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May 2005

 
Clinical Update: Cataract
Years After Implantation: Managing Dislocated Bag-IOLs
By Lori Baker Schena, Contributing Writer
 
 

It’s a delayed complication that can take cataract surgeons by surprise—spontaneous bag-IOL dislocation years after the original surgery. For many ophthalmologists, the problem comes out of the blue, especially considering the routine nature of the procedure.

Alan S. Crandall, MD, professor of ophthalmology at the University of Utah, Salt Lake City, and Nick Mamalis, MD, director of the university’s ophthalmic pathology laboratory, first described the phenomenon in 1999 when they recognized spontaneous bag-IOL dislocation years after cataract surgery.

It continues to be a problem. This past February, a patient came to Dr. Crandall’s practice complaining of a sudden “white-out” for 20 minutes. The next day, his vision was poor. “Other patients complain of a classic jiggling in their vision,” Dr. Crandall said. “It comes on so suddenly that many patients mistake it for a stroke or retinal tear. When we first saw this, we were puzzled because many of the symptoms are subtle. Now we recognize it quickly.”

Dr. Crandall has published on the link between pseudoexfoliation and late IOL dislocation, and the feedback he receives from cataract surgeons all over the country indicates that dislocated IOLs are still an issue. Yet much about the problem remains unknown, including risk factors and incidence.

Diagnosing the Problem
Before malpositioned IOLs can be surgically managed, they first must be detected. Symptoms such as blurry vision and “jiggling” of the lens are immediate red flags that the patient may be experiencing a classic case of late bag-IOL dislocation.

The diagnosis of pseudophacodonesis or IOL subluxation is made during a dilated slit-lamp examination. David F. Chang, MD, clinical professor of ophthalmology at the University of California, San Francisco, cautions that diagnosis can be complicated by the fact that the position of a dislocated bag-IOL can shift, depending upon whether the patient is seated or supine. “Depending on the extent of the zonular loss, the bag-IOL may simply exhibit pseudophacodonesis, or a lateral subluxation. However, if most of the zonules are gone, the bag-IOL may reside just behind the iris when the patient is sitting at the slit lamp, then descend back to the mid vitreous when the patient lies down,” he noted. “The surgeon may not realize this until the patient is under the operating microscope.”  

Surgical Management
For mild cases, ophthalmologists may want to consider a conservative approach, said Uday Devgan, MD, assistant clinical professor of ophthalmology at the University of California, Los Angeles. “The anatomic center of the eye is not necessarily the visual axis, and any shift in the lens can impact the quality of vision,” he pointed out. “If there is only mild decentration and patient satisfaction is not too adversely affected, then it may be judicious to defer surgery.

“On the other hand,” he added, “if patients are symptomatic, where they are actually seeing the edge of the IOL or their vision is poor because they are not looking through the center of the lens, then surgery may be in order.”

When Surgery Is Essential
Depending upon the degree of vitreous liquefaction, if the bag-IOL is almost completely dislocated then surgery is  necessary and should be done in a timely manner. Dr. Chang recalled one patient with pseudoexfoliation whose bag-IOL complex was partially subluxated posteriorly at the slit lamp, but had dropped down onto the retina by the time of his scheduled surgery two weeks later. Dr. Crandall has seen the same phenomenon occur in just two days.

Dr. Crandall’s surgical management guidelines are straightforward. First, “get it done.” Second, make every attempt to know the position of the lens prior to surgery so that a surgical plan may be developed. Finally, be ready for any contingency, including vitrectomy, suturing and pars plana vitrectomy. 

Sophisticated Techniques
Paracentesis. The most challenging cases are those in which the bag-IOL complex has descended posteriorly into the anterior vitreous. In some cases, the bag-IOL will migrate forward to the pupil plane as one empties the anterior chamber by depressing the paracentesis edge. But Dr. Chang notes that explantation can be difficult even when the bag-IOL is sitting just behind the pupil. “Bag-IOL dislocations are very different from situations where a subluxated IOL still has posterior capsular support, and we can readily grasp a haptic or hook the haptic-optic junction,” he explained. “Here, the haptics are inaccessible and encased in a free-floating 10-millimeter diameter phimotic bag. Furthermore, with pseudoexfoliation, the pupil is often small, and you will want to use iris retractors because of the need to explant the entire bag—not just the IOL,” Dr. Chang said.

