Phakic Intraocular Lenses 15 Dennis C

Phakic Intraocular Lenses 15 Dennis C. Lu, David R. Hardten, Richard L. Lindstrom

| Core Messages grees of refractive error.Recently there has been ∑ Phakic IOLs may be appropriate for some a revival in interest on the lenticular component potential refractive surgery patients of the optical system – leading to advances in in whom keratorefractive surgery phakic intraocular lenses, refractive lens ex- is unsuitable change and accommodative and multifocal in- ∑ Patients to consider include those with traocular lenses. The lenticular refractive pro- higher ametropia or those with thin cedures have provided an effective alternative corneas solution for the correction of higher degrees of ∑ Phakic IOLs are classified into three ametropia and for eyes that are otherwise un- categories: anterior chamber angle fixated, suitable for keratorefractive procedures. anterior chamber iris fixated and posterior chamber lenses ∑ The main potential complication 15.1.1 of anterior chamber lenses is contact Limitations of Keratorefractive Procedures with the endothelium whereas the main complication of posterior chamber Conductive keratoplasty has been limited to low lenses is iatrogenic cataract formation degrees of hyperopia. Likewise, Intacs is con- ∑ Assessment of key anatomic factors, fined to the correction of low degrees of myopia such as anterior chamber depth and without astigmatism. The excimer laser proce- endothelial cell count, is critical dures such as photorefractive keratectomy (PRK), in evaluating a patient laser subepithelial keratomileusis (LASEK) and laser in situ keratomileusis (LASIK) are more versatile with regards to the range of refractive errors that they are able correct. However, even 15.1 LASIK, which is the most versatile, has less pre- Introduction dictable results and optical quality at the higher ranges of ametropia as a result of larger alter- The latter part of the 20th century has been a ations in corneal biomechanics and wound revolutionary age for refractive surgery. There healing. Larger degrees of tissue ablation in has been an explosive growth in the number of turn may lead to the induction of increasing technologies that have developed for refractive amounts of higher order aberrations [41]. The surgery. Most of the focus has been placed on emergence of wavefront guided ablation, how- the corneal component of the optical system, ever, promises to reduce higher order aberra- such as with the current wavefront technolo- tions when compared to traditional excimer gies. Although the corneal refractive surgeries laser ablation.Yet,the corneal thickness impos- have been effective for low to moderate degrees es a significant limit on the degree of ametropia of myopia and hyperopia,their efficacy and pre- that may be corrected as deep ablations may in- dictability has been more limited for higher de- crease the risk of induced corneal ectasia [45, 236 Chapter 15 Phakic Intraocular Lenses

48]. In addition, with PRK or LASEK, higher de- correct the residual refractive error has been grees of correction can lead to increased risk of termed “bioptics” by Zaldivar [60]. subepithelial haze and regression [6, 17, 40].

15.2 15.1.2 Evolution and Classification of Phakic IOLs Role of Lenticular Refractive Procedures The concept of using an anterior chamber lens Because lenticular refractive procedures need implant in a phakic eye to correct high myopia not contend with the variables of corneal was originally explored by Strampelli in the wound healing and altered corneal geometry, 1950s [54] and later by Barraquer in 1959 [13]. refractive outcomes are more predictable and However, the phakic anterior chamber lenses of stable when compared to LASIK at higher de- this generation suffered from unacceptably high grees of correction. In fact, barring surgical re- complication rates related to endothelial cell lated issues such as incisional astigmatism and loss, iridocyclitis and hyphema. Consequently, IOL centration, the wavefront remains largely implantation of phakic anterior chamber was unchanged in phakic IOLs compared to corneal abandoned but later revived in the 1980s. Dur- refractive procedures [27]. As with cataract sur- ing this decade, three competing designs arose: gery, the predictability in refractive outcome Fechner and Worst et al. proposed use of an iris depends in large part on the selection of the IOL fixated lens [21], Baikoff et al. used an angle- power.An additional advantage of lenticular re- supported lens modified from the Kelman mul- fractive surgeries is that removal or exchange of tiflex lens [11] and Fydorov designed a phakic the IOL is possible. posterior chamber intraocular lens [24]. Cur- Several types of lenticular refractive proce- rently, phakic IOLs are classified according to dures are currently being performed today: the way in which they are fixated: (1) anterior phakic IOL implantation, refractive lens ex- chamber angle fixated,(2) anterior chamber iris change (RLE) and cataract extraction with a fixated and (3) posterior chamber. Each of these monofocal, multifocal or accommodative IOL. designs has inherent advantages as well as Accommodative IOLs currently represent a rel- unique potential complications. atively new technology but may prove to be a promising refractive device in the future. While RLE has provided a viable solution for the high- 15.2.1 ly ametropic patient in the presbyopic age Anterior Chamber Angle-Fixated Lenses group, phakic IOL implantation provides a dis- tinct advantage for the younger age group in The main advantage of the anterior chamber that this technique preserves accommodation. angle-fixated lens is the ease of insertion and Implantation of phakic IOLs is a versatile proce- the familiarity that most ophthalmologists have dure in its ability to correct myopia and hyper- with insertion of anterior chamber intraocular opia. Furthermore toric IOLs are currently be- lenses (ACIOL). Current designs incorporate a ing developed for the concurrent correction of foldable or non-foldable IOL that requires an astigmatism. However, phakic IOLs currently incision between 3.0 and 6 mm, depending on lack the accuracy of excimer laser procedures at the size of the IOL. the lower degrees of ametropia. Because patients who have undergone phakic IOL implan- 15.2.1.1 tation may have residual spherical and cylindri- Design Considerations cal error, they may undergo additional LASIK enhancement procedures to achieve better un- The unique complications of phakic IOLs are corrected visual acuity (UCVA) [60]. The step- primarily mechanical in nature and result from wise approach of phakic IOL implantation fol- the anatomic relationships between the IOL and lowed by an excimer laser enhancement to its neighbouring ocular structures.With the an- 15.2 Evolution and Classification of Phakic IOLs 237

Table 15.1. Complications arising from phakic IOL contact with ocular structures

Contact with: Complication:

