Anterior Vitrectomy Techniques for the Cataract Surgeon

Cataract Surgery, 3rd Edition

PART VII – Management of Complications

Chapter 45 – Anterior Vitrectomy Techniques for the Cataract Surgeon

David F. Chang, MD*
* David F. Chang MD is clinical professor at the University of California, San Francisco, and in private practice in Los Altos, CA. He has no financial interest in any product or instrument mentioned.

Contents

	•	Preventing Vitreous Loss Following Posterior Capsular
	•	Managing the Nucleus Following Posterior Capsule Rupture
	•	Rescuing a Partially Descended Nucleus – the Viscoat Posterior Assisted Levitation
	•	Managing Vitreous Loss and Residual Lens Material
	•	Bimanual Pars Plana Anterior Vitrectomy
	•	Cortical Removal Following Posterior Capsule Rupture
	•	Emergency Preparedness

CHAPTER HIGHLIGHTS

	≫	Posterior assisted levitation (PAL) technique
	≫	Pars plana anterior vitrectomy
	≫	“Visco trap”
	≫	The “contingency kit”

Every cataract surgeon must have a game plan for when and how to perform an anterior vitrectomy following posterior capsule rupture. This chapter will review the indications, the goals, and the techniques for managing vitreous loss in this setting. Understanding and mentally rehearsing these strategies in advance will better prepare anterior segment surgeons to properly manage vitreous loss amidst the stress of a surgical complication.

Preventing vitreous loss following posterior capsular rupture

Despite a torn posterior capsule, it is frequently possible to avoid rupturing the anterior hyaloid face. The cataract surgeon must avoid the natural reflex to immediately withdraw the phaco tip upon recognizing a posterior capsular tear. Abruptly unplugging the incision causes the anterior chamber to empty and shallow. The resulting posterior pressure gradient will rupture an intact hyaloid face, and vitreous will prolapse anteriorly toward the incision, expanding the capsular defect in the process.

To prevent this undesirable cascade of events the surgeon must fill and stabilize the anterior chamber with an ophthalmic viscosurgical device (OVD) prior to removing the phaco tip. Upon recognizing a capsular tear during phaco or cortical irrigation–aspiration (I–A), the surgeon should keep the anterior chamber pressurized with continuous irrigation while deciding what to do next. Continuing to phaco may be an option with a small zonular dialysis or capsular defect. Before removing the phaco or I–A tip, the surgeon injects OVD through the side port incision while changing from foot pedal position 1 to 0. Once the anterior chamber is filled with OVD, the posterior capsule and anterior hyaloid cannot bulge forward as the incision is unplugged. If phacoemulsification or cortical cleanup is resumed, these same maneuvers must be repeated whenever the instruments are removed.

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Managing the nucleus following posterior capsule rupture

Early recognition of posterior capsule rupture is often the key to avoiding a dropped nucleus. This is because it is much easier to remove the nucleus while it remains anterior to the posterior capsule defect. Because the nucleus is approached from above, continuing instrument and fluidic forces will eventually expand an unrecognized capsular defect enough to allow the nucleus to fall posteriorly.

One must often rely upon indirect clues to recognize a posterior capsular defect because the iris and the nucleus obscure the zonular and posterior capsular anatomy. The first sign of zonular or capsular rupture might be sudden deepening of the chamber with momentary expansion of the pupil, the transitory appearance of a clear red reflex peripherally, or the inability to rotate a previously mobile nucleus. More obvious and alarming signs would be excessive tilting or lateral mobility of the nucleus, or partial descent of the nucleus. Continuing to phaco a large dense lens in the presence of a capsular tear or zonular defect carries a high risk of a dropped nucleus. Recognizing these early warning signs alerts one to manually remove the nucleus through a large incision before it is too late.

If the residual nucleus is small and soft enough, continuing phaco within the anterior chamber over a trimmed Sheet's glide is a consideration. As described by Marc Michelson, the glide serves as an artificial posterior capsule to keep lens material from dropping posteriorly and to shield the phaco tip from aspirating vitreous from below.^[1] The incision should be widened slightly to accommodate inserting the phaco tip alongside the glide. Movements of the phaco tip should be minimized to avoid simultaneously displacing the glide. Using bimanual microincisional phaco instrumentation through separate 1.2mm side ports avoids this problem if the surgeon is adept at this technique.

