Retained, posterior nuclear fragments greatly increase the risk of postoperative complications, and must usually be retrieved through a subsequent three-port vitrectomy. Therefore, the diagnosis and management of posterior capsule rupture is particularly critical while there is still nucleus present within the eye. Every cataract surgeon must understand the principles of how to recognize and manage this complication in order to avoid a dropped nucleus.
Early recognition of zonular or posterior capsular rupture Once a posterior capsular tear occurs, subsequent surgical maneuvers and forces will quickly expand its size. These forces include nuclear rotation, sculpting, cracking, and fluctuations in chamber depth. Therefore, the likelihood of a dropped nucleus increases the longer the rupture goes unrecognized. Early recognition allows the surgeon the opportunity to convert to a large incision, extracapsular cataract extraction (ECCE).
Signs of early posterior capsule rupture or zonular dehiscenceThe following may signal the presence of a posterior capsule rupture or zonular dehiscence:
• Sudden deepening of the chamber, with momentary expansion of the pupil.
• Sudden, transitory appearance of a clear red reflex peripherally.
• Newly apparent inability to rotate a previously mobile nucleus.
• Excessive lateral mobility or displacement of the nucleus.
• Excessive tipping of one pole of the nucleus.
• Partial descent of the nucleus into the anterior vitreous space.
Some of these signs may be brief and momentary. Because the nucleus prevents direct visualization of the posterior capsular anatomy, it is tempting to ignore the warning signs and to continue with phacoemulsification. If the surgeon suspects posterior capsule or zonular rupture, however, he or she must decide whether to continue phacoemulsification or convert to a standard ECCE. This decision should be based upon the amount of nucleus remaining, the density of the nucleus, other accompanying risk factors (eg, small pupil, loose zonules, etc), and the individual surgeon's level of confidence and experience. If vitreous is repeatedly aspirated by the tip, or prolapses through the wound, phacoemulsification must be aborted to avoid placing traction on the retina.
Posterior capsule rupture—avoiding or delaying vitreous loss
If you discover or suspect posterior capsule perforation, avoid the reflex to suddenly withdraw the phaco or irrigation-aspiration (I/A) tip, because unplugging the incision will suddenly empty and collapse the anterior chamber. If a sufficient portion of the nucleus has been removed, the posterior capsule bulges forward and the anterior hyaloid face ruptures, which will allow vitreous to prolapse through the defect toward the wound. Instead, before removing the instrument, first inject viscoelastic through the side port to fill the anterior chamber and block vitreous prolapse. Stay in foot position One until the viscoelastic cannula has been inserted. As viscoelastic is injected, change to foot position Zero. You can safely remove the phaco or I/A tip after the anterior chamber is filled.
Capsular defects without vitreous prolapse
Continuing with phacoemulsification is a reasonable option if the nucleus is soft, and particularly if only a small residual amount remains. The immediate goal is to prevent vitreous prolapse into the anterior chamber or to the wound. Slow the procedure down by reducing the aspiration flow rate; decreasing the vacuum will eliminate postocclusion surge and allow the bottle to be lowered. Confine the use of phacoemulsification and aspiration to zones away from the problem area, and avoid rotating the nucleus if possible. Instead of the phaco tip, use the chopper or a second instrument to manually move or position any remaining nuclear pieces. After enlarging the phaco incision by 0.5 mm, a trimmed Sheet's Glide can be placed beneath the phaco tip to prevent small nuclear fragments from descending through the capsular defect. As mentioned, always fill the anterior chamber with viscoelastic prior to removing the phaco or I/A tip.
Use separate, bimanual I/A handpieces through 1-mm clear corneal incisions to remove the epinucleus and cortex. The lack of incisional fluid leak will reduce fluctuations in chamber depth. The oppositely located bimanual incisions provide better access to the subincisional area, and allow the aspirating port to be positioned peripherally and aimed away from the rent or dehiscence. Lowering I/A flow and vacuum settings will reduce speed and postocclusion surge, respectively.
