From our long-term experience with piggyback intraocular lens (IOL) implantation, we present the first case in which opacification between the IOLs resulted in a loss of best corrected visual acuity (BCVA).
A 55-year-old woman developed moderate nuclear sclerotic cataracts in both eyes, preventing her from passing the driver's license vision test. Spectacle prescription was +8.25 +0.50 × 102 in the right eye and +7.25 +2.50 × 80 in the left. Best corrected visual acuity was 20/100+1 and 20/60, respectively. Rotary and pendular nystagmus were present. Anterior segment examination was remarkable for moderately dense nuclear sclerotic cataracts in both eyes, which were superiorly subluxated by about 2.0 mm, with several clock hours of absent zonular fibers inferiorly. The comprehensive examination was otherwise normal. Mean manual keratometry was 44.06 diopters (D) in the right eye and 44.25 D in the left; axial lengths were 20.06 mm and 19.73 mm, respectively, by contact A-scan and 19.93 mm and 19.70 mm, respectively, by immersion.
In July 1997, phacoemulsification was performed by 1 of us (J.K.S.) through a temporal clear-corneal incision in conjunction with a 30 degree arcuate keratotomy. Two AcrySof® IOLs (model MA30BA, Alcon Laboratories) of 17.5 D and 17.0 D, respectively, were implanted in a piggyback configuration in the capsular bag with the haptics aligned perpendicularly. Intraoperatively, this IOL configuration was noted to eliminate the subluxation of the capsular bag, with the IOL pair acting similar to a capsular tension ring. The capsulorhexis margin was noted to overlap the optic margin of the anterior IOL for 360 degrees. One week later, a similar procedure was performed in the left eye except that the capsulorhexis margin was noted to extend peripheral to the superior optic edge of the anterior IOL.
One day after surgery in the left eye, the uncorrected visual acuity (UCVA) was 20/50−2 in the right eye and 20/40−2 in the left. At 1 month, spectacle refraction with –0.75 +0.75 × 94 in the right eye and −1.00 +1.00 × 88 in the left resulted in a UCVA of 20/50−2 and 20/40−2, respectively. The relationship of the capsulorhexis margin to the edge of the anterior optic remained stable in both eyes, while the IOL pair in the left eye rotated postoperatively with respect to one another so the relative haptic orientation shifted to become closer to parallel (Figure 1). These results remained stable when the patient was seen in routine follow-up 10 months postoperatively, in May 1998.
The patient presented in November 1998, reporting blurred vision in the right eye for the preceding 3 weeks, “like looking through a fog.” Refraction in the right eye had changed to +2.00 + 1.25 × 112 with a drop in BCVA to 20/60−1. The left eye was now correctable to 20/30-2 with –1.00 +2.00 × 88. Dilated examination revealed Elschnig pearls in the peripheral interface between the IOL pair in the right eye (Figure 2), similar to that observed in a previously reported case series.1 Unlike the 6 previously reported cases, however, in this eye the central interface between the IOLs had dense deposition of a fine brownish-gray dust-like material, obscuring the entire visual axis.
Spectacles were prescribed to manage the problem conservatively. After 4 weeks, the patient did not adapt to spectacle correction, complaining that spectacle-corrected vision in the right eye was still blurry and she perceived “a cloud and halos, like my glasses are dirty.”
In December 1998, surgery was performed in the right eye to clean the interface between the IOLs. Intraoperatively, the anterior capsule was found to adhere to the anterior optic. With a bent 27 gauge needle and meticulous dissection, the optic was freed from the anterior capsule (Figure 3, A). Peeling the capsule off the optic surface seemed much like peeling off a “Post-it® note.” Next, it was possible to maneuver a J-shaped cannula between the IOL surfaces and inject a viscoelastic substance between them (Figure 3, B). With a Sinskey hook through a paracentesis port to maintain counterpressure on the posterior IOL, the J-shaped cannula was used to “tire-iron” the anterior optic out of the capsular bag through the pupil while leaving the haptics inside the capsular bag.