Rescuing a partially descended nucleus – the viscoat posterior assisted levitation

How far the nucleus initially descends will depend upon the vitreous anatomy and the size of the capsular tear. If the defect is large and the vitreous is liquefied, the nucleus will rapidly sink to the retina before the cataract surgeon has any chance to react. Alternatively, the nucleus may partially descend when there is enough remaining capsular support and an intact hyaloid face (Figure 45-1). Such slight posterior displacement can be very subtle. Finally, if the hyaloid face is ruptured with some remaining capsule, the nucleus may tip or partially descend until it is suspended and supported by formed vitreous. In this situation, a rescue technique may be possible.



Figure 45-1 Partial descent of nuclear fragments following posterior capsule rupture. Courtesy of David F. Chang.

Attempting to chase and spear a partially descended nucleus with the phaco tip is fraught with risk. Lacking the normal capsular barrier, the posteriorly directed irrigation flow will hydrate and flush more vitreous forward, expanding the rent. The fluid stream will then propel nuclear fragments posteriorly. Attempts to emulsify or aspirate the nucleus may ensnare vitreous into the large diameter phaco tip. The tractional forces from employing suction and ultrasound in the presence of vitreous incarceration can produce a giant retinal tear.

A safer alternative is to elevate the nucleus into the pupillary plane or anterior chamber by manually lifting it from below, but accomplishing this may be difficult for several reasons. First, posterior capsule rupture occurs more frequently when the pupil is small. A small-diameter pupil hampers visibility and together with a small capsulorrhexis will impede levitation of a large nucleus. If the phaco incision is used, the angle of approach may be too steep for an OVD cannula to successfully maneuver behind the nucleus. It is especially difficult to inject OVD beneath the nucleus if there is a small pupil, a small capsulorrhexis, or any prolapsed vitreous. As more and more vitreous exits the eye through the manipulated incision, the nucleus will drop further posteriorly.

Charles Kelman popularized the posterior assisted levitation (PAL) technique by which a cyclodialysis spatula, inserted through a pars plana sclerotomy, is used to lift the nucleus into the anterior chamber from below (“New PAL method may save difficult cataract cases.” Ophthalmology Times 1994; 19:51).^[2] Compared to the phaco incision, a pars plana sclerotomy provides a much better instrument angle for getting behind the nucleus. Richard Packard and the author subsequently published the results of using the dispersive OVD Viscoat (Alcon Laboratories) and the Viscoat cannula to support and levitate the nucleus – the so-called Viscoat PAL technique.^[3] An equally effective dispersive agent is Healon D (AMO).

After opening the conjunctiva and applying light cautery, a disposable micro-vitreoretinal (MVR) blade (Alcon, Katena) is used to make a pars plana sclerotomy 3.5mm behind the limbus. An oblique quadrant should be selected to avoid the long ciliary vessels. The Viscoat cannula tip is then advanced and aimed behind the nucleus under direct visualization. The first step is to inject a bolus of dispersive OVD behind the nucleus to prevent any further descent (Figure 45-2).^[3–5] Periodic palpation of the globe confirms that over-inflation has not occurred.



Figure 45-2 Dispersive ophthalmic viscosurgical device (Viscoat) is injected through a pars plana sclerotomy behind the descending nuclear fragments to provide immediate supplemental support. Courtesy of David F. Chang.

If the nucleus has subluxated laterally, directing dispersive OVD toward the area beneath it will often buoy the nucleus toward a more central position. This is preferable to blindly probing behind the iris with a metal spatula. The cannula tip is then used to mechanically maneuver and elevate the nucleus into the anterior chamber (Figure 45-3). A small capsulorrhexis or pupil will stretch to accommodate the levitation of a greater diameter nucleus. Small aliquots of additional OVD can be injected as needed to maneuver and prop up the nucleus. One should never attempt to float the nucleus into the anterior chamber using a massive infusion of dispersive OVD alone. Unlike using liquid perfluorocarbon in a vitrectomized eye, an excessive injection of OVD in this setting will over-inflate the globe and cause vitreous expulsion through the sclerotomy or phaco incision.