Endothelium Endothelial loss, corneal oedema Iris Pigment dispersion, chronic uveitis Pupil Pupillary block, angle closure glaucoma Irido-corneo-scleral angle Pupil ovalisation, peripheral anterior synechiae Crystalline lens Cataract formation terior chamber lenses, the main complications the dioptric power of the IOL, and a smaller op- arise from: (1) Contact with the endothelium re- tic diameter can lead to glare and halos. Finally sulting in endothelial cell loss and corneal oede- the geometry of the haptics must be designed to ma; (2) contact with the iris leading to pigment provide an even distribution of forces while dispersion and chronic uveitis; (3) pupillary minimising excessive contact with angle struc- block leading to acute angle closure glaucoma; tures. An even distribution of haptic forces is (4) deformation of the irido-corneo-scleral an- necessary in order to provide correct centration gle structures by the haptics, resulting in pupil while preventing IOL rotation and pupil ovali- ovalisation, peripheral anterior synechiae, glau- sation. coma and occasionally (5) contact with the natural crystalline lens leading to cataract forma- 15.2.1.2 tion. In addition, IOL decentration, tilt, pupil Non-foldable Anterior Chamber Angle ovalisation, and the smaller IOL optic required Fixated Lenses by anterior chamber lenses can all contribute to the symptoms of glare and halos for which these Baikoff’s original ZB implant (Domilens, Lyons, IOLs are notorious (Table 15.1). France), which was a modification of the Kel- In order to minimise contact between the man Multiflex lens, incorporated a biconcave IOL and the ocular structures, the following de- negative-powered angle-fixated lens (Fig. 15.1). sign parameters must be considered: (1) vault- This design suffered from unacceptably high ing angle of the IOL, (2) diameter of the optic, rates of endothelial cell loss, with reported rates (3) thickness and profile of the optic, both cen- of 16%–19% at 1 year and 20%–28% at 2 years trally and peripherally and (4) geometry of the [12, 39, 43, 42]. The lens employed a 4.5-mm op- haptics, including the number of haptic contact tic angulated at 25º and consisted of four haptic points and distribution of compressive forces in contact points. This geometry resulted in exces- the irido-corneo-scleral angle. Clearly, the anterior chamber depth, white-to-white distance, pupil size, corneal pachymetry, and specular microscopy must be measured prior to surgery. Excessive vaulting of the IOL results in endothelial contact while inadequate vaulting leads to pigmentary dispersion and/or acute pupillary block glaucoma. A peripheral iridectomy or iridotomy is therefore recommended for all phakic IOLs. The profile of the optic must be designed to minimise contact with the endothelium and iris,which can be achieved by decreasing either or both the thickness and diameter of the optic. However, altering the geometry of the Fig. 15.1. First generation ZB anterior chamber angle IOL will affect the optics: thickness influences fixated implant.(Reprinted with permission from [10]) 238 Chapter 15 Phakic Intraocular Lenses

Fig. 15.2. NuVita anterior chamber angle fixated implant. (Reprinted with permission from [10])

sive contact between the optic edge and the endothelium when patients rubbed their eyes [43]. Subsequently, Baikoff minimised endothelial contact in his second generation design, the ZB5 M lens, by decreasing the angulation to 20º and by reducing the optical edge thickness at the expense of reduced effective optical diame- Fig. 15.3. Vivarte foldable anterior chamber angle ter. The ZB5 M significantly reduced the rate of fixated implant. (Reprinted with permission from endothelial cell loss and provided reasonable [10]) optical quality [2, 12, 43]. Thus the lens enjoyed reasonable longevity between 1990 and 1997.Sev- eral studies reported reduction of endothelial cell loss to ranges of 4.5%–5.5% at 1 year and 5.6%– 6.8% at 2 years [2, 12]. The main complications Various other manufacturers have produced of this lens were related to the haptic design and angle-fixated IOLs that are modifications of the reduced optical zone: pupil ovalisation in Baikoff’s original designs: the ZSAL 4 (Morcher, 22.6% and night time halos in 27.8% [2, 12]. Stuttgart, Germany) and the Phakic 6 (Oph- The successor to the ZB5 M is the NuVita thalmic Innovations International, Ontario, MA20 (Bausch & Lomb Surgical/Chiron Vision, CA). The ZSAL 4 was developed by Pérez-San- Irvine, CA), which is currently available in Eu- tonja et al. and became commercially available rope but not yet approved for use in the United in Europe in 1995. The design is similar to the States (Fig. 15.2). Modifications to the z-shaped NuVita but implements a larger 5.0 effective op- haptic profile and redistribution of compressive tical zone within a 5.5 mm plano-concave optic forces have reduced the incidence of iris ovalisa- at an angulation of 19º. Though this design pro- tion [12]. In addition the geometry of the optic vided reasonable optical quality and reduced was altered to an anterior convex/posterior con- the incidence of night time halos, it did not re- cave profile. This profile minimises endothelial duce the incidence of complications related to contact while increasing the effective optical haptic design: pupil ovalisation, IOL rotation zone (4.5 mm) within the same overall optic di- and chronic low-grade uveitis.However,the rate ameter (5.0 mm). According to the manufactur- of endothelial cell loss was lower: 3.50% at 12 er, the increased effective optical zone and use months and 4.18% at 24 months [43]. The of an antireflective process applied to the optic ZSAL 4 is supplied in powers ranging from –6 to edges, termed Peripheral Design Technology, –20 D in increments of 1.00 D,and is available in combine to reduce the incidence of glare and lens lengths of 12.5 or 13.0 mm. halos [9]. 15.2 Evolution and Classification of Phakic IOLs 239

Fig. 15.4. a Unassembled Kelman Duet anterior chamber angle fixated implant (courtesy of Tekia Inc.) b Kel- man Duet implant assembled (courtesy of Tekia Inc.)

The Phakic 6 implant shares similarities to drophilic acrylic (Fig. 15.3). A unique manufac- the ZSAL 4 but features a larger 6-mm optic in turing process allows for the selective polymeri- efforts to reduce the incidence of halos. Howev- sation of each IOL component and thereby pro- er, the larger optic poses the increased risk of duces a soft optic and footplate while creating a endothelial contact. Long term studies are not rigid haptic. Thus, the soft optic allows the IOL yet available. Furthermore, the implant is avail- to be folded while the rigid haptic provides sup- able with heparin-surface modification, which port within the angle at three contact points. aims to reduce the formation of synechiae. The The optic diameter is 5.5 mm and is available in Phakic 6 is available in myopic ranges of –2 to lengths of 12.0, 12.5, 13.0 and 13.5 mm. The pow- –25 D and hyperopic ranges of +2 to +10 D. The er ranges from –7 to –25 D in 0.5 D increments. lens lengths range from 12.0 to 14.0 mm [47]. Using a different approach to the design of a “foldable” angle-fixated lens, the Kelman Duet 15.2.1.3 employs a two piece IOL wherein the compo- Foldable Anterior Chamber Angle nents are sequentially inserted through a small Fixated Lenses incision and assembled in the anterior chamber (Fig. 15.4a,b). At present, the PMMA haptic is Innovative designs and novel materials have led manufactured in lengths of 12.0, 12.5, 13.0 and to the development of foldable angle-fixated 13.5 mm, and the silicone optic is produced at a lenses that can be inserted through small inci- diameter of 5.5 mm. Power of the lens ranges sions. The Vivarte (manufactured by Ioltech, from –8 to –20 D [57]. The device is currently La Rochelle, France and distributed by Ciba undergoing clinical trials in Europe and is not Vision) is a single piece IOL composed of hy- yet approved for use in the United States. 240 Chapter 15 Phakic Intraocular Lenses

