Cataract surgery with implantation of an intraocular lens (IOL) is a safe and cost-effective procedure that usually leads to long-lasting visual rehabilitation. Nevertheless, in some cases, the IOL needs to be explanted. There is no single register for explanted IOLs today, but some laboratories have specialized in registering, storing, and analyzing explanted IOLs. Evaluation of such databases might lead to a better understanding of current problems in IOL surgery, thus leading to improvements in IOL technology.
In the 1990s, IOL dislocation, incorrect IOL power, and inflammation were the main reasons for explantation in the David J. Apple Laboratory.1 Several recent studies reported on IOL explantation due to lens opacities.2–4 The reasons lens opacification develops can depend on the IOL's material. IOLs made from hydrophobic acrylic material can develop liquid-filled vacuoles that can lead to a loss of clarity of the lens.3,5 In silicone and hydrophilic acrylic lenses, deposition of calcium phosphate can degrade the optical quality to a point requiring IOL exchange.4,6–8
The reasons for IOL explantation have varied over time, depending on the IOL design, its material, power calculation, and changes in implantation techniques.1,9–13
This study aimed to analyze the demographics, the reasons for explantation, and material changes in a recently explanted group of 200 explants received at our laboratory.
This was a retrospective cross-sectional study of 200 explanted IOLs that were sent to the David J. Apple International Laboratory for Ocular Pathology in the Department of Ophthalmology of Heidelberg University Hospital. We received the lenses mainly from clinics in Germany and the United Kingdom within a 12-month period (March 2016 to February 2017). Explantation surgery was performed between September 2015 and February 2017. Information about each case was obtained from the donating surgeon using a standard questionnaire form that requested patient data (age and sex), date of IOL implantation/explantation, IOL manufacturer, IOL type, model, power, and reason for explantation. As the standard protocol of our laboratory requires, every IOL explanted from a German surgical center was notified to the Bundesinstitut für Arzneimittel und Medizinprodukte (BfArM—the German Federal Institute for Drugs and Medical Devices).
Handling of the Explants
On receipt, all the information provided by the explanting surgeon was recorded in a data sheet, and the lens was examined under an Olympus BX50 light microscope (Olympus Optical Co., Ltd.). If gross microscopic examination revealed abnormalities, material analysis was performed using a standard protocol as described in several former studies, including histological staining.4,6 Where cases required further analysis, part of the lens was sent to the Max Planck Institute for Polymer Research in Mainz, Germany, to perform scanning or transmission electron microscopy, local elementary analysis using energy-dispersive X-ray spectroscopy, or diffraction pattern analysis.4,6
Descriptive statistics were entered in an Excel data sheet (Excel v14.7.7, Microsoft). Numerical data are presented as mean (±SD), median (range), or number (percentage) as appropriate.
Lenses were explanted from 194 patients, 108 female and 83 male. In 3 cases, the patient's sex could not be determined, as only their initials were provided. The mean age of patients at the time of IOL explantation was 74 years (range 19 to 94 years). The mean time the lens was in the eye was 5.8 years ± 4.5 (SD). The median IOL power was 21.5 D (range 5.0–31.0 D).
Reasons for IOL Explantation
The reasons for IOL explantation are presented in Figure 1. In 4 (2%) cases with a phakic lens, explantation of an anterior chamber IOL was necessary due to development of cataract with subsequent cataract surgery. We recorded no cases of IOLs explanted because of inflammation. Opacification of the IOL mainly occurred within the first 7 years after implantation. The prevalence of dislocation increased with the time the IOL was in the eye (Figure 2).
Gross examination of opacified lenses showed a whitish blurred appearance of the whole lens (optics and haptics) in 134 (67.0%) cases. In 132 (66.0%) cases, histological staining with von Kossa stains (which reveals calcium in subsurface deposits) revealed primary calcification as the reason for the opacity. A band of granular calcium phosphate crystals was found under the whole surface of the IOL including the haptics. In two hydrophobic acrylic IOLs, small vacuoles (glistenings) within the bulk of the lens were identified as the reason for opacification.
