Cataract Surgery, 3rd Edition

PART V – Special Techniques for Cataract Extraction

Chapter 28 – Dense Brunescent Cataract

Roger F. Steinert, MD


Contents

  

   

Anterior Capsular Staining

  

   

Protecting the Endothelium and the Posterior Capsule (The “Visco Vault”)

  

   

The “Leathery” Posterior Nucleus

  

   

Special Instruments

CHAPTER HIGHLIGHTS

  

   

Selecting the best ophthalmological viscosurgical device to protect the cornea

  

   

The “Visco Vault” to protect the posterior capsule

  

   

Surgical maneuvers for the leathery posterior nucleus

A darkly brunescent nucleus, with the color of molasses or a cola soft drink, presents special surgical challenges. First the surgeon must select the basic surgical strategy. Depending on a surgeon's experience, the details of the patient's pathologic condition, and the treatment goals, the patient may be best served by phacoemulsification, by extracapsular cataract extraction, or by referral to a surgeon with experience and good results in phacoemulsification of dense nuclei.

Paradoxically, patients with particularly strong indications for small-incision phacoemulsification are often the patients who present with these advanced, technically challenging cataracts. A common clinical scenario is a patient with one functional eye who was told by an eye doctor decades earlier, “Don't let anyone touch your good eye.” Today, such a patient is often better served by small-incision phacoemulsification surgery under topical anesthesia, retaining the use of the good eye. Other patients with a particular indication for small-incision cataract surgery include high myopes, at risk for scleral collapse or with liquefied vitreous inhibiting nuclear expression in extracapsular extraction, and high hyperopes who may have microphthalmos or nanophthalmos, with increased risk for positive pressure vitreous loss and/or choroidal effusion (see Chapter 33).

If phacoemulsification is thought to be the best alternative for the lens extraction, several special aspects of cataract surgery in this setting are important to maximize the probability of a successful outcome in the presence of a densely brunescent cataract.

Anterior capsular staining

Staining the anterior capsule is a critical step in performing successful phacoemulsification cataract surgery in situations in which the red reflex is insufficient to allow adequate visualization of the anterior capsule edge. In addition, a stained peripheral anterior capsule facilitates later phacoemulsification. The surgeon who can see the anterior capsule edge is less likely to nick it with the ultrasound tip or misplace a phaco chopping instrument on top of the anterior capsule.

The technique for anterior capsule staining is illustrated in detail in the chapter on the intumescent cataract (see Chapter 27).

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Protecting the endothelium and the posterior capsule (the “visco vault”)

The protection of the corneal endothelium is especially important in phacoemulsification of dense nuclei, for which the surgery is prolonged, more manipulation is required, and more ultrasound power is employed. The corneal endothelium in such cases is often clinically “stressed” on the first postoperative day, with striae of Descemet's membrane and stromal edema.

In addition to meticulous surgical technique, protection of the endothelium is best achieved by a dispersive, retentive ophthalmic viscosurgical device (OVD) (see Chapter 6).

Cohesive viscoadaptive devices, typically high-molecular-weight hyaluronic acid, often are flushed out of the anterior chamber within several seconds of initiating phacoemulsification. The dispersive agents (most commonly Viscoat [Alcon] and Healon D [AMO]) are more likely to be retained as a protective layer against the endothelium.

Dispersive, retentive viscoadaptive agents can also be used to create an artificial epinucleus to protect the posterior capsule. A dense brunescent cataract usually has little to no epinucleus; the epinucleus has stiffened and become part of the nucleus. The posterior capsule, therefore, has no protective layer to guard against laceration from the sharp and bulky nuclear fragments. In addition, the posterior capsule is usually thinner and more vulnerable because the advanced cataract has stretched the capsule as the cataract expanded.

A helpful maneuver is to pause the phacoemulsification once enough of the nucleus has been removed to expose a small portion of the posterior capsule, heralded by the appearance of a “window” of bright red reflex. The viscoadaptive agent is injected between the posterior capsule and remaining nucleus. This creates an artificial epinucleus, physically separating the posterior capsule from the nucleus undergoing phacoemulsification. I call this maneuver the “visco vault” because the OVD acts like a protective wall, or “vault,” to protect the posterior capsule.

In addition, the viscoadaptive agent stabilizes the remaining nucleus, reducing tumbling of the nuclear fragments (Figure 28-1). The OVD also will elevate the remaining nuclear fragments toward the phaco tip, facilitating access of the phaco tip to a favorable edge of nucleus that can then be engaged and removed.

