A dislocated posterior chamber IOL may occur after complicated cataract surgery with loss of capsular/zonular integrity. Usually, the dislocation appears in the first weeks after surgery. Dislocation may also occur after uneventful surgery. In these cases, the IOL-capsular complex dislocates due to loose zonules.

AFTER COMPLICATED SURGERY
Dislocation due to zonular or capsular break is preventable with proper management of complications. For instance, in case of a minor tear in the capsulorrhexis or a small, defined tear in the posterior capsule, the IOL may still be placed in the capsular bag. The IOL haptics should be positioned away from the tear and the IOL gently folded to avoid widening the tear. In case of a larger tear in the posterior capsule, anterior vitrectomy is often necessary. If the capsulorrhexis is intact, the IOL should be placed with the haptics in the sulcus and the optic in the capsular bag (ie, optic capture), thus ensuring a stable and centered IOL. If the capsulorrhexis is not continuous, the IOL may be placed in the sulcus if there is enough capsule left to secure the IOL. However, an alternative location must be considered if there is too little capsular support. Alternatives include implantation of a scleral, iris-fixated, or anterior chamber IOL.

If the posterior chamber IOL dislocates after surgery, it may be repositioned in the sulcus to regain stability. However, fixation usually requires suturing the haptics to the scleral wall. If this is unachievable, IOL exchange may be the best choice.

In-the-bag IOL dislocation often occurs many years after surgery, mostly due to progressive weakening of zonules.^1-5 Davison6 first described the condition in 1993; it was virtually nonexistent before the advent of the capsulorrhexis. Predisposing conditions, such as pseudoexfoliation (PXF) syndrome, trauma, uveitis, previous vitrectomy, high axial length, and retinitis pigmentosa are present in approximately 90% of dislocation cases.^1-7 Zonular dehiscence, fibrosis, and capsular shrinkage may further compromise weakened zonules.4 The true incidence of in-the-bag IOL dislocation is unknown; only case reports have been published.

Loose zonules at the start of surgery present an increased risk of further weakening during hydrodissection, phacoemulsification, and IOL implantation. If the divide-and-conquer technique is used and the incision is made at the 12-o'clock position, stress will be focused on the superior zonules during creation of the initial groove. IOL implantation in this position may also compromise zonules surrounding the 12-o'clock area. Eventually, continuous gravitational force will further act on these zonules.

Recently, surgeons have become more daring in performing phacoemulsification in eyes with loose zonules. As a consequence, late in-the-bag IOL dislocation may dramatically increase in the future.⁴ In our hospital alone, we have performed 53 surgical reconstructions due to in-the-bag IOL dislocation over the past 4 years. Approximately 90% of cases had PXF syndrome. In our practice in the eastern part of Norway, approximately 15% of patients scheduled for cataract surgery have PXF syndrome.^8,9

Late in-the-bag IOL dislocation is graded as small, moderate, or total dislocation. In small dislocation (Figure 1), the IOL is centered; however, a gap is present between the pupillary margin and the IOL. Furthermore, pseudophacodonesis may be observed at the slit lamp. In moderate dislocation (Figure 2), the IOL is still observed in the pupillary area; however, it is decentered, and the patient's visual reduction is caused by looking through the peripheral part of the optic. In total dislocation, the IOL is either not visible in the pupillary area or a tiny part of it is observed at the lower pupillary margin.

If the IOL-bag complex is not present in the pupillary area, the IOL may often be identified behind the lower part of the iris and ciliary body by examining the eye with a three-mirror contact-lens and/or ultrasound biomicroscopy.

SURGERY
Observation or surgery? A small in-the-bag IOL dislocation is, in most cases, asymptomatic. Observation is an option, at least in elderly patients. In case surgical intervention is postponed, the patient must be followed carefully for further loosening of the IOL-capsular complex.

Anterior or posterior approach? Surgery is indicated if the IOL is either moderately or totally dislocated. An anterior approach is possible in most cases. Even if only a tiny part of the IOL is visible in the lower part of the pupillary area, it may be grasped with forceps and carefully lifted up to the pupillary space. In total dislocation, scleral indentation may facilitate observing the IOL-bag complex.

There is minimal risk for the IOL-bag complex to sink to the posterior pole if temporarily placed in the pupillary area. With the patient in the supine position, the IOL-capsular complex will float upon the anterior hyaloid membrane, providing primary cataract surgery was uneventful.

If the IOL-bag complex displaces to the posterior pole preoperatively, we prefer a combined procedure. First, the vitreoretinal surgeon performs a pars plana vitrectomy. With forceps, he moves the IOL into the pupillary area and delivers it to the cataract surgeon's forceps (inserted through a corneal incision). The procedure may then proceed with the cataract surgeon suturing the haptics to the scleral wall. Alternatively, the IOL may be exchanged.

