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Up Front | Sep 2007

Cataract Surgical Techniques

An evaluation of the safety and potential dangers associated with broad phaco technique categories.

Capsulorrhexis is often said to be one of the most significant recent developments in cataract surgery, and its importance lies in two areas. First, it allows for a safe, secure, and centered IOL placement. Second, the constraints it placed on prior cataract removal techniques has led to major developments and changes in cataracts removal. Because earlier techniques made it difficult to prolapse the whole nucleus/epinucleus complex into the anterior chamber through a capsulorrhexis—particularly if the diameter was small, as was common in the early days—the concept of nulceofractis was born. Interestingly, some surgeons have since reverted to nonnucleofractis techniques. This article (1) reviews the principles involved in different cataract removal techniques and (2) comments on areas of safety and/or potential dangers associated with each technique.

I. Howard Fine, MD, of Eugene, Oregon, described the chip and flip technique in 1991. He achieved nucleofractis by concentric division of the lens into the central nucleus, epinucleus, and cortex, tackling each layer in turn from the inside out. The concept of hydrodissection and hydrodelineation were relatively new then, and it became important only once capsulorrhexis was developed.

The key step in this technique is hydrodelineation (ie, the injection of balanced salt solution into the lens to develop a cleavage plane between the endo- and the epinucleus). With the endonucleus mobilized within the capsule, it is chipped away with phaco power from the outside in, leaving the epinucleus/cortex complex to protect the posterior capsule. Once the endonucleus is removed, the epinuclear rim is trimmed in three of four quadrants. The epinuclear rim of the fourth quadrant is then used as a handle to flip the epinucleus. It is claimed that during this process, if cortical cleaving hydrodissection has been performed, most of the cortex is removed with the epinucleus.

Safe points.
The nucleus remains within the confines of the capsule, and all phaco is done behind the iris plane. Flipping the epinucleus is efficient and safe for the capsule and may also be used in most of the techniques described herein.

Potential dangers.
The main problem, similar to that of divide and conquer (see description below), is that it uses raw phaco power to consume the nucleus. This is not, however, the most efficient way to deal with it.

In 1990 and 1991, John R. Shepherd, MD, FACS, of Las Vegas, and Howard V. Gimbel, MD, MPH, FRCSC, FACS, of Alberta, Canada, described this technique. Divide and conquer, still one of the most widely used techniques, achieves nucleofractis by radial division of the lens.

Two grooves, intersecting at right angles, are made in the nucleus (Figure 1). The grooves need to pass deeply into the nucleus; most teach that this sculpting should go so deep that the red reflex (which becomes dull and grey as the phaco tip passes through the nucleus) brightens and becomes red again. A second instrument is then placed into one groove alongside the phaco tip. The two instruments are separated, stretching and ultimately cracking the remaining nucleus/epinucleus to produce two separated half-nuclei (Figure 2). Each half is, in turn, fractured into two quarters. The resultant quadrants are then consumed.

Safe points. Divide and conquer is a relatively easy technique to learn. Its main feature is both the division of the nucleus into smaller pieces and creation of space in the center of the lens. The quadrants may, therefore, be pulled out of the periphery of the capsular bag and into the central space (ie, safe zone) for consumption. This avoids the potential dangers of working in the periphery of the capsule and/or near the iris margin. Furthermore, the reduced quadrant sizes are easier to manipulate within the capsule. Most manipulation and phaco power application occurs behind the iris plane.

Potential dangers.
Care needs to be taken when sculpting up to—and potentially beyond—the rhexis margin/iris sphincter so as to not cause damage. Also, if sculpting is attempted with too little phaco power, the nucleus may be pushed ahead of the phaco tip instead of being cut by it. This leads to zonule stress and potential rupture, particularly in the subincisional area (ie, 180º away from where the nucleus is being pushed).

The main drawback of divide and conquer is its use of raw phaco power to remove a significant portion of the lens. Less than half the volume of the nucleus is left for phaco-assisted aspiration, and increased phaco energy delivery has been correlated with side effects including greater endothelial cell loss. Modern power modulations, however, may reduce the amount of energy used.

With soft cataracts, the inexperienced surgeon may unexpectedly sculpt through the nucleus too rapidly, as well as aspirate and possibly phaco the posterior capsule. The fear of sculpting too deeply produces another potential problem, where the surgeon has difficulty cracking the nucleus because the central trench is not deep enough. This may produce excessive zonule strain and rupture, which may lead to a cascade of problems.

