**1. Introduction**

Premium multifocal intraocular lenses (IOLs) became more and more popular in modern cataract surgery after new millennium year [1, 2]. In tandem, the advances in ophthalmologic surgical approach such as femtosecond laser assisted cataract surgery (FLACS) [3], the improvement in biometry and IOL power calculation [4], the development of the intraocular lens techniques [5] led to successfully correct presbyopia, astigmatism and other refractive error through cataract or lens exchange surgery. These premium IOLs surgeries especially the presbyopia-correcting procedures can offer patients more visual and life quality without spectacle. But there are many key issues in the presbyopia-correcting procedure including proper patient selection, preoperative counseling, surgical planning and techniques which should be focused during perioperative stage.

### **2. Premium IOLs**

Comparing with conventional IOL, premium IOLs can offer more and better visual function. But there are no standard criteria about premium IOL due to the continual evolution of the IOLs' technology. The aspherical IOL, blue light filter IOL, toric IOL had been defined as premium IOLs in the past decades. This chapter will highlight the presbyopia correcting IOLs as the premium IOLs in the following paragraph. The presbyopia correcting IOLs can be classified into three groups: accommodative IOLs, refractive or diffractive multifocal IOLs and extended depth of focus (EDOF) IOLs according to its optical design and physical properties.

**Figure 1.**

*Accommodating intraocular lenses. (A): 1CU, HumamOptics; (B): Dual-optic synchrony IOL, AMO; (C): FluidVision accommodating IOL, PowerVision.*

### **2.1 Accommodating intraocular lenses**

Accommodative IOL are designated to produce a dynamic power with the change of IOL optic position, shape or refractive index by pseudoaccommodating and/or accommodating mechanisms with contraction of the ciliary muscle [6]. There are several accommodative IOLs design strategies: single-optic, dualoptic and deformable optic IOLs (**Figure 1**). Single-optic accommodative IOL (Crystalens, Bausch & Lomb; 1CU, Human Optics) possess the hinge design between the optic and the haptic to facilitate the anterior axial movement of effective lenses position with pressure of the capsule bag and vitreous during the accommodative stimulus. Previous studies demonstrated that 1 mm of optic movement is equivalent of 2 D of power change [7]. But the clinical studies had not demonstrated the consistent accommodation amplitude of the pseudoaccomodating IOL eyes especially in the long term follow up. Dual-optic Synchrony IOL (Abbott Medical Optics, AMO) utilize a positively powered biconvex front lens (+32D) connected to a negatively powered concave-convex lens. During the accommodative effort, the distance between the two optic elements increased that lead to increasing effective power of the overall lens [8]. The deformable optic design IOLs like FluidVision accommodating IOL (PowerVision) still underwent investigation in lab or clinical trial research. Though there are no contrast sensitivity loss or dysphotopsias issue, all these accommodative IOLs still have their limitations about the inability to consistently generate large amounts of accommodative power.

#### **2.2 Multifocal IOL**

There are two type multifocal IOLs according to optical design principle: refractive and diffractive IOLs (**Figure 2**).

Refractive multifocal IOLs based on the different dioptic power zone with the light ray's refraction principles. These zones provide various focal points, allowing for an improvement in distance, intermediate, and near vision. Though refractive multifocal IOL can afford good quality vision, the limitation of these symmetric multifocal lens (Array, Abbott Medical Optics; ReZoom, Abbott Medical Optics) are pupillary size and lens centration dependence. The asymmetric segmental refractive IOLs (Lentis Mplus, Oculentis) has been intended to reduce this problem and available for patients with low acceptance for dysphotopsia [9].

Diffractive multifocal IOLs rely on concentric diffractive surfaces on the optic portion of the lens, this causes constructive and destructive interference of optic wavefronts to provide two or three focality which led to bifocal or trifocal IOLs. A different approach about diffractive ring pattern, diffractive ring width and

**135**

**Figure 3.**

*EDOF IOLs: Symfony IOL.*

sensitivity [2].

