Phaco-Chop Procedure: Management and Complications

11   Phaco-Chop Procedure: Management and Complications

Brian A. Hunter

The age- and sex-adjusted rates of cataract surgery between 1980 and 2011 have increased fivefold, to over 1,200 cases per 100,000 people.1 These rates are expected to rise with the aging of the baby-boomer population and increases in second eye cataract surgery due to improved outcomes.2 Given this increase in surgical rates, one may assume that the most efficient and effective means of performing cataract surgery would be clearly understood, and teaching it would be streamlined throughout residency programs. But this is not the case. Graduating from ophthalmology residency, many surgeons are comfortable with conventional techniques like divide and conquer3 or stop and chop,4 but they have little or no experience in phaco chop.5

There are numerous advantages to using the phaco-chop technique, but few surgeons employ this technique.6 I assert that one answer may be simply the fear of the unknown. Anyone practicing the phaco-chop technique should be familiar with the management of several seen and unseen complications that arise frequently7; the ten most common complications that may occur during phaco-chop surgery for beginning surgeons are the following, and they are addressed in this chapter: (1) small capsulorrhexis; (2) inadequate hydrosteps; (3) a lens that does not spin; (4) poor control of the foot pedal, resulting in capsular damage; (5) the use of too much phaco energy in a soft nucleus; (6) not using enough phaco energy in a hard nucleus; (7) failure to remove the anterior epinucleus and delineate the capsulorrhexis edge; (8) the phaco tip placed too far off the center of the nucleus, resulting in tipping or flipping of the nucleus; (9) incorrect placement of the horizontal chopper (such as Seibel) anterior to the capsular bag; and (10) not knowing when to use a vertical, horizontal or hybrid, chopping technique.

This chapter: (1) provides some simple strategies for the beginning phaco surgeon to recognize, avoid, and manage common complications; (2) discusses how to minimize risks for complications, specifically in very soft and in very hard and leathery cataracts; (3) addresses additional complications associated with femtosecond laser–assisted cataract surgery (FLACS); and (4) presents alternatives to techniques previously discussed in the management of anterior chamber (AC) tears or zonular dialysis.

Small Capsulorrhexis

The ideal size of an anterior capsulotomy has been debated extensively, and it depends on a multitude of factors. But creating a consistently round and continuous anterior capsulotomy is a critically important early step in preventing complications from the phaco-chop procedure. Broadly speaking, the continuous curvilinear capsulorrhexis (CCC) should be between 5 and 6 mm in diameter, with most phaco-chop surgeons preferring 5 to 5.25 mm for most cases.8 There may be situations where a larger rhexis of up to 6 mm is needed in extremely dense nuclear sclerotic lenses, or smaller than 5 mm in white mature cortical cataracts under pressure. A CCC less than 4 mm usually necessitates avoidance of horizontal chop techniques and requires enlargement after placement of the intraocular lens (IOL). With the advent of FLACS, there is significantly more control not only of the size of the rhexis (often around 5 to 5.25 mm) but also of the location of the rhexis, which can be chosen to be centered over either the visual or the pupillary (anatomic) axis. This has some obvious benefits to the cataract and refractive surgeon in lens choice, but does not significantly affect the process of nuclear disassembly by the phaco-chop technique. The stability and integrity of the anterior rhexis is critical to good outcomes using phaco chop, and any weakness or irregularity can force the phaco-chop surgeon to change course and use another technique (e.g., changing from horizontal to vertical chopping) to avoid tears and resultant complications.9 Management of AC tears will be discussed separately.

Inadequate or Incomplete Hydrosteps

Hydrosteps were discussed in great detail in Chapter 7, but I cannot stress enough the importance of adequate hydrodissection and hydrodelineation to the phaco-chop surgeon. Inadequate hydrodissection can result in inadvertent zonular dialysis during lens rotation.10 Poor or incomplete hydrodelineation can result in improper positioning of the chopper proximal to the epinuclearnuclear plane, resulting in posterior displacement of the lens and possible posterior chamber (PC) rupture or zonular dialysis. Positioning the chopper distal to this plane can lead to peripheral capsular puncture and vitreous loss.

