Photopic and Mesopic Multifocal IOL Performance

Overview

Modern cataract surgery has become a refractive procedure. Both, multifocal lens implantation and pseudophakic monovision with monofocal IOLs are effective means to address presbyopia correction after cataract surgery. Historically, diffractive multifocal IOLs have provided improved visual acuity at near and intermediate distances and a greater likelihood of spectacle independence than monofocal IOLs. The light transmittance ratio of the crystalline lens is high and as a monofocal ocular medium that has the ability to modify its shape and geometric properties according to the focal point. Therefore, it is capable of delivering the exact same light energy to the retina, regardless of the distance of the object. Trifocal IOL designs split the light in three focal points. By varying the height of the diffractive step, the amount of light distributed to near, intermediate and distant foci is adjusted according to pupil aperture. The distribution of light to three different foci includes several potential disadvantages, such as loss of visual acuity in mesopic conditions and a loss of contrast sensitivity. Thus, the visual performance of multifocal IOLs depends on several factors, the addition (add) power is a major determinant of the actual range of clear vision, another factor is the light transmittance characteristics of the lens (e.g., the incorporation of a blue light filter). As different trifocal IOLs become available, it is important to have information on their characteristics regarding visual acuity in order to be able to recommend an IOL that meets the individualized needs of each patient. In order to provide the patient with a high visual acuity in all promised distances, these IOLs need to be aimed at and achieve emmetropia. Furthermore, multifocal IOLs need good capsular bag centration, they need to remain as unaffected as possible by capsular bag constriction and remain stable in their axial lens position in order to provide a stable refraction after surgery. The investigators compare the anterior chamber depth stability as marker for positional stability and haptic buckling between two different diffractive IOL designs, one with C-loop haptics and one with plate haptics. Furthermore, the refractive outcome of these IOLs with different designs is examined in photopic and mesopic conditions, as well as visual acuity results for both IOLs.