opening in the bag created by the lens haptic. If successful the capsule will distend, allowing gentle separation of the anterior from the posterior capsule. The plane of separation is then carried out for 360 degrees. The IOL can then be dialed out of the capsular bag and inspected. It then can be replaced with both haptics within the capsular bag, or, if the haptics are significantly distorted, replaced. If it is impossible to separate anterior from posterior capsule due to capsular fibrosis, further attempts should be curtailed rather than risk tearing the capsular bag or disinserting the zonule. The IOL can nevertheless be dialed out of the bag, but the new IOL must be placed in the ciliary sulcus.

A second implantation error is that of implanting an IOL upside down, the front side in back, or anteroposteriorly reversed. This is rarely a significant problem with single-plane one-piece or three-piece PMMA IOLs as their orientation is readily observed; however, a foldable IOL can easily unfold upside down if the insertion process is too fast and not properly controlled. Upside-down implantation of the IOL would be of potential refractive significance in the case of a one-piece PMMA IOL with angled loop-haptics, or with toric and multifocal IOLs, where the IOL power is on the anterior surface of the optic. Three-piece IOLs with polypropylene or extruded PMMA haptics have no significant memory. Therefore, after a short time they flatten in the capsular bag, inducing little change in the calculated postoperative power. In the case of a spherical monofocal IOL, even with angulated haptics, the IOL may be left in place with usually no more than0.25 of induced postoperative myopia. However, the silicone plate-haptic toric IOLs (STAAR AA4203T and AA4203TL) and the silicone loop-haptic multifocal IOLs (AMO Array SA40NB), with their added corrections intended to be on the anterior IOL surface after implantation, lose some of their intended effects when implanted reversed.

Because it has been estimated that there may be as much as 8.0 mm from the corneal endothelium to the posterior capsule when fully distended with a dispersive viscoelastic, it is usually possible to turn over a 6.0-mm optic IOL inside the eye. Refolding an IOL inside the eye with two instruments has also been demonstrated.14 Once refolded, rotation and secondary unfolding will correct the IOL orientation problem. Otherwise, the incision may be extended, and the inverted IOL may be removed and reimplanted right side up. The choice of corrective maneuver would depend on the surgeon’s judgment and experience.

Off-axis implantation relates specifically to toric IOLs. It would be extremely unusual and unlikely for a toric IOL to be inadvertently implanted at the incorrect axis. However, it is a simple matter to ro-

tate a plate-haptic silicone IOL to its correct axis at the time of implantation with an instrument through the 1.0-mm side-port incision.

Posterior IOL dislocation into the vitreous at the time of primary implantation is also a rare occurrence. There is a particular propensity for this to occur during unfolding of a three-piece IOL for sulcus implantation in the presence of a large rent in the posterior capsule, particularly after vitrectomy has already been performed. It can also occur during routine PMMA or foldable IOL implantation in the presence of an intact capsule, when the act of insertion or unfolding causes the capsule to tear, allowing the IOL to fall into syneretic vitreous. Tears in the posterior capsule during unfolding of three-piece IOLs usually occur when the unfolding leading haptic catches a fold in the posterior capsule. This can be avoided by the use of adequate viscoelastic to deeply fill the capsular bag to prevent the folds that can capture the unfolding haptic. With slow, controlled implantation, and manipulation of the folding forceps or injector, the tendency for the leading haptic to unfold in the wrong direction can be detected, and redirected, before implantation is completed. This will avert this complication.

POSTOPERATIVE IOL COMPLICATIONS

Postoperative IOL-related complications are usually associated with either malfunction or malposition of an IOL. Malfunction will include either unwanted optical images, such as glare, halos, or edge reflections, as seen with truncated PMMA or squareedged acrylic IOL designs, as well as with concentric multifocal designs, or incorrect or undesirable IOL power resulting in unwanted anisometropia with secondary ametropia.

IOL malpositions are traditionally classified into three categories: decentration, subluxation, and dislocation. With advent of capsular-fixated plate-haptic toric IOLs, however, a fourth category, IOL rotation, must be added.

