*3.1.3 Limitations and possible complications of phakic intraocular lenses*

The complications relating to pIOLs can, at times, be more disabling than those from keratorefractive surgery. Night vision problems, corneal decompensation, glaucoma, cataract formation, dyscoria, uveitis, and endophthalmitis are potential complications after pIOL implantation. Night vision problems such as glare, halos, and diplopia are related to decentration of the pIOL and/or an optic diameter that is too small relative to the pupil size [61].

Surgically induced astigmatism is an issue primarily correlated with rigid Verisyse lenses and incision diameter. However, some investigators reported that the resulting surgically induced astigmatism (SIA) was less than expected [62, 63]. However, when compared with the Veriflex pIOL and ICL, the SIA was significantly higher [64].

Implantation of a pIOL, whether iris fixated or positioned in the posterior chamber, is associated with an accelerated decrease in endothelial cell density (ECD) [60]. Damage to the corneal endothelium may be due to the direct contact between pIOL and the inner surface of the cornea during implantation, from postoperative changes in pIOL position, or from subclinical inflammation, and direct toxicity to the endothelium. The magnitude of ECD loss after phakic intraocular lens implantation surpasses the expected natural annual decrease of 0.6% as reported in a 1997 benchmark study based on 42 adults [65]. Following implantation of an iris-claw phakic intraocular lens, the loss of ECD is highest during the first year varying between 0.75 and 7.2% [66]. Thereafter, the ECD loss continues without following an obvious pattern, to about 8.9% after 10 years. However, with an ICL the impact on the endothelium is claimed to be lower because the implant is placed in the posterior chamber further away from the endothelium itself. For the ICL the ECD loss is about 1.7% after 2 years [60] increasing to 6.2% after 8 years [54] and up to 19.75% after 12 years [67].

In our experience after ICL implantation, there is a linear decrease in ECD over a 3-year period, without any signs of exponential EC loss or reaching a plateau or stable ECD during this time (**Figure 5**).

With modern pIOL designs, increased intraocular pressure (IOP) seems to be relatively uncommon after 3 months postoperatively and is typically thought to be related to corticosteroid response [68]. Posterior chamber pIOLs cause narrowing of anterior chamber angle due to its position in ciliary sulcus, and its sizing (too long lenses which cause excessive vaulting >750 μm) is closely correlated with possible angle-closure glaucoma, pupillary block glaucoma, or pigmentary dispersion glaucoma [69, 70]. Given the risk of pupillary block, peripheral iridectomy or iridotomy is carried out as a preventative measure in anterior pIOL procedures, while in newer models of ICL with aquaport, technology is not needed.

Pupil ovalization/iris retraction is mainly correlated with iris-fixated pIOL and can occur if fixation of the pIOL haptics is performed asymmetrically [61, 68, 71]. No progressive pupil ovalization has been reported.

Formation of cataract due to the iris-claw pIOL is unlikely because the pIOL is inserted over a miotic pupil without contact with the crystalline lens [61]. The incidence of cataract formation was 1.1% for the iris-fixated pIOL. The overall incidence of cataract formation for posterior chamber pIOLs was 9.60%, which is significantly higher in comparison to iris-fixated pIOLs [72]. With various generations of the ICL, appearance of cataract formation is different. The less vaulted

**Figure 5.**

*Mean endothelial cell density during the 3-year follow-up (28 eyes); ± SD error bars are included indicating the variance in the data.*

model V3 caused a higher incidence of cataract formation than the newer V4 and V5 models [73]. With the V4 model, the recently published FDA study showed an incidence of 2.1% anterior subcapsular opacities, which is the most common type of cataract after pIOL [59]. Possible reasons are operative trauma, continuous or intermittent contact of the posterior chamber pIOL with the crystalline lens, insufficient nutrition through anterior chamber flow between the posterior chamber pIOL and the crystalline lens, and chronic subclinical inflammation with disruption of the blood-aqueous barrier due to friction between the pIOL and posterior iris or the haptic on the ciliary sulcus [74–76].

The risk of uveitis is a concern given the proximity of pIOLs to the iris, but it does not seem to be a significant long-term complication with modern designs. With iris-fixated pIOLs, a difficulty with enclavation of the iris can lead to iris atrophy and decentration of the implant [52]. Retinal detachment seems to be uncommon and lower than in clear lens extraction cases [68, 77]. A few cases of endophthalmitis have been reported after pIOL implantation, but it seems less common after pIOL implantation and then after cataract surgery [78, 79].

