Successful Strategies for Piggyback IOLs

Piggyback placement of an intraocular lens can represent a successful strategy for correction of residual refractive error either during the same operation as initial cataract or lens extraction and IOL insertion (primary piggyback implantation) or as a secondary procedure following 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 US, available piggyback styles include aspheric, toric and multifocal lenses. Appropriate power calculation for piggyback IOLs is based simply on residual refractive error and can achieve highly accurate outcomes. Complications of piggybacking can be avoided with proper preoperative planning and IOL selection. Complications include interlenticular opacification, pigment dispersion, iridocyclitis, glaucoma and hyphema.

Successful refractive enhancement with piggyback IOLs has been demonstrated in a series of 18 eyes (out of a total of 74 eyes of 41 patients) following Refractive Lens Exchange with accommodative IOL implantation (eyes with a history of previous keratorefractive surgery were excluded). Eight eyes had planned piggybacks for expected residual hyperopia and 10 eyes had unplanned piggybacks for refractive surprise.1 Among the planned piggybacks the mean axial length was 20.43 ± 0.97 mm (range, 18.47 – 21.42); the total calculated IOL power was 33.12 ± 3.87 D (29.0 – 41.5). These piggyback IOLs were implanted within three weeks of the primary surgery. The eyes with unplanned piggybacks had a mean axial length of 21.46 ± 0.57 mm (20.33 – 22.27). These piggybacks were implanted from 6 to 14 weeks after the initial surgery. Axial length was the best predictor of whether or not a patient would likely need a piggyback IOL (p < 0.001).

IOL power calculation in this series was performed with the HolladayR formula (Holladay IOL Consultant, Bellaire, TX). This formula takes into account the A constant of the piggyback IOL and the residual refractive error (manifest refractive spherical equivalent). In contradistinction to primary IOL implantation, 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 is quite familiar to surgeons who implant phakic refractive lenses). In the US, the most popular piggyback IOL is the AQ5010 (STAAR Surgical, Monrovia, CA) because of its round edge, 6.3 mm optic and 13.5 mm overall diameter.

In this retrospective study of piggyback IOL enhancement there was an excellent correlation between the targeted and achieved spherical equivalent for the unplanned piggyback IOLs (R2 = 0.87). The mean uncorrected distance visual acuity improved from about 20/60 pre op to 20/20 post op, and the uncorrected near acuity 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. However, intraocular surgery carries with it greater cost than corneal refractive surgery, the correction is limited by available powers of IOLs and, at least in the US, no IOLs suitable for piggybacking permit toric correction.

On the other hand, outside the US, the Sulcoflex IOL (Rayner, Ltd., Hove, England) is designed for implantation as a piggyback IOL in the ciliary sulcus of the pseudophakic eye. It is a single-piece hydrophilic acrylic IOL that can be inserted through a 3.0 mm incision. The 6.5 mm optic and haptic edges are round. The haptic is angulated and has an undulated design to preclude rotation. A spherical monofocal version of the Sulcoflex has been implanted in the ciliary sulcus of pseudophakic eyes to correct residual ametropia (Amon M, Kahraman G, Schauersberger J. “Sulcoflex (Rayner 653L), a New IOL for Implantation in the Pseudophakic Eye: Indications and First Results,” presented at the XXIV Congress of the European Society of Cataract and Refractive Surgeons, Stockholm, September 2007. Abstract available at http://www.rayner.com/pdfs/Reference109.pdf. Accessed 27 April 2010).2 Toric, multifocal and aspheric versions of the IOL are also available to correct residual astigmatism, permit presbyopia correction and reduce HOAs in pseudophakic eyes.

