Divide-and-Conquer Technique

55   Divide-and-Conquer Technique


James A. Davison


This chapter discusses prevention of clinically significant complications during the divide-and-conquer phacoemulsification technique through excellent preparation, disciplined routine, and early recognition of aberrant situations accompanied by strategies to resolve them.


Review of the Patient’s Record


Patients and families are normally somewhat anxious in the preoperative area. Review their personal information before you see them and then extend a warm greeting and a friendly smile. Patients need to feel that you recall their office visit and examination as if it were just yesterday, and that you remember them and know them, and that sufficient medication will be administered in the operating room to make them feel relaxed and comfortable and that everything will be fine.


Review of their clinical examination is important. Specifically we need to remind ourselves about previous eye surgery or trauma and anatomic details including the Lens Opacity Classification System (LOCS III) cataract rating, the presence or absence of pseudoexfoliation (PXF), and the dilated pupil size achieved in clinic. We need to verify which eye we are treating, what the refractive goal is, and which intraocular lens (IOL) we are implanting, along with any special needs, such as anticipated difficult positioning because of previous neck surgery.


Preparation in the Operating Room


Your machine settings should be confirmed (Fig. 55.1), and the microscope should be adjusted to your preference. The staff should review the record, confirm the patient’s identity, verify the eye to be operated, and review any special anticipated requirements.


The patient should be placed on the surgical bed so that he or she is comfortable and so that the face is oriented toward the ceiling with the brow and cheek bone at the same height to give symmetrical access to the globe without impingement from those boney structures. I like turning the patient’s head toward me slightly. The patient’s forehead should be taped to the bed (Fig. 55.2).


Relaxing medication is given while the prepping and draping occur. When you enter the room and sit down, make sure that the bed is adjusted so that the face is oriented properly and you have the same amount of sclera showing above and below, that is, a neutral position (Fig. 55.3). Make sure that the wrist rest does not impede your movement or positioning. Make sure that the eye is the right height for you and matches the patient eye level (PEL) setting on the machine, and that there is room for your legs and feet on the pedals. This is your final opportunity to create an optimized playing field for the surgical event. You can make adjustments during surgery if absolutely necessary but force yourself to try to make it perfect before you start. Make sure the microscope is in neutral position and angled properly for you. Turn off the overhead fluorescent lights to eliminate their reflection, enabling you to minimize the amount of light you need to use, which reduces the risk of light toxicity and creates maximum patient comfort and cooperation. Start with low light and ask the patient to look at it. Get an idea of the red reflex and adjust the blend of the microscope light so that the mix is what will be desired for the continuous curvilinear capsulorrhexis (CCC) portion of the procedure, usually about two thirds to three fourths of the total from the zero-degree source and one third to one fourth from the 6-degree source, depending on the microscope being used. More dense cataracts or highly pigmented retinal pigment epithelium (RPE) will yield less red reflex from zero-degree light and may require more 6-degree light during CCC and phacoemulsification as well. Different phases of surgery yield different red reflex illumination, and the ratio can be adjusted during the procedure to optimize the detailed view. Give the patient time to become adjusted to the light and to become comfortable. Ask the patient if he or she feels sufficiently relaxed and ready to proceed, or if more medication is needed for the patient to feel adequately relaxed. Do this as you drizzle more preservative-free lidocaine 1% to test sensation and relaxation and to further anesthetize. With the patient’s confirmation that he or she is adequately relaxed and comfortable, verify that you have adequate light and that the patient’s eye has steady fixation. If so, you are now ready to start surgery.