15.2.2 Anterior Chamber Iris-Fixated Lenses

In order to move the IOL further away from the endothelium and to avoid damage to angle structures, Worst proposed an alternative design for the anterior chamber intraocular lens in 1977 termed the “iris claw” lens. In this design, the lens is fixated anterior to the iris plane by two diametrically opposing haptic claws that incarcerate a portion of mid-peripheral iris a (Fig. 15.5a,b). This process has been termed “enclavation”. Originally used to correct aphakia following cataract surgery,Worst later modified the iris claw lens into a negative powered biconcave design to correct myopia in phakic patients in 1986. In 1991, the lens adopted a convex-concave profile with a larger optical zone of 5.0 mm and a total length of 8.5 mm [37].Since then,this model has been employed and was renamed the Artisan myopia lens in 1998 by the manufactur- b er (Ophtec, Groningen, The Netherlands) without a change in the design.An additional model Fig. 15.5. a Artisan lens (courtesy of Ophtec BV). with a 6.0-mm optical zone was added for pa- b Artisan lens properly positioned in a myopic eye tients with larger pupils.Advanced Medical Op- (courtesy of Ophtec BV) tics (AMO,Santa Ana,CA) is planning to market the lens in the United States upon approval under the name Verisyse. quently limited to a smaller range of powers be- In order to allow for unimpeded constriction cause of its proximity to the endothelium: –3 to and dilation of the pupil, the lens is fixated at –15.5 D in 0.5 D increments. According to the the immobile midperipheral iris. Because en- manufacturer, the distance from the optic edge clavation is the most challenging part of the to the endothelium ranges from 1.5 to 2.0 mm procedure, centration of the lens over the pupil depending on the dioptric power and the ante- can sometimes be difficult [35]. However, the rior chamber depth, as well as the diameter of lens may be fixated at any angle – horizontally, the optic. For the correction of hyperopia, the vertically, or obliquely – depending on surgeon model 203 incorporates a 5-mm optic with an preference. overall length of 8.5 mm and is available in diop- Currently, the Artisan is a non-foldable tric powers ranging from +1 to +12 D in 0.5 D in- PMMA lens capable of ultraviolet filtration and crements. has different models available for the correction Ophtec has introduced two different toric of myopia and hyperopia. Foldable designs are models. In model A, the torus axis is oriented currently under investigation. In addition, a parallel to the axis of the claw whereas in mod- toric design has recently become available for el B the torus axis is perpendicular. Most sur- the concurrent correction of astigmatism. The geons prefer horizontal insertion of the IOL and two models for myopia have differing optic di- would therefore use model A for with-the-rule ameters but the same overall length of 8.5 mm. astigmatism and model B for against-the-rule Model 206 has a 5.0-mm optic with power rang- astigmatism. The toric IOL is available in my- ing from –3 to –23.5 D in 0.5 D increments.Mod- opic powers ranging from –3 to –23.5 D in 0.5 D el 204 has a larger 6.0 mm optic and is conse- increments, hyperopic powers of +2 to +12 D in 15.2 Evolution and Classification of Phakic IOLs 241

0.5 D increments, and cylindrical correction nessing the aqueous flux dynamics to float the from 1.0 to 7.0 D. It is comprised of a spherical hydrophobic IOL away from the crystalline lens anterior surface and a spherocylindrical poste- in such a way that any type of fixation is avoid- rior surface. Because the lens requires an inci- ed.Staar Surgical AG (Nidau,Switzerland) man- sion of approximately 5.5 mm, the amount of in- ufactures the Implantable Contact Lens (ICL), duced astigmatism created by the incision and which employs the sulcus fixated design. By sutures must be taken into account when choos- contrast, Medennium Inc. (Irvine, CA) incor- ing the appropriate lens. porates the floatation approach in their Phakic The Artisan lenses for myopia and hyperopia Refractive Lens (PRL). are currently in phase III of the FDA clinical trials in the United States, and the results have 15.2.3.1 been encouraging. In Europe, the Artisan lens Sulcus-Fixated Posterior Chamber Lenses has already obtained the CE mark for myopia and hyperopia after having undergone a large As with anterior chamber angle fixated lenses, multicentre trial. The toric and foldable lens the concept of vaulting is critical in determining designs are still in the investigational stages in the success of a posterior chamber sulcus fixat- Europe. ed lens. In turn, the vaulting angle is influenced by the length of the IOL and the sulcus-to-sulcus distance. Choosing an IOL that is too short 15.2.3 relative to the sulcus-to-sulcus distance will Posterior Chamber Lenses result in inadequate vaulting and resultant cataract formation [22]. Furthermore, a short While the most daunting risk in anterior cham- IOL may result in decentration. By contrast, ber lenses is endothelial damage,the major con- a long IOL length will lead to excessive vaul- cern in posterior chamber lenses is iatrogenic ting, which in turn can lead to pigmentary dis- cataract formation. Thus, optimising the clear- persion or acute pupillary block glaucoma. ance of the IOL between the crystalline lens and Thus correct sizing of the IOL is critical in pre- the iris has been the primary focus in their de- operative planning. The ideal vaulting is sign. Contact with the crystalline lens would thought to be 500 mm over the crystalline lens provoke iatrogenic cataract formation, while (Fig. 15.6). Currently, no accurate method exists contact with the iris may result in iris chafing to measure the sulcus-to-sulcus distance, and and attendant chronic uveitis. Furthermore, an therefore it is extrapolated from white-to-white anteriorly positioned IOL may result in pupil- measurements. lary block and resultant angle closure glauco- The ICL evolved from Fyodorov’s original ma. Thus, a preoperative peripheral iridotomy design, which was first used to correct high my- is recommended. Two approaches have evolved opia in 1986. In order to avoid the endothelial in maintaining the optimal IOL position be- contact that was associated with anterior cham- tween the iris and lens: (1) sulcus fixation with ber lenses, Fyodorov pioneered the design of appropriate vaulting and,more recently,(2) har- the first posterior chamber phakic intraocular

