(Fig. 21–16), and the Koo cutter (Asico) (Fig. 21–17). All foldable IOLs can be bisected safely with one of these instruments with prior insertion of viscoelastic above and below the IOL and after mobilization of the IOL into the AC. Three-piece IOLs actually need not be completely transected; a cut that is at least 50% across the optic will allow the two halves of the optic to separate as one half is being withdrawn through the 3-mm incision. The trailing hemioptic will either be completely severed at the incision or will remain attached and follow the leading hemioptic out of the eye.27

Removing a plate-haptic silicone IOL may be accomplished in one piece, without sectioning, through a 4-mm incision; firm purchase on the leading haptic with forceps is necessary. However, bisection along the long axis with Chu or Koo cutters may be achieved by bisecting the proximal haptic and hemioptic first, and then rotating the IOL 180 degrees for bisection of the second haptic and hemioptic. Each half may then be removed through a 3-mm incision with forceps.

IOL REPLACEMENT

Intraoperative

Replacing an IOL may be indicated at the time of primary IOL implantation or as a secondary procedure. Removing and replacing an IOL at the time of primary implantation may be indicated if it becomes immediately apparent that the incorrect IOL type or power had been inadvertently implanted—usually an IOL for a different patient. A second indication for immediate replacement is a damaged IOL, such as a fractured haptic that did not permit proper centration or a fractured optic that would interfere with proper visual function. In each of these cases, the

FIGURE 21–17 Serrated-platform Koo cutter for intraocular transection of silicone IOLs (Asico).

damaged IOL may be removed and replaced by an intact IOL of the same power and design. However, if the primary IOL was a plate-haptic design and a tear in the posterior capsule occurred after implantation, the primary plate-haptic IOL must be removed and replaced with a loop-haptic IOL with the loops now being placed into the ciliary sulcus.

Postoperative

There are many indications for secondary IOL replacement (Table 21–4). Whether primary or secondary, IOL replacement is, by definition, always a two-stage procedure: removal of the primary IOL followed by implantation of the secondary IOL. Depending on the anatomy of the eye following IOL removal, replacement implantation may be back into the capsule, into the ciliary sulcus, or into the anterior chamber. If the capsule is intact, this is the preferred location for reimplantation. If the posterior capsule was torn in the process of IOL removal, but

FIGURE 21–16 Heavy-jaw cutter for intraocular transection of silicone and acrylic IOLs.

TABLE 21–4 CAUSES OF IOL REPOSITIONING,

REMOVAL, OR REPLACEMENT

Primary operative complications Undesirable optical phenomena Damaged (dysfunctional) IOL Incorrect power

Rotation (toric IOL) Decentration Subluxation Dislocation

Corneal edema/bullous keratopathy Iritis/uveitis-glaucoma-hyphema (UGH) syndrome Secondary glaucoma

Cystoid macular edema Infectious endophthalmitis

Removal to facilitate vitreoretinal surgery

the anterior capsulorrhexis is still intact, a PC IOL may be placed into the ciliary sulcus or with the haptics in the sulcus and the optic through the anterior capsulorrhexis. Similar secondary bag/sulcus implantation may be performed if a posterior capsular opening was previously created by a neodym- ium:yttrium-aluminum-garnet (Nd:YAG) laser; if the posterior capsular opening is completely stabilized by marginal fibrosis, the IOL may be placed completely into the bag. Additionally, if a small posterior tear occurred during primary IOL explantation, this may be converted to a posterior CCC (see Chapter 5). The capsule, now stabilized, may be implanted with the secondary PC IOL. If, upon removal of the primary IOL from the capsular bag, partial zonulodialysis occurred but the capsule remained intact, a capsule tension ring (Fig. 21–18) may be implanted into the capsular equator to support the remaining zonule prior to IOL implantation.

FIGURE 21–18 PMMA capsule tension ring for capsular bag circularization and stabilization in cases of partial zonulodialysis.

The secondary loop-haptic IOL can then be implanted into the intact capsular bag, orienting the loop axis in the meridian of the zonulodialysis. The combination of the ring and the loop haptic at the meridian of zonulodialysis helps to provide resistance to postoperative capsular fibrotic contraction in that meridian, which, if it occurred, could lead to further “unzipping” of the zonule.

In the event that both the anterior and posterior capsules have lost all integrity or the capsule has become completely dialyzed, the surgeon has three remaining choices for secondary IOL implantation: a sutured PC IOL, an AC IOL,28 or an anterior iris stroma IOL (Worst Artisan Ophtec). At present, the latter two options require PMMA IOLs with the attendant requirement that the incision be enlarged and possibly sutured. In addition, anterior chamber implantation also requires that a patent peripheral iridectomy be created, either with scissors in the traditional fashion or with an automated vitrectomy instrument.

CONCLUSION

Problems during implantation of one-piece PMMA as well as foldable IOLs are reported regularly. Many of these problems can be avoided by careful implantation and appropriate IOL positioning. Many can be managed by surgeon observation of IOL damage with removal and replacement. In those circumstances when IOL decentration or subluxation occurs late, appropriately planned surgery with multiple options should provide for a satisfactory outcome.

REFERENCES

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3.Leaming DV. Practice styles and preferences of ASCRS members: 1998 survey. J Cataract Refract Surg 1999;25: 851–859.

4.Fechner PU, van der Heijde GL, Worst JGF. The correction of myopia by lens implantation into phakic eyes. Am J Ophthalmol 1989;107:659–663.

