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Up Front | Jun 2008

Primary Piggyback Implantation

In a case series piggybacking Tecnis Multifocal and Clariflex IOLs, refractive results and patient satisfaction were good at 6 months postop.

Piggyback IOL implantation—implantation of two or more IOLs into the posterior chamber of the same eye—allows refractive correction in cataract surgery cases that require an IOL power that exceeds the limit of available lenses. The use of this technique was developed primarily to correct high hyperopic refractive errors; however, it may also be used a secondary procedure to correct postoperative refractive errors.1-3

Although piggyback implantation has gained acceptance, little has been published regarding the use of a multifocal IOL in this process.4-6 The first case of piggybacking a multifocal IOL was presented in 1999. The author reported a successful case of multifocal piggyback IOL implantation using the Array7 (Advanced Medical Optics, Inc., Santa Ana, California; no longer available). Recently, we published our experience with piggyback implantation using two multifocal IOLs, the AcrySof Restor (Alcon Laboratories, Inc., Fort Worth, Texas) and the Tecnis Multifocal (Model ZM900; Advanced Medical Optics, Inc.), showing excellent results.8-9 We have also piggybacked the Tecnis Multifocal and ClariFlex (Advanced Medical Optics, Inc.) IOLs, the results of which are described in this article.

PATIENTS AND METHODS
The two IOLs used most often at our institution, the Hospital Oftalmologico de Brasilia in Brazil, are the Tecnis Multifocal and ClariFlex IOLs. The innovative aspect of the Tecnis is its combined modified prolate anterior surface and posterior diffractive surface, providing excellent near and distance vision. The ClariFlex is a three-piece monofocal IOL with a 6-mm biconvex square-edged silicone optic and 10° angulated C PMMA haptics.

A total of 20 eyes (12 patients) were included in our study. To determine IOL power, we used the Holladay formula if the axial length, determined by the IOLMaster (Carl Zeiss Meditec AG, Jena, Germany), was short (less than 22 mm) or the SRK/T formula if the axial length was average (22 mm or greater). The targeted postoperative refractive error was plano. All Tecnis IOLs had an A-constant of 119.8 and all ClariFlex IOLs had an A-constant of 118.4.

All patients received topical anesthesia (lidocaine 2% gel). First, a 2.75-mm self-sealing clear cornea incision was created temporally. Second, phacoemulsification was performed with the Infiniti (Alcon Laboratories, Inc.) or Sovereign (Advanced Medical Optics, Inc.) phacoemulsification system. Third, both IOLs, first the Tecnis into the capsular bag and then the ClariFlex into the ciliary sulcus, were inserted. The highest power available for the Tecnis Multifocal was used, and we completed the total IOL power required with the addition of the ClariFlex. The viscoelastic material was completely removed at the end of the procedure. No sutures were used in any case.

RESULTS
Patients were followed for 6 months. The mean preoperative axial length was 20.80 mm (range, 19.61–22.41 mm; standard deviation [SD] ±0.8), and the mean distance UCVA (logMAR) was -1.30 (range, -0.30 to -2.00; SD ±0.54). At 6-month follow-up, the mean UCVA increased to -0.16 (range, 0.00 to -0.40; SD ± 0.1; P<.001), and 19 eyes (95%) achieved a distance UCVA of 20/40 or better and 16 eyes (80%) 20/25 or better. At the last follow-up, 18 (90%) and two eyes (10%) achieved a near UCVA of J1 and J2, respectively. Preoperatively, the mean BCVA (logMAR) was -0.16 (range, -0.10 to -0.30; SD ±0.05). At 6 months, the mean BCVA increased to -0.04 (range, 0.00 to -0.10; SD ±0.05; P<.001). No eye lost any lines of BCVA. The average spherical equivalent (SE) at referral was 6.35 D (range, 2.25–12.25 D; SD ±2.45). At 6-month follow-up, the average SE was -0.25 D (range, -1.00 to 0.50 D; SD ±0.40; P<.001).

