8 Intraocular Lens Exchange Abstract This chapter deals with the method, technique, and difficulties encountered in intraocular lens (IOL) exchange when adopted for residual refractive error correction and for other reasons. It is often necessary to exchange an IOL and the reasons can vary from placement of wrong power of IOL to decentrations and dislocations. Depending on the clinical scenario, the surgeon should be well versed with the various techniques of IOL exchange. This chapter highlights the causes and the surgical details that the surgeon should be acquainted with in order to perform a successful IOL exchange. Keywords: IOL exchange, IOL scaffold, decentered IOL, IOL cutting, IOL explantation, IOL insertion Occasionally an intraocular lens (IOL) must be exchanged as the IOL may have simply been the wrong power or is not tolerated due to glare or dysphotopsia. The IOL may have opacified with time; or most commonly, the IOL may have become unstable or subluxed due to progressive zonular laxity1 or the IOL may be causing inflammation, uveitis, hemorrhage, or ocular hypertension.2 Removing an IOL can be difficult due to the development of adhesions, especially if it has been in place for several years.3 This chapter outlines the indications for IOL exchange with an emphasis on explantation and capsular placement, as other chapters discuss the techniques for IOL implantation without capsular support. Dr. Nick Mamalis and his colleagues at the University of Utah produced a classic paper on the indications for explanted IOLs. In this paper, the indications for IOL explantation depend on the type of IOL ( In many ways, the simplest indication for IOL exchange comes when the wrong power of IOL is placed inside the eye. It may be difficult to explain to the patient why the surgical team placed the wrong power IOL, but the actual surgery is relatively easy. The surgery is straightforward as the error is often detected early in the postoperative course. As such, the haptics are not yet excessively adherent to the capsule that allows one to easily free the IOL from the capsule. Freeing the IOL, especially the IOL haptics, is the most difficult part of an IOL exchange. Jin et al prepared a nice series of cases where the wrong power of IOL was placed. They showed that the most common reason for placing the wrong power of IOL was incorrect estimation of the corneal power, followed by incorrect axial length measurement and thus followed by simply placing the incorrect IOL.2 The time from original surgery to the exchange varied from 1 day to 14 months with an average of 2.6 months.2 Following exchange in their series, 95% of patients had a best-corrected visual acuity of better than 20/40.2 Another option in patients with the wrong power IOL is to use refractive corneal surgery rather than lens exchange.3 Table 8.1 Intraocular lens (IOL) explantation by IOL type
8.1 Introduction
8.2 Indications for Intraocular Lens Exchange
Table 8.1) with IOL explantation most common in dislocated or decentered single-piece acrylic (SPA) IOL.1 The strategy for and the issues surrounding explantation differ depending on the reason for explantation.
8.2.1 Refractive
8.2.2 Visual Aberration
Visual aberrations such as glare disturbances, halos, and dysphotopsia are a common indication for IOL exchange, especially with multifocal IOLs.1 Unlike the situation where the wrong power IOL is placed, the decision to remove the IOL with visual aberrations is often delayed as the surgeon waits for symptoms to resolve.4 As a result, removing these lenses can be difficult as the capsule may be more adherent to the optic and more importantly to the haptics. In addition, it can be difficult to determine if the symptoms are related to the IOL, the wound, or the posterior capsule.
Davison reported on a large series of acrylic IOLs and described the positive and negative dysphotopsia with these popular square edge optic high refractive index IOLs.5 However, these visual aberrations have been associated with most of the IOLs in use including the rounded three-piece silicon IOLs.1 Geneva and Henderson nicely outlined the difficulty with treating negative dysphotopsia.6 In general, positive dysphotopsia are more associated with square edge lenses and the high index IOL materials, and the exchange strategy is to replace the existing IOL with one of a different material. In general, negative dysphotopsia is associated with high index IOL material and a square edge, and the strategy is to place the new IOL more anteriorly in the sulcus or with the optic anteriorly captured by the anterior capsule.
8.2.3 Inappropriate Intraocular Lens in the Sulcus
A perfect sulcus IOL would have a large optic (6 mm or greater), long thin haptics (14 mm or greater), and has smooth anterior optic surface to lessen iris irritation. In addition, avoiding silicon may be of some benefit if the patient is at risk for the future placement of silicon oil or an air–fluid exchange during pars plana vitrectomy, as the silicon lenses can cloud with these procedures. Most of the three-piece IOLs in the U.S. market have haptics that are too short (13 mm). We reported on our experience with the Alcon MA50 three-piece acrylic IOL with a 6.5-mm optic, which worked well except in long eyes where the 13.0-mm haptic length was not long enough to ensure centration.7
Unfortunately, not all IOLs placed in the sulcus are suited for sulcus placement. The popularity of SPA IOLs has led some to place SPA IOLs in the sulcus either inadvertently or when presented with an intraocular complication such as a posterior capsular tear. Dr. David Chang and the cataract clinical committee of the American Society of Cataract and Refractive Surgery (ASCRS) reported on a series of patients with poorly placed SPA IOLs.8 In this series, at least one of the SPA haptics was in the sulcus. The thick square edged haptics of the SPA IOLs placed in the sulcus led to a variety of problems including chronic uveitis, glaucoma, and hemorrhage.
