*3.2.2.3 Preoperative examination and patient selection*

Some significant parameters that should be taken into account during *preoperative examination* for the patient selection for mIOL implantation and, then, for the selection of the appropriate type and power of the IOL are the following:


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

corneal astigmatism into account [94].

with time through the process of neuroadaptation [99].

• *Visual axis, angle kappa:* In pseudophakic presbyopic corrections with implantation of mIOLs, the angle kappa (misalignment between the visual and pupillary axis) [100] should be taken into consideration, especially for hyperopic patients with a large angle kappa [101, 102]. It has been found that large angle kappa is correlated with more glare and halos after implantation of mIOLs [86, 103]. This happens because when decentration of mIOLs is present (intraoperatively or postoperatively), which is more common in eyes with large angle kappa, the light rays pass through a multifocal ring instead of the central optic zone, resulting in glare and halos [104]. Decentration higher than 0.75 mm

non-mIOL pseudophakic presbyopic correction when an ultrasound biometry is used for the IOL power calculation. The surgeon should discuss with the patient the risks caused by the measurement inaccuracy, and may choose an alternative

• *Corneal astigmatism:* Patients undergoing multifocal IOL implantation may not tolerate residual astigmatism of > 1 D or even 0.75 D according to some studies, and a toric multifocal IOL may be required in such cases [92]. For the best possible calculation of the corneal astigmatism, the performance of more than one keratometry technologies is suggested, since no perfect method is available [13]. Ideally, rotary prism technology (auto-keratorefractometers), PCI, corneal Scheimpflug tomography (which also takes into account posterior corneal astigmatism) or Placido-based corneal topography, and keratometry taken by image-guided systems for lens extraction surgery could be used [16]. In case of agreement in corneal cylinder power and axis among the utilized technologies, the surgeon can safely choose the appropriate common cylinder power of the toric IOL and the alignment axis. If the different methods of measuring corneal cylinder produce inconsistent results, the treatment of the ocular surface should be considered and the measurements should be repeated. In addition, the proper patient positioning should be confirmed [93]. Online calculators are also available for the toric/multifocal toric IOL power calculation with very good results because most of them take IOL power and posterior

• *Pupillary size:* Pupil size, but also pupil position in relation to the near and distance zones of the lens, seem to affect the optical performance of the implanted mIOLs in terms of VA, optical aberration, diffraction, and retinal luminance. Patients with wide pupils in scotopic light conditions who were implanted with mIOLs have a higher risk of poor postoperative contrast sensitivity under mesopic illuminance levels and optical phenomena such as glare, halos, and starbursts [95]. In fact, large pupil size is one of the most common causes of dissatisfaction and photic phenomena in patients with mIOLs [96–98]. Therefore, the pupillary size under photopic and mesopic light conditions before mydriasis must be determined preoperatively to minimize subjective postoperative side effects [95]. Everyday clinical practice has shown that a mesopic pupil size smaller than 5 mm can minimize photic phenomena. In case of pupil size larger than 5 mm, the surgeon should discuss with the patient the risks for dysphotopic phenomena and decide whether to proceed with the multifocal IOL implantation or not depending on the patient's visual needs and lifestyle. An alternative surgical solution could be proposed if multifocal IOLs are excluded. Nevertheless, in all cases regardless of the pupil size, patients should be informed about the possibility of appearance of some optical phenomena which, however, may be reduced

surgical solution according to patient's visual needs and lifestyle.

*Current Cataract Surgical Techniques*

from mIOL implantation [13, 61].

ruled out from insertion of mIOLs.

*3.2.2.3 Preoperative examination and patient selection*

results in long eyes [82, 85].

vision [64]. In addition, patients who drive at night for long periοds of time

• *Occupation:* Patients with high occupational visual demands such as pilots and commercial (public service vehicle, taxi, or truck) drivers should be avoided

• *Expectations*: Hypercritical patients with unrealistic expectations are not suitable candidates for mIOL implant. For instance, people whose main concern is the sharpest clearest vision and who do not mind wearing near glasses even when reading very small letters or under low lighting conditions, should be

The surgeon should never promise full spectacle independence, but they should explain to patients that there is a good chance that they will not need glasses for the majority of their activities of daily living and that no perfect IOL to simulate their pre-presbyopic continuous vision exists yet [61]. However, spectacles may be needed under highly demanding conditions or during reading under low lighting conditions. Additionally, patients should be counselled about the optimal level and direction of light for easier reading. Finally, patients should be counselled about adverse events including halo, glare, reduced contrast sensitivity as well as discussing neuroadaptation in greater detail [75]. If patients are able to understand all benefits and risks of mIOLs, they could be good candidates to continue the preoperative examination for a potential pseudophakic presbyopic correction with mIOL

