STEPWISE IOL FIXATION STRATEGIES FOR VARYING SEVERITY OF ZONULOPATHY

David F. Chang, MD

As discussed in Chapter 1, zonulopathy significantly increases the risk of capsular complications during phacoemulsification. During nuclear emulsification and cortical clean-up, the capsular bag can be stabilized using a variety of devices such as capsular tension rings (CTR; Morcher GmbH, Ophtec BV), the Ahmed capsular tension segment (CTS; Morcher GmbH, distributed in the United States by FCI Ophthalmics), the Assia capsular anchor (AssiAnchor; Hanita Lenses), and capsule retractors.^1–5 Assuming that the capsular bag is successfully preserved, the surgeon must next determine if it is suitable for long-term intraocular lens (IOL) centration and fixation. Which IOL to use and whether a CTR or other implantable fixation device, such as a Malyugin/Cionni ring (Morcher GmbH) or capsular support segment, is necessary must be decided. These considerations are particularly important for eyes with pseudoexfoliation because of the risk of progressive zonulopathy leading to spontaneous late dislocation of the capsular bag-IOL complex.^6–15

Jehan, Mamalis, and Crandall were the first to report a series of patients with pseudoexfoliation who presented with late spontaneous dislocation of the capsular bag⁶ (Figures 13-1 and 13-2). Their original 2001 case series was comprised of 8 polymethylmethacrylate (PMMA) IOLs and 1 plate-haptic silicone IOL that dislocated between 5 to 10 years after the original surgery. Soon after, I published the first report of late spontaneous 3-piece foldable IOL dislocation in pseudoexfoliation patients.⁷

Although rarely discussed, one should consider that the capsulorrhexis acts like a sphincter that starts to progressively constrict during the early postoperative period. This concentric contracting force is counterbalanced by the centrifugal capsular tension exerted by the zonules. Therefore, diffuse zonular weakness will be associated with excessive capsulorrhexis contraction or capsulophimosis, and this is typically seen in cases of late bag-IOL dislocation^16–18 (see Figures 13-2B and C). However, it is also likely that more extensive anterior capsule fibrosis and contraction exerts excessive centripetal strain on the already-weakened zonules in these eyes.⁵ This would more likely occur with incomplete cortical clean-up, excessive iridocyclitis, a small-diameter capsulorrhexis, and silicone IOLs. This vicious cycle of zonulopathy permitting greater capsular contraction, which further weakens or stretches the zonules, may lead to severe capsulophimosis.

Complicating any evaluation of preventive measures is the fact that late dislocation may take more than 10 years to occur. Nevertheless, making educated choices based upon our knowledge of IOL design and materials and interaction with the capsular bag is the subject of this chapter. One should conceptualize zonular weakness as representing a continuum of severity, rather than being a single uniform condition. This principle is equally important whether one is considering phaco technique or long-term IOL fixation. Conceptually, I will describe 5 different clinical scenarios that represent the spectrum of mild to severe zonulopathy with pseudoexfoliation. I employ different IOL fixation strategies with each scenario, forming a stepwise surgical algorithm.

Whether every eye with pseudoexfoliation should receive a CTR is the subject of some debate.1–4 Because of the likelihood of progressive loss of zonules, I recommend placing a CTR whenever an eye with pseudoexfoliation exhibits any degree of zonulopathy during surgery. However, many eyes with pseudoexfoliation show no sign of zonular laxity during surgery, and for these cases I do not believe that a CTR is necessary. When a CTR is not used with pseudoexfoliation eyes, there are several surgical and IOL design considerations that should reduce the risk of capsular contraction, progressive zonular traction, and late bag-IOL dislocation.

It is widely acknowledged that thorough cortical clean-up is particularly important in these eyes. Although circumferential anterior capsular overlap of the optic edge is desirable, an excessively small-diameter capsulorrhexis must be avoided in these patients, as discussed in Chapter 1. Following IOL implantation, a small capsulorrhexis can be secondarily enlarged if necessary. After obliquely cutting one edge with long intraocular scissors, one retears a larger-diameter opening while maintaining anterior chamber depth with ophthalmic viscosurgical device (OVD). To reduce the likelihood of capsulorrhexis contraction, I also discussed the rationale for enlarging the diameter out to or beyond the optic edge in eyes with weak zonules or pseudoexfoliation in Chapter 1 (Figure 13-3). As an alternative to enlarging a small-diameter capsulorrhexis, one could make relaxing incisions in the continuous curvilinear capsulorrhexis edge after placing the IOL in the bag.