Three months after cataract surgery, two eyes required a second procedure (LASIK) for the correction of low residual myopia. Both surgeries were without complications. At the last follow-up, 10 patients (83.3%) were satisfied with their quality of vision without glasses (ie, spectacle-independent for near and distance vision). Only three patients (25%) reported halos as moderate or severe with no daytime disability; the remaining patients considered halos to be absent or mild. No other complaints were reported. Good distance and near vision were reported by all patients. In our series, no interlenticular opacification (ILO) or other postoperative complications related to piggybacking IOLs were observed.

DISCUSSION
Multifocal IOLs, divided into the subcategories of diffractive and refractive, are designed to provide distance and near vision after cataract surgery. Several multifocal models are available; however, these lenses have yet to gain wide acceptance because of associated halos, glare, and decentration.

The Tecnis ZM900 Multifocal IOL is a diffractive lens with an aspheric design. Recently, Mester et al10 studied the clinical outcomes and patient satisfaction of the Tecnis ZM900 and Array SA40 IOLs. The investigators concluded that the Tecnis ZM900 provided better near vision, better contrast sensitivity, greater spectacle independence, and higher levels of patient satisfaction.

Unfortunately, the powers available for multifocal IOLs are not high enough to fully correct high degrees of hyperopia. In cases in which the intended IOL power exceeds that of any available multifocal IOL, piggyback implantation is an alternative method to provide adequate pseudophakic optical correction. Gayton and Sanders1 reported that bilateral pseudophakes have become more common since 1993. Reports of implanting two or more posterior chamber IOLs, including PMMA, silicone, or acrylic, during separate and the same surgeries have been published.1-5 In optic models, Hull and coauthors11 demonstrated significant improvement in axial modulation transfer function, which can be translated clinically into better contrast sensitivity in highly hyperopic eyes, when double implants were used.

UNIQUE COMPLICATION
ILO is a unique complication related to piggyback implantation.12-14 Although the exact cause of ILO is unknown, we do know that implanting both IOLs into the capsular bag causes bioadhesion. The anterior surface of the front lens adheres the anterior capsule edge, and the posterior surface of the back lens adheres to the posterior capsule, preventing cell migration from the equatorial bow to the posterior capsule. This migration may be directed toward the interlenticular space; it is not material specific. Recommendations to reduce the occurrence of ILO include complete removal of lens epithelial cells with thorough and repeated hydrodissection combined with irrigation and aspiration of the capsule; making the continuous curvilinear capsulorrhexis larger than the IOL optic, preventing migration of cells from the capsule edge to the optic; and using bag-sulcus piggybacking to avoid an interlenticular space that could support cellular ingrowth.

In our series, we implanted one IOL into the capsular bag and one IOL into the ciliary sulcus to prevent ILO. After 6 months of follow-up, we have not observed opacities between the IOLs. Previously, ILO formation was particularly related to the implantation of two hydrophobic acrylic IOLs and less with silicone IOLs.14 For this reason, we implanted IOLs composed of different materials to avoid the formation of ILO.

Overall, the use of multifocal IOLs in a piggyback fashion appears to be a safe and efficient procedure and a good refractive solution. Attention to detail in regard to proper patient selection, preoperative measurements, intraoperative technique, and postoperative management has resulted in excellent outcomes and improved patient acceptance of this effective technique. As with all refractive procedures, realistic expectations should be established prior to surgical intervention.

Leonardo Akaishi, MD, practices at the Brasilia Ophthalmologic Hospital, Brazil. Dr. Akaishi states that he has no financial interest in the products or companies mentioned. He may be reached at E-mail: leonardoakaishi@hobr.com.br.

Patrick F. Tzelikis, MD, practices at the Brasilia Ophthalmologic Hospital, Brazil. Dr. Tzelikis states that he has no financial interest in the products or companies mentioned. He may be reached at E-mail: tzelikis@terra.com.br.

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