Fig. 15.6. Ultrasound biomi- croscopy of the PRL positioned in the posterior chamber. Note that the PRL is not fixated in the ciliary sulcus but rather floats above the crystalline lens. (Reprinted with permission from [53]) 242 Chapter 15 Phakic Intraocular Lenses

lens. Staar Surgical made further modifications term results and safety. The ICL gained the Eu- to the design, and the first implantations were ropean CE mark of approval in 1997.In the Unit- accomplished in 1993 [8, 58]. After several re- ed States, the ICL began FDA trials in 1997 and finements, Staar Surgical now offers the current the spherical models have been recommended model of the ICL: the ICH V4 (Fig. 15.7).The ICL for approval by the FDA Ophthalmic Devices is a single piece plate-haptic foldable lens that Advisory Panel and are awaiting final approval may be inserted through an incision of less than [52]. Toric models are in the early phases of the 3 mm. The lens is composed of a proprietary FDA trials. material termed Collamer (Staar Surgical AG, Nidau, Switzerland), a hydrophilic collagen 15.2.3.2 polymer (34% water and <0.1% collagen), that Non-fixated Posterior Chamber Lenses appears to be highly biocompatible and allows the crystalline lens to maintain a normal metab- The posterior chamber lens manufactured by olism. Both myopic and hyperopic models are Medennium Inc., named the Phakic Refractive available. Toric models are currently undergo- Lens (PRL),requires no fixation (Figs. 15.8,15.9). ing clinical trials and will correct up to 6 D of This lens floats on the crystalline lens by nature astigmatism. The myopic lens is concave-con- of its hydrophobic material in conjunction with cave in design and is available in powers rang- the aqueous flux dynamics. This lens is com- ing from –3 to –20 D. The hyperopic model is posed of a highly purified, optically clear sili- convex-concave and is available in powers from cone. Because of its lack of fixation, stability of +1.50 to +20.00 D. Depending on the power centration and rotation are concerns. For these of the lens, the optical zone varies between 4.5 reasons, this particular design may not be suit- and 5.5 mm. While the thickness is only 50 mm able for a toric lens. According to the manufac- at the optical zone, the thickness increases to turer, centration is achieved by the self-center- 100 mm at the footplates and up to 500–600 mm ing design of the optic body. at the haptic zone.Although the width is fixed at The PRL is a one-piece foldable plate haptic 7.0 mm, the lengths range from 11.0 to 13.0 mm lens that may be inserted through a 3.2-mm in- in 0.5-mm increments. Choice of lengths is crit- cision. Because it does not require sulcus fixa- ical in determining the appropriate position tion, sizing is not as critical with the PRL as it is and vaulting above the crystalline lens. with the lenses that require fixation and vault- Short term results of the ICL have been en- ing. Thus the manufacturer offers one length of couraging and quality of vision has been excel- 11.3 mm for the myopic model and one length of lent. Clinical trials are still evaluating the long 10.6 mm for the hyperopic model. A 10.8 mm

Fig. 15.7. STAAR implantable contact lens. Fig. 15.8. Phakic refractive lens. (Reprinted with (Reprinted with permission from [59]) permission from [56]) 15.3 Evaluation of the Phakic IOL Patient 243

∑ Geometry of the haptics, including the number of haptic contact points and distribution of compressive forces in the irido-corneo-scleral angle for angle fixated implants

15.3 Evaluation of the Phakic IOL Patient

Because implantation of a phakic IOL is an elec- tive procedure for the correction of ametropia, patient selection and education is imperative. The surgeon must have a clear understanding of the surgical options available,as well as the con- traindications and indications of each. A thorough discussion of the risks, benefits and alter- natives must then be undertaken in order to allow the patient to make an informed decision. Fig. 15.9. Slit lamp photograph of the PRL properly Realistic patient expectations are essential to a positioned. (Reprinted with permission from [53]) successful outcome. myopic model was previously offered but was 15.3.1 discontinued because of decentration issues General Patient Factors [28]. In both the hyperopic and myopic models, the width of the lens is 6.0 mm.Thickness varies In general, patients less than age 18 should not according to the dioptric power, with a maxi- have any refractive surgery, as their refractive mum thickness of 0.6 mm. The myopic model is error has not stabilised. Refractive stability may offered in powers ranging from –3 D to –20 D in occur at an older age for patients with higher half diopter increments, which allows for cor- levels of myopia. Patients with unrealistic ex- rection of myopia up to –23.0 D. For the hyper- pectations of “perfect vision” after surgery opic model, power ranges from +3 D to +15 D in should also be identified. These patients will half diopter steps and corrects a maximum of generally be unhappy with the outcome. +11 D. Whereas the diameter of the optical zone for the myopic model varies between 4.5 and 5.0 mm depending on the power, the diameter 15.3.2 for the hyperopic model is fixed at 4.5 mm. Refraction The PRL has gained the CE mark of approval in the European Union and is currently un- Phakic IOLs are suitable for myopia in the range dergoing Phase III FDA trials in the United of –8 D to –22 D and hyperopia in the range of States. +3 D to +10 D. The Artisan toric iris-fixated lens is able to correct from 1 to 7 D of astigmatism, Summary for the clinician: while the toric Staar ICL may correct up to 6 D Important considerations when choosing of astigmatism. Lower refractive errors are a phakic IOL: better suited for corneal refractive procedures, ∑ Vaulting angle of the IOL unless the patients’ corneas are unsuitable with ∑ Diameter of the optic regards to thickness or topography. For best re- ∑ Thickness and profile of the optic, sults, the refractive error should be stable prior both centrally and peripherally to the surgery. Both cycloplegic and non-cyclo- 244 Chapter 15 Phakic Intraocular Lenses

plegic refractions should be performed to determine the contribution of accommodation. 15.3.5 IOL Sizing for Fixated Lenses