With a minor amount of prolapsed vitreous, you may conservatively continue phaco or perform I/A if you avoid repeated vitreous aspiration. A retentive, dispersive viscoelastic, such as Viscoat® (Alcon Surgical, Fort Worth, TX) or Vitrax® (Allergan Surgical, Inc., Irvine, CA), can be used to wall off the prolapsed vitreous. Compared to Healon V® (Pharmacia Corporation, Peapack, NJ), dispersives are less likely to cause IOP spikes if not completely removed.
Converting to standard ECCE from topical/clear cornea
If you suspect or discover a posterior capsule rupture, I advise converting to a large-incision ECCE if there is substantial residual nucleus, and particularly if it is brunescent, or other surgical risk factors are present. You may abandon the temporal corneal or scleral incision because it is self-sealing. Insert a blunt-tipped, curved Simcoe cannula through a tiny, inferior fornix conjunctival buttonhole and inject 2% xylocaine posteriorly into the sub-Tenon's space. After repositioning the microscope for a standard superior ECCE incision, place a superior rectus bridle suture to improve exposure and avoid scleral collapse. In place of bimanual expression, use an irrigating lens loupe to extract the nucleus with the help of a generous amount of viscoelastic. To expel the nucleus, use the lens loupe to apply pressure against the posterior lip of the wound, rather than lifting and dragging the nucleus against the cornea.
Rescuing a partially descended nucleus
The key to avoiding a dropped nucleus is early recognition of a posterior capsule or zonular rupture. Usually, the continued phaco maneuvers and forces cause the initial defect to expand enough to permit the nucleus to drop. Without capsular support, the nucleus will sink as vitreous is either mechanically excised or escapes through the wound. A brunescent nucleus may abruptly and rapidly sink through liquefied vitreous without antecedent “vitreous loss.” However, if enough supporting formed vitreous is present, the nucleus will descend only partially, allowing time for rescue maneuvers.
The worst strategy for recovering a descending nucleus is to try to chase and spear the nucleus with the phaco tip. The downward fluid infusion will flush more vitreous out, expanding the rent and propelling the nucleus away. Attempting to phacoemulsify or aspirate it may snag vitreous into the tip, potentially leading to giant retinal tears or detachment. A safer, alternative strategy is to levitate the nucleus into the pupillary plane or anterior chamber for extraction through a standard ECCE incision. However, depending upon its size and location, it is often difficult to inject viscoelastic behind the nucleus using a limbal approach. This is especially true if the capsulorhexis is small and intact, if the pupil is small, if vitreous has already prolapsed around the nucleus, or if it has subluxated laterally or posteriorly.
For this reason, Charles Kelman, MD, of New York, NY, popularized the “PAL” technique (posterior assisted levitation) utilizing a cyclodialysis spatula through a pars plana stab incision to push the nucleus up into the anterior chamber from below.1 I prefer a technique advocated by Richard Packard, MD, of London, England.2 Using Kelman's PAL principle, a Viscoat® cannula is inserted through a pars plana stab incision located 3.5 mm behind the limbus. Through a combination of injecting Viscoat® and maneuvering the cannula tip itself, the nucleus can be elevated through the capsulorhexis and pupil, and into the anterior chamber. This minimizes iatrogenic vitreous traction, and reduces the chance of touching the retina with a metal spatula tip.
Once a fragment descends from view, it is dangerous to blindly fish for it with the phaco or vitrectomy instruments. Instead, following a thorough anterior vitrectomy, remove as much cortex and epinucleus as possible with the vitrector or I/A instruments. An IOL can be implanted because the vitreoretinal specialist will later use a three-port fragmatome/vitrectomy approach to secondarily remove the retained nucleus.
Managing vitreous loss and residual nucleus
The goal is to remove the remaining nucleus, epinucleus, and as much cortex as possible without causing vitreoretinal traction. If the nucleus has been levitated largely intact into the anterior chamber as previously described, converting to an ECCE is generally advisable. Smaller fragments may require phacoemulsification using a Sheets Glide to serve as both a safety support and a vitreous barrier. If it can be accomplished safely, performing some bimanual I/A of cortex and epinucleus prior to the vitrectomy decreases the chance that lens material will fall posteriorly as the supporting vitreous is excised. However, vitreous that becomes ensnarled in the aspiration port must be addressed.
