Design
Retrospective comparative case series
Setting
Ophthalmology, Tsukazaki Hospital, Japan
Patients
We reviewed a consecutive case series of cataract patients who underwent bilateral implantation of Tecnis bifocal IOLs (ZMB00) and Tecnis EDOF IOLs (ZXR00V) from August 11, 2011, to February 22, 2020, with the right and left lenses implanted within 3 months of each other in the same way as in our previous study [9, 16]. Participants were recruited for enrollment in this consecutive case series study (outpatients with or without doctor referral). There was no potential self-selection bias which is likely to impact results. The exclusion criteria were a history of other ocular diseases that could affect visual function, |subjective equivalent (SE)| > 2.00 D, |subjective refraction cylinder (CYL)| > 3.00 D and |corneal astigmatism (keratometric cylinder)| > 3.00 D at 10 weeks after surgery.
Preoperative examination
Preoperative examinations were performed in the same way as in our previous study [9, 16]. All patients received full ophthalmologic examinations, including evaluations of the corneal curvature radius, corneal astigmatism, axial length, refractive status, ocular aberrations, pupil diameter, distance/intermediate/near visual acuity, contrast sensitivity, and contrast sensitivity under the glare, as well as anterior segment evaluations using a slit lamp, tonometry, and indirect fundoscopy. The quality of vision was evaluated using the Japanese version of the 25-item National Eye Institute Visual Function Questionnaire (VFQ-25) [17]. The VFQ-25 was administered by experienced technicians or nurses in a face-to-face setting. Spectacle use was also evaluated by inquiring how often the patient used spectacles for distance, intermediate and near vision (with possible responses of ‘never,’ ‘sometimes’ or ‘always’).
Uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) were measured at 5.0 m. Uncorrected intermediate visual acuity (UIVA) and corrected intermediate visual acuity (CIVA) were measured at 0.5 m. Uncorrected near visual acuity (UNVA) and corrected near visual acuity (CNVA) were measured at 0.3 m. Visual acuity was measured using the decimal visual acuity chart, and the measured decimal values were converted to the logarithm of the minimum angle of resolution (logMAR) scale. The corneal curvature radius, corneal astigmatism, and objective refractive status were measured using a KR-8900 autorefractor keratometer (Topcon, Tokyo, Japan). The axial length was measured using IOL Master (Carl Zeiss, Oberkochen, Germany) and AL-3000 (TOMEY, Nagoya, Japan) biometers. Contrast sensitivity and contrast sensitivity under glare (visual angle of the test target: 6.3°/4.0°/2.5°/1.6°/1.0°/0.7°; 13 contrast levels: 0.01 to 0.64 contrast or 2.00 to 0.34 log10CS) were measured using a CGT-1000 contrast glare tester (Takagi Seiko, Nakano, Japan) [9, 10, 16], and the pupil diameter and ocular aberrations were measured using a KR-1W Wavefront Analyzer (Topcon, Tokyo, Japan). Experienced technicians obtained all measurements.
IOLs and surgical technique
Two types of diffractive lenses from Johnson & Johnson Vision, Tecnis Symfony EDOF IOL (ZXR00V) and Tecnis Multifocal + 4.0 D (ZMB00) were examined in the same way as in our previous study [9, 16]. Both have acrylic optics measuring 6.0 mm in diameter, a biconvex optical structure, and an aspheric optical section designed to suppress corneal spherical aberration. ZMB00 is a clear lens, and ZXR00V is a yellow lens with the same coloring as ZCB00V (OptiBlue®, Johnson & Johnson Surgical Vision, Inc. New Brunswick, NJ, USA), which has been reported to have a minor effect on visible wavelengths [18]. The ZXR00V IOL contains an achromatic diffraction surface (echelette grating) to correct for corneal chromatic aberration, and this feature elongates the range of focus. The ZMB00 IOL is a double-focus diffractive lens with + 4 D near power [19–22]. The patients chose to undergo implantation with either bifocal or EDOF IOLs after they had been informed of the advantages and disadvantages associated with each type. The patients in the bifocal group received Tecnis bifocal IOLs (ZMB00) bilaterally, while those in the EDOF group received Tecnis EDOF IOLs (ZXR00V) bilaterally. The goal for all eyes was emmetropia for distant vision. Cataract surgeries were performed by 15 experienced cataract surgeons using the same standard technique of sutureless microincision phacoemulsification and the same protocol. The surgical procedures consisted of topical anesthesia, the creation of a scleral or corneal incision of 1.8 to 2.8 mm, 5 mm of continuous capsulorhexis, phacoemulsification cataract extraction and IOL implantation with an injector.