15.3.3 Correct sizing of the IOL is critical in determin- Anatomic Factors ing the proper vaulting angles for the anterior chamber angle-fixated and posterior chamber In anterior chamber lenses, the depth required sulcus-fixated lenses. For the anterior chamber to avoid endothelial contact depends in part on lenses, the white-to-white (W-to-W) measure- the power of the IOL, but in general requires at ment is used to estimate the diameter of the iri- least 3.2 mm as measured from the epithelium docorneal angle and the appropriate lens size is [26]. Posterior chamber phakic IOLs also re- subsequently chosen. As for the ICL posterior quire a sufficient anterior chamber depth of at chamber lens, the ciliary sulcus distance is ex- least 3.2 mm in order to allow for atraumatic in- trapolated from the white-to-white measure- sertion and manipulation of the IOL. The ante- ments. For myopic patients, 0.5 mm is added to rior chamber depth may be determined via the W-to-W length. With hyperopic correction, A-scan ultrasound or by the Orbscan II. A large the ICL length is the same as the W-to-W. By pupil may result in postoperative glare and contrast, sizing of the IOL is less of an issue for haloes, and yet many patients still find this the iris-fixated Artisan Lens and the Phakic Re- acceptable. fractive Lens, both of which do not require vaulting or angle fixation.

15.3.4 Pre-existing Ocular Pathology 15.3.6 IOL Calculations Implantation of phakic IOLs should be performed on healthy eyes without pre-existing The calculation of power in phakic IOLs is dif- ocular pathology. Thus a thorough slit lamp ex- ferent from that in cataract surgery. For phakic amination should be performed. Of particular IOLs, the lens manufacturers typically provide concern,patients with pre-existing cataract may nomograms with which to determine the ap- fare better with natural lens replacement or propriate power. These nomograms are based cataract surgery. Phakic IOLs, particularly ante- upon standard vertex conversion formulas. rior chamber lenses, may be associated with en- With cataract surgery, a refracting element – dothelial cell loss. Eyes with iris abnormalities, namely the crystalline lens – is removed, and such as iridocorneal endothelial syndrome,may thus the preoperative refraction does not direct- not have adequate angle support for anterior ly affect IOL calculations. By contrast, no re- chamber lenses [26]. A history of anterior fracting element is removed in phakic IOL im- uveitis is also a relative contraindication, as in- plantation. Hence, the power of the phakic IOL traocular surgery may reactivate quiescent dis- is simply determined from the patient’s refrac- ease. Any history of peripheral retinal patholo- tion and adjusted according to vertex conver- gy warrants a thorough dilated fundus exam sion formulas. Consequently, axial length is not and preoperative prophylactic laser treatment a variable in phakic IOL calculations. For ante- may be helpful [23]. Ancillary tests should in- rior chamber phakic lenses, the calculation of clude specular microscopy and pachymetry. power is based upon the Van der Heijde nomo- Furthermore, corneal topography should be gram. For the ICL posterior chamber lens, soft- obtained to identify keratoconus. ware supplied by the manufacturer will com- pute the IOL power at the ciliary sulcus plane. 15.4 Surgical Technique 245

15.3.7 15.4.1 Peripheral Iridectomy or Iridotomy Anterior Chamber Angle Fixated

Because of the potential to cause pupillary The size and location of the incision depends block and resultant angle closure, all phakic upon whether the lens is foldable or non-fold- IOLs require preoperative peripheral irido- able. The meridian of the incision is chosen so tomies or intraoperative iridectomies. Surgical as to minimise astigmatism. In repositioning iridectomy carries the risk of traumatic cataract these lenses, care must be taken to minimise or zonular dialysis in the phakic patient. The pupil ovalisation. manufacturers recommend that two iridotomies be placed superiorly 90º apart in the 15.4.1.1 event that part of the IOL occludes one of the Non-foldable Angle Fixated Lenses iridotomies. With non-foldable lenses, the incision may be Summary for the Clinician created via a corneal or corneoscleral approach Considerations in the evaluation and the size of the incision ranges from 5.5 to and planning: 6.0 mm depending upon the size of the IOL op- ∑ Assessment of the anterior chamber depth tic. Though a glide may facilitate insertion of is critical for both anterior and posterior the IOL into the angle, the glide itself may pose chamber lenses a potential hazard to the crystalline lens. The ∑ IOL sizing is critical for angle or sulcus lens is inserted into the anterior chamber with fixated lenses and may be estimated from forceps and repositioned with a Sinskey hook. white-to-white measurements The corneoscleral incision is then sutured and ∑ Nomograms for IOL power are determined the viscoelastic is removed. from the patient’s refraction and adjusted for vertex distance 15.4.1.2 ∑ Peripheral iridotomies are required Foldable Angle Fixated Lenses for all types of phakic IOLs The two types of“foldable”lenses,both of which have tripod haptics, require vastly different 15.4 techniques. The Vivarte lens may be folded and Surgical Technique inserted with forceps through a 3.2-mm incision. Because of its smaller size, the self-sealing Depending upon the surgeon’s familiarity with incision may be created in clear cornea or via a the technique, general, retrobulbar, peribulbar corneoscleral approach. The knee of the tripod or topical anaesthesia may be used. The anteri- haptic is inserted first and the trailing haptic is or chamber lenses require preoperative miosis, positioned with a Sinskey hook. The lens is then while the posterior chamber lenses require pre- repositioned with hooks via two paracentesis operative dilation. A viscoelastic is injected ports situated perpendicular to the main through a paracentesis port prior to the inser- wound. tion of the lens in order to form the anterior The Kelman Duet lens is not actually foldable chamber and to protect the endothelium and but consists of two separate components – the lens during manipulation of the IOL. optic and the haptic – that are sequentially inserted through a small incision and assembled in the anterior chamber. Two 1-mm clear corneal incisions are created at 3 and 9 o’clock and facilitate manipulation of the components. The haptic is first inserted with forceps through one of the incisions and repositioned in the an- 246 Chapter 15 Phakic Intraocular Lenses

