*3.2.3.1 Conventional non-image-guided surgical technique*


#### **Figure 5.**

*Anterior capsule opacification following multifocal intraocular lens implantation: the opacification of the remaining anterior capsule contributes in the reduction of potential optical phenomena.*

**111**

tion of a non-mIOL.

*Pseudophakic Presbyopic Corrections*

and dysphotopsia.

center [131].

*DOI: http://dx.doi.org/10.5772/intechopen.96528*

bimanual irrigation/aspiration.

• The nucleus is aspirated with or without ultrasound phacoemulsification energy according to the hardness of the crystalline lens, and residual cortex removal and posterior capsule polishing are performed using commonly

• The mIOL is always inserted into the capsular bag through the main incision. The IOL should be injected directly in the capsular bag in order a possibly traumatic surgical manoeuvre to be avoided. For this reason, adequate dilation

and an adequate capsulorrhexis of about 4.50 to 5.00 mm is necessary.

• For the optimal mIOL centration and the minimization of photic phenomena, especially for eyes with a large angle kappa, the mIOL is suggested to be decentered towards the visual axis, namely to be gently moved so as the microscope light reflex to fall within the central ring of the multifocal pattern [102]. This is an easy intraoperative manipulation that can effectively result in the desired centration on the visual axis. The centration of diffractive mIOLs on the visual axis is critical to their optimal performance. However, refractive mIOLs are also suggested to be centered on the visual axis because severe cases of decentration can increase the lens' effective power and induce astigmatism

• Additionally, since, normally, the visual axis is nasal to the optical center (the geometric center of the cornea, crystalline lens, and bag after nuclear and cortical removal), positioning the haptics of especially diffractive, but also refractive, IOLs at the 12 and 6 o'clock position may facilitate the desirable nasal displacement of the IOL optic. On the other hand, positioning the IOL haptics horizontally leads to the return of IOL to the geometrically horizontal

• To stabilize the mIOL centered on the visual axis during the first postoperative days, in contrast to the literature, the authors suggest that a minimal amount of cohesive ophthalmic viscosurgical device (OVD) could be left in the capsular bag without increasing the risk for elevation of the postoperative IOP [132].

• Since mIOL patients usually benefit from having a small pupil, eyes with a small pupil after the instillation of mydriatics before the cataract surgery should be managed with special caution in order the pupil to remain functionally and morphologically intact, as in its preoperative status. Therefore, it is strongly recommended to cataract refractive surgeons to avoid surgical maneuvers such as synechiolysis, pupil stretching, iris cutting [133] and the use of mechanical devices such as iris hooks and pupil expansion rings (e.g. Malyugin ring etc.) because of the high risk of intraoperative disruption of the pupillary sphincter and postoperative pupil enlargement [134]. Thus, intracameral administration of mydriatic agent, combined intracameral use of mydriatic agent and local anesthetic or the injection of OVD into the anterior chamber (viscomydriasis) should be preferred for the pupil dilation [134]. For an experienced refractive cataract surgeon, a possible threshold of pupil size for a successful phacoemulsification ranges between 4.5 and 5.0 mm [134, 135]. In smaller pupils which cannot be dilated pharmacologically or with OVD use, the surgeon should weigh the benefits and the risks of the pupil dilation with surgical maneuvres and mechanical devices and should consider the implanta-

### *Pseudophakic Presbyopic Corrections DOI: http://dx.doi.org/10.5772/intechopen.96528*

*Current Cataract Surgical Techniques*

following practices are suggested:

of iodine povidone.

surgical technique, will be discussed in the text below.

*3.2.3.1 Conventional non-image-guided surgical technique*

(commonly 2.2-mm) cataract surgery.

of parameters for the conventional non-image-guided, but also for an image-guided

• Topical anesthesia and mydriatic drops are instilled before the operation.

• Periorbital skin, eyelids, and the conjunctival sac are prepared with a solution

• The surgical technique is performed using a standard technique of sutureless

• Intracameral anesthesia and potentially intracameral mydriatics are injected.