Some significant parameters that should be taken into account during *preoperative examination* for the patient selection for mIOL implantation and, then, for the

• *Optical biometry:* Careful biometry is crucial to accurate IOL power calculation and astigmatism management, since inaccurate biometry is the most common cause of residual refractive error postoperatively [76]. Third generation formulas such as the Holladay [77], SRK/T [78] and Hoffer Q [79] provide good outcomes for patients with average AL (22 – 25 mm) and keratometry. In cases of short eyes (AL < 22 mm) with a shallow ACD (< 2.40 mm), formulas that take preoperative ACD into account, such as Haigis, or alternatively Hoffer Q, could be used [80–82]. When dealing with long eyes (AL > 25–26 mm), SRK/T (with optimized constants), is still an accurate solution [83]. Haigis (with optimized constants) is accurate especially for eyes with AL < 30 mm [84]. Finally, new formulas such as Barrett Universal II and Olsen provide good

• *Dense cataract:* In case of dense cataracts when optical biometry measurements have low accuracy, the repetition of measurements could increase the accuracy in IOL power calculation. When no measurements can be taken, A-scan ultrasound biometry can be used. However, since the accuracy of this method is lower than the accuracy of optical biometry, [86–88] and taking into account that even a residual refractive error of 0.50 D, especially in mIOL implantation, can reduce the vision quality and increase photic phenomena, [89–91] the surgeon should be cautious with the choice of the mIOL or even with the decision for a possible

selection of the appropriate type and power of the IOL are the following:

should not be considered as good mIOL candidates.

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implantation.

non-mIOL pseudophakic presbyopic correction when an ultrasound biometry is used for the IOL power calculation. The surgeon should discuss with the patient the risks caused by the measurement inaccuracy, and may choose an alternative surgical solution according to patient's visual needs and lifestyle.


irrespectively of IOL design has shown both far and near visual function deterioration [96, 105]. Clinical practice and research has shown that inclusion of patients with an angle kappa and angle alpha < 0.5 mm, ideally < 0.3 mm, (primarily in vertical and secondarily in horizontal axis in the Cartesian coordinates plot) both in mesopic and photopic conditions of illumination can minimize the risk for mIOL decentration and postoperative photic phenomena [103]. On the other hand, when angle kappa and angle alpha are > 0.5 mm, multifocal IOLs should be avoided, and monofocal IOLs for binocular distance vision or monovision could be chosen [106].

	- It is assumed that corneas which have undergone a refractive surgery such as laser in situ keratomileusis (LASIK), photorefractive keratectomy (PRK) or radial keratotomy (RK), have been rendered multifocal and show many

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powers are used [64, 118].

aberrations by the laser procedure. As a result, it also assumed that the implantation of a mIOL would further deteriorate the visual function.

○ An additional difficulty is the inaccuracy in IOL power calculation that comes from the inaccuracy in the determination of the total corneal refractive power, [64, 117] and the inaccuracy in the estimation of the effective lens position by various IOL power calculation formulas when post-laser corneal

○ Patients having corneas with irregular astigmatism, or more than 1 micron of higher corneal aberrations (HOA), especially if they are caused by high levels of coma, are not good candidates for mIOLs [64]. In addition, eyes with a large pupil (> 4 mm) have more possibilities to appear photic phenomena caused by existing aberrations in comparison with eyes with a small pupil (< 4 mm). As a result, a poorer visual quality under mesopic or glare conditions may occur [119].

○ Although mIOLs are usually well tolerated and effective after corneal refractive surgery, refractive surprises can be common, especially in patients with myopia greater than 6.0 D or in those that have undergone LASIK [120, 121]. To increase the refractive predictability and reduce the risk of a suboptimal refractive outcome, the precise IOL power calculation is of paramount importance. Since keratometers are unable to measure accurately K values of the central post-laser cornea and the outer and inner corneal surfaces may change unpredictably after corneal refractive surgeries, a variety of IOL power calculation methods have been suggested [64]. The most accurate method is the *clinical history method*. To apply this method and calculate the central corneal power, the refractive error (spherical equivalent) and the K values prior to the keratorefractive surgery as well as the stable refractive error after the surgery must be available [122, 123]. Apart from the numerous methods and formulas that are available, some online calculators can also be

used complementarily for the IOL power calculation [124–126].

implantation of the mIOL [130].