#### **3.2 Refractive lens exchange**

Refractive lens exchange (RLE) is by definition used to indicate the replacement of the cataractous/clear crystalline lens with an intraocular lens (IOL) to achieve emmetropia/near emmetropia. The improved efficacy, predictability, and safety of modernday phacoemulsification have resulted in a resurgence of lens extraction as a modality for correction of high myopia. Increased numbers of RLE are being performed worldwide, especially in patients not suitable for LASIK or pIOL or with early lens changes in the presbyopia age group [80, 81]. Optics of the IOL confer better quality of vision as compared with LASIK, and this optical quality does not degrade with time except in the presence of a posterior capsular opacification. The refractive results are predictable and stable with a larger range of refractive correction possible than with either LASIK or pIOL. RLE addresses refractive error and cataract and with the use of modern multifocal IOLs results in a significant degree of spectacle independence for the patient. Visual recovery is faster, and it is more cost-effective, as the higher cost of pIOLs and future cataract surgery is eliminated. The principles of surgery are in the domain of most cataract/anterior segment surgeons [82].

Overall, patient satisfaction scores after implantation of multifocal IOLs are high. For example, using a 0–10 self-recording analogue scale, you can expect

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*Surgical Correction of Myopia*

*DOI: http://dx.doi.org/10.5772/intechopen.85644*

acuity as demonstrated in **Figure 6**.

**Figure 6.**

*multifocal IOLs.*

visual performance and jeopardize the result [85].

typical average satisfaction scores of 8.8 (Zeiss bifocal IOL, n = 48, range 2–10) and 9.00 (Zeiss trifocal IOL, n = 52, range 4–10). On closer examination satisfaction scores are closely linked to post-op uncorrected distance and intermediate, visual

*Postoperative uncorrected distance visual acuity and patient satisfaction after RLE with implantation of* 

Advanced technology multifocal IOLs tend to be less forgiving with respect to the surgical technique, multifocal IOL power selection, ocular comorbidities, and patient selection. Comorbidities such as dry eye, vitreomacular pathology, or implant decentration may be tolerated in patients after a monofocal IOL implantation. However, these are much less tolerated by the multifocal IOL patients [83, 84]. Presbyopia-correcting intraocular lenses should provide post-op emmetropia for the best visual outcome, as small amounts of residual refractive errors can limit

In evaluating the highly myopic patient, several aspects apart from the routine cataract/refractive surgery assessment should be noted. A detailed past ocular history is important, as previous refractive surgery or phakic intraocular lens implants or retinal problems (e.g., vitrectomy for previous retinal detachment) will affect lens formula choices and their final prognosis. Preoperative assessment should also include a detailed clinical examination of their lens status (e.g., cataract density and any zonular weakness) and refraction status of both eyes, as well as a dilated examination of the fovea and periphery for any retina disorder (e.g., myopic choroidal neovascular membrane, macular schisis, retinal tears, or detachment). Other issues for discussion include the potential use of toric or multifocal IOLs. Ideally, a larger haptic platform toric lens should be used in high myopes to reduce the risk of postoperative lens rotation, as the capsular bag is often large and floppy. In some cases, the use of a capsular tension ring to stretch the capsular bag may be required to prevent rotations.

*3.2.1 Preoperative examination and indications for refractive lens exchange*

Multifocal IOLs should only be used in an eye with no retinal disorder [86].

pathology, absence of uveitis, or any kind of ocular inflammation.

Inclusion criteria are more than 40 years of age with myopia not amenable to conventional laser refractive surgery (e.g., high refractive error, corneal irregularities, thin cornea) or phakic IOLS (e.g., shallow anterior chamber, poor endothelial cell count, early cataract changes), presbyopic myopic patients who want reasonable independence from glasses for both distance, and near-vision, myopic patients with early lens changes who desire refractive correction [80, 86]. For multifocal IOL it is important to rule out any irregularities of iris or pupil function, evolving retinal

**Figure 6.**

*Intraocular Lens*

**Figure 5.**

*variance in the data.*

model V3 caused a higher incidence of cataract formation than the newer V4 and V5 models [73]. With the V4 model, the recently published FDA study showed an incidence of 2.1% anterior subcapsular opacities, which is the most common type of cataract after pIOL [59]. Possible reasons are operative trauma, continuous or intermittent contact of the posterior chamber pIOL with the crystalline lens, insufficient nutrition through anterior chamber flow between the posterior chamber pIOL and the crystalline lens, and chronic subclinical inflammation with disruption of the blood-aqueous barrier due to friction between the pIOL and posterior iris or

*Mean endothelial cell density during the 3-year follow-up (28 eyes); ± SD error bars are included indicating the* 