In these cases, the IOL-bag complex has no support from the vitreous; the surgeon must take care to not drop the IOL into its previous dislocated position.

IOL exchange or suturing the dislocated IOL to the scleral wall? Several surgical approaches may be used to offset late in-the-bag dislocation, such as IOL exchange for an anterior chamber or iris-fixated IOL or repositioning the dislocated IOL. In the latter option, the IOL is sutured to the scleral wall; this is now our preferred technique because IOL exchange carries a high risk for pigment dispersion and corneal endothelial cell loss. Additionally, IOL exchange with a relatively large incision is required. With repositioning, the IOL is still in the preferred posterior chamber, and the risk of vitreous loss is much lower compared with removing the IOL-bag complex.

Complications, such as intraocular hemorrhage, IOL tilt, and suture break or erosion, may also occur with suturing of the haptics to the scleral wall. However, these risks may be minimized with proper precaution during surgery.

SUTURING HAPTICS, USING A CTR
The superior haptics will most frequently be observed in the upper temporal or upper nasal position. Suturing should be initiated by making scleral grooves or small scleral flaps where the haptics are located. If the pupil is too small to localize the haptics, consider using iris retractors.

The next step is to make a small limbal incision opposite the inferior scleral incision. After injecting an ophthalmic viscosurgical device (OVD), a double-armed, 10-0 Prolene suture with straight needles is inserted through the limbal incision and left in the anterior chamber. The incision may be spread with forceps to prevent the sharp needle from capturing any corneal tissue. Subsequently, a 26-gauge bent needle is introduced into the eye through the superior scleral groove or bed, approximately 2 mm from the limbus.

After inserting the straight needle through the fused anterior and posterior capsules, just inside the haptic and into the lumen of the 26-gauge needle (Figure 3), the needle is retracted and removed from the eye. There is no risk of extending the capsular tear because there are strong adhesions between the fused capsules.

The procedure is then repeated with the second straight needle, meeting the 26-gauge bent needle—introduced approximately 1 mm behind limbus—in front of the capsule and haptic. The needles are cut, and the suture is loosely tightened with a temporary knot. Repeating the maneuver on the opposite side, the inferior haptic is secured. To ensure IOL centration, both sutures should be tightened to the same extent. Finally, the knots are rotated, and the scleral flap and conjunctiva are closed.

If a capsular tension ring (CTR) was used during primary surgery, the suture may be looped around the CTR. This is a useful procedure, especially if the haptics are difficult to identify. When plate haptics with holes are present, the sutures may be threaded through the holes, ensuring adequate IOL positioning as long as the scleral incisions are properly placed. Sutures around a J- or C-haptic should be carefully placed in the middle of the haptic loops to avoid tilt and decentration. Because the haptics are embedded in the capsular bag, there is minimal risk of slippage of the sutures, which could result in postsurgical redislocation.

When posterior capsular opacification is present, Nd:YAG capsulotomy should be postponed until after repositioning. Furthermore, replacing the IOL-bag complex may cause peripheral opacities to move centrally, and capsulotomy will be needed.

PREVENTION
Prevention of late in-the-bag IOL dislocation is possible only during the primary surgery. In eyes with loose zonules, gentle surgery is important. Chopping technique and temporal approaches are preferable because they reduce zonular stress. The diameter of the capsulorrhexis should be relatively large, minimizing the force exerted on the capsule and zonules while manipulating the nucleus inside the bag. A small capsulorrhexis may also increase the risk of capsular fibrosis and shrinkage.^10,11 Although CTRs may further loosen the zonules during surgery,¹² most surgeons prefer to use these rings in eyes with compromised zonules, thus stabilizing the capsular bag during surgery. In advanced cases of loose lenses, implanting a Cionni Ring (Modified Capsular Tension Ring; Morcher GmbH, Stuttgart, Germany) or other surgical approaches, such as intracapsular cataract extraction or pars plana lensectomy, are alternatives.

To prevent total dislocation, reoperation must occur as soon as possible after IOL dislocation in complicated cataract surgery. IOL dislocation may also occur after uneventful surgery. In these cases, the in-the-bag IOL complex usually dislocates many years after surgery. The reasons for IOL dislocation include progressive loosening of the zonules; predisposing conditions, such as PXF syndrome, are often present. Surgeons should be aware of be prepared to perform reoperations for this increasingly frequent complication. The in-the-bag IOL complex may be removed or repositioned by suturing it to the scleral wall. For prevention, surgeons must be most careful during cataract surgery in eyes predisposed to loose zonules.

Liv Drolsum, MD, PhD, is a Professor of Ophthalmology, Ulleval University Hospital, Oslo, Norway. Dr. Drolsum states that she has no financial interest in the products or companies mentioned. She may be reached at tel: +47 91346143 or +47 23016114; fax +47 22119989; e-mail: liv.drolsum@medisin.uio.no.

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