Materials and methods
Study design
This prospective observational comparative clinical study included patients after bilateral implantation of Tecnis Symfony or Acrysof IQ PanOptix for routine clinical practice. All patients were included at the Department of Neurosciences, Biomedicine and Movement Sciences, Eye Clinic, University of Verona, Verona, and at the Carones Ophthalmology Center, Milano, Italy. The calculation of the sample size was based on the primary outcomes of Best Corrected Distance Intermediate Visual Acuity (BCDIVA) at 60 cm under photopic condition and Best Corrected Distance Visual Acuity (BCDVA) at 40 cm.
The sample size of 50 subjects (25 for each group) reaches a power equal to 95% capable of detecting a difference between the averages of BCDIVA equal to 0.006 with SD 0.04 in the Symfony group and 0.07 in the PanOptix group with an alpha significance level of 0.05 using the T test for independent sample.8–12 The sample size was calculated with PASS V.14 software, in order to obtain a valid statistical analysis.9–11 13 14 Twenty-five consecutive patients were prospectively recruited the day after the implantation of the second eye with the Tecnis Symfony IOL (Symfony group) and 25 consecutive patients were prospectively enrolled the day after the implantation of the second eye with the Acrysoft IQ PanOptix IOL (PanOptix group), being careful to enrol patients who respected inclusion criteria and in order to create two homogeneous group for age and ocular parameters with a randomisation of 1:1. For routine clinical practice, each patient underwent surgery in the second eye 1 week after the first. All patients enrolled in the study were informed and written informed consent was obtained. The study adhered to the tenets of the Declaration of Helsinki and was notified to the local ethical committee (Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona).
Only the investigators carrying out the follow-ups were masked to the implanted IOLs. Neither surgery treatment nor outcomes were masked.
Patient and public involvement statement
This study was done without patient or public involvement. Patients were not invited to discuss on the study design or interpret the results. Patients were not asked to contribute to the writing or editing of this paper.
Patients’ choice
Inclusion criteria for the study were patients with bilateral IOL implantation (Tecnis Symfony IOL, or Acrysoft IQ PanOptix IOL) with a pre-existing corneal astigmatism within 1.00 D and axial length between 22.0 mm and 24.5 mm before surgery. Exclusion criteria included patients with intraoperative complications, previous ocular surgery including corneal, retinal or refractive surgery, previous ocular trauma, and any ocular disease such as amblyopia, chronic or recurrent uveitis, acute ocular disease, diabetes mellitus with retinal changes, glaucoma, pseudoexfoliation syndrome or zonular laxity, optic nerve atrophy, keratoconus, alteration in colour perception and corneal endothelial dystrophy. All patients were evaluated at the baseline (1 day after the surgery), 1 week, 1 month and 3 months after the baseline, but all results reported refer to the 3-month follow-up visit.
Surgical technique
All included patients previously underwent a standard sutureless phacoemulsification surgery without any intraoperative complications. The surgery was performed by two experienced surgeons (EP, FC). In all cases, topical anaesthesia was administered and pharmacological mydriasis was induced using a combination of cyclopentolate 1.0% and phenylephrine 0.1%. IOL power and predicted postoperative refraction were calculated with a Lenstar Optical Biometer (Haag-Streit, USA), using SRK/T biometry for all eyes (between 22.00 mm and 24.5 mm). IOL dioptric power was selected targeting emmetropia, using the IOL power corresponding to 0 or to the negative (myopic) predicted refractive outcome closest to 0. At baseline all patients received the same postoperative medication, which was a combination of topical netilmicin 0.3% and dexamethasone 0.1% four times a day for 2 weeks and then tapered off by one drop per week. Likewise, non-steroidal anti-inflammatory diclofenac 0.1% drops were prescribed three times a day for 4 weeks to prevent macular oedema.
Intraocular lens (IOL)
Tecnis Symfony ZXR00 is an ERV IOL that is distributed by Johnson & Johnson (Johnson & Johnson, New Brunswick, New Jersey, USA). It is a UV blocking hydrophobic acrylic, single piece IOL, aspheric in the anterior surface and achromatic diffractive in the posterior one. Unlike diffractive MIOLs which split the light in different discrete foci, Symfony technology elongates the depth of focus, thanks to echelette design, and it is characterised by a typical continuum range of foci that induces a defocus curve with a single large peak. Moreover, Symfony technology includes a compensation for positive corneal spherical aberration which allows to achieve a better quality of vision. In this IOL it has been calculated that light transmission to the retina reaches 92%.6
Acrysof IQ PanOptix TNFT00 is a tri-quadrifocal IOL that is distributed by Alcon (Alcon Laboratories, Inc, Fort Worth, Texas, USA). It is a hydrophobic acrylic, single piece, aspheric non-apodised diffractive IOL. PanOptix design presents four focal points (40 cm, 60 cm, 120 cm and infinity) even if this quadrifocal technology is modified, so the light energy for intermediate focal point (120 cm) is redistributed to the infinity focal point, in order to obtain better performances in the distance (Enlighten Optical Technology). For this reason, patients with PanOptix IOLs could only use three focal points: at distance, at 60 cm and at 40 cm. Light entering the eye is distributed 50% for far distance focus, 25% for near distance focus and 25% for intermediate distance focus, with a total transmission of 88% of light to the retina with a pupil diameter of 3.0 mm.7
Outcomes
Monocular visual acuity, corrected for distance and uncorrected were measured using the corresponding Early Treatment Diabetic Retinopathy Study (ETDRS) chart under photopic conditions (683 lm/W) and 100% contrast (ESV-3000 ETDRS System, Vectorvision, Inc) at 4 m.
To obtain the defocus curve, binocular visual performances were tested under photopic conditions (683 lm/W) and 100% contrast (ESV-3000 ETDRS System, Vectorvision, Inc) at 4 m. Each patient was corrected for distance acuity in both eyes and additional lenses were added sequenced over the range of +1.00 to −4.00 D in 0.50 D steps, recording visual acuity for each step. In order to avoid memory effects presenting letter sequences were randomised and patient’s eyes were occluded between each lens presentation, so that the subject was not aware of which lens had been inserted and whether the letter on the chart had been changed or not.8
Intermediate and near visual acuity were measured monocular, respectively, at 60 cm and 40 cm using ETDRS near acuity charts (Sloan ETDRS format near vision, precision vision) with 100% contrast and photopic condition (683 lm/W).
Objective quality of vision was measured with objective CS (MTF cut-off) and objective optical quality (Strehl ratio), calculated with Optical Quality Analysis System (OQAS, Visiometrics SL, Terassa, Spain).
Aberrometry (root mean square, RMS 4 mm) was calculated with Hartmann-Shack aberrometer (Topcon, Tokyo, Japan).
Last, the subjective quality of vision was evaluated using the National Eye Institute Refractive Error Quality of Life score test (NEI-RQL-42 score), and in particular we focused our attention on subscales of ‘clarity of vision’, ‘near vision’, ‘dependence on correction’ and ‘symptoms’.
Statistical analysis
Data analysis was performed using SPSS for Windows software (V.19.0, IBM Corporation, Armonk, New York, USA). Normality of data samples was evaluated using the Kolmogorov-Smirnov test. When parametric analysis was possible, the Student’s test for unpaired data was used for comparison between IOLs, whereas the Mann-Whitney test was used when parametric analysis was not possible. A p value <0.05 was considered statistically significant.