The risk of uveitis is a concern given the proximity of pIOLs to the iris, but it does not seem to be a significant long-term complication with modern designs. With iris-fixated pIOLs, a difficulty with enclavation of the iris can lead to iris atrophy and decentration of the implant [52]. Retinal detachment seems to be uncommon and lower than in clear lens extraction cases [68, 77]. A few cases of endophthalmitis have been reported after pIOL implantation, but it seems less common after

Refractive lens exchange (RLE) is by definition used to indicate the replacement of the cataractous/clear crystalline lens with an intraocular lens (IOL) to achieve emmetropia/near emmetropia. The improved efficacy, predictability, and safety of modernday phacoemulsification have resulted in a resurgence of lens extraction as a modality for correction of high myopia. Increased numbers of RLE are being performed worldwide, especially in patients not suitable for LASIK or pIOL or with early lens changes in the presbyopia age group [80, 81]. Optics of the IOL confer better quality of vision as compared with LASIK, and this optical quality does not degrade with time except in the presence of a posterior capsular opacification. The refractive results are predictable and stable with a larger range of refractive correction possible than with either LASIK or pIOL. RLE addresses refractive error and cataract and with the use of modern multifocal IOLs results in a significant degree of spectacle independence for the patient. Visual recovery is faster, and it is more cost-effective, as the higher cost of pIOLs and future cataract surgery is eliminated. The principles of surgery are in the

Overall, patient satisfaction scores after implantation of multifocal IOLs are high. For example, using a 0–10 self-recording analogue scale, you can expect

the haptic on the ciliary sulcus [74–76].

**3.2 Refractive lens exchange**

pIOL implantation and then after cataract surgery [78, 79].

domain of most cataract/anterior segment surgeons [82].

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*Postoperative uncorrected distance visual acuity and patient satisfaction after RLE with implantation of multifocal IOLs.*

typical average satisfaction scores of 8.8 (Zeiss bifocal IOL, n = 48, range 2–10) and 9.00 (Zeiss trifocal IOL, n = 52, range 4–10). On closer examination satisfaction scores are closely linked to post-op uncorrected distance and intermediate, visual acuity as demonstrated in **Figure 6**.

Advanced technology multifocal IOLs tend to be less forgiving with respect to the surgical technique, multifocal IOL power selection, ocular comorbidities, and patient selection. Comorbidities such as dry eye, vitreomacular pathology, or implant decentration may be tolerated in patients after a monofocal IOL implantation. However, these are much less tolerated by the multifocal IOL patients [83, 84].

Presbyopia-correcting intraocular lenses should provide post-op emmetropia for the best visual outcome, as small amounts of residual refractive errors can limit visual performance and jeopardize the result [85].

#### *3.2.1 Preoperative examination and indications for refractive lens exchange*

In evaluating the highly myopic patient, several aspects apart from the routine cataract/refractive surgery assessment should be noted. A detailed past ocular history is important, as previous refractive surgery or phakic intraocular lens implants or retinal problems (e.g., vitrectomy for previous retinal detachment) will affect lens formula choices and their final prognosis. Preoperative assessment should also include a detailed clinical examination of their lens status (e.g., cataract density and any zonular weakness) and refraction status of both eyes, as well as a dilated examination of the fovea and periphery for any retina disorder (e.g., myopic choroidal neovascular membrane, macular schisis, retinal tears, or detachment). Other issues for discussion include the potential use of toric or multifocal IOLs. Ideally, a larger haptic platform toric lens should be used in high myopes to reduce the risk of postoperative lens rotation, as the capsular bag is often large and floppy. In some cases, the use of a capsular tension ring to stretch the capsular bag may be required to prevent rotations. Multifocal IOLs should only be used in an eye with no retinal disorder [86].

Inclusion criteria are more than 40 years of age with myopia not amenable to conventional laser refractive surgery (e.g., high refractive error, corneal irregularities, thin cornea) or phakic IOLS (e.g., shallow anterior chamber, poor endothelial cell count, early cataract changes), presbyopic myopic patients who want reasonable independence from glasses for both distance, and near-vision, myopic patients with early lens changes who desire refractive correction [80, 86]. For multifocal IOL it is important to rule out any irregularities of iris or pupil function, evolving retinal pathology, absence of uveitis, or any kind of ocular inflammation.

