320 Copyright © SLACK Incorporated ORIGINAL ARTICLE mplantation of a secondary sulcus-based intraocular lens (IOL) (add-on or piggyback) allows fine-tuning of residual refractive errors and extends the variety of op- tions for better uncorrected vision in monofocal pseudopha- kic eyes. 1 Several studies show that a sulcus-based add-on IOL implantation is safe and efficient, and also easier and more predictable than IOL exchange. 2-5 Secondary add-on multifocal IOL implantation in previously monofocal pseu- dophakic eyes improves uncorrected near vision and reduces spectacle dependence. 6-7 Like all new methods, the piggyback multifocal procedure requires evaluating potential advantag- es and disadvantages in comparison to existing methods. One strength of the sulcus-based add-on multifocal IOL implanta- tion is the potential reversibility of the procedure in cases of multifocality intolerance. However, a possible disadvantage could be a reduction in visual or optical quality compared to standard primary in-the-bag multifocal IOL implantation. Finally, piggyback implantation is related to specific compli- cations such as pigmentary dispersion from iris rubbing, in- terlenticular opacification, and pupillary capture. 8,9 The purpose of the current study was to intraindividually compare the visual performance of a secondary sulcus-based add-on multifocal IOL in previously unilateral monofocal pseudophakic eyes with a primary in-the-bag multifocal IOL. PATIENTS AND METHODS ENROLLMENT AND BASELINE This prospective intraindividual clinical trial comprised patients having a secondary sulcus-based add-on multifocal I ABSTRACT PURPOSE: To compare the clinical outcomes of add-on sulcus-based multifocal and standard in-the-bag multi- focal intraocular lens (IOL) implantation. METHODS: Twenty-one patients with unilateral monofo- cal pseudophakia underwent add-on sulcus-based Acri. LISA 536D multifocal IOL (Carl Zeiss Meditec, Jena, Germany) implantation (add-on multifocal IOL group) and contralateral phacoemulsification with in-the-bag Acri.LISA 376D multifocal IOL (Carl Zeiss Meditec) im- plantation (primary multifocal IOL group). Uncorrected distance visual acuity, uncorrected near visual acuity, corrected distance visual acuity, distance-corrected near visual acuity, photopic (90 cd/m 2 ) distance, near contrast sensitivity, mesopic (5 cd/m 2 ) distance contrast sensitivity with and without glare, wavefront aberrations, and complications were measured 6 months postopera- tively. RESULTS: Primary in-the-bag multifocal IOLs provided slightly but significantly better uncorrected distance vi- sual acuity (0.08 ± 0.10 vs 0.17 ± 0.15 logMAR, P = .028), uncorrected near visual acuity (0.09 ± 0.17 vs 0.18 ± 0.11 logMAR, P = .005), and corrected distance visual acuity (0.01 ± 0.04 vs 0.04 ± 0.05 logMAR, P = .038). There were no significant differenc- es in distance-corrected near visual acuity, photopic or mesopic contrast sensitivity under different conditions, and wavefront aberrations. Complications included pig- ment dispersion in one eye (4.8%) and pupillary capture in 2 eyes (9.5%) of the add-on multifocal IOL group. CONCLUSIONS: The secondary add-on sulcus-based multifocal IOL provided useful pseudoaccommodation with vision quality similar to the primary in-the-bag mul- tifocal IOL. The technique should be considered in pa- tients diagnosed as having unilateral or bilateral monofo- cal pseudophakia seeking near spectacle independence. [J Refract Surg. 2014;30(5):320-325.] From the Department of Refractive Surgery, Centro Oftalmológico Marqués de Sotelo and Hospital NISA Valencia al Mar, Valencia, Spain (GM, CA-D, LB); the Department of Optics, Optometry Research Group, University of Valencia, Valencia, Spain (GM, CA-D, LB); and Clínica Baviera Castellón, Castellón, Spain (GM, CA-D, SR). Submitted: February 17, 2014; Accepted: March 4, 2014; Posted online: May 2, 2014 The authors have no financial or proprietary interest in the materials pre- sented herein. Correspondence: Gonzalo Muñoz, MD, PhD, FEBO, Centro Oftalmológico Marqués de Sotelo, Avda. Marqués de Sotelo 5, planta 2ª, 46002 Valencia, Spain. E-mail: gon.munoz@ono.com doi:10.3928/1081597X-20140422-02 Add-On Sulcus-Based Versus Primary In-the-Bag Multifocal Intraocular Lens: Intraindividual Study Gonzalo Muñoz, MD, PhD, FEBO; César Albarrán-Diego, MSc; Lurdes Belda, MSc; Stephanie Rohrweck, MD, PhD