Loose Zonules and Subluxated Lens: Surgical Management

Robert J. Cionni, MD

Zonular compromise, whether congenital, iatrogenic, traumatic, or due to disease, presents a serious challenge to cataract surgeons. Every step of the surgical procedure from capsulotomy to final removal of the viscoelastic is challenging and intraoperative complications such as vitreous loss are more likely. Postoperative decentration of an IOL is also more likely. However, new devices and techniques can minimize stress on the compromised zonules during and after surgery and have been shown to decrease the risk of complications in these patients.

Indications

In young children, if the lens is not threatening to dislocate posteriorly or anteriorly and an accurate refraction can be obtained, observation is warranted and amblyopia treatment begun. However, if amblyopia cannot be effectively treated by conventional means such as glasses, contact lenses, patching, or a combination of the three, lens extraction may be the best option. For older children and adults, lens extraction should be considered if there is poor visual acuity attributed to the subluxated lens that is not amenable to spectacle correction or if the lens is threatening to dislocate anteriorly or posteriorly. Additionally, an anteriorly subluxated lens may induce elevation of intraocular pressure (IOP), thereby necessitating lens removal.

Examination

A comprehensive preoperative examination will help surgeons better understand the potential challenges of the surgical procedure. The surgeon should characterize the zonular defect by describing the weakness in terms of degree of loss, location of the defect, and presence or absence of vitreous within the anterior segment. Phacodonesis should be noted. Phacodonesis is more evident in an undilated eye because dilation often stabilizes the ciliary body and iris, dampening any iris/lens movement. It is important to perform gonioscopy to look for angle recession or synechiae in case an anterior chamber IOL is contemplated in the absence of sufficient capsular bag support.

Surgery

A number of surgical principles must be understood to improve the chance for a successful outcome. Placing the incision away from the area of zonular weakness will reduce the stress caused by necessary movements of the tip of phacoemulsification handpiece. A generous amount of highly retentive viscoelastic material injected over the area of zonular dialysis should help prevent or limit vitreous prolapse. The surgeon should work through the smallest incision required for the preferred instrumentation. This will minimize chamber collapse and the forward vitreous movement that can occur with egress of fluid or viscoelastic through a larger incision.

Slide 1

The capsulorrhexis should be initiated in an area remote from the dialysis in order to use the stronger remaining zonules for countertraction. In cases with extensive zonular loss or severe generalized weakness, it may be necessary to begin the tear by cutting the anterior capsule with a sharp, 15° steel blade while providing countertraction with a second blunt instrument. The capsulotomy should be large enough to allow for easy nucleus manipulation. It may be necessary to stabilize the capsular bag with a dull second instrument or with an iris retractor to complete the capsulorrhexis. Once a capsulorrhexis has been completed, the surgeon can stabilize the capsular bag by grasping the capsulorrhexis edge with one to four iris retractors ¹ (Slide 1). Generous, yet careful hydrodissection or viscodissection to loosen the nucleus as well as the cortex will reduce zonular stress during nucleus removal and cortical aspiration. If the nucleus is soft enough and the capsulorrhexis large enough, prolapse of the nucleus out of the bag and into the anterior chamber during hydrodissection will markedly decrease zonular stress during phacoemulsification.

Slide 2

Emulsification of the nucleus should be performed using low vacuum and aspiration settings, which will allow a lower bottle height. A high infusion bottle raises IOP, which in turn forces fluid through weakened zonules, hydrating the vitreous. Vitreous hydration can result in positive pressure, chamber shallowing, and vitreous prolapse. However, the bottle should not be so low as to allow hypotony and chamber collapse, which can also lead to vitreous prolapse. Divide and chop techniques diminish zonular stress during the emulsification as long as equal opposing forces are applied so that the nucleus is not displaced. To manipulate the nucleus halves or quadrants forward with minimal zonular stress, a viscoelastic agent should be injected between the halves or quadrants and the peripheral capsular bag to lift the nuclear fragments while expanding and stabilizing the peripheral capsular bag. Cortical viscodissection prior to aspiration will also limit the stress on remaining zonules without requiring the countertraction of weak zonules² (Slide 2). Viscoelastic is injected against the residual anterior capsular rim and peripheral capsular bag, separating the cortex from its adhesions to the capsule. It may be helpful to aspirate the cortex manually using a 24- to 27-gauge cannula within an anterior segment filled with viscoelastic material because automated irrigation and aspiration can lead to vitreous hydration and positive pressure.³ Whenever cortex is aspirated, the surgeon should strip along a vector that is tangential to the capsular bag periphery instead of pulling directly away from the zonules to decrease the risk of damaging the zonules further.

Slide 3

If a small amount of vitreous presents during the procedure, it can be removed from the anterior chamber using a "dry" vitrectomy technique with an automated vitrector and a viscoelastic-filled chamber.⁴ Significant vitreous prolapse is effectively managed by a bimanual vitrectomy using a sideport incision for irrigation with a 25- or 27-gauge cannula. The vitrectomy handpiece can be inserted through the main incision or through a pars plana sclerotomy5 (Slide 3).