Multiple peer-reviewed publications have demonstrated the effectiveness of both primary (at the same time as the initial surgey) and secondary (delayed) placement of piggyback IOLs. Akaishi et al have described placing a silicone piggyback IOL in the sulcus to enhance correction with the Tecnis multifocal (AMO, Santa Ana, CA)3 and the ReSTOR (Alcon Surgical, Ft. Worth, TX);4 recently Jin et al demonstrated correction of residual astigmatism with placement of a toric IOL in the sulcus using an obliquely crossed cylinder technique.5 Alfonso et al have described placing diffractive multifocal IOLs in the sulcus to provide pseudoaccommodation,6 and Boisvert et al have developed a Pediatric Piggyback IOL Calculator to facilitate the strategy of temporary polypseudophakia in children to reduce the amount of myopic shift by removing the anterior IOL when the eye become sufficiently myopic.7

Despite enthusiasm for piggyback IOLs, surgeons should remain cognizant of potential complications. Interlenticular opacification (ILO) has been reported with the implantation of two acrylic IOLs in the capsular bag; in general, the use of a silicone piggyback IOL placed in the sulcus is recommended to prevent the development of ILO.8 Pigment dispersion and pigmentary glaucoma have been reported with placement of IOLs with sharp anterior optic edges in the ciliary sulcus,9,10 hence the requirement of rounded anterior optic edges for piggyback IOLs.11 An unusual complication of piggyback IOL insertion is posterior capsule rupture. I have previously described a case in which this occurred in my hands.12 In this case I undertook the piggybacking for the correction of edge-related dysphotopsia as described by Ernest.13

In summary, piggyback IOLs achieve excellent results and probably represent the best choice for correction of residual spherical ametropia in eyes with a history of prior radial keratotomy and eyes with ocular surface disease or suspicious corneal topography which are not good candidates for LASIK or PRK. When an astigmatic component is present and the eye is otherwise healthy, however, corneal refractive procedures offer an unexcelled degree of accuracy and precision in a cost-effective manner.

References

1. 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 A-Changin’ Sponsored by the International Society of Refractive Surgery of the American Academy of Ophthalmology (ISRS/AAO). Las Vegas, NV, 10 - 11 November 2006. Johnstown, PA: Conference Archives, Inc. Multimedia DVD-ROM Archive (Flash).

2. Sulcoflex: a new IOL concept for the pseudophakic eye. Ophthalmology Times 11 September 2007, available at http://www.oteurope.com/ophthalmologytimeseurope/Meeting+Highlights/Sulcoflex-a-new-IOL-concept-for-the-pseudophakic-e/ArticleStandard/Article/detail/456027. Accessed 27 April 2010.

3. 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 Dec;33(12):2067-71.

4. Akaishi L, Tzelikis PF. Primary piggyback implantation using the ReSTOR intraocular lens: case series. J Cataract Refract Surg. 2007 May;33(5):791-5.

5. 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 Mar;36(3):497-502.

6. Alfonso JF, Fernández-Vega L, Baamonde MB. Secondary diffractive bifocal piggyback intraocular lens implantation. J Cataract Refract Surg. 2006 Nov;32(11):1938-43.

7. Boisvert C, Beverly DT, McClatchey SK. Theoretical strategy for choosing piggyback intraocular lens powers in young children. J AAPOS. 2009 Dec;13(6):555-7.

8. 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 Apr;32(4):655-61.

9. 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 Jun;33(6):1106-9.

10. Iwase T, Tanaka N. Elevated intraocular pressure in secondary piggyback intraocular lens implantation. J Cataract Refract Surg. 2005 Sep;31(9):1821-3.

11. Chang DF, Masket S, Miller KM, Braga-Mele R, Little BC, Mamalis N, Oetting TA, Packer M; 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 Aug;35(8):1445-58.

12. Packer M. The Perils of Piggybacking. Chang DF (ed), Cataract Surgery: My Most Difficult Case. Cataract & Refractive Surgery Today July 2009; 9 (7), 29 – 33, available at http://bmctoday.net/crstoday/pdfs/CRST0709_05.pdf. Accessed 28 April 2010.

13. Ernest PH. Severe photic phenomenon. J Cataract Refract Surg. 2006;32(4):685-686.

Mark Packer, MD, CPI, FACS, is Clinical Associate Professor, Casey Eye Institute, Department of Ophthalmology, Oregon Health & Science University School of Medicine, and in practice with Drs. Fine, Hoffman & Packer in Eugene, OR. He serves on the Cataract Clinical Committee of the American Society of Cataract and Refractive Surgery (ASCRS). In 2005 he was elected to membership in The International Intra-Ocular Implant Club.

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