• Capsulorrhexis should have a diameter between 4.50 to 5.00 mm. Although a diameter larger than 5.00 mm also is recommended to facilitate nuclear and cortical removal, this increases the risk of postoperative optical phenomena caused by the involvement of more concentric rings when the light rays pass through the IOL's optic. Opacification of the remaining anterior capsule can reduce optical phenomena even in eyes with a pupil diameter larger than 5.00 mm (**Figure 5**).

• Another parameter that should be taken into account, especially in eyes with a large angle kappa, is the centration of capsulorrhexis. The capsulorrhexis is suggested to be centered around the microscope light reflection on the anterior capsule (patients' visual axis) rather than around the pupillary axis [131]. However, in the case of a mature cataract where the patient fails to fixate on the microscope light, but also on the lights of the biometry device during the preoperative examination, the implantation of a mIOL should be avoided, since the risk for a decentered implantation is very high. The centration on the pupil center or on the geometric center of the cornea is not considered as a safe alternative solution.

*Anterior capsule opacification following multifocal intraocular lens implantation: the opacification of the* 

*remaining anterior capsule contributes in the reduction of potential optical phenomena.*

For the best possible refractive outcome during mIOL implantation surgery, the

**110**

**Figure 5.**


• Videorecording of every surgery is suggested for refractive cataract surgeons and, generally, for ophthalmic surgeons in order to review their surgeries, criticize their technique, find mistakes that should have been avoided, explain unexpected outcomes and improve their surgical skills [136].

#### *3.2.3.2 Image-guided surgery*

Although the experience and the surgical skills of the refractive cataract surgeon play the most significant role in the final refractive outcome, image-guided lens extraction surgery, which has been recently introduced in phacoemulsification, can increase the surgical accuracy, decrease the risk of complications such as postoperative astigmatism, IOL decentration and photopic phenomena and improve the patient's quality of vision [41].

Image-guided systems such as Verion Digital Marker (Alcon Laboratories, Inc., Fort Worth, TX, USA) [137] and Zeiss Callisto Eye (Carl Zeiss AG, Dublin, CA) [138] are commonly used for the implantation of multifocal toric IOLs. However, since the high accuracy is also necessary during the implantation of multifocal non-toric IOLs for main and sideport incisions, the centration and the diameter of capsulorrhexis, as well as for the centration of the mIOL implantation, the authors suggest that digital image-guidance also during the implantation of multifocal non-toric IOLs could optimize the surgical accuracy and predictability, minimize the risk of complications, and maximize the refractive outcome. **Figure 6** presents the basic steps of lens extraction surgery (a. sideport incisions, b. main incision, c. capsulorrhexis, d. IOL centration, e. finalization) using the Verion image-guided system during the implantation of a multifocal non-toric IOL.

#### *3.2.4 Complications*

Implantation of mIOLs provide patients with a good visual acuity at more than one focal point depending on mIOL design. Patient satisfaction levels after mIOL implantation are high. However, the same characteristics that offer refractive correction at all distances can result in adverse effects at the same time [98].

For instance, light distribution mechanisms split the light to two or three focal points. As a result, less amount of light from each focal point reaches the retina worsening the contrast sensitivity, especially in mesopic light conditions [98, 139]. Therefore, two or three distinct images are produced, one sharp on focus and one blurred out of focus. The light of the latter image reduces the detectability of the on-focus image, resulting in the lower contrast sensitivity, however within the normal range of age-matched phakic individuals, and in the creation of dysphotopic phenomena such as halos [139–141]. These phenomena commonly diminish over time through the process of neuroadaptation.

