This retrospective study received Institutional Ethical Board Committee approval. All patients signed an informed consent, and the study was conducted in accordance with the Declaration of Helsinki (64th WMA General Assembly, Fortaleza, Brazil, October 2013).

Patients bilaterally implanted with MF-IOLs who developed neuroadaptation failure bilaterally and had an exchange with MNF-IOLs were included in the study. Patients that developed dysphotopsia or other complaints unilaterally were not considered to have neuroadaptation failure and were excluded from the study. Patients with anatomical causes for the exchange, such as lens decentration were excluded.

Selection of the explanted cases was performed in the framework of the Iberia Biobank database of explanted ophthalmic devices (UMH, Alicante, Spain). Thereafter, the clinical files of our patients were reviewed, and the data was collected in a spreadsheet (Excel, Microsoft, USA). The intraoperative information was gathered from surgical records and surgical videos. Data collected included patient age at the time of explantation, gender, primary procedure, explantation procedure, time interval between IOL implantation and explantation, implantation site, IOL design, cause for exchange, concomitant diseases, history of ocular interventions, uncorrected visual acuity for far and near, best corrected visual acuity for far and near, attempted spherical equivalent (SE), postoperative SE at three months, intraoperative and postoperative complications, and follow-up time.

The formulae used for IOL calculations for the MNF-IOL to be implanted were: SRKT and Hoffer Q using the IOLMaster (v.5.4, Carl Zeiss Meditec AG, Germany). For patients with previous refractive surgery, IOLs were calculated using the ASCRS IOL calculator (iolcalc.ascrs.org).

All primary MF-IOL implantations as well as their explantations were performed by the same surgeon (JLA) at the same institution, VISSUM Ophthalmology Institute, Miranza Group (Alicante, Spain). Explantation was decided after at least three months of neuroadaptation failure. The decision to proceed with explantation was based on significant patient complaints relating to poor quality of vision and/or quality of life (e.g., dysphotopsia, glare, halos, starbursts, etc.) caused by the implanted lens and in the absence of any residual ametropia or anatomical findings that could justify such symptoms (e.g., dry eye, posterior capsule opacification, etc.). Patients experienced a combination of different complaints, and it was hard for them to point out one neuroadaptation failure symptom causing the complaint. Patients with residual ametropia that improved more than one line of CDVA were prescribed glasses for a month’s trial. After the trial, if the patient was satisfied with his vision with glasses and all complaints disappeared, then the patient underwent a corneal refractive surgery, either LASIK or PRK depending on the case and was excluded from this study. Therefore, residual ametropia was discarded as a cause of neuroadaptation failure when patients’ dissatisfaction and symptoms remained even after correcting the ametropia either with a spectacle trial or by performing a corneal laser enhancement. Any type of irregular astigmatism was ruled out in all the patients before the first surgery which was the cataract surgery and before the second surgery which was the IOL exchange. The endothelial cell density and morphology were done before the cataract surgery in all the patients.

The aim was to preserve the capsular bag in order to re-implant into it a MNF-IOL. The optic cut technique was used to explant the MF-IOL [10]. Local peribulbar anesthesia and intravenous sedation was used in all cases; Two paracentesis of 1.0 mm and a 3.0 mm main incision were constructed. The pupil was dilated using intracameral injection of a mixture of tropicamide, phenylephrine, and lidocaine (Fydrane, Théa, France). The anterior chamber was filled with a dispersive viscoelastic (Viscoat, Alcon, USA), followed by the dissection of the IOL from the capsular bag, especially the rim of the anterior capsule using a cohesive viscoelastic (ProVisc OVD, Alcon, USA) with a 30G cannula. Using a Sinskey hook and a Lester hook (Katena, USA), the IOL was loosened from the capsular bag. Afterwards, the IOL was overlapped onto the anterior capsular rim. Subsequently, after fixing the IOL with the Sinskey hook, it was cut with IOL cutting microscissors (Katena, USA) and passed through the main incision. The cut was performed radially to the center of the IOL, followed by its extraction through the main incision using two forceps that were alternated in grasping the IOL while eliminating it from the anterior chamber. Then, the capsular bag was filled with cohesive viscoelastic (ProVisc OVD, Alcon, USA) and the MNF-IOL was implanted into the capsular bag. The procedure was finalized routinely with intracameral antibiotics (Cefuroxime 10 mg/ml, Normon, Spain). If a 10/0 nylon interrupted suture was required for incision sealing, this was then removed after three weeks of follow-up. Postoperative treatment consisted of the standard topical tobramycin combined with dexamethasone four times a day for one week and a non-steroidal anti-inflammatory three times a day for a month.

When the surgeon considered the capsular bag as unsuitable for the new IOL implantation (in relation with the integrity of the posterior capsule), a 3-piece MNF-IOL was implanted in the sulcus.

Outcomes were evaluated at three months following the IOL exchange. The following parameters were evaluated:

Uncorrected and best corrected visual acuities for far distance (5 m) and near distance (40 cm) were measured.

The subjective quality of vision before and after IOL exchange was evaluated using the validated Quality of Vision (QoV) questionnaire. Patients were interviewed three months after each IOL was implanted [11]. They rated 10 visual symptoms on the basis of their frequency, severity and bothersomeness. Glare, halos, starbursts, hazy vision, blurred vison, distortion, double or multiple images, fluctuation in vison, focusing difficulties, and difficulties in judging distance or depth perception were assessed. Raw data were Rasch-scaled on a 0-100 scale, with lower scores indicating better quality of vision [12].

The validated VF-14 questionnaire was used to evaluate the visual function three months after implantation of each IOL. It includes 14 questions about difficulties patients encounter in their activities of daily living even with glasses. The respondents chose one of five ability levels that ranged from “no difficulties” to “unable to do”. The total score was calculated by the previously described method [13]. The best score is 100, however, a score of 0 signifies the patient answered to all questions “unable to do”. In order to study the visual function in daily activities at different distances, we divided the questions into three groups. The first group contained six questions that best described far vision, the second group had three questions for intermediate vision and the third group had five questions relating to near vision. The scores for each distance were calculated using the same method. In addition, due to concerns raised over the scoring of the original VF-14, we have also performed Rasch analysis (using WINSTEPS, Version 3.93.2, Chicago, IL) to score the eight items of the refined version. This version is known as the VF-8R [14].

Patients were asked about their overall satisfaction with their near, intermediate and far vision, spectacle independence for these distances, and if the patient would repeat the surgery again either with the MF-IOL or the MNF-IOL.

Descriptive analyses were performed using SPSS for Windows (v.18, IBM SPSS Corporation, USA). The analysis of data was based on whether data were normally or non-normally distributed. The Student’s t-test was performed to evaluate the significance of differences. The data analyzed were expressed by the mean ± standard deviation (SD) and a P value of less than 0.05 was considered statistically significant.