In 19 (9.5%) cases, the pattern of secondary IOL calcification was observed as a small circular area of granular deposits on the surface of the lens optic. Alizarin red staining (which reveals calcium in superficial deposits) confirmed central calcification that spared the haptics in these cases. Local energy-dispersive X-ray spectroscopy elementary analysis identified that deposits consist of calcium and phosphorus (Figure 3).
The IOLs analyzed comprised of 188 (94%) posterior chamber lenses and seven (3.5%) anterior chamber lenses. Five IOLs could not be categorized. Distribution of the lens material is shown in Figure 4. Of the 125 hydrophilic lenses with a hydrophobic surface coating, 123 were explanted due to opacification, 1 due to dislocation, and 1 due to dysphotopsia. In total, 21 manufacturers were represented in this study. Twenty-three of the explants could not be allocated to a manufacturer. One company (Oculentis GmbH) represented the largest subgroup, with 119 (59.5%) explants. Lenses from Rayner and Alcon Laboratories, Inc. were represented with 10 IOLs each, followed by Carl Zeiss Meditec AG with 8 lenses, Argonoptics with 6, and J&J Vision and 1stQ with 5 IOLs each. Other manufacturers were represented with 1 IOL each (Table 1). Nine of 10 Rayner lenses were explanted due to secondary IOL calcification and 1 due to IOL dislocation. Six of 10 Alcon lenses were explanted due to dislocation. One lens was explanted due to glistenings, and 1 trifocal IOL model due to dysphotopsia. In 2 cases, the reason for explanting the Alcon lens could not be determined.
Apart from 2 lenses, all 119 Oculentis lenses were explanted due to late primary IOL calcification. One LS-313 MF15 was explanted 1 month after implantation due to IOL dislocation, and 1 LS-313 was explanted due to dysphotopsia (halos/glares). Table 2 summarizes the characteristics of the largest subgroup of explanted IOLs including 8 different models: LS-502-1 (43), LS-313 MF30 (39), LS-312 MF30 (11), LS-402 (15), LS-313 MF15 (1), Lentis L-303 (1), LS-313 (1), and LS-312 (5). Three IOLs made from HydroSmart material could not be allocated to a specific IOL model number. All lenses from this subgroup were made from hydrophilic acrylic material with a hydrophobic surface coating. Regarding the IOL design, 104 IOLs had a 1-piece design, and 15 had a three-piece design.
The reasons for IOL explantation have changed over time. This is due to a continuous evolution of IOL designs and materials, as well as in surgical techniques and lens power calculation. Our retrospective cross-sectional analysis of 200 lens explantations in the period 2016 to 2017 revealed that the main reason for IOL explantation was late postoperative primary calcification of hydrophilic acrylic IOLs, whereas the second most common reason was IOL dislocation. The high proportion of primary calcification in this group reflects a recent epidemic series of primary IOL calcification in different lens models by Oculentis.
Between 1986 and 1990, the most common reasons for IOL replacement were IOL luxation (36%) and implantation of an IOL with incorrect refractive power (25%).14 In 100 silicone lenses explanted between 1984 and 1994, IOL dislocation (42%) was the most common reason for explantation, and inflammation (27.7%) and incorrect IOL power (8%) were the second and third most common reasons, respectively.1 From 1998 to 2004, incorrect IOL power (41.2%), IOL dislocation (37.3%), and dysphotopsia (7.8%) were described as the main reasons.15 Leysen et al.16 reported on 128 lens explants from 2002 to 2007: IOL dislocation (37%), IOL opacification (31%), and capsular bag contraction (14%) were the chief reasons for explantation.
A survey from 2003 reported the reasons for IOL explantation according to the lens material and design categories. In accordance with the most commonly used IOLs at that time, three-piece silicone IOLs provided the largest group, with 27% of all IOL explants and the most common reason for silicone IOLs was dislocation (34%).9 Fernandez-Buenaga et al.17 reported on 257 IOLs explanted in Spain. Overall, dislocation was the main reason (56.3%), and incorrect lens power (12.8%) and IOL calcification (11.3%) were the second and third most common reasons, respectively.