Figure 45-3 The Viscoat cannula is used to carefully levitate the nuclear fragments into the anterior chamber. Courtesy of David F. Chang.

Using dispersive OVD to first support and reposition the nucleus prior to definitive manual levitation is the major advantage of the Viscoat PAL variation.^[3–5] Because there is no aspiration involved, these PAL maneuvers should minimize iatrogenic vitreous traction and reduce the chance of accidentally touching the retina with a metal spatula tip. However, it is important to keep the cannula tip under direct visualization by focusing the microscope slightly posteriorly.

Once a fragment descends into the mid or posterior vitreous cavity and beyond the microscope's range of focus (without a special viewing lens), it is dangerous to blindly fish for it with any instrument. One should abandon the dropped nucleus and concentrate on removing the residual epinucleus and cortex, while preserving as much capsular support as possible. A thorough anterior vitrectomy must be performed prior to inserting the IOL. Depending upon the capsular anatomy, either an anterior or a posterior chamber IOL can be selected.^[5–8] In the absence of capsular support, sutured posterior chamber IOLs are more time consuming to implant and superiority over anterior chamber IOLs has not been demonstrated.^[9,][10]Since the vitreoretinal surgeon will later use a three-port pars plana fragmatome and vitrectomy technique to remove any retained nucleus, it is preferable to insert an IOL during the initial surgery if possible.

Managing vitreous loss and residual lens material

Converting to manual extracapsular cataract extraction

Any residual nucleus retrieved with the Viscoat PAL technique can be removed using either of two different approaches. As described earlier, one can resume phaco over a Sheet's glide if there is no vitreous prolapse and the nucleus is soft and of limited size. However, a larger dense nucleus would be more safely removed by converting to a large incision manual extracapsular cataract extraction (ECCE) approach. This is best done by abandoning the self-sealing temporal phaco incision, and re-positioning the surgeon and microscope for a superior incision location.

For patients under topical anesthesia, a posterior sub-Tenon's block can be administered with 2mL of 2% lidocaine. A small conjunctival-Tenon's buttonhole is made in the inferior conjunctival fornix, avoiding the inferior rectus muscle insertion. Through this, a curved blunt Simcoe sub-Tenon's cannula is threaded alongside and behind the globe. The anesthetic is injected until conjunctival ballooning occurs. After making an adequately large superior ECCE incision, the nucleus should be surrounded and sandwiched by OVD. An irrigating lens loops should be used to extract the nucleus being careful not to lift it against the endothelium as it is withdrawn. Bimanual nuclear expression is contraindicated with an open posterior capsule.

The visco trap

As residual nucleus and cortex are removed, the phaco or I–A tip may at some point ensnare prolapsing vitreous. To avoid vitreous traction, the surgeon must immediately stop to perform an anterior vitrectomy before extraction of the remaining lens material can be resumed. Instead of using a coaxial infusion sleeve, a separate self-retaining irrigating cannula should be inserted though an obliquely directed limbal paracentesis. The objective is to keep the irrigation circulating within the anterior chamber where it cannot expand the capsular defect or hydrate the vitreous.

Most cataract surgeons insert the vitrectomy probe through the phaco incision. However, there are multiple drawbacks to this approach. First, the phaco incision is too wide for the sleeveless vitrectomy instrument and will leak. This results in poor chamber stability and allows both irrigation fluid and vitreous to prolapse externally alongside the vitrector shaft. Second, performing the vitrectomy in the anterior chamber will tend to draw more vitreous from the posterior segment forward into the anterior segment. Finally, as more and more vitreous exits the eye through either the vitrectomy instrument or the incision, the residual lens material that it was supporting will sink posteriorly toward the retina. It bears repeating that if the posterior capsule is open, it is the formed vitreous that is preventing the remaining nucleus and epinucleus from descending.