Since hydrophobic acrylic IOL material is associated with less anterior capsule fibrosis compared to silicone, I believe that the former material is preferable for pseudoexfoliation eyes^17,19 (see Figure 13-3). Three-piece designs with broad, stiff PMMA haptics are able to exert the maximum centrifugal tension against the capsular equator (Figure 13-4). In my opinion, they are preferable to the soft, floppy single-piece haptics for this reason. Finally, one should specifically examine the anterior capsule reaction during the early postoperative period in patients with pseudoexfoliation. If one already sees signs of early contracture and fibrosis after only a few weeks, prophylactic YAG relaxing cuts in the capsulorrhexis edge should be considered.²⁰

I therefore insert a 3-piece hydrophobic acrylic IOL without a CTR when the zonules appear reasonably strong in an eye with pseudoexfoliation. However, occasionally a round capsulorrhexis becomes ovalized following insertion of a 3-piece IOL, and this indicates significant zonular laxity (see Figure 13-4A). The longitudinal expansion of the capsular bag by the stiff 3-piece haptics is usually counterbalanced by zonular traction 90 degrees away from this axis. However, if the zonules are diffusely weak, the lack of this countertraction frequently results in an ovalized capsulotomy. At this point, a CTR can still be implanted into the capsular bag to redistribute the capsular tension (see Figures 13-4B through D).

Scenario 2: Mild to Moderate Zonular Weakness (Capsular Tension Ring)

In anticipation of progressive future zonular loss, even mild evidence of zonulopathy should warrant CTR placement in eyes with pseudoexfoliation. The objectives are to (1) prevent capsular contraction and capsulophimosis, (2) reduce progressive centripetal zonular stress caused by capsulorrhexis contraction, and (3) avoid IOL decentration caused by asymmetric capsular fibrosis.1–4 Clearly, a CTR alone will not always prevent late bag-IOL dislocation^21–23 (Figure 13-5). However, should this complication occur years later, the presence of a CTR may afford the surgical option to suture fixate the ring to the sclera.²³ Even following CTR insertion, a small capsulorrhexis diameter should still be avoided. In eyes with weaker zonules, the capsulorrhexis will exhibit a sphincter-like effect that is stronger with a smaller diameter opening. For this reason, my personal preference even following CTR insertion is still to secondarily enlarge the capsulorrhexis diameter out to the edge of the optic in eyes with pseudoexfoliation (see Figure 13-3).

There are numerous situations where a CTR alone may not provide sufficient long-term capsular support. These would include eyes with severe, diffuse circumferential weakness or a larger zonular dialysis. Although most commonly associated with pseudoexfoliation, delayed bag-IOL dislocation can occur in virtually any eye manifesting zonular abnormalities, such as trauma,8–11,13 uveitis,^8,9,11 and retinitis pigmentosa.^10–13 Prior vitrectomy appears to be the next most common risk factor after pseudoexfoliation.^9–11,13 Suture fixating a bag-stabilizing device can be considered (see Scenario 4), but this technique is time consuming and surgically demanding, and requires that the device be available in the operating room.

In my opinion, an underused option is to place a 3-piece foldable acrylic IOL in the ciliary sulcus⁵ (see Figures 1-8, 1-9, and 13-6). With saccadic lateral eye movements, there is a certain amount of IOL inertial displacement force that is transmitted to the zonular complex if the lens is encased by the capsular bag. It seems logical that these lateral saccadic forces would continually strain the nasal and temporal zonules to some degree. In the setting of significant diffuse zonular weakness, this cumulative strain may contribute over time to eventual dislocation of the bag-IOL complex. The rationale of sulcus placement of 3-piece IOLs is that the haptics provide additional 2-point fixation; they will lie in contact with and transmit saccadic IOL inertial displacement forces directly to the ciliary body, instead of the zonules.

If there is no optic capture, the capsulorrhexis will aggressively constrict in the absence of an intracapsular IOL. This may avulse the remaining weakened zonules and result in a dehisced and crumpled mass of capsule suspended in the visual axis. Therefore, if sulcus placement is elected because of severe zonular weakness, I still implant a CTR to prevent this from occurring (see Figures 13-6D through F). Capsulorrhexis capture of the IOL optic can also be considered as a measure to prevent capsulophimosis (see Figure 13-6H). With pseudoexfoliation, there is also a risk of an occult zonular dialysis that is hidden from the surgeon’s view by the iris. Therefore, an additional benefit of optic capture with sulcus IOL placement is to prevent later rotation of one haptic through a potential zonular dialysis, resulting in delayed postoperative IOL subluxation (see Figures 1-8L, 1-9J, and 13-6H). Finally, there is no need to reduce the spherical power of a 3-piece IOL in the sulcus if the optic is captured by the capsulorrhexis.

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