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Up Front | Mar 2012

Drop and Stop: The Dropping and the Dropped Nucleus

Techniques for effective management of fallen fragments.

In 2009, the United Kingdom National Cataract Dataset of 55,567 cases reported overall posterior capsule rupture (PCR) or vitreous loss rates of 1.92%.1 The British Ophthalmological Surveillance Unit (BOSU) reported 610 nuclear fragments displaced into the vitreous during 1 year in the United Kingdom, which is an incidence between two and three per 1,000 operations, or approximately 0.3%.2 Although the frequencies of these are low, the complications of a dropped nucleus or vitreous loss may include raised intraocular pressure (IOP), uveitis, corneal edema, cystoid macular edema, and retinal detachment. When managed properly, however, the risk of further complications can be minimized, and the results can be as good as if it had never happened. This is reflected in the fact that two-thirds of all patients with a dropped nucleus between 2003 and 2004 had a final corrected vision of 6/12 or better.3

Risk Factors

The many publications investigating risk factors associated with PCR and vitreous loss (Table 1) have allowed surgeons to more accurately predict complications prior to surgery, plan more effectively, and counsel patients who are at risk.1

Early recognition of PCR or zonular dehiscence is key to preventing further problems as surgery progresses; it allows the surgeon to avoid certain maneuvers that can upset a precariously perched nucleus. Robert Osher, MD, carried out a series of experiments on cadaveric eyes to better understand what role vitreous contributes to the nucleus drifting downward.4 His findings suggest that, in most cases, the nucleus will sit supported by the vitreous if undisturbed. Older vitreous with more syneresis, however, will allow easier passage of the nucleus into the posterior segment. He also noted that high infusion pressures and pressure gradients have little bearing on the behavior of the nucleus, as the pressure is equal across the whole eye. The effect of high aspiration and postocclusion surge due to high vacuum settings, however, can easily pull the vitreous supporting the nucleus toward the phaco tip, allowing the nucleus to drop. He also identified the turbulence created by phacoemulsification as a contributing factor in shifting vitreous support.

Anterior Vitreous Removal

It is important to note that the underlying principle of complication management in any surgical setting must be to reduce the risk of further complications. Although the nucleus may sit on the vitreous, it may not be safe to deal with it in that position, as surgical maneuvers can disrupt vitreous or cause retinal traction, increasing the risk of retinal complications. We therefore present a straightforward didactic plan for dealing with PCR and/or vitreous loss, together with an algorithm for handling dropped nuclear fragments and a view of how the two surgical teams, anterior and posterior, should proceed. Three surgical videos, available on Eyetube.net, demonstrate several of these helpful maneuvers, including vitreous management in cataract surgery (eyetube.net/?v=wagalo), vitrectomy pearls after capsular tears (eyetube.net/?v=sikulu), and posterior polar cataracts (eyetube.net/?v=dasmo).

Primary Goal, Risks

The primary goal for the surgeon following early PCR or zonular dehiscence is to remove as much of the remaining nucleus as possible, but not without considering the risks that this involves.

The most important intraoperative risk factor is vitreous traction. Continued irrigation alone following PCR is unlikely to cause the nucleus to drop, as demonstrated by Dr. Osher. Rather, it allows time to reassess the situation, move the nuclear fragments to a safe position if possible, and remove the second instrument. An ophthalmic viscosurgical device (OVD), preferably dispersive, can then be injected to coat and tamponade the vitreous and support the nucleus, allowing the phaco needle to be withdrawn without letting the vitreous surge forward toward the wound. This acts as a freeze-frame, allowing one to assess the situation and plan further strategies. Performing bimanual vitrectomy through two paracenteses with a low bottle height and high cut rate, the surgeon can then remove vitreous, using triamcinolone acetonide for visualization (Figure 1A). This allows further surgical maneuvers to be performed in a vitreous-free environment, reducing or eliminating vitreous traction. Because all vitreous in the anterior chamber must be removed, it is usually a good idea to debulk the anterior vitreous from behind the posterior capsule to discourage the vitreous from prolapsing forward during further maneuvers. Teixeira et al5 examined the effects of vitrectomy on retinal traction through a pars plana approach in vitro and found that traction is directly related to the vacuum and inversely related to the cut rate and distance from the retina; these principles can be applied to anterior vitrectomy. Settings should therefore be low vacuum (100 mm Hg to 150 mm Hg) and the highest cut rate possible.