The most common reason for patient dissatisfaction is *blurred vision* (approximately in 95% of the dissatisfied patients) caused by residual ametropia/astigmatism [98] or posterior capsular opacification (PCO), [97] although these subjective complains usually do not correspond to the objective VA [98, 142]. An additional cause of dissatisfaction is *dysphotopsia*, which is caused by the IOL itself or/and by a potential IOL decentration or IOL tilt or/and by a large pupil diameter. Refractive mIOLs appear to be related with higher levels of photic phenomena than diffractive mIOLs [143, 144]. Moreover, the existence of *dry eye disease* postoperatively found to be one of the patient complaints resulting in symptoms of discomfort, visual disturbance, and tear-film instability. Finally, *IOL explantation* has been reported in

**113**

perception [148].

**Figure 6.**

*3.3.1 Accommodative IOLs*

distances [149].

*Pseudophakic Presbyopic Corrections*

*DOI: http://dx.doi.org/10.5772/intechopen.96528*

a frequency between 0.85% and 7 % [98, 145, 146] due to IOL dislocation, refractive error, PCO, failure to neuroadaptation [147] and, rarely, loss of normal color

*The basic steps of multifocal IOL implantation using the Verion image-guided system ((a) sideport incisions,* 

Apart from monovision technique with bilateral implantation of monofocal IOLs and bilateral implantation of multifocal IOLs, accommodative and EDOF IOL, as well as a combination of different IOL types and designs are some new alternative solutions of pseudophakic presbyopic correction. However, these options are beyond the scope of this chapter and they will not be analytically described.

Accommodative IOLs (aIOLs) are designed to simulate the mechanism of accommodation of the crystalline lens, which is capable of changing dynamically its dioptric power with accommodating effort, namely by modifying its shape after contraction of the ciliary muscle and providing functional vision at different

**3.3 New IOL technologies for presbyopic correction**

*(b) main incision, (c) capsulorrhexis, (d) IOL centration, (e) finalization).*

*Pseudophakic Presbyopic Corrections DOI: http://dx.doi.org/10.5772/intechopen.96528*

*Current Cataract Surgical Techniques*

*3.2.3.2 Image-guided surgery*

patient's quality of vision [41].

non-toric IOL.

*3.2.4 Complications*

• Videorecording of every surgery is suggested for refractive cataract surgeons and, generally, for ophthalmic surgeons in order to review their surgeries, criticize their technique, find mistakes that should have been avoided, explain

Although the experience and the surgical skills of the refractive cataract surgeon

play the most significant role in the final refractive outcome, image-guided lens extraction surgery, which has been recently introduced in phacoemulsification, can increase the surgical accuracy, decrease the risk of complications such as postoperative astigmatism, IOL decentration and photopic phenomena and improve the

Image-guided systems such as Verion Digital Marker (Alcon Laboratories, Inc., Fort Worth, TX, USA) [137] and Zeiss Callisto Eye (Carl Zeiss AG, Dublin, CA) [138] are commonly used for the implantation of multifocal toric IOLs. However, since the high accuracy is also necessary during the implantation of multifocal non-toric IOLs for main and sideport incisions, the centration and the diameter of capsulorrhexis, as well as for the centration of the mIOL implantation, the authors suggest that digital image-guidance also during the implantation of multifocal non-toric IOLs could optimize the surgical accuracy and predictability, minimize the risk of complications, and maximize the refractive outcome. **Figure 6** presents the basic steps of lens extraction surgery (a. sideport incisions, b. main incision, c. capsulorrhexis, d. IOL centration, e. finalization) using the Verion image-guided system during the implantation of a multifocal

Implantation of mIOLs provide patients with a good visual acuity at more than one focal point depending on mIOL design. Patient satisfaction levels after mIOL implantation are high. However, the same characteristics that offer refractive cor-

For instance, light distribution mechanisms split the light to two or three focal points. As a result, less amount of light from each focal point reaches the retina worsening the contrast sensitivity, especially in mesopic light conditions [98, 139]. Therefore, two or three distinct images are produced, one sharp on focus and one blurred out of focus. The light of the latter image reduces the detectability of the on-focus image, resulting in the lower contrast sensitivity, however within the normal range of age-matched phakic individuals, and in the creation of dysphotopic phenomena such as halos [139–141]. These phenomena commonly diminish over

