Strategies for Piggybacking IOLs
Primary or secondary implantation of these lenses can correct residual refractive error when laser corneal surgery is not appropriate.
By Mark Packer, MD, FACS
Piggyback placement of an IOL can be a successful strategy for correcting residual refractive error. These IOLs can be implanted during cataract surgery or clear lens extraction and IOL insertion (primary piggyback implantation) or as a secondary procedure following the initial IOL implantation (secondary piggyback implantation). In the United States, options for appropriate piggyback IOLs are limited to the correction of residual spherical error. Outside the United States, approved piggyback styles include aspheric, toric, and multifocal lenses. Power calculation for piggyback IOLs is based on residual refractive error and can achieve highly accurate outcomes. Complications, which include interlenticular opacification (ILO), pigment dispersion, iridocyclitis, glaucoma, and hyphema, can be avoided with proper preoperative planning and IOL selection.
Successful refractive enhancement with piggyback IOLs was demonstrated in 18 eyes in a series of 74 cases (41 patients) following refractive lens exchange with accommodating IOL implantation.1 Eyes with previous keratorefractive surgery were excluded from the study. Piggyback implantation was planned in eight eyes for expected residual hyperopia; the lenses were implanted within 3 weeks of the primary surgery. In 10 eyes, unplanned piggybacks were implanted 6 to 14 weeks after the initial surgery to correct a refractive surprise.
Among the planned cases, mean axial length was 20.43 ±0.97 mm (range, 18.47–21.42 mm), and the total mean calculated IOL power was 33.12 ±3.87 D (range, 29.00–41.50 D). Among the unplanned cases, mean axial length was 21.46 ±0.57 mm (range, 20.33–22.27 mm). Axial length was the best predictor of whether or not a patient would likely need a piggyback IOL (P <0.001; Figure 1).
In this series, IOL power calculation was performed with the HolladayR formula (Holladay IOL Consultant Software; Holladay Consulting, Inc., Bellaire, Texas; Figure 2). This formula takes into account the A constant of the piggyback IOL and the residual refractive error (manifest refraction spherical equivalent). Unlike in primary IOL implantation, the eye’s keratometry, axial length, lens thickness, and corneal white-to-white values are irrelevant when calculating the power of the piggyback IOL. Only the intended correction and the lens constant (representing the effective lens position) are taken into account. This approach should be familiar to surgeons who implant phakic refractive lenses. In the United States, the most popular piggyback IOL is the AQ5010 (STAAR Surgical, Monrovia, California) because of its round edge, 6.3-mm optic, and 13.5-mm overall diameter.
There was an excellent correlation between the targeted and achieved spherical equivalent for the unplanned piggyback IOLs (R2 = 0.87; Figure 3). The mean distance UCVA improved from approximately 20/60 preoperatively to 20/20 postoperatively, and the mean near UCVA improved from about J10 to J3. The advantages of using piggyback IOLs for enhancement in these cases included rapid rehabilitation, excellent predictability, and no need for an excimer laser. Disadvantages of intraocular surgery included greater cost than corneal refractive surgery, correction limited by available IOL powers, and, at least in the United States, a lack of IOLs approved by the US Food and Drug Administration (FDA) for piggybacking that allow toric correction.
Outside of the United States, the Sulcoflex IOL (Rayner Intraocular Lenses Ltd., East Sussex, United Kingdom) is designed for implantation as a piggyback IOL in the ciliary sulcus of a pseudophakic eye. (Please see Piggybacking With the Sulcoflex, page 14, for more information.) Amon et al2 reported initial results after implanting a spherical monofocal version of the Sulcoflex in the ciliary sulcus of pseudophakic eyes to correct residual ametropia. Toric, multifocal, and aspheric versions of the IOL are also available to correct residual astigmatism and presbyopia and to reduce higher-order aberrations in pseudophakic eyes.
Multiple peer-reviewed publications have demonstrated the effectiveness of both primary and secondary placement of piggyback IOLs. Akaishi and colleagues3,4 have described placing a silicone piggyback IOL in the sulcus to enhance correction with the Tecnis Multifocal (Abbott Medical Optics Inc., Santa Ana, California) and the AcrySof Restor (Alcon Laboratories, Inc., Fort Worth, Texas) IOLs. Recently, Jin et al5 demonstrated correction of residual astigmatism with placement of a toric IOL in the sulcus using an obliquely crossed cylinder technique. Alfonso et al6 described placing diffractive multifocal IOLs in the sulcus to provide pseudoaccommodation. Boisvert et al7 developed the Pediatric Piggyback IOL Calculator to facilitate the strategy of temporary polypseudophakia in children, whereby the amount of myopic shift is reduced by removing the anterior IOL when the eye becomes sufficiently myopic.