*3.2.3 Surgical technique*

○ In general, patients that had a previous keratorefractive surgery and want to have an additional pseudophakic presbyopic correction with mIOLs have high expectations for spectacle-free good vision [127]. However, they should always be informed for the possibility of inaccurate measurements, residual refractive error, hyperopic shift, and/or aberrations resulting in photic phenomena especially in mesopic light conditions [128]. Additionally, the surgeon should explain to patients that there is a possibility that they will need to use a miotic agent postoperatively, especially in mesopic and scotopic light conditions, in case of photic phenomena, [129] and that an additional corneal refractive surgery or even a further surgery for exchanging the mIOL may be needed in the future [130]. Ideally, if the corneal surface is irregular with corneal aberrations and a second laser treatment is necessary to correct this irregularity, such a treatment should be better performed prior to the

Phacoemulsification is the gold standard technique for cataract surgery and refractive lens exchange. Since mIOL implantation requires high precision and various factors should be taken into consideration, in addition to the common ones for the conventional cataract surgery with monofocal IOL implantation, a variety

*Current Cataract Surgical Techniques*

preferred [34].

vision or monovision could be chosen [106].

the visual and optical quality [111].

pre- and/or postoperatively [112, 115, 116].

irrespectively of IOL design has shown both far and near visual function deterioration [96, 105]. Clinical practice and research has shown that inclusion of patients with an angle kappa and angle alpha < 0.5 mm, ideally < 0.3 mm, (primarily in vertical and secondarily in horizontal axis in the Cartesian coordinates plot) both in mesopic and photopic conditions of illumination can minimize the risk for mIOL decentration and postoperative photic phenomena [103]. On the other hand, when angle kappa and angle alpha are > 0.5 mm, multifocal IOLs should be avoided, and monofocal IOLs for binocular distance

• *Pupil center shift (PCS):* It has been found that not only the photopic kappa angle, but also the PCS is associated with dysphotopsia after mIOL implantation [102]. In case of patients having a PCS higher than 0.4 mm, surgeons should decide whether the optical zone of mIOL should be centered on the photopic or mesopic/scotopic pupil center. In fact, when interpolated (from photopic 2 mm to scotopic 7 mm pupil) PCS is higher than 0.7 mm, the implantation of mIOLs should be avoided and other types of IOLs should be

• *Aberrations – ocular scattering:* Although aberrations, such as comma, SA or first order astigmatism, contribute to the enlargement of the depth of focus, they can also result in a decrease in contrast sensitivity and quality of vision. For instance, it has been found that anterior corneal coma values higher than 0.32 or 0.33 mm may create intolerable photic phenomena when a diffractive mIOL is implanted, thus contraindication of mIOL implantation has been suggested in higher coma values [13, 107, 108]. Additionally, since angle kappa [109] and PCS [110] can influence ocular aberrations, they should also be co-evaluated with ocular aberrations in order to provide patients with the best possible vision quality. Apart from aberrations, ocular scattering may have an impact on the quality of retinal image, which may be overestimated when only aberrations are taken into account. Therefore, measurement of both aberrations and ocular scattering could contribute to a more accurate assessment of

• *Dry eye disease:* Since dry eye disease and cataract are very common in the elderly population, but also the ocular surface and tear film play a significant role in the quality of vision, dry eye disease treatment should be considered as an integral part of the pre- and postoperative patient's management. It is well known that dry eye may reduce the vision quality after mIOL implantation [112]. Additionally, it has been observed that cataract surgery is also responsible for causing dry eye disease or aggravating existing dry eye symptoms [113, 114]. Therefore, artificial tears and eyelid hygiene, but also cyclosporine or autologous platelet-rich plasma (PRP) in more severe cases, should be used

• *Previous corneal refractive surgery:* Particular attention should be given to

ering a pseudophakic presbyopic correction with mIOL implantation.

patients who have undergone a prior corneal refractive surgery and are consid-

○ It is assumed that corneas which have undergone a refractive surgery such as laser in situ keratomileusis (LASIK), photorefractive keratectomy (PRK) or radial keratotomy (RK), have been rendered multifocal and show many

**108**

aberrations by the laser procedure. As a result, it also assumed that the implantation of a mIOL would further deteriorate the visual function.

