9 Piggyback Intraocular Lens Abstract This chapter discusses the applicability of piggyback intraocular lenses (IOLs) including the method to calculate the IOL power of piggyback IOL and technique of implanting along with its advantages and disadvantages. The first primary piggyback IOL procedure was performed in 1992 in a nanophthalmic eye with a bag/sulcus technique. The procedure was modified to a bag/bag positioning for improved calculation outcome. This led to the postoperative complication of interlenticular opacity. In order to prevent this complication, the surgical technique returned to the original bag/sulcus IOL positioning. Due to improved IOL technology and calculations, primary piggyback procedure is rarely performed today. A secondary piggyback is much more common and is used to correct pseudophakic refractive error and dysphotopsia and to impart multifocality to pseudophakic patients. Keywords: primary piggyback IOL, secondary piggyback IOL, effective lens position, refractive vergence formula, interlenticular opacification, pseudophakic refractive error In 1992, a 31-year-old male presented with bilateral nanophthalmos desperate for help. He was employed by the state of Georgia and they had recently instituted uncorrected vision requirements of 20/60 for his position. His phakic spectacle prescription was + 19.25 + 0.25 × 054 right eye and + 19.52 + 0.25 × 145 left eye yielding best-corrected acuity of 20/50 bilaterally. He had mild nuclear sclerosis cataracts and refractive amblyopia compromising his vision. Axial length was measured at 15.80 mm right eye and 15.50 mm left eye. Keratometry was 46.50 sphere right eye and 46.50/47.25 in the left eye. Calculations were performed with the Sanders–Retzlaff–Kraff (SRK)/T formula indicating that a power of approximately 46 diopters would be needed to achieve a near plano postoperative refractive error. The dioptric range of IOL powers in the 1990s was limited to 10 to 30 diopter lenses to correct the normal axial length range. We were unable to find a manufacturer willing or able to produce such a high-powered lens for these nanophthalmic eyes. After much thought, he was offered the possibility of inserting two intraocular lenses (IOLs); one three-piece plano convex lens in the bag with the plano side anterior and a second three-piece plano convex lens in the sulcus with the plano side posterior. After careful consideration and obtaining a second opinion, he agreed, as it was his only option. Initially a 25.0-diopter lens was implanted posteriorly and a 20.0-diopter lens anteriorly. The author seriously underestimated the power required, which led to the first IOL exchange of an anterior piggyback. The 20.0-diopter lens was exchanged for a 30.0-diopter lens and his resulting refraction was + 1.75 + 1.00 × 95. On the fellow eye, a 28.0-diopter lens implanted posteriorly and a 30.0-diopter lens anteriorly based largely on the results of his first eye. His refraction postoperatively was −1.25 + 1.00 × 60 with best-corrected acuity of 20/50. His bilateral uncorrected visual acuity (VA) was 20/60 and he was able to continue working for the state until his retirement. The piggyback IOL procedure ( As exemplified by the first case, the available IOL calculation formulas were not accurate for extremely long or short eyes. The available A-scan technology also was not as accurate in long or short eyes. Measurement error in short axial length eyes results in a magnified refractive error. The leading IOL power consultants of the day (Holladay and Hill) began analyzing these early results and were able to make significant advances in available formulas. Dr. Jack Holladay and Dr. Jim Gills proposed that both lens be placed in the bag to improve power accuracy by controlling effective lens position. That was easily done since the bag is so much larger than the lens. The initial refractive outcome predictability improved dramatically with the double bag positioning and the advancement of IOL calculation software. The Holladay R IOL consultant created a module (refractive vergence formula) specifically for both primary and secondary piggyback procedures. Prior to the development of the Holladay R, 13% of the eyes receiving piggyback IOLs in our practice required secondary lens exchange to correct refractive error. It is still prudent to advise highly hyperopic patients of the possibility that an IOL exchange may be necessary, but it is an uncommon event today. It is also prudent to first operate on the nondominant eye so that the refractive results can be used to plan the dominant eye surgery for optimum outcome. Fig. 9.1 Pristine postoperative piggyback lens. Inherent complications exist when operating on the hyperopic eye. The anterior chamber being smaller provides less working space. Positive vitreous pressure, posterior capsule rupture, iris prolapse, choroidal effusion, and aqueous misdirection have all been reported.2 The corneal tunnel should be more anterior to lessen the likelihood of iris prolapse, and intravenous mannitol should be considered. The author makes a side port incision and temporal self-sealing corneal incision. The phacoemulsification wound is constructed so that the entry into the anterior chamber is made at least 2 mm anterior to the limbus. The blade starts at the limbus, tunnels through the stroma, and enters through Descemet’s membrane. This 2-mm tunnel is important in an effort to avoid iris prolapse. The capsulotomy should be made after filling the anterior chamber with a retentive viscoelastic. A less-than-full anterior chamber increases the risk of the capsular opening running radial. Radial extension can be particularly detrimental or disastrous in nanophthalmic eyes. The procedure gained popularity and began to be performed around the world. The technique seemed successful with complications generally related to residual refractive error for about 3 years. Douglas Koch told the author that he was seeing cases with cell growth between the lenses.3 The author also began to see cases of interlenticular opacification (ILO), a complication that progressed from a hyperopic shift in refraction (shift of IOL position) to a significant loss of vision caused by opacity between the piggyback lenses ( Two of my patients had acrylic lenses explanted that were fused together ( Dr. Joel Shugar determined that the migration of the epithelial cells between the lenses only occurred in piggybacks when the anterior capsule was on the anterior surface of the most anterior IOL 360 degrees.5 We decided it was akin to grass growing through the cracks in concrete. The residual epithelial cells take the path of least resistance. When one lens was in the bag and one in the sulcus, the problem did not occur. When both lenses were in the bag, with a large capsulorhexis that was not in 360-degree contact with the anterior lens, the problem also did not happen. That led to prevention and treatment of ILO.
9.1 Origin
Fig. 9.1) was born.1
9.2 Refractive Considerations
9.3 Surgical Complications
9.3.1 Long-Term Complications
Fig. 9.2) that was also noted by Dr. Joel Shugar.
Fig. 9.3). They were sent to Dr. David Apple, ophthalmic pathologist at Storm Eye Institute, for analysis. Histopathology of the opaque, membranelike material localized between the piggyback lenses identified retained regenerative cortex and proliferating lens epithelial cells, including bladder (Wedl’s) cells. The composition replicated the pathologic process seen in posterior subcapsular cataracts and in the typical “pearl” form of posterior capsule opacification (PCO). Both sets of lenses with ILO analyzed seemed to be related to two PC IOLs being implanted in the capsular bag through a small capsulorhexis, with margins overlapping the optic edge of the anterior IOL for 360 degrees. Additionally, these lens sets were AcrySof material that demonstrates bioadhesion of the anterior surface of the front lens to the anterior capsule edge and of the posterior surface of the back lens to the posterior capsule.4 The sealing of the space sequestered the lenses into a closed microenvironment. The cells, having nowhere else to go, accumulate in the interlenticular space.
9.4 Treatment of Interlenticular Opacity
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