Once access to the space between the IOLs was obtained, a straight automated irrigation/aspiration (I/A) cannula was used to vacuum the posterior surface of the anterior IOL and the anterior surface of the posterior IOL. The Elschnig pearls were readily aspirated from the interface; however, the dense brown pigmentary material was extraordinarily adherent to the IOL surfaces. The silicone sleeve of the straight I/A tip was retracted to create higher vacuum at the aspiration port by more tightly occluding it against the IOL surface, as well as using it to mechanically scrape, while providing counterpressure with a Sinskey hook (Figure 3, C). This maneuver allowed successful removal of much of the material; however, it was not possible to clean the interface completely. A silicone Terry Squeegee® (Alcon Surgical) was used to wipe both IOL surfaces (Figure 3, D); however, little additional material was removed. Finally, a curved I/A tip was used to remove as much of the residual material as possible. Despite all these interventions, substantial pigmented material remained adherent to the paracentral optic surfaces.
At this point, the option of removing at least the anterior IOL was considered. The operating microscope did not provide nearly as good a view of the interpseudophakos opacification as did the slitlamp, and it was difficult to tell how much material remained on each IOL surface. The anterior IOL provided tectonic support for the capsular bag, since its loops were aligned along an axis in which zonular weakness had been noted preoperatively. Because of concern about loss of zonular support if the IOL were removed and since substantial cleaning of the interface had been achieved, it was decided to replace the anterior optic in the capsular bag (Figure 3, E) and evaluate whether sufficient material had been removed to ameliorate the patient's symptoms. The optic was positioned so a portion of the capsulorhexis margin remained peripheral to the optic edge to avoid resequestration of the interface as well as provide an easy site for access should lens exchange subsequently prove necessary.
By day 6, UCVA in the right eye had improved to 20/50−3; refraction of –1.00 + 0.75 × 95 did not improve it. The patient noted her vision was much clearer but still “a little foggy.” At 1 month, she felt the “fogginess” was about 50% better than before the interface was cleaned. Uncorrected visual acuity was 20/70−2, improving to 20/60−3 with –1.00 +0.50 × 105. Examination showed a 1.0 mm clear zone surrounded by several islands of residual, dense, brownish-gray appearing opacification between the lenses, with a clear periphery almost totally free of Elschnig pearl-type material (Figure 4).
The patient has been observed for 5 months since the interface was cleaned. Snellen acuity and refraction have remained stable. She is unhappy with the quality of vision in her right eye and requests further surgical intervention. Preparations are being made to exchange both IOLs, with sulcus placement of the anterior IOL. The anatomic and functional surgical results in the left eye have remained stable (Figure 5).
Late ingrowth of Elschnig pearl material in the peripheral interface between pairs of acrylic, poly(methyl methacrylate) (PMMA), and silicone IOLs placed in a piggyback fashion in the capsular bag has been reported.1 Several diopters of hyperopic shift were also noted in each of the eyes with acrylic and PMMA lenses reported in the series. However, each of these eyes has maintained BCVA.
Concurrent with the preparation of the current report, Gayton reported 3 eyes similar to the 1 we present in which opacification of the interface between piggyback posterior chamber (PC) IOLs implanted in the capsular bag reduced BCVA (Johnny L. Gayton, MD, “Long-Term Membrane Formation Between Piggybacked Implants,” presented at the Symposium on Cataract, IOL and Refractive Surgery, Seattle, Washington, USA, April 1999). Two of the eyes had pairs of acrylic lenses and 1, operated on for phacomorphic glaucoma, had a pair of PMMA lenses (Johnny L. Gayton, MD, oral communication, May 1999). Some of the IOLs were explanted and submitted for pathologic analysis (David L. Apple, MD, “Update on Database of 15 000 Explants/Autopsy Globes Accessioned Between 1983 and 1999,” presented at the Symposium on Cataract, IOL and Refractive Surgery, Seattle, Washington, USA, April 1999).
Although late Elschnig pearl proliferation in the peripheral interface between the IOLs appears to be common to eyes containing pairs of PMMA, silicone, and acrylic IOLs, opacification of the central interface between these IOLs may be more common in eyes in which a pair of acrylic lenses has been implanted in the capsular bag. The long-term incidence of this complication with different optic materials is currently unknown.
By April 1999, 1 of us (J.K.S.) had implanted 80 pairs of acrylic lenses in a piggyback fashion in the capsular bag; the first case dates back to September 1995.2 The case reported here represents the first eye in the series that has lost BCVA postoperatively. None of these eyes has required a neodymium:YAG (Nd:YAG) posterior capsulotomy. Most of the eyes implanted with piggyback acrylic PC IOLs at our facility have retained crystal clear central interfaces; however, a minority have a faintly visible, translucent, filmy opacification in the paracentral interface between the IOLs that has not affected BCVA. Previously, this was thought to be clinically insignificant and appears to have remained stable for up to several years in eyes with this finding. This phenomenon may represent a form fruste of the gross interface opacification described in this report.
