Phaco forward-chop technique for managing posterior nuclear plate of hard cataract

Abstract

 

Surgical management of hard cataracts can be problematic despite improvements in phacoemulsification devices. Phaco chop, considered one of the best techniques for dealing with hard cataracts, cannot always divide the hard cataract completely. We have devised a phaco forward-chop technique that can be implemented safely and efficiently following incomplete phaco chop in a hard cataract.

Financial Disclosure: 

Neither author has a financial or proprietary interest in any material or method mentioned.

Phacoemulsification technology generally allows surgeons to minimize risks during cataract surgery. However, even with phacoemulsification, the management of hard cataracts can be difficult. Successful cataract surgery may depend on how well the surgeon divides the lens nucleus.

Many surgeons^1,2 use the phaco-chop technique in hard cataracts to reduce ultrasonic energy. However, in many cases, the lens cannot be completely divided by phaco chop because of the presence of a leathery posterior nuclear plate. An additional chop may be helpful in these cases. Surgeons may attempt to perform the subsequent chop in an unchopped region of the lens by rotating the lens but may not be able to do this until the posterior segment of the lens is reached. In attempting this, they may chop the posterior capsule as well as the posterior nucleus. The perception that this procedure is difficult may affect a surgeon's ability to handle the phaco chopper, and this increases the likelihood of chopper tears in the anterior capsule, which can result in zonulysis.

We present a phaco forward-chop technique that we believe improves the safety of the surgical management of hard cataracts when the first chop is unsuccessful. Cataract grading used the Emery-Little classification.³

SURGICAL TECHNIQUE

Phacoemulsification is performed through a clear corneal incision or through a scleral tunnel incision with a side port. When a white cataract with a hard nucleus (Figure 1) is involved, the anterior capsule must be visualized using trypan blue⁴ or indocyanine green⁵ staining. With the soft-shell technique,⁶ the anterior chamber is filled with an ophthalmic viscosurgical device.

Figure 1: The hard nucleus with white cortex.

The anterior capsule is opened using the continuous curvilinear capsulorhexis (CCC)⁷ with a diameter of approximately 6.0 mm (Figure 2). Hydrodissection is performed, and the lens nucleus is chopped with a phaco-chop technique. The phaco machine is set at a power of 40% ultrasound with a flow rate of 25 mL/min and a vacuum of 200 mm Hg. If the nucleus does not separate into 2 pieces (Figure 3) with the standard phaco-chop technique, the technique is converted to the forward-chop technique.

Figure 2: The CCC is performed following effective visualization of the anterior capsule facilitated by trypan blue staining.

Figure 3: The nucleus is not completely separated into 2 hemispheres by the phaco-chop technique.

One side of the lens is dislocated forward with the phaco handpiece tip until half the lens is at the level of the anterior capsule. The other side of the lens is fixed with the phaco chopper, which is then slipped into the space between the posterior nuclear plate and the posterior capsule through the crack created by the first chop (Figures 4 and 5). The phaco chopper is located just behind the posterior nuclear plate. The exact position of the phaco chopper prevents damage to the posterior capsule.

Figure 4: One hemisphere is dislocated anteriorly with the phaco handpiece tip until 50% of the nucleus is anterior to the plane of the anterior capsule.

Figure 5: The phaco chopper is slipped through the crack created by the first chop into the space between the posterior nuclear plate and the posterior capsule. The posterior nuclear plate is then chopped from posterior to anterior by the phaco chopper.

The phaco chopper moves in an anterior direction, from an anteroposterior plane located anteriorly to the posterior capsule toward the plane of the anterior capsule. Simultaneously, the wound side (toward the main port incision) of the posterior nuclear plate is fixed with the phaco handpiece tip; ie, the forward chop. Consecutive forward chops are then performed around the remainder of the posterior nuclear plate (Figure 6). After the nuclear plate has been safely removed, the procedure continues in the surgeon's routine fashion.

Figure 6: Consecutive forward chops are performed.

CASE REPORT

A 73-year-old man was referred to our clinic because of visual loss in the right eye. The corrected distance visual acuity (CDVA) was hand motions in the right eye and 0.4 in the left eye. The nucleus sclerosis was classified as grade 5 with white cortex visible in the right eye and as grade 3 nuclear sclerosis in the left eye.

Although the patient had a history of mild trauma to the frontal region, phacodonesis was not clearly seen in the right eye. Because of the history of orbital trauma and the between-eye difference in the nuclear sclerosis density, it was thought the zonules in the right eye might have been mildly compromised.

Cataract surgery was performed in the right eye in January 2009. Trypan blue was used to visualize the anterior capsule. The hard lens could not be divided when the posterior nuclear plate was reached using phaco chop. With forward-chop phaco, the remainder of the nucleus was safely removed (Video 1). Irrigation/aspiration was then performed and a single-piece AcrySof SN60WF intraocular lens (IOL) (Alcon, Inc.) implanted uneventfully.

On the first postoperative day, the CDVA in the right eye had improved to 1.5 and intraocular pressure was unaltered at 12 mm Hg. No corneal edema or Descemet folds were seen. There was evidence of 1+ cells and flare in the anterior chamber.

RESULTS

The forward-chop technique was performed from April 2008 to February 2009 in 8 eyes of 7 patients with hard cataracts that could not be divided completely by the phaco-chop technique because of leathery posterior nuclear plates. The nucleus sclerosis was estimated as grade 4 in 7 eyes and grade 5 in 1 eye.

In all cases, phacoemulsification was safely performed with the forward-chop technique and the IOL was implanted in the capsular bag. No intraoperative complication such as posterior capsule rupture, anterior capsule tears, or zonulysis occurred during surgery, and no postoperative complication such as fibrin formation, synechias, or endophthalmitis was observed in any patient at 3 months.

DISCUSSION

The phaco-chop technique is considered one of the best techniques for surgery of hard cataracts as separating the nucleus into several pieces reduces ultrasonic energy. However, in some cases, separation cannot be easily and safely achieved because of the physically robust nature of the dense posterior nuclear plate of the hard cataracts. Surgeons often try to perform a subsequent chop in an unchopped region of the nucleus by rotating the nucleus but frequently encounter the same problem.

In cases in which the first chop is unsuccessful, the phaco-flip technique⁸ may be beneficial. However, this technique applies significant force to the zonules and, as a result, may be unsuitable in cases in which the zonules are weak.

The forward-chop technique has the following advantages: (1) Chopping forward at the level of the leathery posterior nuclear plate improves the likelihood of safe and adequate nuclear disassembly. (2) Moving the chopper in an anterior direction may reduce the risk for posterior capsule rupture. (3) When adequately large CCC diameters are used, the technique minimizes the force on the posterior capsule and the zonules.

When performing the phaco forward-chop technique in hard cataracts, the following provisos should be remembered: (1) An approximately 6.0 mm capsulorhexis should be created. This will allow less forceful forward dislocation by the phaco handpiece of the inferior nuclear pole, which should minimize zonular trauma. (2) The chopper should be positioned so the chopping blade is posterior to the posterior nuclear plate/nucleus, but moving anteriorly, and therefore is less likely to result in posterior capsule trauma.