Eyeworld

JUN 2012

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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24 EW NEWS & OPINION June 2012 Phaco with weak zonules: Part 2 Complicated cataract cases by David F. Chang, M.D. I n this month's issue of EyeWorld, David F. Chang, M.D., presents the second part of his two-part series on pha- coemulsification in eyes with zonular weakness. In part 1 he discussed intraoper- ative clinical findings and strategies for managing loose zonules during the early steps of cataract surgery, including the cap- sulorhexis and hydrodissection. In this issue, he discusses pearls for managing the later steps of the procedure including nuclear emulsification and cortical cleanup. Zonular laxity is a common comorbidity of cataract, which greatly increases the risk of intraoperative and post-op complications. Surgery in these eyes is often associated with increased nuclear density and phacoemulsification time, anterior vitre- ous migration through small breaks in the zonules, and trampolining of the lens-iris di- aphragm. Post-op complications may include capsulorhexis contraction, pseudopha- codonesis, and late decentration or disloca- tion of the capsular bag complex. It is incumbent upon the surgeon to minimize further damage to the already weakened zonular apparatus. Dr. Chang nicely outlines the benefits of phaco chop; discusses the logic behind using low vacuum levels as the last frag- ments of nucleus are being aspirated; and describes the advantages of keeping an in- strument behind the final fragment as it is being emulsified. He also describes the ben- efits of bimanual irrigation and aspiration and the tangential cortex stripping. He closes with a discussion of capsule tension rings and how to insert them without snagging the capsule. Kevin Miller, M.D., Complicated cataract cases editor Figure 1. Despite using a smaller 20- gauge phaco tip and working at a low vacuum level, the lax posterior capsule is aspirated following emulsification of the last nuclear fragment. Iris hooks (4-0 prolene) that were initially used to enlarge the pupil have been repositioned around the capsulorhexis edge to serve as capsule retractors This is the second installment of this two-part article. Last month, Part 1 outlined pearls for the capsulorhexis and nuclear rotation and contrasted the use of CTRs versus capsule retractors during phaco. Nuclear emulsification Fragile zonules are very prone to further damage during nuclear emulsification, and poor capsular bag stability heightens the risk of capsular rupture. Forceful sculpting or rotation of the nucleus may shear zonules in the oppositely located quadrants. Care should be taken to avoid causing excessive nuclear movement with sculpting, chop- ping, or rotation. Phaco chop signif- icantly reduces the stress placed on the zonules and capsule by replacing sculpting and cracking motions with the manual forces of one instrument pushing inward against another. Because of the centrally directed instrument forces, horizontal chop- ping is particularly effective at avoiding nuclear tilt or displace- ment, and it is this author's prefer- ence for weak zonule cases. The supracapsular flip tech- Read part one of Dr. Chang's article (May EyeWorld) on your smartphone or iPad using your QR code reader. (Scanner available for free at your app store.) Or copy and paste the following into your web browser: http://bit.ly/MtMyOb nique, as popularized by David Brown, M.D., prolapses and flips the endonucleus out of the capsular bag prior to emulsification. If ac- complished, this prevents the capsu- lar bag from bearing any of the phaco instrumentation forces. The ease with which this flipping ma- neuver can be accomplished varies depending upon the size of the en- donucleus relative to the capsu- Figure 2. Dispersive OVD is injected behind the few remaining fragments to push the pliant posterior capsule further away. The dispersive OVD resists aspiration and serves as an "artificial epinucleus" Figure 3. With posterior capsule laxity due to weak zonules, the chopper tip blocks the posterior capsule from being aspirated as the final piece is removed. The presence of residual dispersive OVD can be seen lorhexis diameter. Using this tech- nique with a nucleus that is too large or a capsulorhexis that is too small risks further zonular dehis- cence. Care must also be taken to avoid endothelial trauma during the nuclear flipping maneuver. With chopping, one should consider bringing larger sections of nucleus out of the capsular bag where they can be sub-chopped within the supracapsular space. For example, it may be possible to lift each heminu- cleus out of the capsular bag follow- ing the initial bisecting horizontal or vertical chop. Throughout phaco and cortical cleanup, one should anticipate that deficient centrifugal zonular tension will result in greater posterior cap- sule laxity. The flaccid posterior cap- sule will tend to trampoline toward any aspirating tip as the last nuclear fragments, epinucleus, and cortex are removed. Because the nuclear bulk will initially mask this situa- tion, one must be vigilant as increas- ingly more nucleus is removed. Compared to a standard 19-gauge phaco tip, a smaller-diameter, 20- gauge tip greatly reduces the risk of inadvertently aspirating the periph- eral or posterior capsule. If one sus- pects or encounters zonular laxity, the aspiration settings can be low- ered as progressively more of the nucleus is removed. To slow the pace down, a lower than usual aspiration flow rate is advisable. A pre-pro- grammed vacuum setting that usu- ally avoids post-occlusion surge with routine cases may not be safe with a lax posterior capsule that is lacking normal centrifugal zonular tension (Figure 1). Therefore, one should consider decreasing the vacuum to lower than normal levels to prevent trampolining of the capsule. Repeat- edly inflating the capsular bag with a dispersive OVD can further re- strain a flaccid posterior capsule from vaulting toward the aspirating instrument as the final fragments and epinucleus are aspirated (Figure 2). This is especially important if there is no epinuclear shell remain- ing as the last nuclear fragment is emulsified. Finally, placing the chopper behind the phaco tip as the last piece is removed can block the tip from aspirating the lax posterior capsule (Figure 3). Cortical cleanup As adherent cortex is aspirated, the usual centrifugal capsular counter fixation afforded by stronger zonules is deficient. Lacking circumferential zonular tension, a lax posterior cap- sule tends to cling to epinucleus and cortex that is being aspirated, and redundant capsular folds can be easily ensnared by the aspirating instrument or snagged by a capsule polisher. While removing cortex, inadvertently aspirating the more pliant anterior capsule may cause a zonular dialysis. Effective hydrodis- section is crucial because the more easily lens material separates from a floppy capsule, the less likely it is for the capsular folds to be aspirated. As mentioned above, continu- ally reinflating the capsular bag with

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