Despite enthusiasm for piggyback IOLs, surgeons must remain cognizant of potential complications. ILO has been reported with the implantation of two acrylic IOLs in the capsular bag.8 In general, the use of a silicone piggyback IOL in the sulcus is recommended to prevent the development of ILO. Pigment dispersion and pigmentary glaucoma have been reported with placement of IOLs with sharp anterior optic edges in the ciliary sulcus;9,10 hence, IOLs with rounded anterior optic edges are required for piggybacking.11
An unusual complication of piggyback IOL insertion is posterior capsular rupture (PCR). I have previously described a case in which this occurred.12 In this case, I undertook the piggybacking for the correction of edgerelated dysphotopsia, as described by Ernest.13 The PCR occurred after implantation of the piggyback IOL as I introduced irrigation to remove the ophthalmic viscosurgical device, despite a lowered bottle height. I was able to rescue the falling primary IOL and place both it and the piggyback in the sulcus, where the lenses remained stable until they were ultimately explanted due to persistent dysphotopsia.12
In summary, piggyback IOLs can achieve excellent results and probably represent the best choice for correcting residual spherical ametropia in eyes with a history of previous radial keratotomy and eyes that are not good candidates for LASIK or PRK due to ocular surface disease or suspicious corneal topography. However, when an astigmatic component is present and the eye is otherwise healthy, corneal refractive procedures offer an unrivaled degree of accuracy and precision in a cost-effective manner.
Mark Packer, MD, FACS, is a Clinical Associate Professor at the Casey Eye Institute, Department of Ophthalmology, Oregon Health & Science University, and is in private practice at Drs. Fine, Hoffman & Packer, LLC, Eugene, Oregon. He states that he is a paid consultant to Abbott Medical Optics Inc., Advanced Vision Science, Bausch + Lomb, Carl Zeiss Meditec Surgical, Inc., Celgene Corp., GE Healthcare, Haag-Streit USA, Ista Pharmaceuticals, Inc., and Rayner Intraocular Lenses, Inc., and holds stock options with LensAR, Inc., Surgiview LLC, Transcend Medical, Inc., TrueVision Systems, Inc., and WaveTec Vision Systems. Dr. Packer may be reached at tel: +1 541 6872110; e-mail: email@example.com.
- Packer M. Frequency and risk factor analysis of piggyback IOL enhancement following refractive lens exchange with an accommodative IOL. Refractive Surgery 2006: The Times They Are AChangin’ Sponsored by the International Society of Refractive Surgery of the American Academy of Ophthalmology (ISRS/AAO). Las Vegas, Nevada, November 10-11, 2006; Johnstown, PA: Conference Archives, Inc. Multimedia DVD-ROM Archive (Flash).
- Amon M, Kahraman G, Schauersberger J. Sulcoflex (Rayner 653L), a new IOL for implantation in the pseudophakic eye: indications and first results. Paper presented at: the XXIV ESCRS; September 11, 2007; Stockholm, Sweden.
- Akaishi L, Tzelikis PF, Gondim J, Vaz R. Primary piggyback implantation using the Tecnis ZM900 multifocal intraocular lens: case series. J Cataract Refract Surg. 2007;33(12):2067-2071.
- Akaishi L, Tzelikis PF. Primary piggyback implantation using the ReStor intraocular lens: case series. J Cataract Refract Surg. 2007;33(5):791-795.
- Jin H, Limberger IJ, Borkenstein AF, Ehmer A, Guo H, Auffarth GU. Pseudophakic eye with obliquely crossed piggyback toric intraocular lenses. J Cataract Refract Surg. 2010;36(3):497- 502.
- Alfonso JF, Fernández-Vega L, Baamonde MB. Secondary diffractive bifocal piggyback intraocular lens implantation. J Cataract Refract Surg. 2006;32(11):1938-1943.
- Boisvert C, Beverly DT, McClatchey SK. Theoretical strategy for choosing piggyback intraocular lens powers in young children. J AAPOS. 2009;13(6):555-557.