Posterior assisted levitation. In cases where the bag-IOL complex has descended into the anterior vitreous, and is therefore not supported, Dr. Chang performs a variation of the posterior assisted levitation technique1 first popularized by Charles D. Kelman, MD.

He first inserts a Viscoat cannula through a pars plana sclerotomy 3.5-mm behind the limbus. “Injecting a dispersive viscoelastic behind the IOL will immediately provide supplemental support so that it does not descend further with manipulation,” Dr. Chang said. Next, under direct visualization with the operating microscope, he uses the cannula tip to elevate the bag-IOL complex into the pupillary plane, and to tip one end up through the pupil where the optic can be grasped with toothed forceps. “Because the fibrotic bag is so wide, it helps for the levitating instruments to have the more posterior angle of approach afforded by the pars plana sclerotomy,” he said. “Obviously, IOLs in the posterior vitreous cavity should be retrieved by a vitreoretinal surgeon.”

Suturing. Where the bag-IOL complex is loose, but has not dislocated posteriorly or peripherally, “it is possible to secure the bag-IOL without losing vitreous,” said Dr. Chang. “You can use a double-armed 9-0 polypropylene suture to suture each haptic to the sulcus. One of the needles will pass right through the peripheral bag and behind the haptic, so that it doesn’t have to be externalized.”

Pseudoexfoliation as a Risk Factor
Little is known about what causes delayed bag-IOL dislocation after cataract surgery, but Dr. Crandall did report that patients with pseudoexfoliation syndrome were at risk for experiencing a late spontaneous dislocation of the IOL within the capsular bag.

“This raises the question,” said Dr. Chang, “of whether placing capsular tension rings (CTR) in patients with pseudoexfoliation will prevent late bag-IOL dislocations. If I have patients with pseudoexfoliation in whom the zonules appear to be of normal strength, I don’t place a ring. However, if there is any sign at all of zonular weakness, I suggest using a CTR because it should resist the forces that produce capsulophimosis and centripetal zonular traction.”

Dr. Chang noted that if there is major zonular loss, then a CTR alone will not stabilize the bag. Unfortunately, the Cionni-modified ring and the Ahmed capsular tension segment, which would allow scleral suture fixation of the ring, are not available in the United States. 

Other Preventive Measures
Dr. Chang notes additional steps to consider for lowering the risk of late bag-IOL dislocation.2 He suggests using an acrylic optic because of the decreased tendency for anterior capsular fibrosis and capsulorhexis shrinkage as compared with silicone. He also recommended selecting a three-piece acrylic IOL because the PMMA haptics are stiffer and have greater rigidity compared with single-piece haptics. “Finally,” he said, “you should secondarily enlarge a small diameter capsulorhexis in pseudoexfoliation patients at the end of surgery. If you already see fibrosis of the capsulorhexis edge developing one month after cataract surgery in these patients, you may want to make relaxing cuts in the edge with the YAG laser.”

Dr. Devgan suggested using modern generation lenses with haptics that keep the lenses well centered, and lenses that have a uniform power from the center to the edge. “Thus, decentration by even 2 mm doesn’t necessarily cause a significant degradation in image quality—and this is a key point,” he said.

“The diameter of the capsulorhexis should be slightly smaller than the diameter of the IOL optic,” he added. “If I have a 6-mm optic, I will make a 5.5-mm diameter capsulorhexis. This allows the edge of the capsulorhexis to surround, and hold in place, the lens optic.”

Recognition Is Vital
Dr. Chang concluded that because it takes so long for spontaneous bag-IOL dislocation to develop in patients with abnormal zonules, it will be years before we can assess whether these preventive measures will help. Added Dr. Crandall, “The important thing to stress is that while we don’t have the answers to prevent the problem, it is vital that ophthalmologists recognize late-dislocated IOLs—especially in patients with pseudoexfoliation—and either treat the patient or refer them to an expert.”

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1 Chang, D. F. J Cataract Refract Surg 2002; 28:1515–1519.
2 Chang, D. F. Ophthalmology 2002;109: 1951–1952.

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Drs. Crandall and Devgan have no related financial interests. Dr. Chang is a consultant for AMO and has received educational travel support from Alcon, but has no financial interest in any product.