gle. The optic is then injected into the anterior ing paracentesis ports are created on either side chamber. Two diametrically opposed tabs on of the main incision and allow for manipulation the optic are then fastened to corresponding of the ICL. The ICL is injected through a clear “snaps” on the haptic. cornea incision, which is approximately 3.0–3.2 mm. Once inside the anterior chamber, each footplate of the plate haptic is gently 15.4.2 tucked under the pupil using specially designed Anterior Chamber Iris Fixated spatulas that are inserted through the paracentesis ports. Care must be taken not to touch the Two opposing paracentesis ports are created on surface of the crystalline lens. When proper po- either side of the main incision and serve as en- sitioning is verified, the pupil is pharmacologi- try sites for enclavation of the iris to the lens. cally constricted with miotics. The angle of these incisions is therefore direct- ed downward towards the mid-peripheral iris rather than parallel to the iris as in cataract sur- 15.4.4 gery. The main incision may be corneal or cor- Posterior Chamber Phakic Refractive Lens neoscleral and varies between 5 and 6.5 mm depending on the size of the lens chosen. Using Although the design of the PRL differs from that long-angled forceps, the lens is then inserted of the ICL,the implantation procedure is practi- into the anterior chamber, taking care to avoid cally identical. Two opposing paracentesis ports the natural lens. With a Sinskey hook, the im- are created on either side of a 3.2-mm clear plant is then rotated into the horizontal position cornea incision. The lens may be inserted with for superior incisions or the vertical position for either specially designed forceps or with an in- horizontal incisions. While stabilising the lens jector. Like the ICL, the four corners of the plate with the Artisan implantation forceps (Ophtec), haptic style lens are then gently tucked under- a specifically designed enclavation needle (Op- neath the pupil with specially designed spatu- eraid) is then inserted through one paracentesis las.Unlike the ICL,the PRL does not require fix- site and used to draw a portion of mid-periph- ation within the ciliary sulcus. eral iris into one claw of the lens. A similar process is performed for the opposing claw while taking care to centre the optic over the 15.5 iris. If centration is poor or the pupil ovalisation Post-operative Course and Enhancements is excessive,the iris may be released with the enclavation needle and the lens may be reposi- The visual recovery with phakic IOL implanta- tioned. The main incision is then closed with tion is rapid. Intraocular inflammation is mini- sutures. Unlike the angle or sulcus fixated lens- mal compared to cataract extraction with pha- es, the iris-fixated lens may be centred over the coemulsification because no ultrasound energy pupil even if the pupil is not centred in relation is transmitted to the ocular structures. Unlike to the limbus [26]. the excimer laser procedures, there is no regression effect with phakic IOLs because corneal healing is not required. Patients with phakic 15.4.3 IOL implantation may desire a subsequent ex- Posterior Chamber Angle Fixated cimer laser enhancement procedure for residual spherical or astigmatic refractive error. Proper loading of the lens into the injection cartridge is a critical step in the implantation of the ICL. Because the ICL is manufactured with a predetermined vault, correct orientation within the cartridge is necessary and may be verified by positioning markers on the lens. Two oppos- 15.6 Results 247

The Artisan lens has remained unchanged 15.6 since 1991 and thus has the largest series of pa- Results tients available for evaluation. As demonstrated by Table 15.2, both the Artisan lens and the ICL There are several ways to evaluate the effective- lens have demonstrated remarkable results, ness and quality of vision following refractive with 20%–30% achieving an UCVA of 20/20 or surgery. The most common method is to evalu- better and 70%–80% achieving an UCVA of ate the percentage of patients achieving 20/40 20/40 of better. and 20/20 and the percentage that fall within Recently, Vukich compared data of 559 0.50 D and 1.00 D of emmetropia. Another LASIK eyes with 210 ICL eyes for the treatment method is to compare the mean preoperative of myopia in the range of 8–12 D [46, 56]. At spherical equivalent to the mean postoperative 1 year, the LASIK eyes achieved 20/20 UCVA in spherical equivalent.In addition,the efficacy in- 36% and 20/20 BCVA in 82% compared to 52% dex is defined as the ratio of the post-operative and 90% of the ICL eyes, respectively. Pre- UCVA to the pre-operative BCVA.Larger ratios dictability was within 0.5 D at 1 year in 57% of are the desired outcome. Loss of BCVA is a LASIK eyes and 69% of the ICL eyes. Further- measure of safety and may be reflected in the more,the LASIK eyes showed an average regres- safety index, which is the ratio of post-operative sion from –0.06 D at 1 week to –0.51 D at 1 year BCVA to pre-operative BCVA.More recently, the while the ICL group had no regression. Wave- emergence of aberrometers now allows for the front analysis of ten eyes in each group at least evaluation of the wavefront and quality of vi- 6 months post-operatively revealed coma of sion. 0.46 mm and spherical aberration of 0.39 mm in The results of the major clinical studies are the LASIK eyes compared to 0.22 and 0.13 mm, summarised in the following tables. Table 15.2 respectively, for ICL eyes. summarises the myopic results for the ICL,PRL, Artisan, NuVita, and the ZSAL-4. Likewise, Table 15.3 summarises the hyperopic results. 15.6.2 Hyperopic Results

