EyeWorld Asia-Pacific September 2012 Issue

31 EWAP CAtArACt/IOL September 2012 Phaco with weak zonules: Part 2 by David F. Chang, MD Pearls for managing the later steps of the procedure, including nuclear emulsification and cortical cleanup. 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, chopping, or rotation. Phaco chop significantly 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 chopping is particularly effective at avoiding nuclear tilt or displacement, and it is this author’s preference for weak zonule cases. The supracapsular flip technique, as popularized by David Brown, MD , prolapses and flips the endonucleus out of the capsular bag prior to emulsification. If accomplished, this prevents the capsular bag from bearing any of the phaco instrumentation forces. The ease with which this flipping maneuver can be accomplished varies depending upon the size of the endonucleus relative to the capsulorhexis diameter. Using this technique with a nucleus that is too large or a capsulorhexis that is too small risks further zonular dehiscence. 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 heminucleus out of the capsular bag following 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 capsule laxity. The flaccid posterior capsule will tend to trampoline toward any aspirating 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. 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”. 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. During bimanual cortical I/A, the floppy capsular bag is repeatedly refilled with dispersive OVD to block the pliant posterior capsule from trampolining toward the aspirating tip. The absence of the coaxial infusion sleeve permits the aspirating instrument to reach across to the opposite equatorial regions of the capsular bag. In the setting of weak zonules, capsule retractors do not trap the cortex in the equator of the capsular bag, unlike a CTR. Bimanual cortical I/A instrumentation facilitates sub-incisional cortical aspiration and dissociates the irrigation and aspiration fluid currents. Source: David F. Chang, MD tip as the last nuclear fragments, epinucleus, and cortex are removed. Because the nuclear bulk will initially mask this situation, one must be vigilant as increasingly 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 peripheral or posterior capsule. If one suspects or encounters zonular laxity, the aspiration settings can be lowered as progressively more of the nucleus is removed. To slow the pace down, a lower than usual aspiration flow rate is advisable. A pre-programmed vacuum setting that usually 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. Repeatedly inflating the capsular bag with a dispersive OVD can further restrain 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 remaining 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. continued on page 32