Postoperative examination
The patients were evaluated at 10 weeks postoperatively. The postoperative examination protocol at 10 weeks was identical to the preoperative protocol.
Statistical analyses
The sample size was calculated for an alpha of 0.00068 and a power of 0.80. A standard deviation in the VA of 0.10 logMAR units was presumed in addition to a minimum detectable difference of 1 line of VA (0.1 logMAR), based on our previous study [9]. This calculation recommended the inclusion of 39 eyes per group. The bifocal group comprised 1326 eyes of 663 patients, and the EDOF group comprised 210 eyes of 105 patients, respectively; thus, the sample size was sufficient.
Similar to our previous study [9, 16], the two groups (bifocal IOL and EDOF IOL) were compared in terms of the following postoperative parameters at 10 weeks after surgery on both eyes: (1) mixed-effects linear regression: visual acuity (uncorrected/corrected, distance/intermediate/near), contrast sensitivity (with/without glare), and higher-order aberrations (ocular/internal, scaled to a pupil size of 4 mm/6 mm); (2) linear regression model or logistic regression: VFQ-25 scores; and (3) cumulative logistic regression: spectacle dependence (distance/intermediate/near). Analyses in both groups were adjusted for age, sex, axial length, subjective refraction spherical equivalent, subjective refraction cylinder, corneal astigmatism, corneal higher-order aberrations and pupil diameter. In regression analyses (2) and (3), the data were divided into two parts (left-eye data and right-eye data), and the regression model was applied to each dataset. Since discrete scores were observed for "peripheral vision", "color vision", "driving daytime", "driving nighttime", and "driving adverse conditions" on the VFQ-25, we treated them as binary data. We divided the patients into two groups (those with scores of 75 or lower and those with scores above 75) and applied the logistic regression model to these groups. The threshold was determined from the distribution of the following variables: Peripheral_Vision, Color_Vision, Driving_Daytime, Driving_Nighttime, and Driving_Adverse_Conditions. A threshold of 75 was used in this study because most VFQ-25 scores are > 75 after surgery. The results of the left- and right-eye analyses were combined using the inverse variance method; the corrected values were calculated for the left- and right-eye datasets, and the average values were used. In the regression analysis, the Wald test was applied to evaluate the significance of differences in postoperative parameters between the two groups, and the significance level was set to 0.00068 after Bonferroni’s correction. Correlation analysis between postoperative parameters was applied for the bifocal focal and trifocal groups, and a heatmap of Pearson’s correlation coefficients was generated for each group. In the correlation analysis, two-sided t-tests were used to evaluate whether the correlation coefficients were significantly different from zero, and the significance level was set to 0.00002 after Bonferroni’s correction.
The statistical analyses were performed by using a commercially available software program (R, version 3.6.1; R Core Team, 2019, Vienna, Austria) [23].
Ethics statement
This study conformed to the tenets of the Declaration of Helsinki and was approved by the Ethics Committee of Tsukazaki Hospital. All research was performed in accordance with relevant guidelines/regulations. Written informed consent was obtained from each subject. This study was registered as UMIN000035630: ‘‘Performance comparison among different intraocular lenses in cataract surgery.’’