The most common reason for patient dissatisfaction is *blurred vision* (approximately in 95% of the dissatisfied patients) caused by residual ametropia/astigmatism [98] or posterior capsular opacification (PCO), [97] although these subjective complains usually do not correspond to the objective VA [98, 142]. An additional cause of dissatisfaction is *dysphotopsia*, which is caused by the IOL itself or/and by a potential IOL decentration or IOL tilt or/and by a large pupil diameter. Refractive mIOLs appear to be related with higher levels of photic phenomena than diffractive mIOLs [143, 144]. Moreover, the existence of *dry eye disease* postoperatively found to be one of the patient complaints resulting in symptoms of discomfort, visual disturbance, and tear-film instability. Finally, *IOL explantation* has been reported in

rection at all distances can result in adverse effects at the same time [98].

time through the process of neuroadaptation.

unexpected outcomes and improve their surgical skills [136].

**112**

#### **Figure 6.**

*The basic steps of multifocal IOL implantation using the Verion image-guided system ((a) sideport incisions, (b) main incision, (c) capsulorrhexis, (d) IOL centration, (e) finalization).*

a frequency between 0.85% and 7 % [98, 145, 146] due to IOL dislocation, refractive error, PCO, failure to neuroadaptation [147] and, rarely, loss of normal color perception [148].

#### **3.3 New IOL technologies for presbyopic correction**

Apart from monovision technique with bilateral implantation of monofocal IOLs and bilateral implantation of multifocal IOLs, accommodative and EDOF IOL, as well as a combination of different IOL types and designs are some new alternative solutions of pseudophakic presbyopic correction. However, these options are beyond the scope of this chapter and they will not be analytically described.

#### *3.3.1 Accommodative IOLs*

Accommodative IOLs (aIOLs) are designed to simulate the mechanism of accommodation of the crystalline lens, which is capable of changing dynamically its dioptric power with accommodating effort, namely by modifying its shape after contraction of the ciliary muscle and providing functional vision at different distances [149].

AIOLs are still a developing field in the technology of premium IOLs where a variety of designs are still examined [150]. The mechanisms of action of the different types of aIOLs that are currently available are based on the three following principles: (a) change in axial position (i. single-optic aIOLs, and ii. dual-optic aIOLs), (b) change in shape or curvature, and (c) change in refractive index or power. Apart from the aforementioned aIOL designs, the following new design strategies of aIOLs, still in preclinical stage, have been proposed: (i) lens-filling aIOL techniques, and (ii) electroadaptive aIOLs [149, 151]. Another issue that remains to be solved is the best location for implantation of aIOLs. Implantation inside the capsular bag seem to be a less successful approach in comparison to the sulcus, since in sulcus, the dynamics from the ciliary body induce further movements of the IOL [149, 150].

Despite the significant development and evolution of aIOLs and the great variety of IOL designs, the majority of them are still in a development process and have shown some contradictory clinical data about their efficacy. The optimal aIOL with a broad range of accommodation still remains elusive, and different challenges exist for each lens design. However, new innovative and promising designs and technologies now exist having the restoration of accommodation as their common goal [149, 151].

## *3.3.2 Extended depth-of-focus (EDOF) IOLs*

Extended depth-of-focus (EDOF) IOL is a new technology in the treatment of presbyopia-correcting IOLs. The basic optical principle of EDOF IOLs is to create a single elongated focal point, in contrast to monofocal IOLs, in which light is focused on one single point, and mIOLs, in which light is focused on two or three discrete points (**Figure 7**). In this way, EDOF IOLs eliminate the overlapping of far and near images caused my mIOLs, thus eliminating the halo effect. Specifically, EDOF IOLs provide a continuous focus range that extends from the far focus area until the intermediate distance, without the clearly asymmetric IOL power distribution that is provided by the mIOLs. In this way, EDOF IOLs avoid the presence of secondary out-of-focus images that originates the halos [152–154].