Once the anterior chamber is vitreousfree, it is usually advisable to pass the cutter through the opening in the posterior capsule and continue to remove a generous amount of anterior vitreous (Figure 1B). This step should be performed carefully—it is not unusual for this to take several minutes. Residual soft lens matter can then be removed using the vitrector in aspiration mode (Figure 1C). If no nuclear fragments have descended into the posterior vitreous and the anterior capsulorrhexis is intact, an IOL can be placed in the sulcus with optic capture (Figure 1D). We routinely use off-label intracameral triamcinolone (Kenalog; Bristol Myers-Squibb) again at the end of the operation to ensure there is no residual vitreous, following the initial description of its use for this indication by Burk et al.6 Preservative-free preparations designed for intraocular use, now available in some markets (eg, Triesence; Alcon Laboratories, Inc.), should be used when available. When they are unavailable, we continue to advocate off-label use of triamcinolone acetonide because we believe the advantages outweigh the theoretical disadvantages associated with off-label use.7

Considerations For Nuclear Material Removal

For safe nuclear material removal, the cutting rate should be dropped. In the case of a dense nucleus, an alternative strategy is to enlarge the wound and remove nuclear fragments directly. At this stage, it is dangerous to continue to use phacoemulsification in the presence of vitreous in order to remove nuclear fragments. The phaco tip cannot cut vitreous gel and would instead aspirate, leading to vitreoretinal traction via the vitreous base and creating a high risk of retinal tear.

An alternative approach is to use a dry technique, in which vitreous is cut and removed without infusion. This is called dry anterior vitrectomy and is particularly useful for small amounts of vitreous presenting toward the end of a procedure (eg, if a strand of vitreous presents through a small area of zonular loss toward the end of cortical clean-up or after IOL implantation). In this situation, the most efficient method is to refill the anterior chamber with an OVD and cut and remove the strand of vitreous with the cutter (Figure 2), topping up the OVD in the anterior chamber to avoid anterior chamber collapse. Because minimal maneuvering is required—and only a small volume removed—the anterior chamber will not collapse, and the surgical goal is rapidly achieved. A dispersive OVD that tamponades the vitreous is preferred in this setting.

If the nucleus has drifted out of reach, an attempt at retrieval via the anterior chamber is ill-advised. Rather, we recommend clearing the anterior vitreous and converting to pars plana vitrectomy (PPV). In cases managed by an anterior segment surgeon who lacks the experience and equipment, the eye should be closed and the patient referred to a vitreoretinal surgeon.

The question of whether to implant an IOL at the time of nucleus drop if no PPV is undertaken is contentious. The BOSU data suggest that 77% of IOLs inserted at the time of cataract surgery were removed or replaced upon subsequent PPV.3 It is best if anterior and posterior segment surgeons practice comanagement and agree upon whether an IOL should be implanted if no PPV is to be performed. Most vitreoretinal surgeons currently agree that placement of a secure IOL at time of primary surgery is advisable as long as it is stable. With an intact capsulorrhexis, a three-piece IOL can be placed using optic capture with the haptics in the sulcus but the optic behind the capsulorrhexis, resulting in a stable IOL position. A one-piece IOL should not be used in this situation. Anterior chamber IOLs should be avoided at the time of primary surgery in the presence of a displaced nuclear fragment; however, they may be an option at the time of PPV or at a later date in the absence of sufficient capsular support.

If a nuclear fragment has dropped into the posterior segment, the anterior segment surgeon should make no attempt to pursue it (Figure 3). Once the anterior segment has been cleared, it is important to manage inflammation as well as any rise in IOP with appropriate medication. A full explanation should be made to the patient, emphasizing that although a complication has occurred, a good outcome is still likely, with appropriate further surgery undertaken by the vitreoretinal team. Although this is not an emergent situation, prompt contact between the cataract and vitreoretinal surgeon is essential; the outcomes of vitrectomy with removal of nuclear fragments within 1 week are favorable; a more prompt procedure is likely to provide the best outcomes. In high-risk situations, such as unstable traumatic cataracts and posterior polar cataracts where the risk of PCR and nucleus displacement is significant, it is best for the vitreoretinal surgeon to see the patient preoperatively. This drives home the importance of potential complications and emphasizes that good pathways for professional collaboration are in place to deal with any complications that may occur.

Pars Plana Vitrectomy

The underlying principle of PPV for displaced nuclear fragments is to perform a complete vitrectomy, including removal of the vitreous base as far as possible, employing a standard three-port pars plana approach (Figure 4A) with a conventional 20-gauge system or a smaller-gauge sutureless system (23 or 25 gauge). There are limited data available on the use of small-gauge instrumentation for lens fragment removal, but initial reports of outcomes with 25-gauge PPV without the use of a fragmatome are similar to those with 20-gauge instrumentation.8

There are also reports of 23- and 25-gauge instrumentation combined with a fragmatome in a mix-andmatch approach, using a local periotomy and a single enlarged port. The advantages of the mix-and-match approach include having only one incision to suture at the end of a case, performing a faster surgery, and speeding postoperative healing.9

Smaller-gauge vitrectomy systems require high infusion pressures and high flow rates to meet the demand of the aspiration through the wider-bore fragmatome, which might lead to more vitreous traction and intraoperative hypotony. A fragmatome, which is similar to a phaco probe without an infusion sleeve, cannot cut vitreous, so a complete vitrectomy must be performed prior to introducing the fragmatome to the eye. This can be aided by triamcinolone staining, particularly if visibility is limited. Also, because there is no counterresistance by the capsular bag, it is essential to use a pulse or micropulse setting on the fragmatome, with low to moderate vacuum, to avoid bouncing the nuclear fragments around the vitreous cavity due to the repulsion caused by ultrasound energy (Figure 4C).