15.6.1 As demonstrated by Table 15.3, correction of Myopic Results high hyperopia with phakic IOLs appears to be a relatively safe procedure with regards to loss Few long-term studies exist for phakic IOLs and of BCVA.An average of 7% of eyes lost one line a direct comparison of each different type is dif- of BCVA, and 1.8% lost two or more lines of ficult because of rapid changes in the lens de- BCVA. An average of 17% gained two or more signs. Furthermore, the range of refractive er- lines of BCVA. All the reported safety indices rors corrected varies from study to study, with were greater than one. Moreover the hyperopic some studies enrolling the more extreme refrac- phakic IOLs demonstrated very good pre- tive errors. This context must be considered dictability, with 70% of eyes falling within 0.5 D when evaluating the outcomes. In general, the of the targeted refraction and 93% of eyes results have been encouraging with regards to falling 1 D. In addition, the phakic IOLs pro- refractive outcomes, efficacy, and safety. As a duced relatively good results with respect to whole, the latest generation of phakic IOLs ap- UCVA. pears to be quite safe with regards to loss of BCVA.On average,5% of eyes lost one line of visual acuity, while <1% of eyes lost two or more lines of vision. About one-third of patients gained two or more lines of vision. 248 Chapter 15 Phakic Intraocular Lenses from [32]) from lines lines (%) (%) (%) more more Worst-Fechner and Worst. and Worst-Fechner d Efficacy Safety –22.75 –22.50 –29.00 –20.0 –19.25 –26.00 –28 –15.50 –28.00 up(months) (D) S.E. (D) fraction S.E. op (D) ±0.5 D ±1.0 D (%) (%) (%) [%] 1 line or or Concurrent limbal relaxing incisions to reduce corneal astigmatism; reduce to incisions relaxing limbal Concurrent ) follow- pre-op of re- post- op op 20/20 20/40 index loss of loss 2 gain 2 index c 7 7 –8.14 N.R. –0.13 N.R. N.R. N.R. N.R. 1.01 N.R. N.R. N.R. 1.43 n c [25] 22 7 –11.5 –6.87 to –1.19 32 45 18 68 N.R. 0 0 N.R. N.R. [36] 94 49 –14.73 –7 to –0.84 49 80 13 62 1.00 0 0 82 1.52 [38] 12 18 –16.00 –11.50 to –0.73 33 43 0 75 1.04 0 0 75 1.59 a b d ICM V2–V4; b Major case series involving implantation of implantation case series involving Major of courtesy correct myopia. a phakic to intraocular lens (Table J. Anthony Lombardo, MD, [reference] ( Menezo Alexander [1] 135 6 –12.66 –4.88 to –0.35 63 90 N.R. 83 N.R. 3.0 0.74 22 N.R. Gonvers Maloney [34]Maloney 155 6 –12.69 –5.50 to –0.54 55 90 26 83 N.R. 9.5 0 12 N.R. Uusitalo [55] 38 13 –15.10 –7.75 to –2.00 71 82 5.3 53 N.R. 6.3 0 41 N.R. Menezo Bleckmann [15]Arne [7] 58 6 –13.85 –8.00 to –1.22 N.R. –16.25 57 N.R. N.R. 0.84 5 0 40 1.46 [14] Lens author First Eyes Mean Mean Range Mean Post- Post- UCVA UCVA Efficacy BCVA BCVA BCVA Safety Artisan [16] Budo 249 36 –12.95 –5.0 to –0.6 57 79 34 77 1.03 2.0 1.2 43 1.31 PRL [28] Hoyos 17 12 –18.46 –11.85 to -0.22 53 82 N.R. N.R. 1.04 0 0 18 1.14 ICL Bloomenstein 65 24 –8.47 –3.00 to –0.31 75 92 52 92 N.R. 8 0 1.5 N.R. ICM V3 and V4; S.E., spherical equivalent; visual UCVA,uncorrected acuity; BCVA, best-corrected visual acuity; N.R., recorded. not Table 15.2. a 15.6 Results 249 lines lines (%) (%) Toric model. Toric e (%) more more Worst-Fechner and Worst; and Worst-Fechner d Efficacy Safety –12.00 –21.25 –0.50 83 100 6.3 85 1.03 0 0 33 1.25 –22.75 –28.00 up(months) (D) S.E. (D) fraction S.E. op (D) ±0.5 D ±1.0 D (%) (%) (%) [%] 1 line or or Concurrent limbal relaxing incisions to reduce corneal astigmatism; reduce to incisions relaxing limbal Concurrent ) follow- pre-op of re- post- op op 20/20 20/40 index loss of loss 2 gain 2 index c n [19] 45 6 – 8.90 –1.25 to ICM V2–V4; b e Continued [43] –23.25 –0.65 56 83 0 61 1.12 N.R. 0 N.R. 1.45 [20] [33]Malecaze 25 12 –10.19 –8.00 to –0.95 24 60 –19.38 N.R. 60 0.71 12 0 24 1.12 [reference] ( El Danasoury 43 12 –13.93 –9.50 to –0.64 42 65 21 88 N.R. 5 0 16 N.R. Landesz [30] 78Dick 11 – 17 –6.25 to –2 50 68 30 73 1.00 6.4 2.6 28 1.21 NuVita Allemann [5] 20 24 –18.95 –14.75 to –1.93 10 10 5 N.R. 0.68 0 0 65 1.67 ZSAL-4 Pérez-Santonja 23 24 –19.56 –16.75 to Lens author First Eyes Mean Mean Range Mean Post- Post- UCVA UCVA Efficacy BCVA BCVA BCVA Safety ICM V3 and V4; Table 15.2. a S.E., spherical equivalent; visual UCVA,uncorrected acuity; BCVA, best-corrected visual acuity; N.R., recorded. not 250 Chapter 15 Phakic Intraocular Lenses MD, [32]) from lines lines (%) (%) (%) more more Efficacy Safety Toric model. Toric b +5.62 +10.88 +11.00 +11.75 up(months) (D) S.E. (D) fraction S.E. op (D) ±0.5 D ±1.0 D (%) (%) (%) [%] 1 line or or ) follow- pre-op of re- post- op op 20/20 20/40 index loss of loss 2 gain 2 index n 7 8 +2.65 N.R. +0.30 N.R. N.R. N.R. N.R. 0.96 N.R. N.R. N.R. 1.05 a [19] 22 6 +3.25 +6.5 0 to -0.24 50 100 18 96 1.03 0 0 14 1.25 b Major case series involving implantation of implantation case series involving Major correct of a phakichyperopia. to intraocular lens courtesy (Table J. Anthony Lombardo, Bleckmann [reference] ( Rosen [49]Rosen 9 3 +4.26 +2.25 to +0.26 89 89 44 89 0.98 11 0 22 1.16 Sanders [51]Sanders 10 6 +6.63 +2.50 to +0.20 80 90 70 100 N.R. 0 0 20 1.13 [14] [15] [44]Pesando 15 12 +7.77 +4.75 to +0.02 69 92 +7.75 0 +0.06 80 46 N.R. 95 40 0 80 7.7 N.R. N.R. 25 N.R. 5 10 N.R. Dick Artisan Alió [4] 29 14 +6.06 +9 +3 to +0.10 79 97 7 66 0.83 3.4 0 28 1.11 Lens author First Eyes Mean Mean Range Mean Post- Post- UCVA UCVA Efficacy BCVA BCVA BCVA Safety PRL [28] Hoyos 14 12 +7.77 +5.25 to -0.38 50 79 N.R. N.R. 0.60 7.1 0 0 1.00 ICL 20 Bloomenstein 24 +5.55 to +3.00 Concurrent limbal relaxing incisions to reduce corneal astigmatism; reduce to incisions relaxing limbal Concurrent S.E., spherical equivalent; visual UCVA,uncorrected acuity; BCVA, best-corrected visual acuity; N.R., recorded. not Table 15.3. a 15.7 Complications 251

