**4.4 Ocular surface disease (OSD)**

*Current Cataract Surgical Techniques*

**4.3 Previous corneal refractive surgery**

IOL implantation [5].

**Figure 6.**

significant corneal coma.

tion and provide an elongated depth of focus [35].

Patients who have undergone myopic or hyperopic LASIK/PRK/RK tend to select the premium IOLs with higher expectations regarding the refractive outcome. But intraocular lens power calculation for these patients is challenging because it is difficult to calculate the true corneal power. The optical quality of corneal is another factor to consider for IOL selection. The high order aberration is increased after the laser myopic corneal which led to decrease the visual result of multifocal IOLs and increase the photophobia like halo, glare [31]. If cornea high order aberration is higher than 1 μm especially it caused by corneal irregularities, the presence of irregular astigmatism/coma, a decentered/uneven treatment bed, the patient should not be considered as good candidate for multifocal

*Corneal irregular astigmatism with history of corneal refractive surgery. HO RMS is 0.679 um, over 0.50 um.*

The post-myopic LASIK patients who had previous treatment was less then −6 D, ablation bed was fairly well centered with no or little irregular astigmatism and did not experience problems with night vision can be considered to use presbyopia correcting IOLs. [32] Some surgeon preferred EDOF IOls (Symfony, Johnson and Johnson Vision) in these patients, because its larger size central optic and higher light transmission provides an enhanced contrast sensitivity as compared with other refractive or diffractive multifocal IOls [33, 34]. If monovision was already created with LASIK or PRK, and monovision is probably a much better way to go. In the patients who had underwent the hyperopia laser correctio have increased negative spherical aberration and are best suited for aberration-free multifocal IOLs or IOLs with positive spherical aberration. The accommodating IOL was recommend by some surgeon if multifocal IOLs and EDOF IOLs were intolerant by the

A monofocal IOL is often the best choice in patients with previous RK who often had irregular corneal or increased corneal aberration. Now, pinhole IOLs (Xtrafocus, Morcher GmbH) is an effective presbyopia correcting solution for irregular astigmatism RK patients. It can correct of postoperative residual refrac-

**140**

Understanding the patient's ocular surface is of critical importance because ocular surface pathologic features can lead to false corneal power, induced astigmatism and unstable bad visual acuity.

Preoperative dry eye will lead to post-operative refractive surprise, blur vision and foreign body sensation, excessive tearing, and photophobia that makes patients unhappy [36]. Surgeon and assistor should address the OSD issue as part of preoperative discussion to management the patient expectation.

The most common OSD is meibomian gland dysfunction and dye eye. A thorough evaluation of the lids and lashes, testing for lacrimal gland function and tear film should be included in preoperative examination. A symptoms questionnaire also helps to capture OSD before surgery.

The treatment is based on severity and subtype of OSD. Steroid and preservative-free lubrication can be used for improving the corneal surface. Other therapy included moisture chamber glass, punctal occlusion, and oral omega fatty acid supplements. If the ocular surface condition is not improved after advanced therapies, the multifocal IOLs is not recommend due to significantly high and persistent postoperative OSD symptoms [37]. The low tear breakup time, increased meibomian gland dropout will increase the high order aberration leading to decrease the visual quality after the premium IOLs implantation [16].

Besides OSD, there are some corneal disease inducing irregular astigmatism will affect the premium IOLs section, such as addressing anterior basement membrane dystrophy (ABMD), epithelial basement membrane dystrophy, Salzmann nodular degeneration (SND). Appropriate management of these corneal abnormalities should be performed before cataract surgery in order to gain the reliable corneal keratometry and other ocular biometry parameter.

#### **4.5 Pupil size, angle kappa and angle alpha**

Pupil size, shape and centration also have a significant influence on presbyopic IOL surgery. In diffractive multifocal IOLs, the difference of diffractive step height determined the different light energy distribution in far, intermediate and near distance. Light energy distribution of the multifocal IOLs (MIOLs) varies with different aperture. For apodized diffractive IOLs, the near reading will become difficulty due to light energy goes more to distance in dim illumination. It suggested eyes implanted with multifocal IOLs should have a photopic pupil size of 3.5 mm or less and mesopic pupil size of 5 mm or less [38]. The average pupil size of photopic and mesopic are correlated with contrast sensitivity defocus curve [38]. The photophobia phenomenon like glare and halo also more complained in the large pupil patients. For the asymmetric refractive multifocal IOLs, the pupil size is an important parameter which had a significant negative subjective impact for outcomes [39].

Angle kappa (K) is defined as the angular difference between the visual axis and the pupillary axis while angle a refers to the angular distance between the visual axis and the optical axis. Though postoperative far, intermediate, and near vision is not affected by angle K which does not include the fixation point, large angle K might play a role in the decentration of multifocal intraocular lenses (IOLs), potentially resulting in the incident of glare and hola increasing which led to patient satisfaction with multifocal IOLs [40–43]. A well-centered lens in the visual axis is vital for proper functioning of presbyopic IOLs. Chord between the pupil centration and visual axis is the value to be evaluated for IOL location. It was suggested that a MIOL is unacceptable for use if the k value is greater than half of the diameter of

**Figure 7.** *Pupil size, angle kappa and angle alpha.*

the central optical zone. The limitation of k value is different according to the different multifocal IOLs——ReSTOR(Alcon) 0.4 mm, Tecnis multifocal IOL (Abbott Medical Optics) 0.5 mm, FineVision POD F IOL(PhysIOL) 0.6 mm [44].