Perfluorocarbon liquid (PFCL) can be used to cover the macula and float the nucleus away from the retina prior to engaging the fragment with either the vitrector or the fragmatome (Figure 4B). This helps to protect the macula during removal of the lens fragments in the mid-vitreous cavity. Prior to closure, it is important to remove all PFCL and to carefully inspect for residual fragments and iatrogenic retinal tears. It is particularly important to inspect the vitreous base, as tiny retinal breaks close to the ora serrata are easy to miss but can cause subsequent retinal detachments (Figure 4D).

A common misconception among anterior segment surgeons is that PFCL is used to float the nucleus into the anterior chamber from whe it can be extracted through a limbal or corneal incision. In fact, the majority of displaced nucleus fragments can be dealt with safely in the posterior segment, with the PFCL acting only as a cushion to the macula while nuclear fragments are addressed with the fragmatome.

Summary

It is essential to keep potential future complications in mind when dealing with a perioperative complication. In the case of vitreous loss or loss of nuclear fragments at the time of surgery, a careful anterior vitrectomy technique (using triamcinolone and avoiding vitreoretinal traction) and PPV can result in an excellent outcome.

Craig K. Parkes, MD, is with the Wirral University Teaching Hospital NHS Foundation Trust, Spire Murrayfield Hospital, in Wirral, United Kingdom. Dr. Parkes states that he has no financial interest relevant to the products or companies discussed in this article. He can be reached at e-mail: ckparkes@hotmail.com.

Manish Nagpal, MS, DO, FRCS(UK), is Senior Consultant, Retina & Vitreous Services, at the Retina Foundation & Eye Research Centre in Gujarat, India. Dr. Nagpal states that he has no financial interest relevant to the products or companies discussed in this article. He may be reached at tel: +91 79 22865537; e-mail: drmanishnagpal@yahoo.com.

Brian C. Little, MA, FRCS, FRCOphth, is a Consultant Surgeon at Moorfields Eye Hospital in London. Dr. Little states that he has no financial interest relevant to the products or companies discussed in this article. He may be reached at e-mail: brianlittle@blueyonder.co.uk.

Som Prasad, MS, FRCSEd, FRCOphth, FACS, is a Consultant Ophthalmologist at the Wirral University Teaching Hospital NHS Foundation Trust & Spire Murrayfield Hospital. He states that he is a consultant to Bausch +Lomb (UK) but has no financial interest relevant to the products or companies discussed in this article. He can be reached at tel: +44 151 6047193; fax: +44 151 9098091; e-mail: sprasad@rcsed.ac.uk.

  1. Narendran N, Jaycock P, Johnston RL, et al. The Cataract National Dataset electronic multicentre audit of 55,567 operations: risk stratification for posterior capsule rupture and vitreous loss. Eye (Lond). 2009;23(1):31-37.
  2. Mahmood S, von Lany H, Cole MD, et al. Displacement of nuclear fragments into the vitreous complicating phacoemulsification surgery in the UK: incidence and risk factors. Br J Ophthalmol. 2008;92(4):488-492.
  3. von Lany H, Mahmood S, James CR, et al. Displacement of nuclear fragments into the vitreous complicating phacoemulsification surgery in the UK: clinical features, outcomes and management. Br J Ophthalmol. 2008;92(4):493-495.
  4. Osher RH, Yu BC, Koch DD. Posterior polar cataracts. A predisposition to intraoperative PCR. J Cataract Refract Surg. 1990;16:157-162.
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  6. Burk SE, Da Mata AP, Snyder ME, Schneider S, Osher RH, Cionni RJ. Visualizing vitreous using Kenalog suspension. J Cataract Refract Surg. 2003;29(4):645-651.
  7. Angunawela RI, Liyanage SE, Wong SE, Little BC. Intraocular pressure and visual outcomes following intracameral triamcinolone assisted anterior vitrectomy in complicated cataract surgery. Br J Ophthalmol. 2009;93(12):1691-1692.
  8. Ho LY, Walsh MK, Hassan TE. 25-gauge pars plana vitrectomy for retained lens fragments. Retina. 2010;30(6):843-849.
  9. Khanifar AA, Roux HK, Chan RVP. Pars plana vitrectomy and lensectomy with a 23-gauge vitrectomy system. Retina Today. 2010;5(4):34-36.

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