In 1993, Kunihiro Nagahara, MD, of Sakaide City, Japan, introduced—via the American Society of Cataract and Refractive Surgery (ASCRS) film festival—the revolutionary concept of directly chopping the nucleus. He asserted, which has subsequently been confirmed by all who have mastered chopping, that this was the quickest and most efficient way to divide the nucleus into small pieces for consumption by the phaco probe. Since then, other surgeons have introduced variations on the phaco chop theme, and a variety of exotic names are applied to these techniques. I favor the approach of David F. Chang, MD, of Los Altos, California, which is to classify the techniques into horizontal and vertical chop.

Horizontal chopping.
Dr. Nagahara's original method involves first impaling the nucleus center with the phaco tip, usually using short bursts of phaco. The chopper instrument is then passed underneath the capsulorrhexis edge and out to the equator of the nucleus. Ensuring that the tip of the chopper is oriented downward, it is slowly dragged through the nucleus toward the phaco tip. The radial orientation of the lens fibers ensures that a natural radial cleavage plane is produced in the nucleus. When the chopper and the phaco tip are almost touching, the two instruments are separated horizontally (Figure 3) to propagate the cleavage plane past the center—and usually to the opposite equator. The phaco tip is disengaged from the nucleus, which is then rotated through 30º to 90º, depending on nucleus hardness and surgeon preference. The entire procedure is repeated until the nucleus is divided into the appropriate number and size. These individual pieces are then consumed using phaco-assisted aspiration.

Vertical chopping.
This modification involves burying the phaco tip further into the nucleus to ensure a good purchase. The silicone sleeve should be retracted sufficiently to allow the tip to reach the vertical center of the nucleus. The chopper instrument, usually a sharp-tipped chopper, is then placed on top of the nucleus, just in front of, or to the side of the phaco tip. Firm downward pressure with the chopper is used, with upward counterpressure from the phaco tip to initiate a fracture, which is then propagated by a simultaneous horizontal parting of the instruments. This is essentially a three-dimensional movement, unlike the two-dimensional horizontal chop. Again, the nucleus is rotated, and chopping is repeated as many times as required.

Prechop. Devised by Takayuki Akahoshi, MD, of Tokoyo, in the mid 1990s, prechop is a vertical chop variant. A specially designed karate prechopper with two narrow blades is inserted into the top of the lens, and once the appropriate depth has been achieved, the blades are parted to produce a through and through split of the nucleus. The nucleus is then rotated in the same manner as other techniques, and prechop is repeated to create anything from four to eight sectors.

Safe points for all phaco chop techniques.
Less phaco power and time are needed to achieve lens removal. Manual energy, generated by one instrument pushing against the other, replaces the need for ultrasound energy to subdivide the nucleus. Because the nucleus is being impaled and held by the phaco tip and compressed between the two instruments in horizontal chopping, there is less stress on zonules. All forces are directed centrally inward and away from the zonules, rather than outward toward the zonules and capsule with sculpting.

Potential dangers. The main danger is damage to the anterior capsule and/or zonules by a misplaced chop instrument. If the chopper is passed to the equator anterior to the rhexis, considerable damage may be done. The danger is considerably reduced if the superficial cortex within the rhexis margin is first removed from the lens, giving the surgeon a clear view of the interface between cortex/epinucleus and endonucleus. The chopper tip can then be safely inserted at the level of that interface (Figure 4).

With vertical chopping, particularly in harder cataracts, it is possible to push too hard posteriorly without appropriate upward counterpressure from the phaco tip. With prechopping, there is no phaco needle to give counterpressure, however, this could lead to zonule stress or posterior capsule rupture. Again with harder nuclei, the chopped pieces can remain interlocked within the capsule like jigsaw puzzle pieces. These are particularly difficult to mobilize for consumption. A little additional sculpting in the center can remove sharp interlocking edge(s) of the pieces. Many surgeons feel uncomfortable with the concept of passing the chopper out to the equator of the lens without direct vision at all times.

With both chopping styles, it can be difficult to ensure that the tough posterior nuclear plate has been properly chopped in dense brunescent cataracts. These usually also have thick nuclei.

As indicated above, it can prove difficult—especially for an inexperienced surgeon—to disentangle the interlocking pieces of a chopped hard cataract. In 1993, Paul S. Koch, MD, of Rhode Island, described the stop and chop technique, which is essentially an amalgam of divide and conquer and phaco chop. In this technique, a single central groove/trench is sculpted, and the nucleus is split into two halves. At this point, sculpting is stopped, and the technique changes to chop. Each heminucleus is chopped into two, three, or four pieces. Stop and chop is useful because it acts as a transition stage for those who wish to convert from divide and conquer to phaco chop.