In general, IOL opacification can lead to increased light scattering, decreased contrast sensitivity, and deterioration in visual acuity.4–6 Depending on the lens material, IOL opacification has different causation: In lenses made from hydrophobic acrylic material, liquid-filled vacuoles, the so-called glistenings, that develop within the bulk of the lens can opacifiy the lens material.5 In our group, we found only 2 hydrophobic acrylic lenses (one Alcon and one Medennium) that were exchanged because of glistening formation. Generally, surgeons should be careful when deciding to perform an IOL exchange for glistening, as they only cause a decrease in visual performance when present in a very large amount.5,18
IOL calcification is a complication observed in silicone and hydrophilic acrylic lenses. First cases of brown discoloration with central haze in silicone IOLs and nodular geographic calcifications within hydrophilic lenses were reported in the early 1990s.19,20 As foldable hydrophilic acrylic IOLs became more popular, on account of the advantages in handling and biocompatibility, reports on IOL calcification became more frequent.
In 2008, David J. Apple and his group proposed a classification of the major types of IOL calcification according to the assumed underlying pathomechanism.21 Calcification relating to the IOL itself, they suggested, should be referred to as primary calcification. Eyes and patients are presumed healthy, without comorbidities. The origin of the calcification can be found in the IOL polymer itself, its manufacturing processes, or in its packaging and storage.2,6,21–24 On the other hand, secondary calcification described an opacification induced by environmental factors.
Factors considered to increase the risk for secondary IOL calcification include some surgical procedures, such as Descemet membrane endothelial keratoplasty and pars plana vitrectomy; also, ocular or systemic comorbidities, such as diabetes, are linked to calcification.4,7,25–27 Tertiary calcification or pseudocalcification refers to a misdiagnosis or false-positive histological staining.21
In our study, primary IOL calcification was identified only in lenses from Oculentis, Argonoptics, and Mentor Ophthalmic (Ciba Vision). All calcified lenses from other manufacturers showed the pattern of secondary IOL calcification.
Primary IOL calcification has been reported in different hydrophilic IOL models in the epidemic series in the 2000s: Hydroview (Bausch & Lomb), MemoryLens (Ciba Vision), SC60B-OUV (Medical Developmental Research), and Aqua-Sense (Ophthalmic Innovations International) IOLs.22–24,28 There are also recent, single-incident reports about isolated cases of IOL calcification in Lentis IOL models.29–31 Gurabardhi et al.2 presented a larger series of 71 Lentis IOLs including 6 different models: LS-312/-1Y, LS-402/-1Y, LS-313-1Y, and LS-502-1, showing the pattern of primary IOL calcification. In accordance with their findings, we also found the pattern of primary calcification in all the 123 opacified Oculentis IOLs. Opacification consisted of deposits of calcium phosphate that had accumulated underneath the surface of the whole of both IOL surfaces (Figure 3). To our knowledge, we present the largest series of explanted Oculentis HydroSmart lenses, including IOL models that have not yet been reported as problematic, including a large number of segmented refractive bifocal premium lenses such as the LS-313/LS-312 MF30. In 2012 and 2014, Oculentis GmbH released urgent field safety notifications about the HydroSmart yellow IOL material, which had been presented sealed in glass vials. It was suggested that the interaction between phosphate crystals originating from the hydration process of the IOL material and the fluctuating batch-related presence of silicone residues on some IOLs promoted the calcification process.32,33 In 2017, another urgent field safety notification was released by the company, in which a voluntary recall was offered for all IOL models starting with L, LU, or LS, expiring between January 2017 and May 2020 and that have been manufactured between January 2012 and May 2015. In this notification, it was suggested that calcification might result from phosphate residuals from a detergent used in the cleaning process of the lens.34 As there is a large population of patients who have been treated with hydrophilic IOL models that still might be affected by primary IOL calcification, clinicians should be aware of this complication.