The benefits of a bimanual vitrectomy technique with a separate limbal side port infusion and a high cutting rate are widely appreciated. However, an underutilized option is to use a pars plana sclerotomy for the vitrectomy cutter. I recommend stocking disposable microvitreoretinal (MVR) blades for this purpose. Using the phaco wound for the vitrectomy instrument poses several disadvantages. Because the incision is not tight, irrigation flow leaks out and vitreous prolapses alongside the instrument shaft through the wound. As more vitreous is drawn forward by both the vitrector and this prolapse, mobile lens material will tend to fall posteriorly due to loss of support. A smaller, dedicated limbal or pars plana vitrectomy port better stabilizes chamber fluidics, and avoids incisional vitreous prolapse and loss.
If you must interrupt phaco or I/A because of vitreous loss or prolapse, use a generous amount of Viscoat® to elevate residual nuclear fragments and epinucleus anteriorly toward the cornea, and to fill the anterior chamber. Use a separate, self-retaining limbal cannula to direct infusion beneath the level of this Viscoat® partition toward the pupillary plane. Insert the vitrectomy cutter through the pars plana sclerotomy to perform an anterior vitrectomy in a plane just behind the iris. The goal is to transect any vitreous bands that cross through the pupil. However, this technique avoids evacuating the anterior-most Viscoat® layer that is segregating and trapping lens fragments anteriorly. You may resume phacoemulsification or bimanual I/A once these transpupillary vitreous bands have been severed. The sequence can be repeated until all of the epinucleus and cortex are removed. At this point, you should perform a final anterior vitrectomy, taking care to preserve the capsulorhexis margin or other potential capsular support.
IOL Placement
The surgeon will select one of four IOL fixation options depending upon the resulting capsular anatomy. If the capsular bag is intact despite a focal zonular dialysis, the bag-fixated IOL should be positioned so that the haptic axis points toward the area of zonular dehiscence. For example, with a nasal zonular dialysis, the IOL haptics should be positioned at 3 and 9 o'clock. The haptics serve as a partial capsular tension ring to outwardly expand the quadrant of the bag that is lacking centrifugal zonular tension.
Before placing a posterior chamber IOL in the ciliary sulcus, estimate the sulcus diameter by measuring the horizontal white-to-white corneal diameter. The length of most foldable IOLs is either 12.5 or 13 mm, which is too short for sulcus placement in larger eyes. Use at least a 6-mm diameter optic, and attempt a capsulorhexis capture of the optic in larger anterior segments (&Mac179; 12 mm corneal diameter).
Sizing is equally important for anterior chamber IOL insertion. Add 1.5 mm to the horizontal white-to-white corneal diameter to determine the necessary overall lens length. Use a Sheet's Glide to avoid contralateral iris tuck caused by the steep angle of IOL entry during insertion. Perform an iridectomy at a safe distance from the haptic through a separate corneal incision if necessary. Alternatively, in the absence of capsule support, a posterior chamber IOL can be sutured into the ciliary sulcus.
Posterior capsule rupture while nucleus is still present will test a surgeon's ability to operate under pressure. It is incumbent upon all cataract surgeons to prepare for this scenario by understanding the management principles and mentally rehearsing the maneuvers in advance.
Dr. Chang is Clinical Professor of Ophthalmology at the University of California, San Francisco, and is in private practice in Los Altos, CA. He has no financial interest in any of the products mentioned herein. Dr. Chang may be reached at (650) 948-9123; dceye@earthlink.net1. Kelman C: New PAL method may save difficult cataract cases. Ophthalmology Times 19:51, 1994
2. Packard R: Technique prevents nucleus drop through capsular tear. Ocular Surgery News 19:14, 2001
