*2.3.4 Corneal pachymetry*

Ultrasonic pachymetry may contribute to the assessment of overall endothelial function in corneas with a diseased endothelium or with borderline low endothelial cell counts, however, corneal central thickness is not correlated with endothelial cell numerical density within the physiological range. Specifically, an increased preoperative thickness might increase the risk for postoperative clinical corneal edema [26].

#### *2.3.5 Scheimpflug tomography/placido-based corneal topography*

Scheimpflug tomography or, alternatively, placido-based corneal topography can determine patient's total or anterior-surface corneal astigmatism, respectively, and whether the astigmatism is regular or irregular, or even detect possible keratoconus. The corneal topographic analysis should be compared with optical biometry findings for the best possible accuracy in IOL power and astigmatism calculation, especially if a laser refractive surgery has been preceded.

#### *2.3.6 Aberrometry*

The routine preoperative examination should include the determination of the anterior aberration profile looking for elevations of 3rd- and 4th-order aberrations, such as coma and spherical aberrations (SA) [27]. Generally, cornea has an average positive SA of +0.28 μm (positive SA occurs when the peripheral rays entering the eye are focused in front of the central rays) [28]. Among the most common aberrometers are i-Trace aberrometer (Tracey Technologies Corp., Houston, TX), OPD-scan (ARK 10000; Nidek), and Pentacam (Oculus Optikgerate GmbH, Wetzlar, Germany), which calculate total ocular, lens or corneal wavefront aberrations [29, 30].

#### *2.3.7 Pupillometry*

Preoperative pupillometry can measure: (i) pupil diameter under photopic (small pupil) and mesopic (wide pupil) lighting conditions, (ii) distance between the pupil center and the visual axis (angle kappa), between the corneal center and the visual axis (angle alpha), and/or between the pupil center and the corneal center, and (iii) distance (spatial shift) from the photopic to the mesopic pupil center (pupil center shift - PCS) [31–33]. Regarding PCS, two types of PCS can be evaluated: (i) measured PCS, which results from the values measured under photopic and mesopic lighting conditions, and (ii) interpolated PCS, which depicts the predicted spatial shift between a photopic pupil of 2 mm to a scotopic pupil of 7 mm, and can contribute to the better comparability of the measurements [34].

#### *2.3.8 Specular microscopy*

Endotheliometry, especially in suspicion of endothelial dysfunction/dystrophy, is a very useful examination. The average endothelial cell density (ECD) in patients > 40 years old ranges between about 2500 and 2700 cells/mm<sup>2</sup> [35]. A central ECD decline of less than 1000 cells/mm2 preoperatively, and 400 to 700 cells/mm2 postoperatively might cause significant postoperative endothelial cell impairment and corneal edema. The hexagonality should also be assessed [36–38].

#### *2.3.9 Macula and ONH OCT - OCTA*

Since good macular and optic nerve function are necessary for a premium pseudophakic presbyopic correction, many surgeons perform an optical coherence tomography (OCT), or even an OCT angiography (OCTA), of the macula and optic nerve head (ONH) to confirm normal macular and optic nerve anatomy and microcirculation. Macular degeneration, subtle epiretinal membranes, early stages of macular hole or posterior vitreous separation with vitreal macular traction, but also glaucoma or vascular abnormalities in various optic neuropathies can be revealed.

**99**

*Pseudophakic Presbyopic Corrections*

erative IOL position [39, 40].

*2.3.11 B-mode ultrasonography*

surgery systems [41].

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

*2.3.10 Anterior segment OCT (AS-OCT)*

*2.3.12 Image-guided systems – preoperative units*

**3. Surgical procedures – IOL types**

and the bilateral implantation of multifocal IOLs [8].

targeted for monovision or mini-monovision [45].

dominant eye for distance vision [8].

with bilateral monofocal IOL implantation.

success is the weak ocular dominance [49, 50].

*3.1.1 Patient selection*

The application of AS-OCT during the preoperative planning for cataract surgery could be useful in the accurate prediction of postoperative ACD and postop-

This examination could be performed to detect the posterior segment disorders, especially in suspicion of retinal detachment, vitreous opacity or posterior segment

The size and the location of main and sideport incisions, the size and diameter of capsulorrhexis, the centration of the capsulorrhexis, as well as the alignment axis in case of toric or multifocal toric IOLs are predetermined in the preoperative examination with the measurement module of image-guided lens extraction

The two most widely used methods for pseudophakic presbyopic correction are the monovision technique through bilateral implantation of monofocal IOLs

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

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 non-

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

*Inclusion criteria*: The most frequent inclusion criterion was the desire for spectacle independence [48]. One of the most important prerequisites for monovision

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

tumor, especially when the fundoscopy is impossible due to mature cataract.

### *2.3.10 Anterior segment OCT (AS-OCT)*

The application of AS-OCT during the preoperative planning for cataract surgery could be useful in the accurate prediction of postoperative ACD and postoperative IOL position [39, 40].
