Tutorial
Introduction
Capsular Dye - Technique
A Comparison of ICG and Trypan Blue Dye
Phaco Chop for Mature Cataracts
Horizontal vs. Vertical Chopping
Phaco Settings
References
Slides
Mature Cataracts: Capsular Dye and Phaco Strategies
David F. Chang, MD
Mature white (cortical) (Slide 1) and brown (nuclear) cataracts are challenging for many reasons. The capsulorhexis is difficult to visualize because
of the lack of any red reflex and the liberation of cortical "milk" following the initial puncture. The excessive hydration of these lenses
promotes peripheral radial extension of the developing capsule tear. The lack of a red reflex also makes nuclear removal more formidable.
Without good visualization, the phaco tip or second instrument might inadvertently tear an intact capsulorhexis. Gauging the depth of the phaco
tip during sculpting is also very difficult in the absence of any red reflex.
The more brunescent and sizable the nucleus is, the greater the risk of complications. By necessitating increased phaco power and time, the potential for wound burn and endothelial cell loss is increased. In addition, the excessive bulk, density, and size of these nuclei more directly transmits all of the instrumentation forces directly to the capsular bag. The increased capsular and zonular stress induced by maneuvers such as rotation, sculpting, and cracking makes posterior capsule rupture much more likely. Fortunately, improvements in phaco techniques and technology have greatly improved our odds for success.
Capsular dye is by far the most reliable method for anterior capsule visualization in mature cataracts. Indocyanine green (ICG) dye, as reported by Horiguchi,1 and trypan blue dye, as reported by Melles,2 each work well in this regard. They are both superior to fluorescein,3 which, because it is a much smaller molecule, diffuses into the lens and the vitreous. Use of any of these dyes in cataract surgery constitutes an off-label use.
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An identical technique is used with either dye. Through a small paracentesis, the anterior chamber is filled with an air bubble to avoid excessive dilution of the dye (Slide 2). Using a 30-gauge cannula, several drops of dye from a TB syringe are placed directly onto the anterior capsule surface, which is stained immediately (Slide 3, Slide 4A, Slide 4B, Slide 4C and Slide 4D). Through the paracentesis, the air is then exchanged for BSS, which is used to irrigate the dye out of the anterior chamber. Waiting 10 to 15 seconds to remove the dye can intensify the staining. Following viscoelastic placement, the capsulotomy is performed in the usual manner. No special illumination is needed. At first, the capsule may not appear very colored. However, once the tear is initiated, the white cortex creates a "white reflex" against which the stained capsule is easily delineated. As an alternative to the air bubble technique, Kayikicioglu4 (trypan blue) and Akahoshi5 (ICG) have described mixing either dye with viscoelastic.
The use of capsular dye does not eliminate other problems posed by mature, white lenses. The egress of cortical "milk" may still impair visibility of the anterior capsule. An irrigating cystotome has the advantage of lavaging the milky material away and can be employed in young patients to initiate the tear when this problem is anticipated. If there is liquefied cortex, the resulting intralenticular fluid pressure may also cause peripheral radial extension of the capsular tear. One must optimize control of the tear by proceeding slowly, frequently regrasping and redirecting the flap, maintaining a deep chamber, and erring toward a smaller diameter.
Besides the white cataract, capsular staining is helpful in any situation where either the red reflex is poor or visualization of the capsule is compromised. Asteroid hyalosis, corneal scarring, corneal edema, and a dark brunescent nucleus are examples of other such situations. Sometimes, the need for capsular dye does not become evident until the capsulorhexis has been initiated. Fortunately, the technique also works well with a partially opened anterior capsule, in that the cortex does not appear to stain as much of the capsule.6
A Comparison of ICG and Trypan Blue Dye
Clinical studies of both of these capsular dyes have been published. In April 1998, Horiguchi and colleagues reported the results of their technique in a prospective, randomized study of 20 patients with mature white lenses.1 Ten patients underwent ICG capsule staining, and the other 10 served as controls. Specular microscopy and laser flare-cell photometry were compared and showed no statistical difference between the two groups.
ICG creates a pale green staining of the capsule, which is gone by the conclusion of the case. One slight disadvantage is that the dye is lyophilized, and larger particles often remain suspended in the mixture. These may appear in the anterior chamber, but seem to be eliminated during the ensuing irrigation/aspiration steps of the cataract surgery. Because BSS Plus is used for the mixture, the dye must be discarded at the end of the day.