Surgical Procedure


It is best to engage in a circular one-way traffic pattern with your technician. I receive new instruments from the right and pass off the used ones to the left. Blades are always passed and released handle first. Your arms and hands should be in comfortable natural positions while holding the 2.4-mm keratome and 22.5-degree paracentesis blade. For me, the target for each is the slightly vascularized corneal limbus. My primary incision usually ends up being ∼ 10 degrees above midline in right eyes and 17 degrees above midline in left eyes. Penetrate with the paracentesis blade first. Aim toward the lens’s central anterior surface. The 22.5-degree blade creates a larger external opening that accommodates full movement without oar locking while creating a smaller internal opening that accommodates the lens manipulator and that seals easily. After reaching proper depth, use the top back of that blade to slightly pull toward and upward to stabilize the eye as you enter with the keratome. It is important not to waver on the way in or out with the keratome so the incision does not become enlarged (Figs. 55.4, 55.5, 55.6). Subtle angulation adjustments of the blade handle can help create limbal symmetric, parallel external and internal incisions as the blade is slowly driven forward. The shelf length is usually ∼ 1.75 mm, perhaps slightly longer in high myopes so overinflation is not necessary during stromal hydration and pressurization at the end of surgery. The external incision seems to be less irritating that one made in clear cornea. Also, the incision is cosmetically desirable in that the external entry eventually is invisible and the internal entry is very peripheral and not immediately noticeable.


The blades should not be removed from their packaging until you are ready to use them. The keratome blade may become dull if it rolls over even once on the Mayo stand. Get a new blade if either one seems dull at the initiation of the incision. Incision perfection is very important. A dull blade can create irregularities in the superficial stromal entry and deep exit into the anterior chamber. And there is nothing worse than a dull blade bursting through the cornea (usually too central), hitting the lens, and then being withdrawn in an uncontrolled fashion. The inadvertently extended incision with longer shelf length will make all subsequent maneuvers and infusion balance difficult. There would likely be corneal distortion during phaco from the depressed midperipheral cornea, making visibility poor, and the additional trauma will result in early pupillary miosis as well. The lens penetration will need to be included central to the CCC border. This is not a good way to start a case.







If four-cut or eight-cut radial keratotomy incisions are present, carefully go between them. If 16-cut or more incisions are present, perform a small fornix-based flap and use a more scleral incision. Also, if you prefer to use manual blade–created incisions when using the femtosecond laser as I do, be careful to identify and avoid the transverse arcuate incisions made by the laser for astigmatism reduction.


In my technique, preservative-free lidocaine 1% is injected slowly through a 30-gauge cannula, a little inside and then over the globe’s surface with several repeats so it does not cause pain as it affects the iris. Then fill one third to one half of the anterior chamber with Viscoat (Alcon, Fort Worth, TX), and then finish filling with Provisc (Alcon) underneath until some of it just starts to egress from the incision. This egress is not usually necessary especially in high myopes where the lens will just be pushed far posterior. You just get a feeling when the chamber ii full and egress is about to happen. This pressure creates a flat anterior capsular surface, which is the best configuration for capsulorrhexis.


For a 6.0-mm-diameter optic, a 5.0-mm-diameter capsulorrhexis is accomplished with a cystotome starting in the center and spiraling left and peripherally. The final radius will be set as the CCC is nearing the surgeon on the left side, thereby ensuring an accurate radius and a start/finish junction that will be in the proximal half, that is, not located in the distal half, where most of the surgical maneuvering will be (Figs. 55.7 and 55.8). A 4.6-mm diameter is better at preventing postoperative rotation or toric IOLs in high myopes, especially when receiving vertically oriented toric IOLs that can rotate off axis after surgery. This diameter can be better ensured by using an electronic overlay or femtosecond laser.


Hydrodissection is accomplished using a Chang cannula, usually with one injection of balanced salt solution (BSS) near the surgeon to the right. Lift the anterior capsular edge slightly during injection. If the usual fluid wave is not apparent, try the same maneuver on the left side. After hydrodissection, I embed the Chang cannula tip into the left side of the midperipheral lens and dislodge the nucleus attachments with a gentle downward and rotational motion. I then do the same on the right side (Figs. 55.9 and 55.10). I can see the nucleus slowly separating from the cortex. I want the dissection plane to be between the epinucleus and cortex (hydrodissection), not between the nucleus and epinucleus (hydrodelineation). When done, the nucleus and epinucleus, as an uninterrupted unit, should be easily turned by the embedded Chang cannula within the cortex and capsule. If hydrodelineation has occurred, rotation becomes more difficult, especially in soft lenses. If good symmetrical dissection planes cannot be created, then one quadrant can be isolated through two grooves and fractures and then removed; movement of the remaining quadrants should be easier even with disjunctive planes.