**Figure 2.**

**2.3 Extended depth of focus IOLs**

*Successful Premium Multifocal IOL Surgery: Key Issues and Pearls*

step height by different manufactures introduces different add power and light distribution. Larger ring width provides less addition power and small ring width provides more addition power, while higher steps sends more light to distant focal point and lower step sends more lights to near focal point. The IOL (Restor, Alcon) with refractive-diffractive mix pattern and apodized steps which has concentric rings of decreasing height intends to influence light distribution between distant and near focal points on pupil size [10]. Multifocal IOLs are associated

*Multifocal IOL. (A): Array IOL, AMO; (B): Lentis Mplus IOL, Oculentis; (C): ReSTOR IOL, Alcon.*

Extended depth of focus (EDOF) IOLs are a newer category of IOLs that aims to give an elongated focus of vision, that enhances depth of focus rather than introduces several foci. It can reduce photic phenomena, glare, and halos, which have been reported in traditional multifocal IOLs. Tecnis Symfony IOL (Abbott Medical Optics) was the first EDOF IOL approved in 2016 by the U.S. Food and Drug Administration (FDA) (**Figure 3**). Now, there are several EDOF IOLs had been released in the market which had combined with different techniques such as diffractive optical design, spherical aberration, chromatic aberration, pinhole effect [11]. American Academy of Ophthalmology has provided consensus

with higher rates of spectacle independence than monofocal IOLs, but are more frequently associated with dysphotopsias and decreased contrast

*DOI: http://dx.doi.org/10.5772/intechopen.96182*

*Current Cataract Surgical Techniques*

**2.1 Accommodating intraocular lenses**

*FluidVision accommodating IOL, PowerVision.*

**Figure 1.**

Accommodative IOL are designated to produce a dynamic power with the change of IOL optic position, shape or refractive index by pseudoaccommodating and/or accommodating mechanisms with contraction of the ciliary muscle [6]. There are several accommodative IOLs design strategies: single-optic, dualoptic and deformable optic IOLs (**Figure 1**). Single-optic accommodative IOL (Crystalens, Bausch & Lomb; 1CU, Human Optics) possess the hinge design between the optic and the haptic to facilitate the anterior axial movement of effective lenses position with pressure of the capsule bag and vitreous during the accommodative stimulus. Previous studies demonstrated that 1 mm of optic movement is equivalent of 2 D of power change [7]. But the clinical studies had not demonstrated the consistent accommodation amplitude of the pseudoaccomodating IOL eyes especially in the long term follow up. Dual-optic Synchrony IOL (Abbott Medical Optics, AMO) utilize a positively powered biconvex front lens (+32D) connected to a negatively powered concave-convex lens. During the accommodative effort, the distance between the two optic elements increased that lead to increasing effective power of the overall lens [8]. The deformable optic design IOLs like FluidVision accommodating IOL (PowerVision) still underwent investigation in lab or clinical trial research. Though there are no contrast sensitivity loss or dysphotopsias issue, all these accommodative IOLs still have their limitations about the inability to consistently generate large amounts of accommodative power.

*Accommodating intraocular lenses. (A): 1CU, HumamOptics; (B): Dual-optic synchrony IOL, AMO; (C):* 

There are two type multifocal IOLs according to optical design principle: refrac-

Refractive multifocal IOLs based on the different dioptic power zone with the light ray's refraction principles. These zones provide various focal points, allowing for an improvement in distance, intermediate, and near vision. Though refractive multifocal IOL can afford good quality vision, the limitation of these symmetric multifocal lens (Array, Abbott Medical Optics; ReZoom, Abbott Medical Optics) are pupillary size and lens centration dependence. The asymmetric segmental refractive IOLs (Lentis Mplus, Oculentis) has been intended to reduce this problem

Diffractive multifocal IOLs rely on concentric diffractive surfaces on the optic portion of the lens, this causes constructive and destructive interference of optic wavefronts to provide two or three focality which led to bifocal or trifocal IOLs. A different approach about diffractive ring pattern, diffractive ring width and

and available for patients with low acceptance for dysphotopsia [9].

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**2.2 Multifocal IOL**

tive and diffractive IOLs (**Figure 2**).

**Figure 2.** *Multifocal IOL. (A): Array IOL, AMO; (B): Lentis Mplus IOL, Oculentis; (C): ReSTOR IOL, Alcon.*

step height by different manufactures introduces different add power and light distribution. Larger ring width provides less addition power and small ring width provides more addition power, while higher steps sends more light to distant focal point and lower step sends more lights to near focal point. The IOL (Restor, Alcon) with refractive-diffractive mix pattern and apodized steps which has concentric rings of decreasing height intends to influence light distribution between distant and near focal points on pupil size [10]. Multifocal IOLs are associated with higher rates of spectacle independence than monofocal IOLs, but are more frequently associated with dysphotopsias and decreased contrast sensitivity [2].