Achieving IOL centration and long-term stability can be challenging in an eye with significant zonular loss or weakness. I prefer foldable acrylic IOLs with long haptics and an optic diameter not smaller than 6 mm (e.g., MA60BA, Alcon, Ft. Worth, Texas) in case some lens decentration occurs postoperatively. Folding a three-piece lens "mustache style" will allow the haptics to unfold directly into the capsular bag without dialing the haptics in. This technique will minimize the zonular stress that occurs during haptic placement. Plate-haptic style silicones IOLs are a poor choice for patients with zonular dialysis or significant zonular weakness because these IOLs have a greater tendency for postoperative decentration and capsular contraction. Perhaps plate-haptic silicone IOLs would be a better option if inserted while a capsular tension ring is in place.

Some surgeons advocate placing the haptics perpendicularly to the dialysis to expand the partially collapsed capsular bag. However, the IOL then relies on zonular support from only one haptic. Haptic orientation parallel to the dialysis provides better zonular support yet will induce ovaling of the bag and perhaps increases the chance for decentration away from the dialysis. I recommend placing the IOL into the bag and gently rotating the IOL into the axis that provides the best possible centration. I also suggest using a capsular tension ring, which will be discussed later in this tutorial.

Finally, when removing viscoelastic material at the end of the case, the use of a 27-gauge cannula through the sideport incision to aspirate small amounts of viscoelastic material alternated with intermittent refilling with balanced salt solution will help prevent late vitreous prolapse by maintaining a deep anterior chamber.

Over the past several years, newer techniques have been developed to more effectively manage a patient with zonular dialysis. I have already mentioned the use of iris retractor hooks to stabilize the capsular bag after capsulorrhexis. The silicone stop on the hook is adjusted to pull the capsulorrhexis edge toward the scleral wall thereby supporting the loose capsular bag for safer phacoemulsification.

Capsular Tension Ring

Slide 4

The capsular tension ring (CTR), introduced by Drs. Legler and Witschel in 1993 and manufactured by Morcher GmbH (Stuttgart, Germany), and the modified capsular tension ring (MCTR), also manufactured by Morcher GmbH, have truly revolutionized our approach to zonular dialysis. These PMMA rings can be inserted into the capsular bag at any point after the capsulorrhexis has been completed and can remain within the bag postoperatively.⁶ The rings are implanted using either dull forceps or a specially designed shooter (Geuder Shooter) and the effect is a dramatic expansion and stabilization of the capsular bag (Slide 4). Before inserting a CTR, a space should be created between the peripheral capsular bag and any remaining lenticular material with viscoelastic. This will help prevent entrapment of cortex under the CTR, which can be difficult to aspirate. If a CTR is placed before phacoemulsification, a safety-suture should be looped through the leading eyelet. I use 10-0 Prolene (Slide 5) sutures. The suture is left trailing out of the incision and can be used to retrieve the CTR if the capsule breaks during phacoemulsification. Additionally, if the CTR is difficult to place, this suture can be used to help coax the leading haptic around the periphery of the capsular bag. Once the CTR is in place, the remainder of the procedure can be performed with an advantage of having a CTR-stabilized capsular bag.

Slide 5

Although a CTR usually provides adequate expansion and capsular bag stabilization, in more severe cases the capsular bag may remain loose or decentered. Pseudophacodonesis may remain postoperatively, which can result in pigment dispersion and chronic inflammation. Additionally, long-term centration in patients with progressive generalized zonular weakness, such as that caused by pseudoexfoliation, is uncertain. My colleagues and I have seen several cases of complete posterior dislocation of an IOL within the capsular bag, which have occurred years after the original surgery. We are also aware of several cases of complete dislocation of the capsular bag, posterior chamber IOL, and CTR complex postoperatively.

With this in mind, several techniques have been devised to secure the CTR and/or the capsular bag to the scleral wall in patients with more significantly loose zonules. Robert H. Osher, MD, and Vladimer Pfeifer, MD, have independently developed techniques of suturing the CTR to the scleral wall.^7,8 Both of these techniques require the passage of needles through the peripheral capsular bag which risks rupture of the bag.