    

 

Figure 28-1  A, When the red reflex becomes visible, injection of a retentive viscoadaptive device behind the remaining nucleus will create an artificial epinucleus, protecting the posterior capsule and stabilizing the remaining nucleus. B, Later in the procedure, injection of further retentive viscoadaptive agent behind the nucleus helps preserve the protection of the posterior capsule.

 

 

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The “leathery” posterior nucleus

A frequent surgical observation during phacoemulsification of a dense brunescent nucleus, whether by quadrant cracking or phaco chop technique, is that split fragments will, nevertheless, resist being drawn into the mid-anterior chamber for complete destruction and aspiration by the ultrasound needle. The reason for this problem is that tough elastic strands, with a “leathery” quality and appearance, span across and connect the split nuclear fragments on their posterior surface.

These leathery strands emanate from the epinuclear layer, which, in advanced brunescence, is stiffened and becomes more tightly adhered to the nucleus.

These strands on the posterior surface will challenge the surgeon attempting to mobilize nuclear pieces in a controlled manner. The best technique to address these strands is to transect them with an instrument. The nuclear fragment is engaged and stabilized by the vacuum of the phaco tip. While the nuclear fragment is partially drawn anteriorly, but not to the point of breaking the vacuum hold, the second instrument is used to transect the strands. The author prefers the phaco chopper as the second instrument. The handle is rotated so that the chopper is parallel to the posterior capsule, and the chopper is drawn across the strands. As long as the chopper is parallel to the posterior capsule, and the surgeon maintains an infusion of balanced salt solution (phaco foot position 1 or higher), the posterior capsule will not be endangered (Figure 28-2).

    

 

Figure 28-2  A, Chopping instrument can be oriented horizontally and used to cut across posterior leathery nuclear strands. B, Posterior strand cutting must continue across the apex of the nuclear wedge centrally.

 

 

The surgeon must be patient in dealing with these many strands, but, ultimately, the nucleus can be successfully divided and emulsified.

When the remaining nucleus is small enough, sometimes the surgeon can safely “flip” the nucleus within the capsular bag. If this can be accomplished, the remaining leathery strands will be anterior, where the surgeon can visualize them and directly emulsify them. The author does not recommend, however, that the surgeon use a “phaco flip” technique where the large nucleus is delivered above the capsule. The large amount of ultrasound power that would need to be employed, combined with the proximity to the endothelium, increases the risk of corneal edema.

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Special instruments

When confronted with a particularly challenging case, the surgeon generally should not attempt a new, unfamiliar technique. However, for surgeons who routinely employ phaco chop (see Chapter 17), a small adjustment can be helpful. Most phaco chopping instruments have a distal tip length of 1.25–1.5mm. This is sufficient to reach the middle of an average nucleus. Having the tip of the chopper reach the middle of the nucleus is important in achieving a reliable chop.

Some choppers have a longer tip for use with dense nuclei. Elongating the tip to only 1.75mm is sufficient to dramatically improve the reliability of successfully transecting a thicker, dense nucleus. Although such an instrument will look large inside the eye, the nuclear thickness that often approaches 4mm or more means that the posterior capsule is not endangered (Figure 28-3). Alternatively, creation of a preparatory groove will reduce the nuclear thickness and create a weak zone more likely to crack (Figure 28-4).

  

 

Figure 28-3  Chopping a dense, 4-plus nucleus is facilitated by a longer chopping tip, such as 1.75mm (top left), compared with the more common 1.5mm length chopping tip used for average-sized nuclei (bottom right).
(Photo courtesy Rhein Medical, Tampa, Fla.)

 

 

  

 

Figure 28-4  Creation of a groove in a dense nucleus facilitates chopping by thinning the nucleus and creating a weak zone, similar to the grooves that facilitate cracking a chocolate candy bar.

 

 

Manufacturers are devoting increased attention to modulation of the delivery of ultrasound energy and control of fluidics (see Chapter 7).

These advances enhance the surgeon's ability to deal with challenging dense nuclei, as well as more routine cataracts.

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Further Reading

Mehta K.R.: Simplified and safe phacoemulsification of supra hard cataracts.   In: Agarwal A., Agarwal S., Sachdev M.S., et al ed. Phacoemulsification, laser cataract surgery, and foldable IOLs,  New Delhi: Jaypee; 1998:210-211.

Vanathi M., Vajpayee R.B., Tandon R., et al: Crater-and-chop technique for phacoemulsification of hard cataracts.  J Cataract Refract Surg  2001; 27:659-661.

Vasavada A., Singh R.: Surgical techniques for difficult cataracts.  Curr Opin Ophthalmol  1999; 10:46-52.