In 19 (9.5%) cases, the pattern of secondary IOL calcification was observed. It should be noted that the high amount of Rayner IOLs in this group (9/20) is predominantly owing to the circumstance that Rayner routinely sends their IOLs to our laboratory for pathological analysis, whereas IOLs from other manufacturers only reach us through the cooperation of individual ophthalmic surgeons. Schrittenlocher et al.35 found in 564 patients who underwent a Descemet membrane endothelial keratoplasty procedure that IOL calcification occurred in 2.5% overall. The incidence was associated with the number of rebubblings patients had received. In a previous study from our laboratory, secondary IOL calcification was found in 10 explanted lenses after pars plana vitrectomy with instillation of gas with similar calcification patterns irrespective of the IOL manufacturer.4 In general, secondary IOL calcification can be said to be a rare complication in lenses made of hydrophilic acrylic material, rather than a specific problem of one or more IOL manufacturers.
As stated above, IOL dislocation has always been one of the main causes for lens explantation. This complication not only depends on the surgical technique and IOL design used but also on patient-dependent factors such as the constitution of intraocular anatomical structures. Fernandez-Buenaga and Alio12 and Pueringer et al.36 suggest that the risk for IOL dislocation increases the longer the IOL is inside of the eye. Similarly, our results show that as the time inside of the eye increases, IOL dislocation becomes more prevalent (Figure 2). Thus, because of an increasing patient age and as a result of a growing pseudophakic population, this complication can be expected to remain a major reason for IOL explantation in the future.12
The proportion of explantation due to iatrogenic anisometropia varies from about one third to a tenth of cases.14,17 In our 200 explants, only one case was explanted for this reason. One may speculate that it has become less common because of progress in the use of IOL power calculation formulas, refinements in IOL biometry equipment, improved measuring, and labeling procedures at IOL manufacturing facilities–all or some of that plus the possibility of postoperative power correction (enhancement with laser refractive surgery or implantation of a supplementary IOL).
Intraocular inflammation used to be a major reason for IOL explantation in early studies on explanted lenses, making up one third of all explanted IOLs (27.7%).1 Presumably, through advances in IOL biocompatibility and surgical techniques, and improved pharmaceutical control, this complication has decreased, making inflammation a less common reason for IOL explantation. Recent literature rarely reports on inflammation as a reason for IOL explantation, and in this group of 200 lenses, no IOL was removed because of intraocular inflammation.
Postoperative photic phenomena depend on a large variety of factors including IOL material, optical design, ocular surface, and retinal function. Although introduction of complex optics that allocate light to more than one focal points can lead to an increased potential for dysphotopsia, IOL explantation due to this reason still is rarely reported. In our study, only one monofocal and one trifocal IOL model required to be removed because of unbearable dysphotopsia.
The retrospective character of this study does not permit conclusions about absolute numbers of explanted IOLs and does not reveal pathomechanism for any of the complications mentioned. Furthermore, it is possible that some reasons for explantation (eg, incorrect IOL power or IOL dislocation) might be underrepresented in this study, as they might be sent for analysis less frequently to our laboratory. Nevertheless, we believe that this cross-sectional report provides important information about trends and changes in the rationale for IOL explantation. This might serve in directing IOL technology to an even safer and more efficient procedure.
This study describes a large series of primary IOL calcification and reports on a shift over time in reasons for IOL explantation. Lenses made from hydrophilic acrylic material (especially Lentis IOL models) bear the risk for late postoperative calcification. The leading cause for IOL opacification (primary IOL calcification) could be avoided if greater care is taken in the production of IOL.
WHAT WAS KNOWN
- Complications and reasons for IOL explantation have changed depending on the IOL design, material, power calculation, and surgical techniques used at a certain period and in a region of the world.
- IOL opacification used to be a rare reason for IOL explantation.
WHAT THIS PAPER ADDS
- In Europe, the main reason for IOL exchange has shifted toward IOL calcification.
- A large number of recent hydrophilic IOL models, including modern refractive bifocal IOLs, required explantation due to primary IOL calcification.
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