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EW CATARACT 34 April 2018 Piggyback continued from page 33 Dr. Fram and Dr. Crandall prefer reverse optic capture when possible in these cases. In addition to choosing the right patient for this procedure, there are some other challenges. One is deciding which type of IOL to use. Two years ago, the STAAR AQ5010V (STAAR Surgical, Mon- rovia, California), a silicone lens popular as a piggyback IOL, was dis- continued. This was unfortunate as it came in negative powers and was "sulcus friendly" due to the round edge and silicone material, Dr. Fram said. The LI61AO SofPort (Bausch + Lomb, Bridgewater, New Jersey) is a silicone lens, but it does not come in negative powers. Dr. Crandall said he chooses the material of a piggyback lens based on what's already in the eye. If there is an acrylic already placed, he will use a silicone piggyback. The LI61AO and Tecnis Z9002 (John- son & Johnson Vision, Santa Ana, California) are reasonable options with easy availability, Dr. Crandall said. Without the STAAR AQ5010 available as a negative power sili- cone lens, Dr. Crandall leans toward an alternative treatment for residual myopia. "I will usually prefer lens ex- change or laser vision correction for necessary treatment. The negative power acrylic lenses tend to have very thick edges, so I have worries about iris chafing and UGH syn- drome in the long run," he said. He will also opt to place piggy- back lenses in the sulcus, finding it a safer and quicker option than reopening the bag. There are several ways to go about calculating the power of a piggyback IOL, Dr. Hill said. These include the refractive vergence for- mula (available on Dr. Hill's website, doctor-hill.com), the Holladay R formula, or the Barrett Rx formula (available on the Asia-Pacific Asso- ciation of Cataract and Refractive Surgeons website). "Because this type of calculation is based on the refractive error (and to a lesser degree the Ks), the accu- racy is generally very good," Dr. Hill said. "The main limitation, however, for lower power or minus power IOLs is that they typically come in 1.00 D steps, so an exact correction may not be possible with a piggy- back IOL, unless the required power lines up with what's available." Dr. Fram provided a shortcut calculation formula. "A well-known shortcut is to take a myopic error and multiply 1.2 x the spherical equivalent of your refraction of the missed target. If it's hyperopic, you multiply 1.5 x the spherical equivalent of the refraction. That works out well for most cases," she said. The Barrett Rx formula is also useful, however, you need preoperative and postoperative measurements. As for injection of the IOL, Dr. Fram said you have to understand how to pronate and supinate to make sure the haptic is going into the sulcus correctly. The LI61AO comes out planar, so you don't have to worry about twisting your wrist to get the right conformation. Sur- geons can practice inserting piggy- back IOLs with SimulEYE (InsEYEt, Westlake Village, California) prior to live surgery. Dr. Fram said this allows surgeons to get the move- ments down and familiarize them- selves with what's going to happen intraoperatively. Dr. Fram recommended the use of a dispersive ophthalmic visco- elastic device (OVD) to protect the cornea and a cohesive to give your- self room to manipulate in the eye; this is where an adaptive OVD could be handy. In addition, intracameral miotics are useful to bring the pupil down after the insertion of the pig- gyback IOL. Complications to be aware of include pupillary capture. You'll want to use acetylcholine chloride and/or carbachol to bring the pupil down and prevent this, Dr. Fram said. Other postoperative issues include pigment dispersion, second- ary glaucoma, iris transillumination defects, and intermittent iritis, Dr. Hill said. There is also the issue of inter- lenticular opacification to be aware of. This, Liliana Werner, MD, PhD, professor of ophthalmology and visual sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, who has researched the topic extensively, said seems to occur when two posterior chamber hydro- phobic acrylic IOLs are implanted in the capsular bag through a small capsulorhexis with the margins overlapping the optic edge of the anterior IOL. 2 She pointed out that all of the explanted lenses with this issue that were sent to the Inter- mountain Ocular Research Center for analysis were three-piece AcrySof IOLs (Alcon, Fort Worth, Texas). Dr. Werner said the adhesive nature of the hydrophobic acrylic material may have contributed to this com- plication. Its pathogenesis is likely similar to that of posterior capsule opacification, derived from retained/ regenerative cortex and pearls, Dr. Werner said. Surgical methods to prevent interlenticular opacification include implanting both IOLs in the capsu- lar bag with a capsulorhexis that's larger in diameter, but Dr. Werner acknowledged that the implantation of two hydrophobic acrylic IOLs in this case should be avoided; and implanting the secondary IOL in the sulcus with the primary IOL in the bag with the traditional small capsulorhexis. Sulcus-placed IOLs should have sufficient posterior iris clearance (obtained with posteri- or optic/haptic angulation) with a smooth anterior optic surface, a rounded anterior optic edge, and an overall IOL diameter of at least 13.0 mm for centration and stable fixation, Dr. Werner said. 3–5 IOLs specially designed to be used as piggyback (supplementary) IOLs for sulcus fixation are available in some markets. 6–8 Overall, Dr. Fram said piggyback IOLs are within the skillset of young ophthalmologists. Surgeons need to understand the criteria for patient selection; that they'll be limited in the IOLs available for use; how to put in a three-piece lens in the sul- cus; and the signs of pigment disper- sion or iris chafing that might merit the secondary lens being removed. "I think the critical point is un- derstanding the appropriate clinical indications—it's these hyperopic outcomes with deep chambers and healthy sulcus—and understanding the postoperative signs of UGH or pigment dispersion. Chronic pigment in the angle can lead to irreversible damage and can be avoided with close observation," Dr. Fram said. EW References 1. Makhotkina NY, et al. Treatment of negative dysphotopsia with supplementary implantation of a sulcus-fixated intraocular lens. Graefes Arch Clin Exp Ophthalmol. 2015;253:973–7. 2. Werner L, et at. Interlenticular opacification: dual-optic versus piggyback intraocular lens- es. J Cataract Refract Surg. 2006;32:656–61. 3. Chang WH, et al. Pigmentary dispersion syndrome with a secondary piggyback 3-piece hydrophobic acrylic lens. Case report with clinicopathological correlation. J Cataract Refract Surg. 2007;33:1106–9. 4. Kirk KR, et al. Pathologic assessment of complications with asymmetric or sulcus fixation of square-edged hydrophobic acrylic intraocular lenses. Ophthalmology. 2012;119:907–13. 5. Ollerton A, et al. Pathologic comparison of asymmetric or sulcus fixation of 3-piece intraocular lenses with square versus round anterior optic edges. Ophthalmology. 2013;120:1580–7. 6. McIntyre JS, et al. Assessment of a single- piece hydrophilic acrylic IOL for piggyback sulcus fixation in pseudophakic cadaver eyes. J Cataract Refract Surg. 2012;38:155–62. 7. Reiter N, et al. Assessment of a new hy- drophilic acrylic supplementary IOL for sulcus fixation in pseudophakic cadaver eyes. Eye (Lond). 2017;31:802–809. 8. Tsaousis KT, et al. Assessment of a novel pinhole supplementary implant for sulcus fixation in pseudophakic cadaver eyes. Eye (Lond). 2018;32:637–645. Editors' note: The physicians have no financial interests related to their comments. Contact information Crandall: dackakarot@hotmail.com Fram: nicfram@yahoo.com Hill: hill@doctor-hill.com Koch: dkoch@bcm.edu Werner: Liliana.Werner@hsc.utah.edu " The best thing young eye surgeons can do when first encountering this is ask for advice from more experienced colleagues. " —David Crandall, MD

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