In January 1999, Melles reported on the use of trypan blue dye in 30 patients with mature white cataracts.2 There were no complications attributable to the dye. He also cited trypan blue’s long track record of safety when used to stain and examine endothelial cells in donor corneoscleral buttons. In my experience, both dyes have provided consistently excellent visualization and clinical results.5,7 I have not experienced any adverse problems attributable to the dye, such as increased inflammation or corneal edema. No residual staining of the iris or capsule is apparent by the following day.
Trypan blue creates a much darker staining and provides superior visualization when compared to ICG. Unlike ICG, there is no particulate
suspension with trypan blue, and it is much more convenient to use because there is no mixing involved. Because it is supplied in a smaller amount,
it is less expensive. Finally, trypan blue staining lasts longer and usually persists throughout the entire phaco step (Slide 5).
Without a red reflex, phaco of the nucleus is challenging even with a completed capsulorhexis because the capsule edge cannot be seen during sculpting or chopping. For this reason,
dye-aided visualization of the anterior capsule can decrease the risk of inadvertently cutting or tearing the capsulorhexis edge during these phaco
maneuvers. The more intense and persistent capsule staining provided by trypan blue dye is particularly advantageous in this regard. Until trypan
blue becomes available in the United States, ICG provides a useful alternative.
Dr. Suresh Pandey, in Dr. David Apple’s group, has published a comparison study of fluorescein, ICG, and trypan blue dye for anterior capsule staining in postmortem human eyes.8 He found that trypan blue and ICG dye were superior to fluorescein for improving visualization, with ICG being slightly better than trypan blue. However, unlike the surgical techniques described, his method was to inject the dye subcapsularly. Injecting dye through a capsule puncture into these overly hydrated lenses might result in an uncontrolled capsular rip. Supracapsular dye application is sufficient and avoids this potential complication.
Phaco Chop for Mature Cataracts
I believe that the safest technique for mature or brunescent cataracts is phaco chop. Although "stop and chop" involves chopping, I use the term "nonstop" phaco chop to describe pure chopping techniques that eliminate all sculpting.9 This affords three advantages that increase overall safety and efficiency. With the elimination of sculpting, chopping reduces phaco power and time by using manual forces instead of ultrasound to fragment the nucleus. Ultrasound energy is reserved for the phaco-assisted aspiration of the individual nuclear fragments once they have been elevated out of the capsular bag. As with other "supracapsular" techniques, all of the emulsification in non-stop chop occurs, therefore, at a safe distance from the posterior capsule.
Second, phaco chop reduces stress on the capsule and zonules by replacing sculpting and cracking forces with the centripetally directed manual forces of one instrument pushing against another. In chopping, the phaco tip braces the nucleus against the force of the chopper. In contrast, it is the capsular bag that fixates and braces the nucleus against the forces of sculpting. This significant difference in zonular stress is readily appreciated when chopping and sculpting are compared from the Miyake-Apple viewpoint in cadaver eyes.
A final advantage applies to mature lenses. A poor or missing red reflex makes it difficult to judge the depth at which the phaco tip is cutting. This is a problem for cracking techniques where sculpting an adequately deep central trough is essential and where the appearance of an increasingly brighter red reflex is used to gauge the proximity of the posterior capsule. Unlike sculpting, phaco chop is a more kinesthetic technique in which visualization of the phaco tip depth is not important. Proper positioning of the chopper and phaco tips relies more on tactile rather than visual clues.
Horizontal vs. Vertical Chopping
There are two main variations of non-stop phaco chop. I refer to the classic Nagahara method as horizontal chopping, because the chopper hooks the lens equator and moves along the horizontal plane toward the phaco tip (Slide 6, Slide 7A, Slide 7B, Slide 7C, Slide 7D, Slide 7E, Slide 8A, Slide 8B and Slide 8C). I refer to the quick chop method as vertical chopping, because the two instrument tips move toward each other in the vertical plane. Both methods achieve the same common benefits through different strategies.
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For brunescent nuclei, I find that vertical chopping works best. The Maloney-style vertical chopper (Storz) has a sharp, spiked tip
(Slide 9, Slide 10A, Slide 10B and Slide 10C).
This impales downward into the nucleus just anterior to the centrally embedded phaco tip. The denser the lens, the sharper the tip should be.
The Chang chopper (Katena) is maximally sharpened to better penetrate the firmest nuclei. The most important step is to bury the phaco tip
as deeply into the central nuclear core as possible. Depressing the spiked tip downward while simultaneously lifting the nucleus slightly
upward creates a shearing force that fractures the nucleus. A slight sideways separation of the instrument tips extends the fracture deeper
until the entire nucleus is cleaved in half.