- Werner L, Mamalis N, Stevens S, Hunter B, Chew JJ, Vargas LG. Interlenticular opacification: dual-optic versus piggyback intraocular lenses. J Cataract Refract Surg. 2006;32(4):655-661.
- Chang WH, Werner L, Fry LL, Johnson JT, Kamae K, Mamalis N. Pigmentary dispersion syndrome with a secondary piggyback 3-piece hydrophobic acrylic lens. Case report with clinicopathological correlation. J Cataract Refract Surg. 2007;33(6):1106-1109.
- Iwase T, Tanaka N. Elevated intraocular pressure in secondary piggyback intraocular lens implantation. J Cataract Refract Surg. 2005;31(9):1821-1823.
- Chang DF, Masket S, Miller KM, et al; ASCRS Cataract Clinical Committee. Complications of sulcus placement of single-piece acrylic intraocular lenses: recommendations for backup IOL implantation following posterior capsule rupture. J Cataract Refract Surg. 2009;35(8):1445- 1458.
- Packer M. The perils of piggybacking. Cataract & Refractive Surgery Today. 2009; 9 (7):29–33.
- Ernest PH. Severe photic phenomenon. J Cataract Refract Surg. 2006;32(4):685-686.
When to Avoid Piggybacking
This strategy is inadvisable in several less-than-ideal conditions.
By Richard S. Hoffman, MD
Implanting a piggyback IOL in the ciliary sulcus in pseudophakic patients is a rapid and safe way to reduce residual refractive errors in most patients. The best IOLs for this purpose are thin, round-edged lenses with a large overall diameter to fit in the sulcus. Despite the ease of inserting piggyback IOLs, there are many clinical scenarios in which these lenses are not ideal.
Pigment dispersion. Perhaps one of the greatest contraindications for piggyback IOL placement is the presence of significant pigment dispersion, especially with concomitant glaucoma or elevated intraocular pressure. Even if the IOL is specifically designed for sulcus placement, the potential for aggravating pigment dispersion warrants extremely conservative use of sulcus lenses in these patients.
Loose zonules. In eyes with loose zonules from trauma or pseudoexfoliation, piggyback IOLs may aggravate pseudophacodonesis if both of the haptics are not perfectly placed in the ciliary sulcus. Eyes with missing zonules have a similar relative contraindication because it is possible that a haptic could work its way through the opening in the zonules if it is not fixated appropriately in the sulcus. For this reason, eyes with subluxated cataracts that require prosthetic devices to recenter the capsular bag should probably not have a piggyback IOL unless it is fixated to the iris or the sulcus.
Posterior synechiae. Another contraindication to piggyback IOL placement is the presence of significant posterior synechiae to the capsular bag. Small areas of adhesion can be lysed before piggyback placement; however, when extensive synechiae are present, it is probably best to avoid a piggyback lens.
Residual astigmatism. The presence of large degrees of residual astigmatism is a relative contraindication for piggybacking, specifically for surgeons in the United States. Toric lenses that can be safely placed in the sulcus are currently not available in the United States. In Europe, the Sulcoflex toric IOL corrects up to 6.00 D of cylinder, treats residual hyperopia and myopia, and is available in 0.50 D steps. HumanOptics AG (Erlangen, Germany) also offers a toric sulcus-fixated IOL, the Add- On. Until these IOLs—or others like them—are available in the United States, eyes with significant residual hyperopic or myopic astigmatism that falls outside the range for accurate correction with limbal relaxing incisions are probably best treated with excimer laser corneal surgery.
Endothelial cell count. Prior to implantation of a piggyback lens, corneal endothelial cell counts should be measured to confirm that corneal edema will not result from the secondary surgery. Piggyback IOL placement is fairly atraumatic, with little if any endothelial cell loss; however, any intraocular surgery—regardless of how brief and seemingly simple—can push a borderline cornea over the edge.
Most patients will be excellent candidates for piggyback IOL placement. Visual rehabilitation is fast, and the surgical procedure has minimal risks. However, when the conditions inside the eye are not ideal for piggyback lenses, corneal refractive surgery should be considered to reduce or eliminate residual refractive errors.
Richard S. Hoffman, MD, is a Clinical Associate Professor of Ophthalmology at the Casey Eye Institute, Oregon Health & Science University, and is in private practice at Drs. Fine, Hoffman, & Packer, LLC, Eugene, Oregon. He states that he has no financial interest in the products or companies mentioned. Dr. Hoffman may be reached at tel: +1 541 687 2110; e-mail: firstname.lastname@example.org.