5.Foster JA, Lam S, Joondeph BC, Sugar J. Suprachoroidal dislocation of a posterior chamber intraocular lens. Am J Ophthalmol 1990;109:731–732.

6.Sandramouli S, Kumar A, Rao V, Khosla A. Subconjunctival dislocation of posterior chamber lens. Ophthalmic Surg 1993;24:770–771.

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8.Stark WJ, Goodman G, Goodman D, Gottsch J. Posterior chamber intraocular lens implantation in the absence of posterior capsular support. Ophthalmic Surg 1988;19:240–243.

9.Chakrabarti A, Gandhi RK, Chakrabarti M. Ab externo 4-point scleral fixation of posterior chamber intraocular lenses. J Cataract Refract Surg 1999;25:420–426.

10.Helal M, El Sayyad F, Elsherif Z, El-Maghraby A, Dabees M. Transcleral fixation of posterior chamber intraocular lenses in the absence of capsular support. J Cataract Refract Surg 1996;22:347–351.

11.Epley KD, Levine ES, Katz HR. A simplified technique for stable transcleral suture fixation of posterior chamber intraocular lenses. Ophthalmic Surg Lasers 1999; 30:398–402.

12.Wasserman D, Apple DJ, Castaneda VE, Tsai JC, Morgan RC, Assia EI. Anterior capsular tears and loop fixation of posterior chamber intraocular lenses. Ophthalmology 1991;98:425–431.

13.Assia EI, Legler UFC, Merrill C, et al. Clinicopathologic study of the effect of radial tears and loop fixation on intraocular lens decentration. Ophthalmology 1993;100:153–158.

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16.Nagamoto S, Kohzuka T, Nagamoto T. Pupillary block after pupillary capture of an Acrysof intraocular lens. J Cataract Refract Surg 1998;24:1271–1274.

17.Tognetto D, Agolini G, Ravalico G. Spontaneous dislocation into the vitreous of a poly (methyl methacrylate) disc lens 9 years after surgery. J Cataract Refract Surg 1999;25:289–292.

18.Carlson AN, Stewart WC, Tso PC. Intraocular lens complications requiring removal or exchange. Surg Ophthalmol 1998;42:417–440.

19.Schneiderman TE, Johnson MW, Smiddy WE, Flynn HE, Bennett SR, Cantrill HL. Surgical management of posteriorly dislocated silicone plate-haptic intraocular lenses. Am J Ophthalmol 1997;123:629–635.

20.Smiddy WE. Modification of scleral suture fixation technique for dislocated posterior chamber intraocular lens implants. Arch Ophthalmol 1998;116:1116– 1117.

21.Panton RW, Sulewski ME, Parker JS, Panton PJ, Stark WJ. Surgical management of subluxed posteriorchamber intraocular lenses. Arch Ophthalmol 1993; 111:919–926.

22.Shakin EP, Carty JB. Clinical management of posterior chamber intraocular lens implants dislocated in the vitreous cavity. Ophthalmic Surg Lasers 1995;26:529– 534.

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Currently, most intraocular lenses (IOLs) are implanted at the time of cataract extraction. However, situations arise in which it may be beneficial for a patient to receive an IOL placed weeks, months, or even decades after the removal of a cataract. An IOL may be placed in an aphakic eye in a secondary IOL implantation procedure. As the average age of aphakic patients continues to rise, many patients find it increasingly difficult to tolerate aphakic spectacles or manipulate and care for their aphakic contact lenses. The overwhelming majority of these patients will benefit from secondary IOL implantation. A number of alternatives to aphakia now exist when faced with a planned or unplanned lack of capsular support during anterior segment surgery. The new IOL the surgeon can implant may be an iris fixated posterior chamber lens (PCL), a residual capsulesupported or transsclerally sutured (TS) PCL, or an anterior chamber lens (ACL).

An unsuitable IOL may be removed from a pseudophakic eye at the same time a new one is placed in an IOL exchange procedure. Intraocular lens exchange is performed to replace a poorly tolerated IOL with another that will be better tolerated. Inflammation from an inappropriately sized or malpositioned ACL, PCL, or iris-supported IOL may cause chronic cystoid macular edema (CME). Glaucoma from peripheral anterior synechia (PAS) or uveitis- glaucoma-hyphema (UGH) syndrome secondary to malpositioned IOLs may also be occasionally seen. In addition, corneal decompensation from IOL-endothe- lial touch may be caused by either ACLs or iris supported PCLs. IOL exchange can also be performed for

refractive reasons, to eliminate anisometropia due to inappropriate IOL power.

ANTERIOR CHAMBER

INTRAOCULAR LENSES

Advantages of ACLs include ease of insertion and decreased intraoperative surgical time. Disadvantages include corneal endothelial cell loss, compromise of angle tissue, formation of peripheral anterior synechia, fibrosis of haptics into the angle, pupillary block, increased intraocular pressure, iris chafe, iritis, CME, and hyphema.1–10 Most of these complications were seen with closed-loop lenses. More recently designed flexible open-looped ACLs have decreased but not eliminated the above complications.5

TRANSSCLERAL FIXATION OF

POSTERIOR CHAMBER

INTRAOCULAR LENSES

Transscleral fixation of IOLs in the posterior chamber has a number of theoretical and practical advantages over ACLs. There are no lens elements in the angle, and transscleral fixation reduces the formation of PAS, fibrosis of haptics into the angle, or the development of the UGH syndrome. No lens elements traverse the pupil, decreasing the incidence of iris chafing, iritis, and CME. Finally, with the optic behind the iris there is a reduced chance of endothelial cell touch and pupillary block. However, both iris and TS lens