This non-randomized, observational study was performed at the Eye Hospital of Wenzhou Medical University (Zhejiang, China), approved by the institutional review board and ethics committee of Wenzhou Medical University. Practices and research were conducted in accordance with the Declaration of Helsinki. All patients signed informed consent before participation.
Patients’ records between October 2016 to August 2017 were evaluated and fifty patients (50 eyes) with phacoemulsification and IOL implantation surgery were included. Twenty-five patients were implanted with refractive rotationally asymmetrical MIOLs (Oculentis MF30) and twenty-five patients were implanted with all optic zone diffractive MIOL (TecnisZMB00). Inclusion criteria were patients older than 50 year of age with age-related cataract, axial length between 21 and 25 mm and IOL was implanted in the capsular bag. Exclusion criteria were patients less than 50 years of age; with corneal astigmatism of more than 1.0 D; with cornea lesions or scars, macular diseases, ocular inflammation or any other ocular diseases; with any ocular surgical history. All patients provided informed consent.
First operated eye was selected in the study when the patient underwent binocular cataract surgeries. Visual functional data was collected by clinical researchers who did not know the IOL type the patient received.
All patients had a full pre- and post-operative ophthalmologic assessment. The preoperative examination included refraction, uncorrected distance visual acuity (UDVA), best-corrected distance visual acuity (BCDVA), slit-lamp examination (SL115;Carl Zeiss, Oberkochen, Germany), fundus examination under dilation, corneal topography (Pentacam, Oculus, Inc.), endothelial cell count (SP 2000P specular microscope, Topcon Europe BV), biometry (IOLMaster, Carl Zeiss Meditec AG), retinal optical coherence tomography (Cirrus 4000 OCT, Carl Zeiss MeditecAG). Patients were evaluated at 1 day, 1 week, and 1 and 3 months. At each follow-up visit, the UDVA and BCDVA, Uncorrected near visual acuity (UNVA) and distance corrected near visual acuity (DCNVA), Uncorrected intermediate visual acuity (UIVA) and distance corrected intermediate visual acuity (DCIVA), refraction, Optical Quality Analysis System (OQAS) II were measured At the 3-month evaluation, defocusing curve was measured and patients were requested to complete a purpose-developed satisfaction questionnaire.
The Lentis Mplus LS-313 MF30 (Oculentis GmbH) (figure 1a) is an asymmetric refractive MIOL that has been extensively used. This refractive MIOL is designed with a 6.0 mm optic and a sector-shaped 3.0 diopter (D) near segment. The special principle of this MIOL is that the light is not refracted symmetrically around the optical axis. The ZMB00 (Advanced Medical Optics, Santa Ana, California,USA) (figure 1b) is a diffractive MIOL with 4.0 diopter (D) near segment. It has a full diffractive optic in posterior surface with a special margin design that is round in the front portion and square in the back. Optical analog diagrams stimulate the ray tracing of these two MIOLs and show that the MF30 model has a long and narrow blur spot s (figure 2a), while the ZMB00 model has a relatively short and wide blur spot(figure 2b), which indicates the MF30 model may has an extended focal depth than the ZMB00 model.
All cataract surgeries were done by an experienced surgeon. The surgical procedure was the same for both lenses. All surgeries was performed under topical anaesthesia, using 2.2 mm transparent corneal incision. Phacoemulsification was performed using Infiniti vision system unit (Alcon Laboratories, Inc.). Polishing of the posterior capsule was also performed. The IOL was implanted in the capsular bag.
UDVA and BCDVA of each selected eye was measured at 5m using standard logarithmic visual acuity chart with illumination of 80 cd/m2. UNVA and DCNVA were measured at the reading distance of 33cm using near logarithmic visual acuity chart. UIVA and DCIVA were measured at distance of 80 cm using logarithmic visual acuity chart. Both intermediate and near visual acuity were measured under photopic conditions with illumination of 80 cd/m2. Visual acuity results were recorded in logMAR.
Optical Quality Analysis System (OQAS) II is a system based on a double-pass technique, analyzing the visual quality in human eyes. OQAS analyzes all optical information of a surface, taking into account the influence of scattering, aberration and diffraction, and obtains the correct PSF image. It is the only available system to analyze the visual quality objectively at present.[18, 19]. In this study, OQAS II was used to obtain the ocular objective optical quality parameters including modulation transfer function (MTF) cut-off frequency, objective scatter index (OSI), Strehl ratio (SR), and OQAS values (OVs 100%, 20% and 9%) 3 months after IOL implantation. MTF is the ratio of contrast between the retinal image and the original objective. The MTF cut off indicates the The corresponding spatial frequency when MTF value is 0.01. Normal value is larger than 30, the larger the better.. The OV100%, OV20%, and OV9% mean the OQAS value calculated by the system at three contrasts which are used in ophthalmic practice commonly. Therefore, these three OVs are related to the MTF curve closely. SR describes the area under the MTF curve reflects the sum of low, medium and high frequency information. Value range is 0 ~ 1. The closer it is to 1, indicates the smaller the aberration. OSI is an index of intraocular scattered light.[19, 21]. The higher the value of the MTF cut off, SR and OVs, and the lower the OSI, indicate the better the objective optical quality. The instrument was set to measure with the artificial pupil diameter of 4.0mm, which is a standard size used in clinical double-pass studies .
Defocus curves were used to analyze the correlations between logMAR visual acuity and image quality measures for the two MIOLs [23, 24]. It was evaluated at 5m using standard logarithmic visual acuity chart. Defocus was performed from 1.0 D to -4.0 D in 0.5 diopter (D) steps, and started from the best correction at distance. .
The subjective visual quality of post-surgery patients was investigated by using a Chinese version of the National Eye Institute Visual Function Questionnaire (CHI-VFQ-25) , including subjective visual evaluation, independence spectacles ratio, and visual disturbance symptoms. Patients' subjective visual quality was evaluated with 0 ~ 10 points, with 10 points being full marks. Whether it is necessary to wear frame glasses or corneal contact lenses at distance, medium and near after surgery would be recorded to calculate the rate of independence from spectacles. Symptoms of visual interference include glare and halo would also be asked.
Statistical analysis was performed using SPSS software for Windows (version 19.0, SPSS Inc.). χ2 test and Spearman rank correlation was used in categorical data; t test and Pearson correlation were used in measurement data; Mann–Whitney U test and Spearman correlation were used when a normal distribution was not expected. Results are presented as the mean±SD. Differences with p<0.05 were considered to be statistically significant.