Unlike IOLs made of silicone and to a greater degree than those made of PMMA, acrylic IOLs become adherent to the capsular bag during the early postoperative period.3,4 Thus, in eyes with piggyback acrylic IOLs in which the capsulorhexis margin overlaps the optic of the anterior IOL by 360 degrees, the interior of the capsular bag likely becomes hermetically sealed to fluid egress or ingress, except the flow that might occur from diffusion through an intact capsule. When the patient first presented with this complication, our hypothesis was that a 360 degree overlap of the capsulorhexis margin of the edge of the anterior IOL optic might be a necessary condition for interface opacification to occur. This was based partly on the clinical impression that no ephemeral interface opacification was observed at our facility in any eye with piggyback acrylic lenses in which the capsulorhexis margin extended peripherally to the optic of the anterior IOL for more than 1 clock hour.
Since this case of interface opacification initially presented, eyes requiring cataract surgery with more than +30 D of total IOL power have received a larger capsulorhexis (6.25 to 6.50 mm) than in the originally reported procedure for placement of piggyback acrylic PC IOLs.2 Since the diameter of the optic of acrylic lens model MA30BA is 5.5 mm, with a well-centered capsulorhexis of this larger diameter, the capsulorhexis remains peripheral to the optic margin. This is intended to prevent sequestration of the interface between the IOLs within a fluidically isolated and closed capsular bag. Physical separation of the interface from close proximity to the undersurface of the anterior capsule may also eliminate a “scaffold” for direct migration of residual lens epithelial cells (LECs) from this surface into the interface. Additionally, not sandwiching the interface between the IOLs in a closed space adjacent to the equator of the capsular bag may reduce the probability of late proliferation of Elschnig pearls in the space between the lenses because of the availability of other pathways that offer minimal resistance to cellular migration. Fashioning the capsulorhexis margin to extend peripherally to the optic margin reduces the force compressing the 2 IOL optics. The contact area between the IOLs has been noted to be smaller for IOL pairs in which this large capsulorhexis was used. It is hoped this will reduce the close apposition of the 2 optic surfaces and perhaps alter the surface chemical interaction between them. To maximize LEC removal, 12 hydrodissection waves, 1 for each clock hour, are now used rather than the 6 fluid waves used in our originally reported technique. Initial results with this strategy have been excellent, with no observable interface opacification.
Interpseudophakos IOL surface opacification may result from deposition of acellular material on the IOL surfaces, from cellular ingrowth into the interpseudophakos space, or from both. In this case, the visible material had an amorphous and acellular biomicroscopic appearance. This opaque material, which was densely adherent to the IOL surfaces, may represent metabolic products of the LECs within the closed interpseudophakos space produced by sealing the capsulorhexis margin to the anterior IOL optic surface for 360 degrees. In eyes in which the capsulorhexis margin overlaps most or all the anterior optic, sealing the interpseudophakos interface would be more common in eyes with acrylic lenses. Gayton's case of interpseudophakos opacification involving PMMA lenses likely occurred because these lenses were implanted in an acutely inflamed eye, resulting in adherence of the capsule to the anterior optic. Deposition of such material may be physically enhanced by the surface chemistry relating to the close apposition of the IOL surfaces.
Cellular ingrowth into the interpseudophakos space could be occasioned by close contact between the peripheral interpseudophakos interface and the undersurface of the anterior capsule or the equator of the capsular bag providing a nidus for cellular migration into the interface, while the closely apposed IOL surfaces serve as a scaffold. In areas in which the capsulorhexis margin overlaps the edge of the anterior optic, the interpseudophakos space will serve as the path of least resistance for proliferating LECs, while extending the capsulorhexis margin peripheral to the anterior optic allows the LECs to escape, sparing the interpseudophakos space.
This phenomenon requires further study. To date, neither surface opacification nor interpseudophakos Elschnig pearls have been reported in eyes in which IOLs have been primarily or secondarily implanted in a piggyback fashion in the ciliary sulcus.