A Cataractous Lens that Does Not Spin

Many surgeons are easily frustrated when they are unable to obtain an adequate hydrodissection and rotation of the phakic lens. Repeated attempts using large volumes of balanced salt solution (BSS) is not always successful and is often counterproductive. (We all know the adage that doing the same thing over and over again but expecting different results is the definition of insanity.) Incomplete hydrosteps may be due to the surgeon’s inexperience or overabundance of caution, but may also be a result of certain lenticular pathologies, such as in patients with zonular laxity or dehiscence, a soft nucleus, highly myopic eyes, or pseudoexfoliation.10 Often these conditions, if not diagnosed preoperatively, will only become evident during hydrodissection, but many times more significant zonular compromise may not become clear until after initial chopping (Fig. 11.1). What should the surgeon do if the lens still does not rotate even after the first piece has been removed? Two techniques can make a big difference: The first is manual chopping of pieces with the second instrument and subsequent phacoemulsification to increase space within the capsular bag. The goal is to methodically remove the first hemi-nucleus segment by segment. Alteration of the fluidics and the increased amount of irrigation of the remaining segment as a result of achieving this goal will often produce enough separation to enable the remaining hemi-nuclear segment to rotate. But what if it still won’t rotate? In this circumstance, it is advisable to take a deep breath and proceed with plan B: hemi-nuclear lift and carry. Leaving quadrant removal mode and returning to the phaco-chop setting, the phaco tip is impaled into the subincisional nucleus, which is subsequently lifted and carried into the desired position. The lift is a move in which the segment is impaled and then elevated anteriorly and centrally. The carry is accomplished by carefully pushing the impaled segment in a direction opposite the main incision while concomitantly rotating in a clockwise direction (Fig. 11.2). This lift-and-carry technique often creates sufficient movement to break the few adhesions to the capsular bag and allow the hemi-nucleus to rotate in a desired position directly opposed to the main phaco incision. Aggressive hydration or even viscodissection can be employed if the above techniques fail.

Phaco Chop in a Soft Nucleus: The “Manual-Chop” Technique

How should the dreaded soft nucleus be managed? Once a horizontal chop technique is mastered, it is possible to remove a very soft cataract or, in the case of a refractive patient, a clear lens, without significant trouble. Most beginning choppers dread the soft nucleus because the usual techniques of chopping in a 2 to 3+ nuclear sclerotic cataract (NSC) no longer apply. In very soft cataracts, overuse of the aspiration or phaco ultrasound mode will easily “eat” through a soft nucleus and risk perforating the capsular bag.11 In these cases, its possible to avoid using any aspiration or vacuum during the phaco chop maneuver. By positioning the phaco tip against the nuclear segment to produce sufficient countertraction, the nucleus is stable enough to enable correct placement of the second instrument into the epinuclear–nuclear plane. This manual chop technique enables efficient disassembly of the nucleus and epinucleus.

Failure to Delineate the Anterior Chamber Rhexis Edge, and Removal of the Central Anterior Epinuclear Shell

In most cases, after completing the capsulorrhexis, it is advisable to delineate the borders of the capsulorrhexis by aspirating the central anterior epinuclear shell using the phaco needle. This can be performed using either the sculpt or chop settings with a phaco tip of any angle. Usually a modest application of aspiration is required to complete this step. Of course, this step should be skipped in white mature cataracts, not only because of the scarcity of epinucleus in this setting, but also because attempting the maneuver may lead to excessive posterior pressure, resulting in submarining of the nucleus or the releasing of counterpressure that may induce anterior displacement of the nucleus, in turn resulting in the dreaded Argentinian flag sign.12

Information about the cataract density and zonular stability is gained during proper performance of this initial epinuclear cleanup and can help determine the most desirable chopping technique and phaco power requirements. The density of the cataract can be assessed either by the color (white, brown, or black) or by manual depression of the phaco tip into the anterior nucleus 3+ to 4+ NSC lenses that leave “ice skate marks” on the hard surface, whereas softer lenses leave “knife in jello”–like stab wounds.

Choosing Between Horizontal and Vertical Phaco-Chop Techniques and Common Pitfalls of Each

Horizontal Chop Phacoemulsification

Horizontal chop requires a small amount of horizontal displacement of the lens centrally during chopping and quadrant removal. To minimize the amount of displacement, each quadrant should be removed immediately after it is created. After a few pieces have been removed, there will be more space in the capsular bag to enable the remaining nuclear remnants to be removed without having to blindly chop in the peripheral capsular bag. In certain phacoemulsification platforms, settings can be maximized to increase the efficiency of the phaco-chop technique by obviating the need to select between chop and quadrant removal settings on the foot peddle during nuclear disassembly.

Horizontal Chopping Technique

In horizontal chopping, the chopper is placed at the epinuclearendonuclear junction and repositioned horizontally to perform the chop.

In all chopping procedures the superficial nuclear cortex is removed immediately after entry of the phaco tip into the AC.

