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Cataract surgery with intraocular lens (IOL) implantation has evolved in the past 2 decades. The use of phacoemulsification through a small, clear corneal incision continues to increase yearly.1 IOLs have also evolved considerably over this period of time from earlier iris-fixated and anterior chamber IOLs to more modern posterior chamber and foldable IOLs. Newer lens designs and materials are being introduced each year. The complications that necessitate the removal of an IOL have also changed with the evolution of both surgical techniques and IOL designs.
This tutorial will review the complications that result in explantation of both traditional and modern foldable IOLs
Complications associated with early types of IOLs, as well as the reasons for removal or exchange of these IOLs, have been well documented in previous reviews by Apple and colleagues,2 and Carlson and colleagues.3 Generally, the complications associated with anterior chamber, iris-fixated, and earlier types of posterior chamber IOLs were more severe than those associated with more modern lenses.
My colleagues and I have analyzed explanted lenses that were sent to the Intermountain Ocular Research Center at the University of Utah over the past 1½ decades.4 We found that pseudophakic bullous keratopathy with corneal decompensation was the most common reason for removal of anterior chamber IOLs. This was the case in both older, closed-loop lenses, as well as modern, open foot-plate anterior chamber IOLs. Inflammatory complications such as uveitis glaucoma hyphema (UGH syndrome) with associated cystoid macular edema (CME) were also noted in patients with these lenses. Interestingly, the complications that led to explantation of anterior chamber IOLs often took 9 to 10 years after implantation to become severe enough to require lens explantation.
The number of iris-fixated lenses that required explantation in our study has been decreasing rapidly over the past several years. The complications associated with these iris-fixated IOLs are similar to anterior chamber IOLs. Pseudophakic bullous keratopathy and inflammatory problems such as the UGH syndrome are commonly seen in this group of patients. Once again, there is a long time between implantation of the lenses and explantation; the IOL was in the eye for an average of 14 years. Therefore, it is important that patients who received either anterior chamber or iris-fixated IOLs 10 to 15 years ago continue to be followed closely.
Our evaluation of older styles of posterior chamber IOLs, as well as all recent PMMA posterior chamber IOLs, showed that decentration or dislocation was the most common indication for removal of the lenses. More serious complications such as corneal edema and inflammation were seen less frequently. Of interest, the posterior chamber IOLs were explanted much sooner than either iris-fixated or anterior chamber IOLs.
Complications of Foldable IOLs
We are performing an ongoing study at the Intermountain Ocular Research Center evaluating explanted foldable IOLs from the United States as well as other parts of the world.4 Our most recent retrospective analysis of 159 explanted foldable IOLs revealed that three-piece monofocal silicone IOLs were the most common explanted lenses (41%), followed by three-piece acrylic lenses, which accounted for 31.4% of the explanted IOLs [unpublished data]. Silicone one-piece, plate IOLs comprised 27% of the lenses analyzed. When evaluating the group of patients who required explantation of a three-piece silicone IOL, the most common reason was dislocation (48%), followed by incorrect lens power (7.7%) and optical aberrations (4.6%). The three-piece acrylic lens group showed somewhat different findings. The leading indication for explantation was incorrect lens power (24%), followed by dislocation (18%) and optical aberrations (12%). In the group of patients who had a silicone plate one-piece IOL explanted, dislocation was the most common cause (56%), followed by incorrect lens power (7%). Thus, the types of complications requiring explantation of foldable IOLs varied depending on the type of IOL used.
Anterior chamber IOLs that are angle-fixated and implanted with one or more peripheral iridectomies may rotate and decenter in such a way that a haptic passes through and becomes incarcerated in the iridectomy. This form of IOL malposition may result in chronic iritis, pigment dispersion, corneal endothelial touch, as well as visual symptoms related to optic decentration and tilting.
Trauma can cause an IOL's malpositioning that will require explantation. An indication observed more recently and one that will become commonplace in the future includes the removal of phakic anterior and posterior chamber IOLs from eyes that develop cataracts.
Survey of Foldable IOL Explantation
To analyze the complications requiring explantation of foldable IOLs, a yearly survey of the members of the American Society of Cataract and Refractive Surgery (ASCRS) as well as the European Society of Cataract and Refractive Surgery (ESCRS) was designed by members of the Cataract Clinical Committee. This survey was initially completed in 1998, and has been updated yearly.5 This survey allows clinicians to analyze trends in complications requiring the explantation of foldable IOLs from throughout the United States and Europe without limiting the results to implants that were sent directly to our laboratory for evaluation.
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In 2000, 259 surveys of foldable IOL explantations were evaluated.6 Four main types of IOLs were explanted: three-piece monofocal silicone IOLs (34%), three-piece acrylic IOLs (30%), one-piece or plate silicone IOLs (21%), and three-piece multifocal silicone IOLs (15%) (Slide 1)
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The complications found in each of these groups varied depending on which type of IOL was studied. In the three-piece monofocal silicone IOL group, the most common reason for removal or exchange was incorrect lens power (40%). This was followed by decentration/dislocation (32%), as well as glare/optical aberration and damaged IOL during insertion (9%), respectively (Slide 2).
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In the category of explanted three-piece acrylic IOLs, incorrect lens power was the most frequent reason for removal or exchange (39%). This was followed by glare/optical aberrations (24%) and dislocation/decentration (15%) (Slide 3)
One-piece, plate-haptic silicone IOLs were most commonly removed or exchanged due to dislocation/decentration (more than 50%). This was followed by incorrect lens power (22%) and IOL damage during insertion (18%) (Slide 4).