sult versus the gradual decline that results from 15.6.3 intermittent IOL contact and chronic low grade Toric Results inflammation.Most studies have concluded that the majority of endothelial cell loss has oc- One study describing the surgical outcomes of a curred at the time of surgery with only minimal toric phakic IOL was recently published [19]. A loss thereafter. The studies with the longest fol- total of 48 myopic eyes with a mean preopera- low-up of each of the lenses show a 12% loss at tive spherical equivalent of –8.90 ±4.52 and 22 4 years with the ICL [18], a 13% loss at 4 years hyperopic eyes with a mean preoperative spher- with the Artisan [37], and a 9% loss at 7 years ical equivalent of +3.25 ±1.98 D were implanted with the ZSAL-4 [2]. with the Artisan toric IOL. There was a signifi- The risk of cataract formation is greatest in cant reduction in spherical and cylindrical er- the posterior chamber lenses. Because of im- rors after surgery.The average magnitude of the provements in vaulting, the latest generation of refractive astigmatism was reduced from 3.7 D ICLs have been shown to have a reduced rate of pre-operatively to 0.7 D post-operatively. Pre- cataract formation [50]. The Artisan lens also dictability was excellent: all eyes were within carries a risk of anterior subcapsular cataracts 1.00 D of the targeted refraction and 72.9% were as well as anterior nuclear vacuoles associated within 0.5 D. with the trauma of insertion. Pupil ovalisation is primarily a risk of anteri- or chamber phakic IOLs,with reported rates be- 15.7 tween 16% and 40%. They are generally pro- Complications gressive in nature and may be due to chronic irritation of the phakic IOL footplates in the The complications that are unique to each type anterior chamber angle. A small percentage of of phakic IOL have been detailed in a previous eyes have ovalisation that is non-progressive in section. While the major concern in anterior nature and related to improper insertion. chamber lenses is endothelial cell loss, the criti- Because anterior chamber lenses require cal concern in posterior chamber lenses is smaller optic sizes that minimise the risk of cataract formation. Table 15.4 summarises the endothelial contact, they are associated with complications for each type of lens as reported the risk of glare and halos. In order to mini- by the major studies. In general, the complica- mise these symptoms, the ZSAL-4 and NuVita tion rates have shown continued improvement lenses have optic edge modifications. The 5-mm with each successive generation of lenses. model of the Artisan lens has a higher risk Endothelial cell loss rates have been accept- of symptoms, but Ophtec has offered a larger ably low with the latest generation of anterior 6-mm optic to reduce glare and halos. However, chamber lenses. It is important to distinguish this model is only available in powers up to endothelial cell loss from the initial surgical in- 15.5 D. 252 Chapter 15 Phakic Intraocular Lenses ardo, MD, from Worst-Fechner and Worst. and Worst-Fechner f 5 and 6 optic; mm e (%) 5 and 6 optic; mm (%) deposits (%) (%) d 2years 2 years 6 mo. 3 years at 6 mo. at 4 years 5 only; optic mm c (months) larity lens or rotation or (%) glaucoma (%) ) follow-up cell loss irregu- dispersion decentration glaucoma block (%) halos n ICM V3 and ICM V4; V3 and ICM ICM b [18] 4 years [1] 135 6 +0.3% at 1.5 0 0.74 0 0 1.5 3 a e [34] 155 6 +0.23% 1.2 N.R. N.R. 0 0 2.4 2.4 [25] 32 7 N.R. N.R. 88 N.R. 62 0 12.5 N.R. [37] 111 38 –13.42% at 0.9 N.R. 13.4 4.5 0 0 1.8 d b f [16] 249 36 –9.4% at 0.4 N.R. 8.8 N.R. 0.8 0.4 8.8 c Reported complications in major case series involving implantation of implantation case series involving in major complications Reported a phakic intraocular lens. of courtesy (Table J. Anthony Lomb Ruhswurm Uusitalo [55]Dejaco- 38 22 34 >24 N.R. –12.3% at N.R. N.R. N.R. N.R. 5.3 N.R. 0 N.R. N.R. 7.9 N.R. 7.9 N.R. N.R. Arne [7] 58 6 –2.0% at 0 100 N.R. 3.4 N.R. 3.4 54 Bloomenstein [15]Bloomenstein 85 24 N.R. 0 0 0 N.R. 1.2 21 0 Menezo [38]Menezo [51]Sanders [49]Rosen 12 10 18 6 9 3 N.R. N.R. 0 N.R. 0 42 N.R. 0 22 17 N.R. N.R. 0 0 N.R. 0 22 0 25 N.R. 0 N.R. 8.3 N.R. Alexander Menezo Maloney [reference] ( Landesz [31] 78 24 +6.1% at 0 N.R. N.R. N.R. 0 2.6 13 Gonvers PRLArtisan [28] Hoyos Budo 31 12 N.R. N.R. 3.2 18 N.R. 6.4 3.2 13 ICL [50] Sanders 523 17 N.R. N.R. N.R. N.R. N.R N.R. 2.9 N.R. Lens author First Eyes Mean Endothelial Pupil Pigment IOL Chronic Pupillary Cataract or Glare ICM V2-V4 and ICH V2–3; V2-V4 and ICH ICM Table 15.4. a [32]) 15.7 Complications 253 (%) (%) deposits (%) (%) 1year 1year 1 year 0 N.R. 2.2 N.R. N.R. N.R. 2.2 7years 6 months 0 1.4 1.4 0 0 0 5.7 2 years >15° rotation (months) larity lens or rotation or (%) glaucoma (%) ) follow-up cell loss irregu- dispersion decentration glaucoma block (%) halos n [3] 263 59, 72 –9.3% at 16 N.R. N.R. 7.2 0 3.4 10 g ZB5 M and ZSAL-4. g Continued Malecaze [33]Malecaze 25 12 –1.8% at N.R. N.R. N.R. 0 N.R. N.R. 52 [42]Alío [4] 29 12 –9.4% at 2 years 5.3 15.8 3.4 N.R. 0 N.R. 6.8 [43] 2 years Pérez-Santonja 30Pérez-Santonja 24N.R. at N.R. –17.6% N.R. N.R. N.R. N.R. N.R. Pérez-Santonja 18Pérez-Santonja 24 at 17 –4.2% 13 48 0 0 0 26 El Danasoury [20] 43 12 –0.7% at [reference] ( Dick [19] 70 6 –4.5% at ZSAL-4 Alió [2], Alió NuVita Allemann [5] 20 24 –14% at 40 N.R. 80% with 4.8 0 0 20 Lens author First Eyes Mean Endothelial Pupil Pigment IOL Chronic Pupillary Cataract or Glare Table 15.4. N.R., recorded. not 254 Chapter 15 Phakic Intraocular Lenses

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