Angle alpha is defined by the radial distance between the center of the limbus and the visual axis, which was found to predict the tilt of the IOL in respect to the visual axis. Wang had demonstrated that angle alpha was relatively stable whereas angle kappa changes from pre- to postoperative situation [45]. Angle alpha seems to be a better predictor for photic phenomena and patient satisfaction with multifocal IOLs [46]. But there still was different aspects on the predictive capacity of angle α on the outcome with multifocal IOLs. Piracha had concluded the angle alpha distance is larger than 0.5 mm, the eye is not suitable for multifocal IOL implantation [47], while Fu found there was no statistically significant correlation between angle alpha and the objective visual quality parameters [41] (**Figure 7**).

#### **4.6 Glaucoma**

Glaucoma patients often presented with the visual field damage, contrast sensitivity loss, small pupils and capsular and zonular issues, to affect vision outcomes must be taken into account when choosing a premium IOL.

Previous generation multifocal IOLs (Restor, Alcon; ReZoom, Abbott Medical Optics) were reported to significantly reduce the contrast sensitivity, especially in refractive multifocal IOL implantation. New advanced technology multifocal IOL or EDOF IOLs seem to mitigate the loss of contrast sensitivity [48]. And multifocal IOL also affect the visual field test and oct scan in the glaucoma patients' follow-up.

But because of a lack of scientific evidence in the form of large trials on the impact of multifocal IOLs in glaucoma, decisions regarding the implantation in a glaucoma patient should be tailored according to the patient' s motivation and the rate of glaucoma progression. The patient who is glaucoma suspect, ocular hypertensive, early stage with controlled and stable visual field damage is the candidate for diffractive multifocal IOLs and EDOF IOLs. The patients with severe, advanced, progressive glaucoma, or with high risk of pupil or zonular changes like chronic miotics, pseudoexfoliation, pigment dispersion will not benefit of multifocality [49].

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

It is a controversial topic of premium IOLs application in retinal disease patients because there are varying degrees of macular lesion, ranging from drusen without visual damage to the late stages of atrophic AMD. Multifocal IOLs are strictly not recommend in retinitis pigmentosa and Stargardt's disease, while diabetic retinopathy, age-related macular degeneration, and epiretinal membranes are relative contraindications [50]. Beside the different character of retinal diseases, the progression is an important issue to consider for premium IOLs solution [17].

For the mild or stable disease, multifocal IOLs is option for patient with careful and thoroughly consent about the prognosis including the issue of lower contrast sensitivity and long-term results with the disease progressing. Many studies had demonstrated the contrast sensitivity decreased in multifocal IOLs. Due to loss of contrast sensitivity at lower spatial frequencies is also presented even in mild forms of AMD, the EDOF IOLs is preferred in these cases. Multifocal IOLs generally are disadvised for patients with severe AMD because pre-existing pathologic features

The presence of an epiretinal membrane (ERM) can lead to more unpredictability with the spherical power of the IOL selection and its refractive outcome. Multifocal IOLs in ERM patients will face to the loss of contrast sensitivity,

There are few studies addressing the multifocal IOLs and retinal disease, which report a significant improvement in visual-related outcomes than the monofocal implantation. Nevertheless, more research is needed to address the aforementioned

Accurate measurements are critical for determining the correct power of a premium IOL before it is implanted during cataract surgery. The emmetropia is key factor of a successful refractive lens exchange to gain spectacle independence. Attaining this goal requires eliminating astigmatism and achieving a precise post-

Ocular biometry involves anatomical measurements of the eye, including the axial length (AL), keratometry, anterior chamber depth (ACD), lens thickness (LT), horizonal white to white (HWTW) which are the parameters for IOL power

Even the ultrasound biometry is still used in some difficult cases such as brunescent cataract, white cataract and severe subcapsular cataract. A hyperopic surprise often appeared in high myopic patients by using ultrasound biometry, because A-scan measured the deepest part of the staphyloma while macula was on the edge

With IOLMaster (Zeiss) introduced in 1999, optical biometry technique provide a directly measurement from the macula to the corneal vertex. It becomes golden standard as it is highly accurate, easy to perform, non-invasive and comfortable for the patient. The accuracy of optical biometry, and in particular the IOLMaster 500 (Zeiss) and Lenstar 900 (Haag-Streit), have been extensively confirmed across a wide range of scientific studies [53, 54]. New generational optical biometry IOLMaster 700 (Zeiss) has integrate swept source optical coherence tomography to measure axial length. It allows for penetration of dense cataracts, determination of lens thickness (not available on the prior generations of IOLmaster), and visualization of the foveal pit to both ensure alignment of the image and possibly detect

increased risk for postoperative cystoid macular edema [51].

**5. Ocular biometry and IOL power calculation**

of the staphyloma which led to false longer axial length.

operative plano refraction within ±0.25 D.

concerns and to optimize the use of MIOLs in eyes with retinal disease.

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

**4.7 Retinal disease**

are a contraindication.

calculation [52].