Much like a chisel would be used with a block of ice or granite, the spiked vertical chopper tip can be used to break the nucleus into multiple "bite-sized" pieces. This is advantageous for large, brunescent nuclei in which smaller pieces can be emulsified more efficiently. Compared to horizontal chopping, quick chop is more likely to divide the leathery posterior plate of a thick lens because the fracture propagates vertically from the anterior nuclear surface toward the back. With Nagahara-style chopping, the fracture propagates in the horizontal direction, from one equatorial side to the other, and may not extend deeply enough to bisect the posterior plate.
High Vacuum
For dense cataracts, both the horizontal and vertical chopping techniques depend upon obtaining a solid purchase of the nucleus.
High vacuum optimizes holding power. This is helpful for fixating the nucleus during phaco chop so that the chopper does not dislodge it from the
phaco tip. It also provides the secure grip necessary to elevate the interlocked chopped fragments out of the capsular bag. Finally, as these
mobilized pieces are removed by "phaco-assisted" aspiration in the supracapsular location, higher vacuum levels increase the force
by which material is drawn through the tip. This lessens the corresponding phaco energy required for this step.
The occurrence of postocclusion surge limits how high the vacuum level can be safely set. Stiff-walled, low-compliance tubing, the ABS tip, a smaller diameter phaco tip and tubing lumen, coiled aspiration tubing, occlusion mode software, and microprocessor-controlled "smart" pumps are all examples of technology designed to reduce the degree of surge. This improves our control and allows us to work safely at much higher vacuum levels than we could before.
Burst Mode
Although inappropriate for softer lenses, this power modality is useful for dense nuclei where it is more difficult to embed the phaco tip. With a
toothpick, a single stab works best to impale a piece of melon. Continuous movement of the tip only serves to weaken the purchase. With brunescent
nuclei, continuous phaco tends to core out a cavitation pocket around the phaco tip causing loss of the surrounding seal. Burst mode allows us to
impale the nucleus with single "burst" strokes of phaco that maintain occlusion of the tip. High vacuum then provides the solid grip that
prevents the piece from being dislodged. Because high vacuum is not attainable if the tip does not stay embedded and occluded, it is the combination
of these two features that is so valuable with dense nuclei.
Cold Ultrasound
Eyes with brunescent nuclei are at greater risk for mild wound burns, because of the increased ultrasound power and time required. Absent a
frank wound burn, there may be some whitening or slight shrinkage of the clear corneal incision indicating greater heat transfer than usual. In
addition to laser phaco, several manufacturers now offer "cold" ultrasound options where the heat generated at the phaco needle
is dramatically reduced. Staar, Allergan, and Alcon all have low heat systems. The challenge for all of these modalities is the ultrabrunescent nucleus.
The Allergan system is able to remove the 4+ brunescent lens.
- Horiguchi M, Miyake K, Ohta I, Ito Y. Staining of the lens capsule for circular continuous capsulorhexis in eyes with white cataract. Arch Ophthalmol. 1998;116:535-537.
- Melles G, de Waard P, Pameyer J, Beekhuis W. Trypan blue capsule staining to visualize the capsulorhexis in cataract surgery. J Cataract Refract Surg. 1999;25:7-9.
- Fritz W. Fluorescein blue light-assisted capsulorhexis for mature or hypermature cataract. J Cataract Refract Surg. 1998;24:19-20.
- Kayikicioglu O, Erakgun T, Guler C. Trypan blue mixed with sodium hyaluronate for capsulorhexis (letter). J Cataract Refract Surg. 2001;27:970.
- Akahoshi T, Chang DF. Demonstration of two staining agents to facilitate visualization in white cataracts. Video Journal of Ophthalmology. Volume XVI, No 3.
- Newsom TH, Oetting TN. Indocyanine green staining in traumatic cataract. J Cataract Refract Surg. 2000;26:1691-1693.
- Chang D. Capsule staining and mature cataracts: A comparison of indocyanine green and trypan blue dyes. Video report. Br J Ophthalmol. 2000;84(August).
- Pandey SK, Werner L, Escobar-Gomez M, et al. Dye-enhanced cataract surgery. Part 1: Anterior capsule staining for capsulorhexis in advanced/white cataract. J Cataract Refract Surg. 2000;26:1052-1059.
- Chang D. Converting to phaco chop: Why? Which technique? How? Ophthalmic Practice 1999;17(4):202-210.