Reproducible retinoscopic and manifest refractive measurements demonstrated the presence of a hyperopic shift in conjunction with the appearance of the interpseudophakos Elschnig pearls and resolution of the shift after surgical aspiration of the pearls. Although BCVA remained reduced by the IOL surface opacification, this observation provides insight into the mechanism underlying hyperopic shift associated with interpseudophakos Elschnig pearls and the potential for surgical treatment if performed before interpseudophakos opacification has occurred.
Piggyback implantation should be confined to eyes in which the benefits of this implantation exceed the potential risks, such as cataractous eyes requiring more than +30 D of IOL power to achieve emmetropia, underpowered pseudophakic eyes, and other special situations. We do not recommend piggyback implantation for the sole purpose of enhancing depth of focus. Piggyback implantation should be approached with great caution in eyes having clear lensectomy for high hyperopia.
Surgical management of cataractous eyes requiring more than +30 D of IOL power requires complex decision making to minimize the chances of intraoperative and postoperative complications. Subsequent to our initial report of piggyback implantation of acrylic IOLs, higher power PMMA IOLs have become available. However, nanophthalmic eyes are at high risk of spontaneous suprachoroidal hemorrhage and uveal effusion during or after intraocular surgery,5 so in this circumstance minimization of wound size during surgery and maintenance of a watertight environment is highly desirable to minimize the chances for these serious perioperative complications. For this reason, it is highly advantageous to be able to use foldable IOLs in these tiny eyes. Because of spherical aberration, the modulation transfer function of IOLs whose power exceeds +30 D is inferior to that provided by pairs of lower power IOLs. In these nanophthalmic eyes, piggyback IOL pairs provide superior optical quality to that provided by single, high-powered IOLs.
Because of the unforeseen emergence of interface opacification as a late complication of piggyback acrylic lens implantation, 1 of us (J.K.S.) has modified his prior recommendation to implant pairs of acrylic lenses in the capsular bag to achieve emmetropia in highly hyperopic eyes requiring cataract extraction. Unless the capsulorhexis diameter exceeds the optic diameter so most or all of the capsulorhexis will be peripheral to the optic margins, both acrylic IOL optics should not be implanted in the capsular bag. It is particularly sobering that this serious complication should first be reported more than 3 years after the first procedure was performed and despite initial results that have been nothing short of spectacular in each of the first 80 cases in our experience. This emphasizes the need for thorough and long-term study of new procedures and devices before widespread adoption. Fortunately, at our center we had almost uniformly limited piggyback implantation to highly ametropic eyes requiring cataract surgery, in which few good alternative modalities were available, and rigorous informed consent was obtained preoperatively.
To date, the only material with sufficient long-term data to conclude that both optics of the IOL pair can be placed with relative safety in a piggyback configuration inside a capsular bag with standard capsulorhexis architecture is PMMA.6 However, nanophthalmic eyes with PMMA lenses stacked inside the capsular bag are still at risk for interpseudophakos Elschnig pearls associated with late hyperopic shift. This risk may increase after Nd:YAG capsulotomy, which may also increase the magnitude of the hyperopic shift.1 Poly(methyl methacrylate) is associated with a relatively high rate of posterior capsule opacification. Should aspiration of interpseudophakos material become necessary, prior capsulotomy would increase the risk of vitreous presentation and other complications. Even with an intact posterior capsule, attempting to aspirate Elschnig pearl material from the interface between the IOLs in an eye in which the capsulorhexis overlaps the anterior optic margin for 360 degrees is a surgically challenging maneuver. Although not as adherent as acrylic, PMMA also develops an adhesion to the anterior capsule.3 Finally, interface opacification requiring surgical invention has been observed in an eye in which a pair of PMMA lenses was primarily implanted. Placing pairs of PMMA lenses in the capsular bag remains a viable surgical option for visual rehabilitation of nanophthalmic eyes requiring cataract extraction and has the longest and best proven track record at present, but other modalities may provide superior long-term results.
Preventing late complications of piggyback implantation is preferable to treating such complications. Probably the most important strategy for minimizing late complications related to cellular proliferation in eyes having piggyback lens implantation as well as in eyes having placement of a single IOL is complete removal of LECs at the time of initial cataract surgery (David Apple, MD, oral communication, May 1999). This involves meticulous attention to removing all LECs from the posterior capsule, equator, and anterior capsule by thorough and repeated hydrodissection, as well as vacuuming and/or polishing all accessible capsular areas. Without adequate attention to these surgical details, it is unlikely that any strategy of IOL placement will satisfactorily reduce the incidence of late complications of piggyback implantation.