The maneuver is initiated by introducing the phaco tip, in position 1 (irrigation only), bevel down, to position it over the middle third of the subincisional nucleus. Phaco power is commenced introducing the needle into the body of the nucleus paracentrally. Foot pedal position 3 is employed to ensure that the phaco tip is completely plunged into the lens nucleus. Prior to entering the eye, the irrigation sleeve should be withdrawn 1 to 1.5 mm from the bottom of the bevel to enable the needle to adequately impale the nucleus. Phaco power is used until the needle is buried within the nucleus. Immediately upon passing the tip into the nucleus up to the sleeve, phaco power is terminated and the needle holds the nucleus with vacuum only (foot pedal position 2).

The chopper is passed through the side port, rotated so that the chopping tip is iris parallel, and is placed at the anterior capsulorrhexis margin (Fig. 11.3). The phaco tip is pulled horizontally toward the incision, continuing to hold vacuum in foot pedal position 2. This predictably will split the endonucleus from the epinucleus, creating a cleavage plane. When this plane is sufficiently visualized, the chopper is rotated to vertical and positioned into the plane (Fig. 11.4).

The two instruments are, at this point, positioned for chopping (Fig. 11.5). Maintaining vacuum in the phaco tip, the tip is pushed up and to the right, thus elevating the endonucleus and moving it right.

The chopper is pulled toward the wound slightly and then moved down and to the left. The shearing force thus produced will crack the nucleus. The crack may or may not extend partway through the nucleus toward the incision. The chopper can be repositioned more centrally to enlarge the crack toward the incision, if preferred (Fig. 11.6).

The vacuum is released (foot pedal position 0), and the chopper and phaco tip are used to rotate the nucleus counterclockwise 10 to 30 degrees, depending on the density of the nucleus. Generally, smaller rotations for a harder nucleus and larger rotation for a softer nucleus are indicated.

It is now straightforward to visualize the thickness of the endonucleus. Using position 3 with phaco power, once again the phaco tip is buried into the nucleus. The minute the phaco tip impales the nucleus solidly, and the tip is buried to the depth of the irrigation sleeve, the ultrasonic energy is turned off and vacuum is used exclusively to hold the nucleus. Once again the chopper is placed horizontally at the rhexus edge and then rotated to vertical and dropped into the endonuclear–epinuclear cleavage plane created by withdrawing the phaco tip toward the incision, with adherent nucleus affixed. Just as previously described, the phaco tip, in position 2, vacuum only, is pushed up and to the right and the chopper pulled down and to the left, producing another crack and resulting in formation of a pie-shaped segment (Fig. 11.7).

In a soft or moderate nucleus, the pie-shaped segment can be mobilized, elevated to the pupillary plane, and emulsified (Fig. 11.7). In a hard nucleus, it is advantageous to continue rotating and chopping for 360 degrees. This will create multiple small pie-shaped segments, until the nucleus loses its inflexibility. At this point removal of the segments is expedited.

Vertical Chopping

Vertical chopping by definition minimizes the risks of peripheral capsular tears that can occur during horizontal chopping, by keeping the vertical chopper at or near the anterior rhexis edge during each chop. In contrast to the horizontal chop technique, during vertical chopping it is recommended to leave each piece in place until the entire nucleus has been chopped. Then each piece can be removed with minimal movement of the capsular bag or stress on the zonules.

Vertical Chopping Technique

The major principles previously explained are utilized with vertical chopping. The foremost difference in technique is that the creation of the endonuclear–epinuclear cleavage plane is unnecessary. Additionally, it is not necessary to place the chopper in the plane where the nucleus is thinner and the posterior capsule closer to the chopping instrument. Even more important is that it may be difficult to visualize the endonuclear–epinuclear plane when the pupil is small. This is not necessary with vertical chopping, making this variation of the procedure stress-free and safe.

In vertical chopping the phaco tip is prepared comparably to horizontal chopping and passed into the paracentral nucleus in the same way. Again, once solidly within the substance of the nucleus, position 2, vacuum only, is used to hold the nucleus on the phaco tip. The major difference in technique occurs at this point, as the chopper, passed through the side port is positioned vertically and hovers over the nucleus near the phaco tip. The phaco tip is now gently elevated vertically, remaining in position 2. The chopper is driven downward, into the nucleus adjacent to the phaco tip. Once the chopper is entirely embedded within the nuclear substance, the phaco tip is moved up and to the right and the chopper down and to the left, thus cracking the nucleus (Fig. 11.8).

May 13, 2018 | Posted by in OPHTHALMOLOGY | Comments Off on Phaco-Chop Procedure: Management and Complications
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