The idea of EDOF was first reported in 1984 by Nakazawa and Ohtsuki who measured an apparent 2.00 D accommodation in 39 pseudophakic eyes implanted with posterior chamber spherical IOLs and found a significant correlation between apparent accommodation and depth of field. This correlation was inversely proportional to the pupillary diameter [155]. After using multiple cornea- or IOL-based strategies, the first EDOF IOL (Symfony, Johnson and Johnson Vision, Jacksonville, FL) was introduced into the market receiving the European Economic Area

**115**

*Pseudophakic Presbyopic Corrections*

*DOI: http://dx.doi.org/10.5772/intechopen.96528*

Drug Administration (FDA) in July 2016 [156].

certification mark in June 2014, and being approved by the United States Food and

Since then, a variety of EDOF-labeled IOLs have been released in the market and are based on the following 3 optical models: i) spherical aberration, ii) chromatic aberration, iii) pinhole effect, all of which allow obtaining greater depth of focus [157]. Apart from the pure EDOF IOLs, there are some IOLs that combine multifocality with low addition power and the EDOF technology, the so-called "hybrid IOLs" [157]. In general, EDOF IOLs provide better optical quality in comparison with monofocal and multifocal IOLs [158–160] Additionally, EDOF IOLs provide high uncorrected intermediate vision, but inadequate near vision [161, 162], thus allowing a relative spectacle independence. A potential disadvantage of EDOF-IOLs is a decreased quality of retinal image if the aberrations are excessively increased. Finally, contrast sensitivity, glare and halos vary depending on the EDOF-IOL technology, however, they seem to be better when compared to mIOLs. [163] Since the literature results about the optical performance of EDOF-IOLs are promising but contraindicating, [164–166] new large-scale studies need to be performed.

In any case, patients should be counseled about potential photic phenomena and the need for low power reading spectacles postoperatively. Moreover, the IOL type

When a large anisometropia is targeted for an optimal near visual acuity, pseudophakic monovision with implantation of monofocal IOLs results in a relative decrease in near stereopsis [49, 153]. Therefore, a new type of monovision with implantation of different IOL types and IOL technologies in each eye has been introduced. For instance, the implantation of a monofocal IOL in the dominant eye and a premium lens such as mIOL (bifocal or trifocal/refractive, diffractive or hybrid diffractive-refractive) [167, 168] or EDOF IOL in the recessive one, the so-called "hybrid monovision" or "mix and match" or "blended vision", has been applied and compared with the conventional myopic monovision techniques and with the binocular implantation of premium IOLs showing promising visual outcomes [153, 154, 169]. Additionally, the use of a refractive IOL in the dominant eye and a diffractive IOL in the recessive eye [170] or vice versa [171] has been reported showing very good visual outcomes including impressive spectacle independence at all distances and a contrast sensitivity being comparable with phakic patients. In general, it seems that hybrid monovision offers spectacle-free postoperative visual

Apart from the full preoperative examination and the high-precision surgery that are necessary for optimal refractive outcomes in patients undergoing a pseudophakic presbyopic correction, especially with mIOLs, the postoperative follow-up plays an equally significant role in the best possible results. The most common follow-up timepoints are 1 day, 1 week, 1 month, 3 months, 6 months, 1 year, 2 years and so forth. Examination at the first postoperative day is commonly applied by many surgeons, However, the current literature supports that first-day examination after an uneventful phacoemulsification surgery is not necessary when patients have not posterior synechiae or chronic/recurrent uveitis and they are operated by experienced cataract surgeons. Thus, healthcare costs can be decreased without an

decision should be made depending on their profile and preferences.

*3.3.3 Monovision techniques with combination of IOLs*

capacity at all distances with minimal optical phenomena.

**4. Postoperative examination – follow-up**

increased risk to the patients [172].