We continue to place pairs of acrylic lenses in the capsular bag in highly hyperopic eyes requiring cataract extraction in which no single foldable IOL is available in sufficient power to achieve emmetropia and in which construction of a large capsulorhexis is achieved. Construction of a large capsulorhexis is challenging in these very short eyes with shallow anterior chambers, requiring meticulous attention during this critical stage of the procedure. If excellent pupillary dilation is not achieved or if the surgeon is not confident that such a capsulorhexis architecture can be achieved, an alternative strategy should be used.
Using currently available IOL technology, the modality that might prove to maximize the risk/benefit ratio for visual rehabilitation of highly hyperopic, cataractous eyes in which standard capsulorhexis architecture is used, as well as for underpowered pseudophakic eyes, could be bag–sulcus placement of IOL pairs made of foldable materials. Pairs of acrylic IOLs in which 1 is placed in the capsular bag and the other in the ciliary sulcus would provide the thinnest combined IOL profile of currently available materials to minimize the odds of iris pigment chafing. Acrylic may also be the most biocompatible material currently available for routine clinical use,7 particularly important if an IOL is placed in the sulcus. It is hoped that spacing the IOLs by placing 1 in the sulcus and 1 in the bag and interposing the anterior capsule remnant between them will prove sufficient to avoid interpseudophakos surface opacification.
A conservative variation of the bag–sulcus approach would be to implant the highest power single foldable IOL available and wait 6 months or longer until epithelial cell growth has “burned out” and the anterior capsular leaflet–IOL adhesions have matured (Kenneth J. Rosenthal, MD, written communication, May 1999). In patients requiring surgical correction of residual hypermetropia, a piggyback posterior chamber IOL could be implanted in the sulcus as a secondary procedure.
An option that combines some of the potential advantages of bag–bag placement with those of bag–sulcus placement is bag placement of both haptic pairs with capsulorhexis capture of the anterior optic. The haptics of the anterior optic would be placed inside the capsular bag and the optic brought forward through the capsulorhexis.
Another potential area of investigation with currently available IOL materials would be to place a high- index, 3-piece silicone lens, such as the SI-40NB (Allergan Medical Optics), in the capsular bag while placing an acrylic IOL in the sulcus. This would avoid the potential for acrylic–acrylic surface interaction, and thus interface opacification, while maintaining the advantage of placing the most biocompatible material available in closest contact with uveal tissue and the thinnest lens of the pair anteriorly.
To date, no intraoperative complications have occurred in any of the first 80 eyes in our experience in which piggyback acrylic IOL placement was planned. However, contingency plans should be formulated before surgery in these unusually challenging eyes. Inability to fashion a capsulorhexis large enough to position most of the capsulorhexis margin peripheral to the IOL optic margins would necessitate sulcus placement of the anterior IOL. Should a severe posterior capsule rupture prevent bag placement of an IOL, our strategy would be to place an MA60BM or MA50BM (depending on capsulorhexis size) as the posterior IOL in the sulcus and then place an MA30BA as the anterior IOL, also in the sulcus. In the event insufficient capsule support were present for sulcus placement, anterior chamber IOLs of +30 D or less will have sufficient power to make some of these eyes emmetropic; however, the white-to-white diameter must be sufficient to allow proper sizing of such an IOL. Some eyes in our series have white-to-white diameters of 10.0 mm or less, which would preclude placement of routinely available anterior chamber IOLs.
Patients in whom piggyback IOL implantation is contemplated should be informed about the possibility of late complications such as interpseudophakos Elschnig pearls, hyperopic shift, and interface opacification. Alternatives such as a high-power single PMMA IOL or residual hyperopia after implantation of the highest available power foldable IOL should be thoroughly discussed. Piggyback implantation should be reserved for situations in which the benefits outweigh the risks of complications specific to this modality of visual rehabilitation. Surgery should include meticulous attention to LEC removal and a large capsulorhexis or bag/sulcus IOL strategy. Patients who receive piggyback IOLs should be examined indefinitely on a periodic basis and complications reported quickly.