9 Stop-and-Chop Phacoemulsification The stop-and-chop phacoemulsification technique entails several simple steps and is a very efficient method for emulsifying the nucleus of any density. Thorough hydrodissection is performed to loosen the nucleus within the bag. Sculpting is performed to prepare space in the middle of the cataract, where the nucleus can be manipulated later on in the procedure. The sculpting should produce a trench in soft and medium-density cataracts and a large crater in dense cataracts. The posterior plate is split, producing two nucleus halves that are free-floating and capable of being manipulated into the space prepared by creating the trench or crater. At this point, nucleus preparation stops and the emphasis shifts to the chop. The nucleus is rotated 90 degrees and the phaco tip is buried deeply into the hemi-nucleus about one third of the way from right to left. The chopper is placed in the periphery of the nucleus and pulled toward the phaco tip. As the instruments reach each other, they are separated, chopping off the nucleus segment. That chopped segment is already impaled on the phaco tip and can easily be emulsified without further manipulation. This step is repeated around the rest of the nucleus, chopping off segments and emulsifying them. The temporal corneal incision should be as square as possible. If the incision is between 2.5 and 3 mm wide, it should also be ∼ 2 mm in length. There are many excellent keratomes designed to make an incision of this proportion. The keratome is designed to be moved in a straight line from external to internal. If the blade is wiggled slightly to the left or to the right during incision construction, the sides of the incision can be nipped and “winged.” When this happens, the central length of the incision could still be the full 2 mm, but the effective side length might be only 1 mm. This is an inadequate incision, and it is a source of fluid leakage and unsatisfactory incision closure. Stromal hydration could be enough to seal this part of the incision, but sometimes a suture is required to make it secure. A persistent and vexing problem is the capsulotomy that has a mind of its own and insists on going where it is not supposed to go. To avoid this problem, we must understand the anatomy of the anterior lens and capsule. The anterior capsule is convex. The center of the capsule is an apex surrounded by down-sloping sides. When the capsulorrhexis is being made, there is a tendency for the tear to extend down toward the periphery. That is a normal reaction in a curved surface—things go downhill. This tendency is avoided by adequately filling the anterior chamber with viscoelastic to flatten the anterior capsule. This eliminates the tendency for the downward/outward movement of the tear because it eliminates the “down.” When a capsulotomy starts to drift toward the periphery, the treatment is the same: add viscoelastic and increase the pressure in the anterior chamber to flatten the capsule so that the tear can be redirected. Phacoemulsification is performed more easily and safely when the nucleus is free to rotate within the capsular bag. Firm cortical capsular adhesions restrict this rotation and can stress the zonules or the bag itself when rotation is attempted. Avoidance of zonulysis and capsule rupture is facilitated by reliable means of nucleus capsule dissection. Fluid hydrodissection is the first and most reliable way to loosen the nucleus. There are many cannulas that permit hydrodissection by injecting a stream of fluid across the posterior capsule. In most patients, these fluid waves are predictable and provide thorough hydrodissection. In some instances, however, dissection does not occur under the incision. What appeared to be a strong fluid wave did not achieve total dissection so that the nucleus is reluctant to rotate. One solution to this problem is to slip a cannula under the anterior capsule from the side port and irrigate more fluid directly under the incision. Another solution to avoid this situation is to begin hydrodissection directly under the incision. This could be performed with a J-shaped cannula, but in my experience the cannula is sometimes difficult to remove because the tip can get caught on the lip of the incision. A better option is the cannula designed by Leif Corydon for viscoexpression of the nucleus. This cannula was designed for hydrodissection, viscodissection, manual dissection between the nucleus and the posterior capsule, and even to hook into the underside of the nucleus and pull it from the eye. The Corydon cannula can also be used for hydrodissection of a nucleus within the bag. Its tip is angled back ∼ 150 degrees so it is easy to pass under the subincisional capsule and it is also easily removed from the anterior capsule without getting caught on the lip of the incision. To perform subincisional hydrodissection, the cannula is first directed under the subincisional capsule. It can be lifted slightly to tent the capsule off the nucleus. With firm but gentle injection, a fluid wave will be generated that will pass around the equator of the nucleus from near to far. After passage of the fluid wave, the cannula can be placed on the top of the nucleus and pressed down against it. This pushes the nucleus posteriorly, against the posterior capsule, squeezing the excess fluid around the equator, thus facilitating cortical cleavage. The cannula can then be rotated so its tip is buried in the nucleus, just inside the capsulorrhexis. The embedded tip can then rotate the nucleus. This effectively completes total separation of the nucleus from the bag. The disruptions of the nucleus/cortical/capsular adhesions make aspiration of cortex during irrigation and aspiration (I/A) easier. The rotation of the nucleus within the capsular bag is a visual check that the hydrodissection is complete. At times it is necessary to elevate the nucleus out of the capsular bag. An example is significant zonulysis with poor bag integrity. The Corydon cannula is excellent for lifting the nucleus into the anterior chamber without turning it over. This technique requires a capsulorrhexis that is at least 5 mm in size for soft cataracts; slightly larger is better. If the cataract is very dense, the largest capsulotomy possible is suggested, even a can-opener capsulotomy if needed. The Corydon cannula is placed under the subincisional capsule and a fluid wave is generated as described above (Fig. 9.1a). Irrigation is continued slowly until the superior pole of the nucleus lifts out of the bag. Once this occurs, the Corydon cannula is rotated so that the curve is horizontal and parallel to the posterior capsule. Irrigation is continued while the smooth curve of the cannula is gently pushed between the posterior capsule and the nucleus. This manually hydrodissects the nucleus from the capsule. Throughout this maneuver the cannula is slightly lifted to prevent it from catching on the capsule (Fig. 9.1b). When the cannula reaches a position more than halfway across the posterior aspect of the nucleus, it is rotated once again so that the tip of the cannula is now lifted up and impaled into the underside of the nucleus. The cannula is gently lifted and tugged toward the incision. The nucleus, now hooked by the cannula, will lift out of the capsular bag (Fig. 9.1c). The cannula tip is then freed with the application of a little irrigation. Disengaged, it is slipped out from under the nucleus and removed from the eye. This one-step maneuver for hydrodissection and for lifting the nucleus into the anterior chamber is safe when used with an adequate capsulotomy. The constant irrigation pushes the posterior capsule rearward, separating it from the nucleus, and creating sufficient room for the cannula to fit between them. The smooth, rounded curve of the cannula advancing under the nucleus tends to move freely without catching either the nucleus or the bag. There are situations in which hydrodissection is inadequate or should not be performed, such as in a posterior polar cataract with capsular involvement. In these conditions, manual dissection is an alternative method for nucleus loosening. The Minami M-hook is an ingenious device for this. This instrument has a rounded distal tip designed to rub against the posterior capsule without breaking it. The various curves of the tip are designed so that the surgeon, by moving fingers or wrist, can direct the hook in almost any orientation within the eye. It can be placed around the lens equator and rotated 270 degrees, giving effective manual dissection of the nucleus from cortex and capsule. The M-hook can also be simultaneously lifted to enhance nucleus separation. This hook is also shaped for dividing the nucleus and for holding the capsular fornix stable in the axis of a zonulysis. I use the M-hook as an adjunct to hydrodissection. Minami uses it instead of hydrodissection (Fig. 9.2).
Technique Overview
Problems During the Procedure
Damaging the Sides of the Corneal Incision
Controlling the Capsulorrhexis
Hydrodissection
Maneuvers to Elevate the Nucleus Out of the Bag
Manual Dissection
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