Safe points. Sculpting the initial trench creates space into which the heminucleus can be pulled. In this way, a space is created peripherally to allow placement of the chopper under direct vision (Figure 5) as well as easy disentangling of potentially interlocking nucleus pieces. This is more efficient (ie, less phaco power is used), and there are fewer potential strains on the zonule than with full divide and conquer.

Potential dangers. As stated above, it does use more phaco power than pure chopping. The danger of damage to the capsule/zonule from an improperly placed chopper is reduced, but it is still present.

Around 1995, David C. Brown, MD, FACS, of Fort Myers, Florida, described phaco flip. Subsequently, William F. Maloney, MD, of Vista, California, also promoted it as supracapsular phaco. Dr. Brown describes it not as nucleofractis technique, because the nucleus and often epinucleus are prolapsed from the capsule during hydrodissection. Many surgeons experience moments during hydrodissection when the nucleus begins to prolapse from the capsule, and the usual response is to reposit the lens into the bag.

Phaco flip actually encourages the prolapse. As the distal nucleus equator comes forward out of the bag, the proximal pole is pushed backward and downward—either by the hydrodissection cannula or by viscoelastic expression—resulting in the lens tumbling through 180º. If the lens has come anterior to the iris, it is reposited behind the iris into the supracapsular space. Some surgeons then chop the lens into smaller pieces, however, Dr. Brown advocates debulking the single piece of nucleus, much like chip and flip.

Safe points. The author of the technique states that its main selling point is that the nucleus is not broken up, and there is no danger of nucleus pieces floating around the anterior chamber to potentially damage the cornea. The nucleus stays in one piece and is more easily managed. By bringing the lens removal out of the bag and away from the posterior capsule, the chance of posterior capsule rupture is reduced.

Potential dangers.
Many surgeons feel that having the whole nucleus out of the capsule presents its own inherent dangers. There is more chance for the nucleus to push into the zonules and cause potential damage than if the nucleus is constrained within the capsule. The main danger with this technique is damage to corneal endothelium, which is caused by the phaco being more anterior compared with endocapsular techniques. Many surgeons have tried and abandoned this technique for that reason, although advocates maintain that once mastered, the technique does not cause a real problem.

In 2004, José L. Güell, MD, PhD, of Barcelona, Spain, described another modern nonnucelofractis technique suitable for softer nuclei, called the phaco roll. Dr. Güell recommends patients aged 65 years or less for this technique, which is dependent on thorough hydrodissection and hydrodelineation. It is essential to assure that there is free rotation of the nucleus within the bag at the outset. The phaco tip is then placed at the edge of the capsulorrhexis, the opening is directed to the nucleus/epinucleus interface, and aspiration is applied (Figure 6). This technique relies on phaco-assisted aspiration, and as the edge of the nucleus is aspirated, it slowly rotates and is removed from the outside to the inside, until a small central nucleus remains.

Safe points. The nucleus remains in the capsule, and there is minimal movement of the phaco tip. Therefore, compared with phaco flip, the risk of endothelial cell damage is reduced. Because there is no deep sculpting, the risk of posterior capsule rupture is also minimized. Dr. Güell states that he uses 20% to 40% less phaco time and power than with his prior technique, which we may assume to be either divide and conquer or stop and chop.

Potential dangers. The technique depends on free rotation of the nucleus within the bag, and if unachieved, problems could arise. The phaco tip is maintained close to the rhexis edge, and there is a danger of damage, potentially leading to anterior capsule tear and extending posteriorly.

This is a brief overview of the main broad phaco technique categories. Many variations have been described in the past 17 years, and all have benefits and drawbacks. Otherwise, we would all use the one truly safe and efficient technique. The commentary about safety and potential danger represents my broad views on the relative merits of each technique, and others may differ in their assessment. It is hoped, however, that this summary provides some ideas about the techniques and stimulates the reader to analyze their own surgery, maximize the safety, and minimize the dangers of their individual technique.

David Allen, BSc, FRCOphth, is a Consultant Ophthalmologist specializing in cataract surgery at Sunderland Eye Infirmary, in England. Dr. Allen states that he has no financial interest in the companies or products mentioned. He may be reached at +44 191 5699071; Allen401@btinternet.com.