The author has proposed a strategy called the Visco Trap which, when combined with a pars plana anterior vitrectomy, can prevent the posterior loss of residual lens material in this situation.^[4,][5] The first step is to use a dispersive OVD such as Viscoat or Healon D to corral and lift any mobile lens fragments up toward the cornea. Next, the anterior chamber is completely filled with dispersive OVD in order to support and trap the residual lens material anteriorly as the vitreous is excised from below (Figure 45-4). Even though vitreous has already prolapsed forward, injecting OVD should not exert traction on the retina.



Figure 45-4 Following anterior vitreous prolapse, the residual lens fragments are elevated toward the cornea, where they are trapped by filling the anterior chamber with Viscoat. Courtesy of David F. Chang.

The Visco Trap is so named because of the need to employ a dispersive OVD. To effectively trap lens material the OVD should be maximally retentive so that it is less easily burped out of the eye by incisional manipulation. In addition, dispersive agents such as Viscoat and Healon D better resist aspiration by the I–A or vitrectomy instruments. Finally, small amounts of retained dispersive OVD are less likely to cause a prolonged or severe pressure spike because of the smaller molecular weight of these agents.^[11,][12]

Bimanual pars plana anterior vitrectomy

As with the Viscoat PAL, the pars plana sclerotomy is made 3.5mm posterior to the limbus in an oblique quadrant with a disposable MVR blade. The appropriate sized MVR blade is selected (19-gauge for most cutters) so as to avoid too tight an opening. The blade tip is oriented so as to produce a 1.2mm slit incision that is parallel rather than radial to the limbus. The blade is aimed toward the plane of the posterior capsule and advanced until it is visualized through the pupil. It is possible to perform this step under topical anesthesia alone. As mentioned earlier, a self-retaining irrigating cannula is placed through a limbal paracentesis, and angled toward the pupil. As described by Scott Burk, staining prolapsed vitreous with a triamcinalone suspension to improve visibility is an option.^[13] The sleeveless vitrectomy shaft is inserted through the pars plana sclerotomy until the tip can be visualized in the retro-pupillary space. If it does not easily pass through the incision, slightly enlarge the opening rather than force the entry.

METHOD OF PREPARING INTRACAMERAL TRIAMCINOLONE (IF NON-PRESERVE TRIAMCINOLONE IS NOT AVAILABLE)

Triamcinolone is supplied in a sterile vial containing 40mg in 1mL of preserved diluent. Burk has recommended a technique of removing the preserved diluent. However, this method of preparation is time-consuming and cumbersome, particularly given the stressful circumstances of a surgical complication. An alternative technique is to store the triamcinolone vial upright so that the precipitated drug settles to the bottom of the vial. Immediately prior to use, the one ml of diluent can easily be drawn off with a 25-gauge needle leaving the precipitated layer of white triamcinolone flakes at the bottom. The triamcinolone is then re-suspended with 3–4mL of sterile balanced salt solution (BSS) for off label use as a vitreous staining agent.

A thorough bimanual anterior vitrectomy is performed, being careful to focus posteriorly enough to keep the vitrectomy tip under direct visualization at all times. Vitreous traction is minimized by using low aspiration flow and vacuum settings, and maximizing the vitrectomy cutting rate (e.g. >400cpm). The vitrectomy tip should be moved very slowly and should never aspirate without simultaneous cutting vitreous. With the Viscoat Trap technique, the vitrectomy tip should be kept behind the pupil if possible. This will sever any trans-pupillary bands of vitreous without removing the dispersive OVD that fills the anterior chamber (Figure 45-5). When properly performed, one will see that the anteriorly trapped lens fragments remain immobilized as the vitrectomy is being carried out from below. This is because the OVD-filled anterior chamber has been isolated and partitioned from the vitrectomized posterior chamber.



Figure 45-5 The sleeveless vitrectomy cutter is introduced via a pars plana sclerotomy, and kept behind the plane of the capsulorrhexis and pupil. This severs the transpupillary bands, but keeps Viscoat–filled anterior chamber isolated from the vitrectomized posterior chamber. The self–retaining infusion cannula (not shown) is placed through a limbal paracentesis incision. Courtesy of David F. Chang.

