Safety and Efficacy of Implantation of Two Multifocal Intraocular Lenses in the Treatment of Senile Cataract

History and current studies Aging-induced degenerative diseases are the leading cause of senile cataract. Phacoemulsification with intraocular lens (IOL) implantation is a commonly employed surgical technique for the treatment of cataract. A traditional IOL is spherical and monofocal. Traditional monofocal IOL implantation allows cataract patients to obtain good postoperative distance vision but loss of accommodation results in poor near vision. Following monofocal IOL implantation, most patients still require the use of glasses. Fortunately, the presence of multifocal IOLs solves this problem. Studies have shown that aspheric IOLs with zero or negative spherical aberration can eliminate or reduce the spherical aberration of the whole eye and can improve contrast sensitivity and night vision compared with a spherical IOL.

As first reported in 1987 by Keatea et al., multifocal IOLs were introduced to provide improved visual acuity, thus eliminating the need to wear glasses and improving the patient's quality of life. Increasing evidence-based medicine evidences have shown that multifocal IOLs are more adept to improving near vision than single-focus IOLs. To date, various types of multifocal IOLs have been developed and according to different design principles, clinically used multifocal IOLs have been divided into refraction type, diffraction type and refraction/diffraction type. Introduced in 2002, the Tecnis Z9001 diffractive multifocal aspherical IOL (Abbott Medical Optics, CA, USA) is clinically proven to give patients improved contrast vision and visual quality when compared with the common IOL, although deficiencies include postoperative glare and reduced contrast sensitivity. Emerging designs for multifocal IOLs aim to provide improvements in postoperative visual quality. The Acri.LISA 366D multifocal aspheric IOL is a relatively novel refractive/diffractive multifocal IOL that is different from traditional IOLs. Its unique optical design improves the patient's full vision and reduces the incidence of light scattering, glare and halo, which is expected to deliver better clinical outcomes. However, its long-term clinical performance and the potential incidence of complications still need further evaluation.

It is worth noting that as age increases, the increase in presbyopia, aberrations and lens scattering reduces the compensation for corneal aberrations, thereby resulting in a decrease in visual acuity and contrast sensitivity. Given this, ideal IOLs should have good biocompatibility and good resolution with no spherical aberration.

Data collection, management, analysis, and open access Data collection Clinical data will be collected and managed using an electronic data capture system. All data relevant to the trial will be recorded in electronic case report forms that will be provided by the sponsor personnel. The case report will be completed after the interview.

Data management After completion of follow-up and data confirmation, only the project manager will lock the database. The locked data will be unable to be altered and will be preserved for future reference by the Affiliated Hospital of Qinghai University in China.

Data analysis All data will be statistically analyzed by professional statisticians.

Open data Published data will be released at http://www.medresman.org.

Statistical analysis All data will be statistically analyzed by statisticians using SPSS v19.0 software. Normally distributed measurement data will be expressed as mean ± standard deviation, while non-normally distributed data will be expressed as quartiles and medians. Categorical variables will be expressed as counts and percentages. Two-sample t-test or Mann-Whitney U-test will be used for intergroup comparison of visual acuity and diopter. The chi-squared test or Fisher's exact test will be used for intergroup comparison of incidence of histocompatibility reactions between the implant and host tissues and the percentage of complications. A value of P < O.05 will be considered statistically significant.