Slide 6

Slide 7

The MCTR has an angled hook with an eyelet extending off the ring that allows suture fixation to the scleral wall without violating capsular bag integrity⁹ (Slide 6). The MCTR can also be placed into the capsular bag anytime after completion of the capsulorrhexis. However, the presence of a large, dense nucleus makes implantation of the ring more difficult. Therefore, I prefer to stabilize the capsular bag using disposable nylon iris retractors at the capsulorrhexis edge during phacoemulsification and then place the MCTR after the nucleus has been removed. I leave the iris retractors in place to lend stability and countertraction during MCTR placement. Before inserting the MCTR, viscoelastic should be placed just under the surface of the residual anterior capsular rim to create a space for the MCTR and to dissect residual cortex away from the peripheral capsule, making cortical entrapment by the MCTR less likely. A 9-0 Prolene suture, double-armed with CTC needles, is pre-placed through the eyelet of the fixation hook (Slide 7). Alternatively, the suture can be single-armed and the free end of the Prolene tied to the fixation hook eyelet. The MCTR is inserted with smooth forceps through the main incision and dialed into the capsular bag with a Y hook (Slide 8). The fixation hook will often "capture" anteriorly to the capsulorrhexis edge. If it does not capture, the hook is easily manipulated anteriorly with an Osher Y hook while using an Osher Nucleus Manipulator to retract the capsulorrhexis edge.

Slide 8

Slide 9

The Y hook is then used to dial the MCTR until the eyelet is centered at the site of zonular dehiscence or weakness where it is then displaced to the scleral wall to be certain that the chosen location will result in bag centration (Slide 9). A scleral flap is fashioned at this site so that once the Prolene suture is tied, the knot can be covered. Viscoelastic is then injected to create space between the undersurface of the iris and the anterior capsule in preparation for needle passage. The needles are placed through the incision, into the pupil, and behind the iris, through the viscoelastic. The needle and suture should remain anterior to the anterior capsule at all times (Slide 10). The needle pass is then continued out through the scleral wall at the site of the fixation hook. The needles should exit the scleral wall approximately 1.5 mm posterior to the corneal-scleral junction. This will position the fixation hook posteriorly enough to prevent postoperative iris chaffing. The sutures are tightened until centration is obtained and a temporary knot tied (Slide 11). If a single-armed suture is used, the needle is passed partial-thickness through scleral bed beneath the scleral flap and the suture is then tied to itself. After suture fixation of the MCTR, any remaining cortex can be aspirated manually with a 24- to 27-gauge cannula. Alternatively, one can use an automated irrigation and aspiration device but vitreous hydration and prolapse may be more likely. The capsular bag is then reinflated with viscoelastic prior to insertion of a posterior chamber IOL.

Slide 10

Slide 11

I recommend foldable style, acrylic posterior chamber IOLs. Three-piece lenses are folded mustache style so that the haptics will spontaneously unfold into the capsular bag without the need for dialing (Slide 12). However, I prefer to inject a single-piece AcrySof lens (model SA60AT). Using the Monarch II delivery system (Alcon), this posterior chamber IOL is easily delivered directly into the capsular bag without zonular stress (Slide 13).

Slide 12

Slide 13

Once the posterior chamber IOL is in the capsular bag, the temporary knot is tightened just enough to affect IOL centration. The tails of the knot should be left somewhat long to prevent erosion through the scleral flap. The conjunctiva is then brought back into position over the scleral flap, which covers the prolene knot. Viscoelastic is removed and the incision hydrated and checked for security before transporting the patient to the recovery room.

Three designs of the MCTR are available (Slide 14). The fixation hook on model 1-L is located on the trailing end of the ring. Model 2-C has the fixation hook on the leading edge of the ring so that it can be injected into the bag using the Geuder Shooter. Model 2-L has two fixation hooks and is used in patients with the most significant generalized weakness where two-point fixation is required.

CTRs and MCTRs of any model should not be used if a complete continuous capsulorrhexis is not attained or if a posterior capsule tear occurs because the expansile forces of the rings may cause the capsular bag to rupture. If it is not possible to place a CTR or MCTR, the surgeon may choose to suture the IOL to the scleral wall or implant an anterior chamber IOL. At the time of this writing, the CTR and MCTR are not yet approved for use in the United States, despite their widespread availability throughout the rest of the world. Although these newer devices have improved the operative management of zonular weakness, these cases still represent some of the most difficult procedures that we encounter. Skilled and knowledgeable management will usually result in a satisfying outcome for both the patient and surgeon.

Slide 14

Video

References

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2. Cionni R, Osher R. Complications of phacoemulsification. In: Weinstock F, ed. Management and Care of the Cataract Patient. Cambridge, Mass: Blackwell Scientific Publications; 1992:198-211.
3. Osher R, Cionni R. The torn posterior capsule: Its intraoperative behavior, surgical management and long-term consequences. J Cataract Refract Surg. 1990;16:157-162.
4. Cionni R, Osher R. Complications of phacoemulsification surgery. In: Steinert R, ed. Cataract Surgery: Techniques, Complications and Management. Philadelphia, Pa: WB Saunders; 1995:327-340.
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7. Osher R. New approach: Synthetic zonules. In: Osher R, ed. Video Journal Cataract Refract Surg. 1997;13:1.
8. Pfeifer V. Suturing the ring. In: Osher R, ed. Video Journal Cataract Refract Surg. 1998;14:4.
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