Using a pars plana sclerotomy is an excellent but underutilized option for performing an anterior vitrectomy. The surgical objectives and principles are the same. One must not aspirate vitreous without cutting it, one should keep the vitrectomy tip under direct microscopic visualization, and one should not attempt to retrieve lens material that is in the posterior vitreous cavity. The main advantage is that using a properly sized pars plana sclerotomy will decrease incisional leak and vitreous prolapse by providing a better fluidic seal. Unlike with a limbal incision, the vitrector will not draw more vitreous forward into the anterior chamber and it will not aspirate the Viscoat partition. Performing the vitrectomy posterior to the pupil and the plane of the capsulorrhexis also decreases the chance of inadvertently cutting either structure. If the capsulorrhexis is preserved, an appropriate foldable posterior chamber IOL may be implanted in the ciliary sulcus with or without optic capture. The sclerotomy can be closed with an interrupted 8-0 Vicryl suture.

Some ophthalmologists would question whether a cataract surgeon has enough training to perform a pars plana anterior vitrectomy. The important distinction is that this is still an anterior vitrectomy performed under direct coaxial microscopic visualization. Posterior vitrectomy requires a special viewing lens, indirect light pipe illumination, and three watertight sclerotomy sites to permit high pressure forced infusion. Anterior vitrectomy following capsular rupture utilizes low-flow, gravity-fed infusion through a limbal cannula, and the sclerotomy need not and should not be tight. Making a 1.2mm wide pars plana incision is, therefore, the only new skill required of the cataract surgeon. All eyes are at greater risk of retinal tear and detachment following posterior capsule rupture and vitreous loss.^[14] Regardless of which vitrectomy incision was used, a careful peripheral retinal exam should be performed postoperatively for this reason. Some anterior segment surgeons may choose to refer these patients to a vitreoretinal sub-specialist.

Cortical removal following posterior capsule rupture

Following the retro-pupillary anterior vitrectomy, one can resume aspiration of the remaining cortex or epinucleus that was securely trapped within the Viscoat-filled anterior chamber. One should attempt to work in “slow motion” by lowering the irrigation bottle, and decreasing the aspiration flow and vacuum settings. There are several advantages to using bimanual I–A instrumentation for epinuclear and cortical extraction once the capsule or zonules have ruptured (Figure 45-6). The snug paracentesis incisions provide excellent chamber stability and reduce exiting fluid streams that might further induce vitreous prolapse. This also decreases the total volume of irrigation fluid circulating through the eye.



Figure 45–6 The bimanual irrigation–aspiration handpieces allow dissociation of the irrigation and aspiration currents. Courtesy of David F. Chang.

Without the constraining silicone irrigating sleeve, the aspirating tip can extend further peripherally into the capsular fornices. Burying the aspirating port within the peripheral-most cortex helps to block vitreous from becoming ensnared. Finally, the surgeon can direct the infusion away from the aspirating tip because the irrigation and aspiration currents are dissociated. This avoids further hydrating the vitreous cavity or flushing loose lens material posteriorly. If the aspirating port becomes entangled with vitreous again, one can repeat the Viscoat Trap maneuver followed by additional pars plana anterior vitrectomy. Bimanual cortical I–A can then be resumed.

Emergency preparedness

Posterior capsule rupture and vitreous loss necessitates an unsettling and stressful departure from the surgical routine for both surgeons and their operating room (OR) staff. Anticipating these difficulties, one can prepare for this contingency in several ways. First, one can assign and pre-program a phaco machine memory setting for “emergency” parameters. These might include a decreased bottle height, and reduced aspiration flow rate (20–24cc/min) and vacuum limit (100–125mmHg). This should avoid the need for nursing personnel to hurriedly and manually adjust the settings in the face of posterior capsule rupture.