The sleeve position on the phaco tip is confirmed. There should be enough tip extended so that nuclear material will not be pushed away by the sleeve edge as the material is aspirated. The infusion openings should be 90 degrees from the tip’s bevel.


Phacoemulsification


To perform my usual micro-coaxial phacoemulsification, I use a 45-degree balanced tip with the ultra-sleeve and a specially modified cyclodialysis spatula. I use the shorter end of a 0.5-mm spatula that has been custom thinned to 0.35 mm, because the standard 0.25 mm is too thin and penetrates the nucleus too easily, making it difficult to push the surface, whereas the 0.5 mm is too thick and awkward and requires too large an incision. Its single-piece construction can withstand inadvertent contact with an active phacoemulsification tip, and its shape is ideal for manipulation and quick insertion and withdrawal through the incision.





The infusion is turned off as the cyclodialysis spatula protects the internal aspect of the incision as the tip enters the eye. The phaco tip traumatizes least when it enters slightly sideways (Fig. 55.11). The infusion is usually turned on as the tip enters the anterior chamber but it can be turned on before or after entry, depending on the situation and anatomy.


The machine is placed on the Sculpt setting. Continuous longitudinal tip movement is used to aspirate the anterior capsule and shave away a superficial layer of the nucleus. Before shaving, this layer is difficult to see through because of the irregularity created by the two penetrations of the Chang cannula. With better clarity, deeper nuclear detail can then be appreciated as lens dissection progresses (Fig. 55.12). With each quarter turn while creating nuclear quadrants, we create a kind of “spiral” deepening pattern as sculpting shaves through progressively deeper surface levels. An adequate final depth can be reached sometimes in three, but usually five, quarter rotations, but maybe more in very hard cataracts. We try to sculpt symmetrical grooves and thus create symmetrical remaining quadrants. It is important to continually adjust the microscope’s focus as sculpting continues. It is important to maintain a sharp view of the cutting edge of the phaco tip as it encounters the surfaces of the posterior nuclear plate. It takes a total of about 50 microscope pedal adjustments to accomplish an average cataract-IOL surgery.



Grooving starts at the surface and descends to about one-half depth becoming about two tips wide depending on lens hardness (thinner grooves with softer lenses). The initial groove length extends through about half of the distal hemisphere and one third of the proximal. The nucleus is rotated, and a similar process occurs in the newly presented proximal and distal hemispheres, only this time we can go deeper and more peripheral. The groove in the distal half is deep enough when it reaches about a three-fourths depth. The proximal needs to be deepened concurrently to accommodate the needle’s shaft to slide through, but care must be taken not to insult the proximal CCC border in the process. The nucleus is quarter turned and the sequence repeated to three-fourths depth once again. One more quarter turn and that usually completes the deep grooving. For the deeper grooving phase, I find that I always orient the tip obliquely with the tip aperture away from my left shoulder so that I get the best three-dimensional view of the edge of the tip and its aperture and the posterior nuclear plate, which is being approached as well as the portion of the plate that has just been thinned. The spiral down process of creating progressively deeper more peripheral grooves has now been completed (Figs. 55.13, 55.14, 55.15, 55.16).





Fracture of the posterior plate and separation of the quadrants can now be accomplished from the outside toward the center with a cross-hand motion (Figs. 55.17 and 55.18). If the center does not tear through and separate, good visualization with an obliquely oriented 45-degree tip enables even deeper central nucleus thinning. (We think that we sculpt almost to the posterior capsule sometimes but we really never get thinner than 500 µm, as can be demonstrated when sculpting a lens that has been dissected to that level with the femtosecond laser chop cylinder pattern. We hardly ever penetrate that preset laser dissection level.)


May 13, 2018 | Posted by in OPHTHALMOLOGY | Comments Off on Divide-and-Conquer Technique
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