#### *3.2.2 Limitations and possible complications of refractive lens exchange*

The commonest disadvantage is the loss of accommodation with the need for near-vision glasses in the cases of monofocal IOL and the inherent risk associated with intraocular surgery, especially in high myopes [80]. The risk for endophthalmitis in general cataract surgery with implantation of a posterior chamber IOL is 0.1–0.7% with an optimal antiseptic perioperative treatment regimen [87]. Lens surgery is significantly more challenging in a highly myopic eye for several reasons. The issues that we take for granted in an eye of normal length (22–25 mm) such as the accuracy of axial length measurements and the choice of lens formula become a significant issue in the highly myopic eye as the predicted refractive outcomes are not achieved consistently. Axial length measurement error has been largely overcome by the use of optical interferometry. Despite this, consistent hyperopic errors are still reported. Improved predictive results are obtained with the Barrett Universal II (software constants), Haigis (ULIB), SRK/T, Holladay 2 (software constants), and Olsen (software constants) formulas in eyes with axial lengths greater than 26.0 mm and IOL powers greater than 6.0 D. In the eyes with axial lengths greater than 26.0 mm and IOL less than 6.00 D, the Barrett Universal II formula (software constants) and the Haigis (axial length adjusted) and Holladay 1 formulas (axial length adjusted) should be used [88, 89].

Intraoperatively, a highly myopic eye is surgically more challenging as the anterior chamber is deeper, with a floppy and large capsular bag and occasionally zonular weakness [90]. The anterior chamber is often unstable, and it is even less stable in a previously vitrectomized high myopic patient. There is also a concern that with elongated axial lengths, there is a higher risk of bag instability that can cause impaired vision, and the more complicated the IOL design is, the more sensitive the IOL is to final centration. A study by Soda et al. found that in uncomplicated cataract surgery with an IOL in the bag, the maximum decentration can be 0.3 mm for a satisfying result [91]. In addition, it is reported that myopic patients may exhibit worse results with more reported subjective symptoms and measurable aberrations like coma and glare in mesopic and scotopic lighting conditions compared to non-myopic controls, after multifocal IOL implantation with approximately the same amount of decentration [91]. RLE may increase the risk for retinal detachment and is generally not considered in myopic pre-presbyopic patients who can still accommodate.

The incidence of retinal detachment is especially high among younger age groups (<50 years) and in the eyes with long axial length > 26 mm. The reported incidence of retinal detachment after RLE ranges from 2 to 8%. Meticulous surgery with minimal intraoperative vitreous disturbance and a regular follow-up postoperatively until the occurrence of posterior vitreous detachment can reduce the risk of retinal detachment further. With the higher risk of retinal detachment in younger patients, it is prudent to defer RLE in patients younger than 40 years if possible [92].

Other possible causes of unfavorable visual outcome after uncomplicated phacoemulsification are cystoid macular edema (CME) and choroidal neovascular membrane (CNVM). Overall incidence of subclinical CME diagnosed with optical coherence tomography (OCT) is 5%, and incidence of clinical CME is 3%; however, high myopia does not increase the risk of CME [93]. Reported incidence of CNVM after RLE for myopia is 12.5% [94]; however, whether this was related to the higher degree of myopia with preexisting lacquer crack that was missed or due to some inflammatory mediators and free radicals released after surgery cannot be conclusively proved. Because the reported incidence of CNVM after uncomplicated phacoemulsification is not high, we assume that it is secondary to the degree of myopia,

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**Author details**

provided the original work is properly cited.

1 Specialty Eye Hospital Svjetlost, Zagreb, Croatia

2 School of Medicine, University of Rijeka, Croatia

\*Address all correspondence to: maja.bohac@svjetlost.hr

*Surgical Correction of Myopia*

**4. Conclusions**

*DOI: http://dx.doi.org/10.5772/intechopen.85644*

and it is prudent to perform OCT preoperatively in all RLE patients, especially those with more than 10 D of myopia. The presence of a myopic CNVM in the fellow eye is also considered as a risk factor for developing CNVM in the operated eye [80, 94].

Surgical treatment of myopia is a viable, safe, efficient, and predictable method for treating patients with myopia. There are several options of surgical treatment; we as doctors must always use our best judgment and available data to make sure we recommend the best method for each patient and their respective needs while taking into account any possible risk and contraindications. Among elective procedures in medicine, myopia treatment is one of the most commonly performed surgeries

because of the positive effect it brings the patients' quality of life.

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Maja Bohac1,2\*, Maja Pauk Gulic1,2, Alma Biscevic1,2 and Ivan Gabric1,2

and it is prudent to perform OCT preoperatively in all RLE patients, especially those with more than 10 D of myopia. The presence of a myopic CNVM in the fellow eye is also considered as a risk factor for developing CNVM in the operated eye [80, 94].
