitate this lens' entry into the wound after folding and holding it with forceps is to pinch the lead edge of the lens with a second forceps, to make the "nose" conform into a bullet or missile shape. This facilitates entry into the eye. Once the nose enters into the eye, the rest of the lens follows with great facility (Fig. 133).

Dodick uses folding and insertion forceps to insert the lens. They must be very fine folding forceps so as to add very little bulk to the combination of lens and forceps that have to enter through the small wound (Fig. 132).

Dodick's Three Stage Implanta-

tion

Dodick likes to divide the implantation of the lens into three stages once it is in the anterior chamber. First, when the lead haptic is in the capsular bag, the lens is allowed to unfold. Stage two is the implantation only of the optic. Stage three, once the optic is implanted the surgeon inserts the superior haptic byrotatingit in withtheLesterhookorplacing it with a Kelman-McPherson forceps. Dodick considers that a common mistake when implanting any soft foldable IOL, is to implant it in only two stages. Once the inferior haptic is placed into the capsular bag, some surgeons proceed immediately to try to place the optic and the superior haptic in one second stage. His experience has taught him that implantation becomessimplerandmorecontrolledbydividing it into the three stages described.

Implantation Technique for Silicone Foldable IOL's Using Cartridge-Injector System

Lindstrompreferstoimplanttheselenses with a cartridge injector system. Since the secondgenerationsiliconelensesareveryflexible, they stretch when implanted through a cartridge-injector system, providing the surgeon with the advantage of inserting the lens through a smaller incision (Fig. 132-A).

Carreño's technique for implantation of siliconefoldablelensesstartswiththeinjection of viscoelastic in the anterior chamber, the capsular bag and into the cartridge. Once viscoelastic has been injected into the cartridge, thelensisloadedcarefullysothatbothsidesare inserted into the lateral channels. The car-

tridge is then closed and placed in the injector. In order not to enlarge the incision, Carreño considers that it is essential to introduce the tip of the cartridge a few millimeters into the anterior chamber, as its thickness increases towards the back (Fig. 132-A). With theinjectorinplace,thelensisadvancedthrough the cartridge. Once it begins to unfold in the anterior chamber, it is guided with the first haptic under the edge of the capsulorhexis and placed in the capsular bag. Once it is unfolded, theemptycartridgeisremoved. Usingaspatula introduced through the lateral paracentesis, the second haptic is gently pushed downward and backward to be placed in the capsular bag as well.

For you to have a mental picture of the concept of foldable lens implantation, we refer you to Fig. 135.

TESTING THE WOUND FOR LEAKAGE

Ifthecornealincisionhasbeenperformed adequately, following the principles outlined in Figs. 90, 91, 92, 93, the surgeon should have a self-sealing stepped valvulated corneal tunnel incision. These incisions should not leak but there is always the possibility that this may occur. Consequently, we must test the wound for leakage as shown in Fig. 73 and explained its accompanying text.

Following the removal of viscoelastic from the anterior chamber and capsular bag, BSS is injected through the paracentesis. If the surgeon finds that there is a leak (Fig. 73) there are two ways to seal the incision without having to suture it: 1) Inject BSS into the lips of the incision to hydrate the tissues and seal the wound. 2) Use Professor Juan Murube's maneuver for the combined placing of a Honan balloon over the eye for 30 minutes at 35 mm Hg pressure and administering orally one tablet of 250 mg Acetazolamide (Diamox).

The way Murube's clever maneuver works is explained in Fig. 96 and accompanying text. In the remote case that the corneal incision leaks and, even more remote, that the two methods for sealing described here do not work and there is a need to suture the incision, it is recommended that the surgeon place one single radial suture.

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MULTIPLICITY OF

TECHNIQUES

Visiting prestigious eye centers and through personal communications with a number of expert consultants throughout the world, it is interesting to observe how many different techniques and modifications of the basic phacoemulsification procedures have been developed. They all work well, if used in skilled hands. In addition, watching videos of phaco procedures performed by outstanding cataract surgeons from different regions, cultures, races and economic status of their countries, surgeons who perform a thousand or more cataract operations a year, we find them using techniques that are quite different from each other. Some use low vacuum, others use high vacuum, one uses a 60º phaco tip while the next one uses a 0 (zero) degree tip for the same type of cataract. One would do a supracapsular while the other emphasizes the need to do all cataracts using an endocapsular technique. Some are cracking, some are chopping.

The Essential Criteria for Success

Therevealingexperienceisthatthegreat majority of their cases have very good results and the operated eyes look very well. What we learn from this experience is that each

surgeon hasdevelopedatechniquewithwhich he/she feels comfortable, that works best for him/her and that fills the essentialcriteriaof not damaging the posterior capsule, the iris and/or the corneal endothelium.

DIFFERENT NUCLEUS CONSISTENCY - TECHNIQUES OF CHOICE

InChapter9,indiscussingthe Management of Disassembling the Nucleus, we presented the surgical principles of the major, late-breaking techniques mostly used now, showing how they work and how they are performed. These can be classified as: 1) Divide and Conquer (D & C) techniques and 2) the chopping procedures based on modifications of the Phaco Chop of Nagahara (Japan). Most of the now extensively used techniques that we present in Chapter 9 have beendevelopedbypioneersanddistinguished surgeons from North America (Gimbel from Canada; and Paul Koch, MacKool, Dodick, and I. Howard Fine, from the U.S.). Many otherprestigioussurgeonsfromallcontinents have made substantial contributions to render this step of the operation more effective and less risky.

Now let us try to get into the crucial subject that most ophthalmic surgeons want