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The fourth IOL group evaluated was three-piece multifocal silicone IOLs. The reasons for IOL exchange in this group of patients were overwhelmingly related to glare/optical aberrations (89%) (Slide 5).
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When evaluating patients who have undergone IOL explantation or exchange, surgical outcomes and visual results are important. In the most recent foldable IOL survey, there was uniform improvement of postoperative visual acuity in all four major lens groups with anywhere from 68% to 81% of the patients reporting a final visual acuity of 20/20 to 20/40. However, the visual acuity may be even better than that reported in the surveys because more than 10% of the surveys did not report a final visual acuity outcome. The complications following IOL explantation or exchange varied, with small numbers of patients having corneal edema, ocular inflammation, or glaucoma. Overall, the incidence of these complications was small.
It is interesting to compare the results of the most recent IOL explantation survey to the surveys performed in the first 2 years. We found that three-piece monofocal silicone lenses comprise the largest group of lenses explanted. Three-piece acrylic lenses are the next most commonly explanted IOL group. The frequency of one-piece, plate silicone IOLs explanted has remained relatively stable throughout each survey of the past 3 years. Finally, the percentage of three-piece multifocal silicone IOLs explanted has decreased over the period of the survey.
When looking at trends in complications for each of the four major IOL groups over the past 3 years of the explantation surveys, several changes can be seen. In the three-piece monofocal silicone IOL group, incorrect lens power is still the leading indication for explantation followed by dislocation/decentration. However, in the three-piece acrylic IOL group, incorrect lens power has now surpassed glare/optical aberration as the primary reason for explantation of these lenses. Patients with one-piece, plate silicone IOLs still have decentration/dislocation as the primary reason for removal. Incorrect lens power is now the second most common reason. Finally, glare/optical aberrations remain the most common reason for removal of three-piece multifocal silicone IOLs during the 3-year period of the survey.
The complications necessitating removal of foldable IOLs show many similarities to those leading to removal of a traditional PMMA posterior chamber IOLs. Dislocation/decentration and incorrect lens powers are the leading indications for explantation of PMMA posterior chamber IOLs. Symptoms of glare and optical aberrations are newer complications necessitating the explantation or exchange of foldable posterior chamber IOLs. The reasons for explantation or exchange of foldable IOLs are different from those associated with removal of earlier anterior chamber and iris-fixated lenses.2,3,7 The complications associated with earlier anterior chamber and iris-fixated lenses were more severe than those seen with modern foldable posterior chamber IOLs. Corneal edema, inflammatory complications, such as the UGH syndrome and chronic CME, were common reasons for explantation of these older style IOLs.
Three-piece monofocal silicone IOLs are the most common type of foldable IOL that requires explantation or exchange. However, this may simply reflect that the three-piece monofocal silicone IOL is the most frequently implanted IOL over past several years. The most common cause of removal of these types of lenses is incorrect lens power followed by decentration/dislocation. There were only a small number of patients who had problems with glare/optical aberration or IOL damage during insertion. These findings are similar to previous reports in the literature regarding complications of three-piece silicone IOLs.8,9
In patients with three-piece acrylic IOLs, glare or optical aberrations are a more common reason for IOL removal. These dysphotopsias may result from the high refractive index of the acrylic material and the truncated square edge that is seen in the three-piece acrylic IOL that is most commonly used.10 Glare or optical aberrations have also been noted in a significant number of patients from other studies with three-piece acrylic IOLs.11-13 Suggested ways of decreasing glare or optical aberrations in these acrylic lenses include increasing the size of the IOL optic, as well as trying to ensure that the optic edge is completely covered by the anterior lens capsule following capsulorrhexis. In addition, changes are being made to the edges of newer acrylic IOLs to help minimize many of these symptoms. Of interest is the fact that there is an increasing number of patients who require explantation or exchange of three-piece acrylic IOLs due to incorrect lens power.
When evaluating patients who require explantation or exchange of a one-piece, plate silicone IOL, decentration/dislocation remains a significant problem. This may be due to the fact that earlier styles of plate-haptic IOLs with smaller positioning holes would not fixate within the capsular bag and required a well-done circular capsulorrhexis for adequate positioning. Newer plate-haptic silicone IOLs have a larger positioning hole which is intended to increase fixation within the lens capsular bag.14,15 However, a recent study found that the larger positioning holes in plate-haptic silicone IOLs did not seem to prevent IOL decentration or rotation.16 In addition, the frequency with which these one-piece lenses are being removed for incorrect lens power is similar to that of the other lens groups analyzed. Lastly, there is a group of IOLs that are still being either torn or damaged during insertion.
The number of patients requiring explantation of a three-piece multifocal silicone IOL has been decreasing recently. The most common reason for removal of these lenses remains glare/optical aberration. As surgeons have become more experienced with multifocal IOLs, the number of these lenses requiring explantation has decreased over the past 3 years. Presumably, this reflects better preoperative patient selection.
There are several ways to decrease the complications that may lead to explantation of foldable IOLs. Because incorrect lens power is now the most common reason for explantation of these lenses, the need for accurate IOL measurements is paramount. Accurate axial length measurements, as well as IOL power calculations, are essential in the proper choice of an IOL power. One cannot overemphasize the importance of proper surgical technique to avoid foldable IOL complications. A properly sized continuous circular capsulorrhexis followed by complete removal of all lens material and placement of an IOL directly within the capsular bag will help to eliminate the problems of dislocation/decentration. Also, care must be taken to ensure that the lenses are properly folded or loaded into an injector for insertion to eliminate potential damage to the IOL during implantation. Lastly, proper patient selection is important to help decrease the incidence glare or dysphotopsias caused by foldable IOLs.