In the anterior chamber, decentration may occur when the AC IOL is improperly sized. An AC IOL that is too short will decenter and be unstable. The haptic may repeatedly traumatize the corneal endothelium with subsequent endothelial damage. An unstable AC IOL may also rotate until a haptic migrates through the peripheral iridectomy, resulting in optic decentration and complaints of monocular diplopia. If an AC IOL is to be utilized, a peripheral iridectomy is mandatory to prevent pupillary block glaucoma. The iridectomy, however, should not be placed at the iris root, but in the mid-stroma. Should the IOL rotate, the mid-stromal position of the iridec-

tomy will prevent entrapment and migration of the IOL haptic.

An AC IOL that is too long may push the peripheral iris posteriorly, ovaling the pupil and causing chronic inflammation and secondary glaucoma—the uveitis- glaucoma-hyphema (UGH) syndrome. Iris-enclaved IOLs may become un-enclaved.15 The loosely fixated IOL may then become decentered with visual symptoms. In addition endothelial damage may occur.

Decentration of a PC IOL in the ciliary sulcus may also occur if the IOL’s overall size is too small for the diameter of the ciliary sulcus. If there is partial absence of the zonule, a haptic may migrate posteriorly, resulting in decentration of the IOL optic; however, this form of decentration may be more accurately described as a subluxation.

Decentration of an IOL fixated in the capsular bag may be caused by the IOL size, by the IOL haptic material, or by the postoperative behavior of residual lens epithelial cells. In the case of fixed-size IOLs whose haptics do not expand to fill the capsular space, such as plate-haptic designs, the overall diameter of the IOL may be shorter than the diameter of the capsule, resulting in decentration along the short or long axis of the IOL. This is particularly likely to occur in the presence of a large anterior CCC or a canopener capsulotomy. One haptic may dislocate anteriorly, out of the bag into the ciliary sulcus, or may actually dislocate through the dilated pupil into the anterior chamber, resulting in pupillary optic capture (Fig. 21–7). Finally, the optic of a loop-haptic PC IOL placed into the ciliary sulcus or capsular bag may be captured by the pupil and may cause pupillary

block.16 Flexible loop haptics made of material with poor elastic memory, such as polypropylene, may decenter under the contractile influence of metaplastic capsular fibrosis. The same fibrotic forces may also force a loop to dislocate anteriorly out of the capsule. Such asymmetric “bag-sulcus” fixation often results in optic decentration (Fig. 21–8). If an unrecognized equatorial capsular tear occurred at the time of original surgery, late subluxation or total posterior dislocation may occur, both the result of capsular fibrotic activity. Both loop-haptic17 (Fig. 21–9) and plate-hap- tic (Fig. 21–10) IOLs are subject to such occurrence. If adequate adhesion has developed between the anterior and posterior capsules around the remaining encapsulated loop-haptic or through the fenestration of a plate-haptic (Figs. 21–11, 21–12, 21–13), then total posterior dislocation into the vitreous (Fig. 21–14) may not occur.

MANAGEMENT OF IOL

COMPLICATIONS

The first decision to be made intraoperatively, when an IOL complication is observed, is whether or not to change the intended surgical procedure. If an IOL problem has been determined to have the potential to threaten positional stability or proper optical performance, then surgical correction is indicated. Similarly, postoperatively, if an IOL is determined to be the cause of pathophysiology or suboptimal optical performance, then secondary surgical intervention may be likewise indicated.18

Whether primarily or secondarily, the action taken usually falls into one of the three R’s: repositioning, removal, and replacement.

FIGURE 21–7 One-day postoperative anterior platehaptic dislocation with pupillary optic capture.

FIGURE 21–8 Superior optic decentration due to superior haptic anterior dislocation with resultant asymmetric bag-sulcus fixation.

FIGURE 21–9 Postoperative subluxation of loop-haptic posterior chamber (PC) IOL due to unstable posterior capsule.

