David F. Chang, MD
During phacoemulsification, avoiding posterior capsule rupture is continually on the ophthalmologist’s mind. However, once this infrequent and unexpected complication arises, the surgeon must immediately recognize it and make a series of critical decisions under stressful circumstances. Proper preparation requires every cataract surgeon to anticipate and think through how he or she would handle a number of different hypothetical clinical situations. Specifically, every cataract surgeon should have a game plan for when and how to perform an anterior vitrectomy following posterior capsule rupture. This chapter will review the goals, indications, and techniques. Understanding and mentally rehearsing these strategies will better prepare cataract surgeons to remain calm under pressure and to make correct decisions amidst the stress of an unexpected complication.
Incidence of Posterior Capsule Rupture and Vitreous Loss
The best current published data on vitreous loss rates come from 5 recent studies of large patient populations. The Cataract National Dataset audit of 55,567 operations from the United Kingdom during 2001 through 2006 reported a 1.9% rate of vitreous loss.1 Using the same UK national database, a subsequent audit of 180,114 eyes operated on from 2006 through 2010 found an identical 1.95% rate of posterior capsule rupture or vitreous loss.2 Greenberg and coauthors’ 2011 published study of cataract surgery in 45,082 US Veterans Administration Hospital cataract surgeries had a vitreous loss rate of 3.5%.3 In 2011, Lundstrom and coauthors reported on all cataract surgeries performed at 52 centers comprising the Swedish National Register during the period from 2002 through 2009.4 From a total of 602,533 cataract procedures, the incidence of capsule complications was 2.1%. Data from 1,541,867 consecutive cataract surgeries performed from 2012 through 2017 at the 10 Aravind Eye Care System hospitals showed a posterior capsule rupture rate of 1.45% (22,381 cases).5 Of these 20,245 (90.5%) had concomitant vitreous loss and the remaining 2,136 (9.5%) did not. The posterior capsule rupture rate with phaco was statistically higher for trainees (6.54%) compared to staff surgeons (1.42%). Assuming that the Greenberg data would have included many resident surgeries, it appears that 1.5% to 2% is a representative estimate of the posterior capsule complication rate for large populations of nonresident surgeons.
Avoiding Vitreous Loss Following Posterior Capsule Rupture
In many instances with a torn posterior capsule, it is possible to avoid rupturing the anterior hyaloid face. Caught unexpectedly by surprise, the surgeon must avoid the natural reflex to immediately withdraw the phaco or irrigation/aspiration (I/A) tip out of the eye upon recognizing a posterior capsule defect. Doing so abruptly unplugs the incision and allows the anterior chamber to collapse. The sudden negative pressure gradient will rupture an intact anterior hyaloid face, and as vitreous prolapses toward the incision, it will expand the capsular rent in the process.
This undesirable cascade of events can be prevented by first continuing irrigation in foot position 1 to prevent collapse of the anterior chamber. Next, using the nondominant hand, the surgeon must fill the anterior chamber with ophthalmic viscosurgical device (OVD) through the side instrument paracentesis prior to removing the phaco tip (Figure 62-1). As OVD is injected through the side-port opening, the surgeon moves from foot pedal position 1 to 0 (see Figure 62-1B) to avoid irrigating the OVD out. Filling the chamber with OVD prevents the posterior capsule from bulging forward as the incision is unplugged (see Figures 62-1C and D). If one resumes phacoemulsification or cortical clean-up, the same maneuver must be repeated whenever these irrigating instruments are removed.
Early Recognition of Posterior Capsule or Zonular Rupture
It is only safe to remove residual nucleus that remains anterior to any posterior capsule defect. Therefore, early recognition of posterior capsule rupture is the key to avoiding a descending nucleus. One must often rely upon indirect clues to recognize a posterior capsule defect because the iris and the nucleus obscure direct visualization of the zonular and posterior capsule anatomy. Sudden deepening of the chamber with momentary expansion of the pupil (Figure 62-2), the transitory appearance of a clear red reflex in the periphery, and the inability to rotate a previously mobile nucleus can all indicate capsular or zonular tears. More obvious and ominous signs would be excessive tipping or lateral mobility of the nucleus or partial posterior descent of the nucleus.