**Figure 7.** *EDOF IOL design.*

#### *Pseudophakic Presbyopic Corrections DOI: http://dx.doi.org/10.5772/intechopen.96528*

*Current Cataract Surgical Techniques*

ments of the IOL [149, 150].

*3.3.2 Extended depth-of-focus (EDOF) IOLs*

out-of-focus images that originates the halos [152–154].

AIOLs are still a developing field in the technology of premium IOLs where a variety of designs are still examined [150]. The mechanisms of action of the different types of aIOLs that are currently available are based on the three following principles: (a) change in axial position (i. single-optic aIOLs, and ii. dual-optic aIOLs), (b) change in shape or curvature, and (c) change in refractive index or power. Apart from the aforementioned aIOL designs, the following new design strategies of aIOLs, still in preclinical stage, have been proposed: (i) lens-filling aIOL techniques, and (ii) electroadaptive aIOLs [149, 151]. Another issue that remains to be solved is the best location for implantation of aIOLs. Implantation inside the capsular bag seem to be a less successful approach in comparison to the sulcus, since in sulcus, the dynamics from the ciliary body induce further move-

Despite the significant development and evolution of aIOLs and the great variety

Extended depth-of-focus (EDOF) IOL is a new technology in the treatment of presbyopia-correcting IOLs. The basic optical principle of EDOF IOLs is to create a single elongated focal point, in contrast to monofocal IOLs, in which light is focused on one single point, and mIOLs, in which light is focused on two or three discrete points (**Figure 7**). In this way, EDOF IOLs eliminate the overlapping of far and near images caused my mIOLs, thus eliminating the halo effect. Specifically, EDOF IOLs provide a continuous focus range that extends from the far focus area until the intermediate distance, without the clearly asymmetric IOL power distribution that is provided by the mIOLs. In this way, EDOF IOLs avoid the presence of secondary

The idea of EDOF was first reported in 1984 by Nakazawa and Ohtsuki who measured an apparent 2.00 D accommodation in 39 pseudophakic eyes implanted with posterior chamber spherical IOLs and found a significant correlation between apparent accommodation and depth of field. This correlation was inversely proportional to the pupillary diameter [155]. After using multiple cornea- or IOL-based strategies, the first EDOF IOL (Symfony, Johnson and Johnson Vision, Jacksonville,

FL) was introduced into the market receiving the European Economic Area

of IOL designs, the majority of them are still in a development process and have shown some contradictory clinical data about their efficacy. The optimal aIOL with a broad range of accommodation still remains elusive, and different challenges exist for each lens design. However, new innovative and promising designs and technologies now exist having the restoration of accommodation as their common goal [149, 151].

**114**

**Figure 7.** *EDOF IOL design.* certification mark in June 2014, and being approved by the United States Food and Drug Administration (FDA) in July 2016 [156].

Since then, a variety of EDOF-labeled IOLs have been released in the market and are based on the following 3 optical models: i) spherical aberration, ii) chromatic aberration, iii) pinhole effect, all of which allow obtaining greater depth of focus [157]. Apart from the pure EDOF IOLs, there are some IOLs that combine multifocality with low addition power and the EDOF technology, the so-called "hybrid IOLs" [157]. In general, EDOF IOLs provide better optical quality in comparison with monofocal and multifocal IOLs [158–160] Additionally, EDOF IOLs provide high uncorrected intermediate vision, but inadequate near vision [161, 162], thus allowing a relative spectacle independence. A potential disadvantage of EDOF-IOLs is a decreased quality of retinal image if the aberrations are excessively increased. Finally, contrast sensitivity, glare and halos vary depending on the EDOF-IOL technology, however, they seem to be better when compared to mIOLs. [163] Since the literature results about the optical performance of EDOF-IOLs are promising but contraindicating, [164–166] new large-scale studies need to be performed.

In any case, patients should be counseled about potential photic phenomena and the need for low power reading spectacles postoperatively. Moreover, the IOL type decision should be made depending on their profile and preferences.