The surgical strategy for eliminating the problems associated with SPA IOLs in the sulcus involves removing the thick SPA haptic from the sulcus either by repositioning the IOL such that both haptics are in the capsular bag or by removing the SPA IOL and exchanging for a large three-piece IOL better suited for the sulcus. In several cases in Chang et al’s series of misplaced SPA IOLS, one haptic was in the bag and the other was in the sulcus. In this situation, ophthalmic viscoelastic devices (OVD) should be used to separate the haptic from the bag to allow explantation of the SPA.8 Samuel Masket has described the technique (personal communication) of simply cutting off and removing the sulcus-based haptic and leaving the remaining portions of the SPA in the capsular bag. In some cases, you may be able to reform the capsular bag with OVD and position the sulcus haptic into its proper location in the bag.
8.2.4 Dislocation/Decentration Intraocular Lens
The most common reason for IOL explantation is decentration or dislocation.1 Decentration is when the IOL is in the proper plane, but not centered. Decentration, especially when it occurs early in the postoperative period, is often caused by inadvertent placement of one haptic in the sulcus and one in the bag. Occasionally, decentration can be caused by a damaged haptic, but this is less common especially with the commonly used SPA IOLs. Decentration of IOLs with both haptics placed in the sulcus is more common when the IOL haptics are too short for sulcus placement (< 12.5 mm). Dislocation of IOLs where the IOL may also be too posterior or loose (pseudophacodonesis) is typically caused by areas of weakened zonules, which can occur even years after implantation.
Rather than explanting a decentered IOL, often the best strategy is to secure or reposition the existing IOL (
Table 8.2). Sometimes the IOL can simply be repositioned and secured using the existing remnant of the capsule. More often, the decentered IOL is freed from capsular remnants and sutured to the iris or sclera or glued to the sclera as outlined in Chapter 14. If it is possible to secure the existing IOL, this is usually the best approach as it minimizes the trauma to the eye that comes with an exchange of the IOL.
One of the most difficult situations presents when the IOL is in the bag, but the bag itself is loose. This situation seems to be more common as we operate sooner on patients who live longer. This is especially noted in patients with pseudoexfoliation, uveitis, trauma, or other conditions with weakened zonules. The surgeon has three choices in this situation: suture the IOL and the bag to the sclera, remove the IOL from the bag and secure the IOL only to the sclera or iris, or finally explant the IOL. The choice depends on the type of IOL, the amount of residual lens material in the capsular bag with the IOL, and the age of the patient.
8.2.5 Uveitis–Glaucoma–Hyphema Syndrome
The uveitis–glaucoma–hyphema (UGH) syndrome is related to uveal tissue in contact with an IOL. Uveal inflammation in the UGH syndrome seems to come from contact of the IOL (usually the haptics) to the iris or ciliary body. The hyphema or vitreous hemorrhage comes from episodic injury to vessels in the iris, ciliary body, or angle. The glaucoma is secondary to the uveitis, treatment of the uveitis, pigment dispersion, hemorrhage, or direct injury to angle structures.
When anterior chamber (AC) IOLs were commonly placed, the UGH syndrome was the second most common indication for IOL exchange behind bullous keratopathy.2 As posterior chamber (PC) IOLs began to dominate our practice, the UGH syndrome became less common, but still important. PC IOLs in the sulcus are at the most risk for UGH syndrome, especially if they are loose7 or are SPA IOLs with wide square haptics.8 Even PC IOLs positioned completely in the capsular bag can cause the UGH syndrome if the zonules are loose and the resultant pseudophacodonesis irritates the iris. The author typically will exchange an AC IOL for a posterior IOL causing UGH and similarly will exchange a posterior IOL for an AC IOL causing UGH.
8.3 Freeing the Existing Intraocular Lens from the Capsule
The ease of IOL removal is mostly dependent on how long the IOL has been in the bag. IOLs that have been in the bag for a few weeks, such as when the wrong IOL is placed, are very easy to free from the bag. IOLs that have been in the bag for years, such as with opacified IOLs, can be very hard to remove. Removing an IOL with an intact posterior capsule is far easier than when the patient has had a yttrium aluminum garnet (YAG) posterior capsulotomy. When the IOL is in the sulcus, it is typically not adherent to the capsule and can easily be removed.
The first step to free the IOL from the bag is to somehow get a dissection plane started between the IOL and the capsule. The author likes to use a viscous and dispersive OVD (e.g., Viscoat) especially when the posterior capsule is not intact. With IOLs that have been in place for a while (e.g., more than a year) it is advisable to use a 27-gauge needle attached to the Viscoat syringe and use the sharp end of the needle to get under the capsule and then inject the OVD to start the dissection (
Fig. 8.1). Sometimes the author uses the micro forceps (such as the Microsurgical Technology [MST] Duet micro forceps) to lift the capsule to allow a cannula to get access under the AC that allows vigorous viscodissection (
Fig. 8.2). The author also like to use a flat hydrodissection cannula attached to the OVD syringe for viscodissection, as the flat surface of the cannula makes it easier to get between the capsule and the IOL yet still allows for vigorous flow of the OVD.
When freeing the IOL, most of the surgeon’s attention should be directed to freeing up the haptics with viscodissection. If the posterior capsule is intact, the OVD will often track around the optic that makes freeing the optic of its posterior attachments fairly easy. However, freeing the haptics can often be very difficult. A generous use of OVD dissection should be adopted to separate the anterior and posterior capsule in the area of the two haptics and carry the viscodissection as posterior as possible. When you think you have freed the capsular adhesions to the haptics, try to spin the IOL clockwise to allow the haptics to work free of the capsule. Sometimes the haptics are just too stuck and must be cut to be free of the IOL. Often the cut haptic can be left in the bag and the remainder of the IOL can be removed. Sometimes the cut haptics will come out more easily without the optic as you may have a better angle to removing the haptic through tunnels formed by adhesion of the anterior and posterior capsules.