Although resuming phaco is tempting, doing so in the presence of an occult posterior capsule defect will invariably expand the defect and increase the risk of any retained lens material descending. Phacoemulsification relies upon high irrigation inflow to inflate the anterior chamber. This inflow, the phaco tip, and the second instrument all approach the nucleus from above, and the underlying posterior capsule is a necessary backstop to support the nuclear fragments and provide a barrier between the vitreous and the phaco tip. Therefore, routine maneuvers that are safely performed above an intact capsule become potentially treacherous once the posterior capsule has ruptured.
Fluctuations in chamber depth and surgical maneuvers such as nuclear rotation, sculpting, and cracking tend to expand any posterior capsule defect. The hyaloid face may be ruptured by the infusion stream or by slight post-occlusion surge that an intact posterior capsule would have normally shielded. The downwardly directed infusion and instrumentation forces will tend to propel the nucleus posteriorly against or through the rent. The large phaco tip diameter makes it hard to selectively aspirate nucleus without vitreous. Therefore, the likelihood of nuclear descent increases the longer the capsular breach goes undetected.
At whatever point a posterior capsule defect is suspected or diagnosed, the surgeon must consider any coincident risk factors before deciding upon a strategy. If only small, soft nuclear fragments remain and there is no vitreous prolapse, continuing phaco over a temporary scaffold (discussed later in this chapter) may be considered. However, with a larger mass of remaining nucleus, especially if it is brunescent or accompanied by zonulopathy or a small pupil, it may be prudent to convert to a large-incision manual extracapsular cataract extraction (ECCE; Figure 62-3). Because the zonular or capsular defect often remains concealed beneath the residual nucleus, there frequently is a strong temptation to resume phaco. However, the safest opportunity to remove the entire nucleus is before it descends through a progressively widening posterior capsule defect.
Converting to a Large-Incision Manual Extracapsular Cataract Extraction
When converting to a manual ECCE, it is preferable to make a new incision superiorly (see Figure 62-3E). This provides lid and brow protection for the larger incision, improves comfort because of less lid movement across the sutures, and avoids the irregular wound architecture associated with extending the shelved temporal clear corneal incision. The latter can be abandoned and left unsutured because it is inherently self-sealing. Creation of the new manual ECCE incision can usually be done under topical anesthesia, particularly if supplemented with a local subconjunctival injection of lidocaine. Alternatively, a posterior sub-Tenon’s injection of 2% lidocaine can be made with a curved 23-gauge blunt-tipped Simcoe cannula. Through a tiny, inferior-fornix conjunctival buttonhole, the cannula is advanced alongside the globe into the posterior sub-Tenon’s space (Figure 62-4). Anesthetic is slowly injected until retrograde flow causes ballooning of the inferior conjunctiva.
If the capsulorrhexis diameter is too small to extract the remaining nucleus, it should be cut with one or more radial relaxing cuts along the superior margin. The large ECCE incision is extended with corneal scissors following a diamond blade limbal groove (see Figure 62-3E). The incision size should be generous enough to permit use of an irrigating lens loop. Because of the risk of forcibly expelling vitreous, bimanual expression should be avoided if a posterior capsule rent is present or suspected. A generous amount of dispersive OVD should be placed both behind and in front of the nucleus, and tipping the superior pole of the nucleus anteriorly with OVD facilitates sliding the lens loop beneath it (see Figures 62-3F and G). The irrigating lens loop is attached to a 3-mL syringe with balanced salt solution, and after it cradles the nucleus it is withdrawn slowly like a kitchen spatula. The resistance of the incision will often cause the nucleus to slide off the lens loop. One must avoid the instinct to lift and compress the nucleus against the cornea, resulting in excessive endothelial cell loss. Instead, the backside of the lens loop should press against the posterior scleral lip of the incision (see Figure 62-3H). This counterintuitive action will generate slight posterior pressure and gape the incision enough to deliver the nucleus as the lens loop is withdrawn
How far the nucleus initially descends through a posterior capsule defect will depend upon the vitreous anatomy. If the vitreous is very liquefied or the eye has undergone a prior vitrectomy, the nucleus will sink to the retina too rapidly to allow any response by the surgeon. Alternatively, the nucleus may partially descend onto an intact hyaloid face. Such slight posterior displacement can be very subtle and go undetected. Finally, if the hyaloid face is ruptured, the nucleus may tip or partially descend until it is suspended and supported by formed vitreous. In these latter 2 situations, a nuclear rescue technique may be possible.
