STOP AND CHOP PHACO

Paul S. Koch

TECHNIQUE OVERVIEW

The stop and chop phacoemulsification technique consists of several simple steps and is an efficient method for emulsifying the nucleus. Thorough hydrodissection is performed to loosen the nucleus within the bag. Sculpting is performed to prepare space in the middle of the cataract in which 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, effectively chopping off the nucleus segment. That segment is already impaled on the phaco tip and can be emulsified without further manipulation. This step is repeated around the rest of the nucleus, chopping off segments and emulsifying them.

PROBLEMS DURING THE PROCEDURE

DAMAGING THE SIDES OF THE CORNEAL INCISION

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 about 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 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.

CONTROLLING THE CAPSULORRHEXIS

A persistent and vexing problem is the capsulotomy that insists on going where it is not supposed to go. To avoid this it is important to 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’s 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 is being performed and the tear 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 cause stress on the zonules or on 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 reliable 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 nucleus is reluctant to rotate.

One solution to this problem is to enter the anterior capsule (AC) 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 the cannula may be difficult to remove. Its tip has a tendency to 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 can be used for hydrodissection, viscodissection, and manual dissection between the nucleus and the posterior capsule, and even to hook into 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 about 150 degrees so it is easy to pass under the subincisional capsule. It is also easily removed from the AC 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 can be generated. The wave will pass around the equator of the nucleus and tends to be prominent and vigorous, creating superb separation.

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 posteriorally, 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, used like a fulcrum, 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.

MANEUVERS TO ELEVATE THE NUCLEUS OUT OF THE BAG