IOL REPOSITIONING

IOL repositioning presumes that the desired IOL was implanted but that it is not in the desired anatomic position. A repositioning procedure may move an IOL without changing its location, such as rotating a toric IOL within the capsular bag or rotating an AC IOL to retrieve a haptic that has migrated through an iridectomy, or to release incarcerated peripheral iris to recircularize an oval pupil. An asymmetric IOL position such as bag-sulcus location, with one haptic in the bag and one in the sulcus, with optic decentration is a common cause for IOL repositioning. The surgeon then has the choice either to replace the sulcus haptic back into the bag or to place the bag haptic into the sulcus. Similarly, an optic or a haptic of a PC IOL may be partially or totally

FIGURE 21–11 Older, small-fenestration and newer, large-fenestration plate-haptic IOL designs.

through the pupil, with “optic capture” necessitating haptic repositioning. All of these maneuvers can be performed under topical anesthesia through a 1-mm paracentesis incision, with appropriate viscoelastic, at the slit-lamp, or in the operating room, depending on patient compliance.

There is another circumstance that may indicate surgical IOL repositioning, and that is total posterior dislocation. A lens that has gone through a large opening in the posterior capsule may be repositioned into the ciliary sulcus. This requires pars plana vitrectomy. If there is adequate anterior capsule remaining and the IOL is of appropriate size, the IOL may be placed into the sulcus without sutures.19,20 Some cases may necessitate polypropylene suture fixation of one or both haptics to the posterior surface of the iris21 or to the sclera.22–25

IOL REMOVAL

IOL removal without replacement is an extremely rare event. It is sometimes performed in eyes in which

FIGURE 21–10 Postoperative subluxation of smallfenestration plate-haptic PC IOL.

FIGURE 21–12 Artist’s diagram of capsular fibrosis through large-fenestration plate haptic.

FIGURE 21–13 Combination plate/loop-haptic silicone PC IOL designed to facilitate capsular fibrotic fixation.

the IOL itself is thought to be the cause of chronic uveitis, chronic endophthalmitis, recurrent spontaneous hyphema, pigmentary glaucoma, or progressive corneal endothelial cell loss—even though there is no malposition or refractive dysfunction of the IOL. In theses instances, an IOL may be removed and not replaced, almost as a diagnostic or therapeutic trial, to see if the chronic pathology will be corrected. A newer material (hydrophilic), more biocompatible IOL, may then be replaced as a tertiary staged procedure later.

IOL removal is also occasionally performed by vitreoretinal surgeons. This might occur if, at the time of posterior vitrectomy or scleral buckle, a welltolerated IOL loses its proper support or loses its transparency due to chemical adhesion, such as silicone oil adhering to a silicone IOL. In these cases, if the appropriate corrective measure is not undertaken at the time of the posterior segment procedure, the eye will be left, intentionally, temporarily aphakic, with reimplantation to be undertaken later by a cataract surgeon.

The method of IOL removal depends on the type and location of the IOL being removed. The incision

size required for IOL removal depends on the IOL optic material. PMMA IOLs require incisions large enough to accommodate the rigid optic to be removed; this usually means 5 to 6 mm. An incision of this length can affect corneal curvature. Therefore, its location, whether scleral or corneal, superior or temporal, may be preselected by the surgeon to achieve the desired astigmatic effect. Some AC IOLs (especially those with closed loops) may have formed peripheral anterior synechiae, “fibrotic cocoons,” around the haptics in the angle. The attempt at manual extraction may then be met with resistance. Excessive traction may result in iridodialysis and hyphema. In these cases, haptic amputation with scissors allows atraumatic optic removal; the haptics then may be either left in or removed by dialing them out of their fibrotic tunnels.

Removal of PMMA PC IOLs that are in the ciliary sulcus must also be removed carefully by dialing the haptics until they are free of any adhesions. Similarly, loop haptics encapsulated in the capsular bag may also be fixed by equatorial fibrosis. Attempt at IOL removal from the capsular bag may then be met with resistance, and continued traction may result in either a capsular tear or, more likely, zonulodialysis. Therefore, if resistance is encountered, after viscoelastic separation of the anterior and posterior capsules, haptic amputation may then be performed and the optic removed. The replacement PC IOL may still be implanted into the capsular bag or into the sulcus.

Foldable lenses may be removed “flat,” unfolded, and in one piece, through 4- to 6-mm incisions,26 if the intention is to use that incision length to alter the astigmatism. However, these IOLs may also be removed through astigmatically neutral 3-mm incisions by refolding the IOL intraocularly or by bisecting the IOL. Several optic cutting instruments have recently been designed for this purpose: the Utrata snare (Rhein) (Fig. 21–15), the Chu cutter (Rhein)