**3.1 Monovision techniques with bilateral monofocal IOL implantation**

Pseudophakic, or IOL, monovision, which was first described by Boerner and Thrasher in 1984, [42] still remains the most common surgical management of presbyopia for cataract patients with good spectacle independence and high patient satisfaction [43, 44]. The 2016 clinical survey of the European Society of Cataract and Refractive Surgery (ESCRS) reported that 43% of cataract procedures are targeted for monovision or mini-monovision [45].

In traditional pseudophakic monovision, monofocal IOLs are implanted in both eyes. However, the recessive eye is intentionally defocused for myopia [8, 10, 12]. Myopic defocus of the recessive eye ranges from over 2 diopters (D) to less than 1 D (mini or micro monovision) [8, 10, 46]. In bilateral myopic monovision, the dominant eye defocus is targeted to -0.50 D, while the recessive one to -1.25 D [47]. However, recently, the crossed monovision has been suggested for high myopic cataract patients, which is to correct the dominant eye for near vision and the nondominant eye for distance vision [8].

### *3.1.1 Patient selection*

A careful patient selection with a specific determination of the inclusion and exclusion criteria is of paramount importance for an optimal refractive outcome and the highest possible patient satisfaction in case of pseudophakic monovision with bilateral monofocal IOL implantation.

*Inclusion criteria*: The most frequent inclusion criterion was the desire for spectacle independence [48]. One of the most important prerequisites for monovision success is the weak ocular dominance [49, 50].

*Exclusion criteria*: Several exclusion criteria have been reported in the literature. Some of them are the following:


In conclusion, regardless of the exclusion criteria, it is suggested that the procedure and possible outcomes of pseudophakic monovision, when selected,

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*Pseudophakic Presbyopic Corrections*

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

*3.1.2 Side effects of monovision technique*

outcome and patient satisfaction to be achieved.

important drawbacks of this method should be described.

caused mainly by asthenopia and spectacle dependence [52].

although it remains within the normal range [52].

ments in multifocal IOL concept have been made [58].

*3.2.1 Optical design and properties of mIOLs*

**3.2 Multifocal IOLs**

mIOLs is required.

and diffraction.

*3.2.1.1 Fully refractive IOLs*

should be thoroughly explained to patients in order the best possible visual

Although monovision is the most common surgical management of presbyopia for cataract patients with millions of people having monovision corrections, some

First, although monovision is related with significant satisfaction, the highest percentages of satisfied patients have been found in age older than 70 years, while patients younger than 60 years have the highest percentages of dissatisfaction

Secondly, it has been reported that anisometropia and blur differences cause a motion illusion that leads to a significant misperception of the distance and threedimensional direction of moving objects, since the blurred and sharp images are processed at different speeds. This phenomenon has a clinical impact on driving behavior, since these millisecond differences in processing speed could lead, for instance, to the misperception of the distance of cyclists by the width of a narrow street lane [54].

Finally, depth perception and distance stereopsis, especially for large disparities, may be compromised increasing the difficulty in navigation through the environment, obstacle avoidance, and stair walking. Reduction of distance stereopsis leads to a decrease in stability during locomotion, as well, increasing the risk factor for falls and hip fractures in aged population [55]. Near stereopsis is also reduced,

Multifocal IOLs have been designed to provide spectacle independence at near, intermediate, and distance vision tasks. The first concept of a truly multifocal IOL was conceived in 1983 by Hoffer, [56] and the first bifocal IOL implantation was performed by Pearce in 1986 [57]. Since then, many modifications and improve-

Before the analysis of the pre-, intra- and postoperative management of patients implanted with mIOLs, a brief description of the optical design and properties of

Two optical phenomena can be utilized to create multifocal optics: refraction

Fully refractive multifocal IOLs direct light at different focal points using concentric zones of varying dioptric power within the optic. The optical power depends on the local surface curvature, with regions of differing curvatures achieving different powers within the lens. These IOLs are also called *multizonal refractive IOLs* (**Figure 1**) [59]. The central circular zone has a power corresponding to distance vision. The surrounding annular zones alternate between powers corresponding to near and distance to achieve the multifocal effect [60]. As the pupillary size changes, the number of zones that are utilized varies, and, subsequently, the relative proportion of light directed to the distant, near and/or intermediate focal points changes as

well [59]. Thus, image quality can fluctuate depending on pupil size [61, 62].

*Current Cataract Surgical Techniques*

Some of them are the following:

suboptimal effect on visual rehabilitation [49].

less than 1.00 D is highly recommended [49].

leads to reduction in visual performance [48, 50].

chosen to minimize the chance of strabismus [48, 51].

beneficial for people older than 60 years [49, 52].

• *Inability to understand the concept of monovision design* [53]

or driving at night [52].

*Exclusion criteria*: Several exclusion criteria have been reported in the literature.

• *Severe ocular diseases:* Patients with pathology of the optic nerve (eg. glaucoma or other optic neuropathies), macular or retinal pathology, corneal pathology or severe opacification of the rest refractive media other than cataract, previous history of ocular inflammation or surgery, amblyopia and other ocular pathology affecting visual performance are commonly excluded from monovision techniques [48], since the aforementioned diseases are believed to have

• *Corneal astigmatism:* Patients with corneal astigmatism of ≥ 1.00 D, but also of ≥ 1.50 D or even ≥ 2.00 D are commonly excluded from monovision surgical methods with monofocal IOLs [48]. In fact, patients with high degree of corneal astigmatism do not benefit from monovision because their monocular and binocular UVA remains suboptimal. However, the implantation of toric IOLs could be considered. Moreover, patient satisfaction is related to the distance UVA of the dominant eye. Therefore, the correction of corneal astigmatism to

• *Strong ocular dominance:* In patients with strong ocular dominance, the artificial anisometropia of monovision causes insufficient blur suppression and

• *History of strabismus and abnormal ocular position (exophoria or esophoria):* Patients with a history of strabismus should be informed that monovision might lead to a recurrence of previous strabismus or asthenopic symptoms, and patients with a significant exophoria or esophoria should be informed that monovision might cause strabismus. Νevertheless, if patients wish to proceed to monovision, small levels of anisometropia, such as 1.25 to 1.50 D should be

• *Age, lifestyle, work: P*atients younger than 60 years undergoing pseudophakic monovision seem to have lower postoperative satisfaction in comparison to patients older than 60 years. Some reasons for dissatisfaction are the higher rates of spectacle independence, asthenopia and difficulty mainly in near vision. This likely reflects the different age-related lifestyle activities between younger and older patients [52]. As a result, age lower than 60 years could be considered as an exclusion criterion, especially if it is combined with work requiring precise near vision. Pseudophakic monovision seems to be more

• *Nighttime driving, work under low illuminance:* In cases of weak ocular dominance, when the optical target appears highly contrasted with the background under mesopic lighting conditions, blur suppression does not function sufficiently. Therefore, pseudophakic monovision should be avoided in patients whose work requires precise vision under low illuminance levels

In conclusion, regardless of the exclusion criteria, it is suggested that the procedure and possible outcomes of pseudophakic monovision, when selected,

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should be thoroughly explained to patients in order the best possible visual outcome and patient satisfaction to be achieved.
