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Solutions offered for mature white cataracts
When the problem is mature white cataracts, the solutions are ICG dye and the phaco chop.
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LAGUNA NIGUEL, U.S.A. — Surgery on mature cataracts is complicated for several reasons, according to David Chang, MD, who addressed the topic here at the Ocular Drug and Surgical Therapy Update meeting, sponsored by Ocular Surgery News.
“The first problem is visualizing the capsulorrhexis because of all the cortical milk and the lack of a red reflex,” Dr. Chang said. “Of all the techniques that I have tried, the most effective in my hands is indocyanine green [ICG] dye. It provides great visualization of the anterior capsule without the need for any special type of illumination, such as a cobalt blue filter as you would need with fluorescein [dye].”
The technique of ICG capsular staining, which was reported by Horiguchi, et al in the April 1998 Archives of Ophthalmology begins with a tiny paracentesis stab incision designed to retain a generous air bubble in the anterior chamber. A TB syringe and 30-gauge cannula is used to inject several drops of dye directly onto the capsule.
On the bubble
“The bubble prevents you from having to fill the entire anterior chamber with dye,” Dr. Chang explained. “Then you can immediately exchange the air bubble for either viscoelastic or balanced slat solution. Initially, it may not look like you’ve stained the capsule that much, but as you initiate the tear, you start to see a ‘white reflex,’ as opposed to a red reflex, and then you realize that you can suddenly visualize the capsule perfectly.”
| Dye Solution |
| ICG Dye Information ICG Dye comes in a bottle containing 25mg lyophilized ICG powder, with a second bottle of single use diluent.
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ICG dye is available through Akorn (Lincolnshire, U.S.A.) and is approved for use in retinal angiography, so this is an off-label use, explained Dr. Chang. It also improves capsule visualization in mature brown lenses lacking a red reflex. “I have used ICG successfully for the capsulorrhexis on seven mature white cataracts so far, and I believe it essentially solves this long-standing problem,” Dr. Chang said.
Phaco technique
The absence of a red reflex also complicates nucleus removal because it is more difficult to judge the depth at which the phaco tip is sculpting. “You can’t rely on an increasingly brighter red reflex to gauge proximity to the posterior capsule during sculpting,” Dr. Chang said. “Phaco chop has some great advantages here because, unlike sculpting, it is a more kinesthetic technique in which visualization of the depth of the phaco tip is less important. Proper positioning of the depth of the chopper tip also relies more on tactile clues, rather than purely visual ones.”
Dr. Chang uses a Lieberman Micro finger (Katena Products, Denville, U.S.A.) to chop the nucleus. “With the Nagahara technique, I hook the equator of the lens with the chopper. With mature cataracts, the chopper tip palpates and hugs the anterior nuclear surface as it moves peripherally to assure staying underneath the anterior capsule. As the core nucleus is compressed between the chopper and phaco tips, a fracture results that bisects the nucleus completely in half without any sculpting,” Dr. Chang said. Subsequent chops create pie-shaped segments that are aspirated out of the capsular bag using high vacuum settings.
The final problem with mature cataracts is that of dealing with very large and brunescent nuclei. According to Dr. Chang, greater amounts of phaco time and power are required, and the increased size and firmness of these nuclei more directly transmit all of the instrument forces (for example, sculpting, rotation, cracking) directly to the zonules and capsule. This increases the risk for endothelial cell loss and posterior capsule rupture.
Phaco chop
--A horizontal chop is performed by hooking the nucleus (left) with the Microfinger and impaling with burst mode. The Microfinger then chops (right) against the phaco tip.
--The horizontal chop continues as a lateral motion completes the split (left). The chop is then repeated after rotation (right).
“Instead of ultrasound, phaco chop uses the manual energy of the chopper pushing against the phaco tip to divide up the nucleus. Ultrasound is reserved for the vacuum-assisted aspiration of the resulting fragments,” Dr. Chang said. “In addition, the manual instrument forces are directed centrally in ward, rather than outward toward the capsule. In contrast, with sculpting, the capsule and zonules bear the stress of anchoring and fixating the nucleus during the phaco stroke. This difference between the two techniques is best visualized in Miyake-view videos of cadaver eye phaco. By eliminating sculpting, the ability of phaco chop to reduce total phaco time and energy and stress on the capsule and zonules is a particular advantage for these firm and higher risk nuclei.”
Something to be aware of with regard to mature lenses, Dr. Chang said, is that sometimes the lens is liquefied — particularly in young patients or in cases of traumatic cataract. “In these situations, because you can’t see the nucleus, you want to first test and palpate the nucleus with the chopper tip. You must be sure you have a formed nucleus before attempting to perform phaco chop,” he said.
For Your Information:Reference:
- David F. Chang, MD, is clinical professor of ophthalmology at the University of California, San Francisco, and is in private practice in Los Altos, Calif. He can be reached at 762 Altos Oaks Drive, Ste. 1, Los Altos, CA 94024; (650) 948-9123; fax: (650) 948-0563. Dr. Chang has no direct financial interest in any of the products mentioned in this article. He did not disclose whether or not he is a paid consultant for any companies mentioned in this article.
- Goriguchi M, et al. Staining of the lens capsule for circular continuous capsulorhexis in eyes with white cataract. Arch Ophthalmol. 1998;116:535-537.