Second, the OR staff can pre-package special instruments in a “contingency” kit that is kept in a separate sterile peel pack. This avoids the need to urgently search for a seldom-used instrument amidst the stress of an unexpectedly complicated procedure. Based upon the scenarios discussed in this chapter for converting to a large incision ECCE or performing a vitrectomy, one might choose to include a Simcoe sub-Tenon's cannula, corneal scissors, an irrigating lens loop, a self-retaining limbal infusion cannula, and a bimanual I–A handpiece set. Such a contingency set is commercially available (Chang Contingency Kit, Katena) (Figure 45-7), but can be easily assembled and customized using any surgeon's preferred instruments. Vitrectomy instrumentation, disposable MVR blades, Sheet's glides, and a dispersive OVD such as Viscoat should also be available in the operating room.



Figure 45-7 Chang Contingency Kit, Katena (author has no financial interest). Courtesy of David F. Chang.

In summary, cautious adherence to these principles may help surgeons to reduce the risk of dropping the nucleus following posterior capsular rupture. However, there is a fine line dividing maneuvers that are reasonable and safe from those that are overly aggressive or dangerous. Cataract surgeons must be honest in assessing their own level of comfort and expertise. Timely surgical management of a dropped nucleus by a vitreoretinal surgeon at a later date is always preferable to overstepping this fine line.^[14]

References

[1]. Michelson M.A.: Use of a Sheets' glide as a pseudoposterior capsule in phacoemulsification complicated by posterior capsule rupture. Eur J Implant Surg 1993.570-572.

[2]. Lifshitz T., Levy J.: Posterior assisted levitation: long-term follow-up data. J Cataract Refract Surg 2005; 31:499-502.

[3]. Chang D.F., Packard R.B.: Posterior assisted levitation for nucleus retrieval using Viscoat after posterior capsule rupture. J Cataract Refract Surg 2003; 29:1860-1865.

[4]. Chang D.F.: Managing residual lens material after posterior capsule rupture. Techniques in Ophthalmology 2003; 1:201-206.

[5]. Chang D.F.: Strategies for managing posterior capsular rupture. Phaco chop: mastering techniques, optimizing technology, and avoiding complications, Thorofare, NJ: Slack Inc; 2004.

[6]. Vajpayee R.B., Sharma N., Dada T., et al: Management of posterior capsule tears. Surv Ophthalmol 2001; 45:473-488.review

[7]. Gimbel H.V., Sun R., Ferensowicz M., et al: Intraoperative management of posterior capsule tears in phacoemulsification and intraocular lens implantation. Ophthalmology 2001; 108:2186-2189.discussion 2190–2192

[8]. Arbisser L.B., Charles S., Howcroft M., Werner L.: Management of vitreous loss and dropped nucleus during cataract surgery. Ophthalmol Clin North Am 2006; 19:495-506.review

[9]. Pokroy R., Pollack A., Bukelman A.: Retinal detachment in eyes with vitreous loss and an anterior chamber or a posterior chamber intraocular lens: comparison of the incidence. J Cataract Refract Surg 2002; 28:1997-2000.

[10]. Kwong Y.Y., Yuen H.K., Lam R.F., et al: Comparison of outcomes of primary scleral-fixated versus primary anterior chamber intraocular lens implantation in complicated cataract surgeries. Ophthalmology 2007; 114:80-85.

[11]. Burke S., Sugar J., Farber M.D.: Comparison of the effects of two viscoelastic agents, Healon and Viscoat, on postoperative intraocular pressure after penetrating keratoplasty. Ophthalmic Surg 1990; 21:821-826.

[12]. Probst L.E., Hakim O.J., Nichols B.D.: Phacoemulsification with aspirated or retained Viscoat. J Cataract Refract Surg 1994; 20:145-149.

[13]. Burk S.E., Da Mata A.P., Snyder M.E., et al: Visualizing vitreous using Kenalog suspension. J Cataract Refract Surg 2003; 29:645-651.

[14]. Scott I.U., Flynn Jr H.W., Smiddy W.E., et al: Clinical features and outcomes of pars plana vitrectomy in patients with retained lens fragments. Ophthalmology 2003; 110:1567-1572.

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