As part of the mental rehearsal for what to do with a partially descending nucleus, one should consider the clinical consequences of different scenarios. Understandably, the surgeon dreads having to refer a disappointed patient for additional surgery following a complication. However, assuming that a vitreoretinal colleague is not simultaneously available in the same operating suite, leaving a dropped nucleus behind is not a disastrous complication if managed properly. This does require the inconvenience of a subsequent posterior vitrectomy to remove the retained nucleus, but the outcome is generally favorable following timely referral to the vitreoretinal surgeon.6–10
Although tempting, the worst tactic for recovering a partially descended nucleus is to try to chase and spear it with the phaco tip.11 Lacking the normal capsular barrier, the posteriorly directed irrigation flow will flush more vitreous forward, expand the rent, and propel the nucleus away. Attempting to emulsify or aspirate the nucleus may ensnare vitreous into the large-diameter phaco tip. Applying suction and ultrasound following vitreous incarceration can produce a giant retinal tear. Regardless of the vitreoretinal surgeon’s expertise, repair of a retinal detachment associated with a giant retinal tear is complicated and carries a very high risk of proliferative vitreoretinopathy.
The subsequent strategies in this chapter are considered advanced techniques and may not be appropriate for the skill set or comfort zone of many good cataract surgeons. Therefore, each individual surgeon must weigh his or her capability and confidence in performing these maneuvers against the very acceptable option of allowing the nucleus to descend. In this case, simply closing the eye following an anterior vitrectomy and implantation of an intraocular lens (IOL), prior to referral to a vitreoretinal colleague, would be a very appropriate option.
Which Ophthalmic Viscosurgical Device?
Which of the many different varieties of OVDs is best for managing posterior capsule rupture? Dispersive agents, such as Viscoat (Alcon Laboratories, Inc) or Healon EndoCoat (Johnson & Johnson Vision), are very retentive. They better resist aspiration and are less apt to be burped out of the eye with slight pressure at the incision site. These properties make dispersive OVDs ideal following posterior capsule rupture, where the objective may be to block a zonular defect, partition and compartmentalize an area, or support lens material on the verge of descending. Of course, when one needs to quickly inflate the anterior chamber prior to removing the phaco tip, whatever OVD is on the instrument tray should be used.
At the conclusion of surgery, one should not aggressively aspirate any OVD in the posterior chamber if the capsule is ruptured—particularly if the anterior hyaloid face is intact. Fortunately, the smaller size and molecular weight of dispersive agents makes prolonged and protracted pressure spikes less likely when small quantities are retained.12–14 The inability to aggressively and thoroughly aspirate OVD in the posterior chamber is a significant drawback to choosing maximally cohesive agents, such as Healon5 or Healon GV following posterior capsule rupture. Because of their larger molecular weight, residual amounts of these agents will produce the most severe and most prolonged pressure spikes.12–15 In the presence of any posterior capsule or zonular defect, it is generally safer to first constrict the pupil with acetylcholine chloride (Miochol) prior to aspirating OVD from the anterior chamber.
Rescuing a Partially Descended Nucleus—The Viscoat PAL
If one elects to retrieve a partially descended nucleus, a safer alternative to aspirating it with the phaco tip is to elevate the nucleus into the pupillary plane or anterior chamber from below. It may be possible to inject dispersive OVD beneath the nucleus via a limbal incision (see Figures 62-3C and D). There may be several obstacles to accomplishing this, however. First, the pupil or capsulorrhexis diameter may be quite small; these problems may have predisposed the eye to capsule rupture in the first place. A small pupil or capsulorrhexis can impede elevation of a large nucleus and make it particularly difficult for an OVD cannula to maneuver behind it. Prolapsed vitreous will further hinder such attempts to inject OVD beneath the nucleus. The nucleus may suddenly sink if these maneuvers induce further vitreous loss and prolapse.