Introduction
Different surgical techniques have been developed to treat high myopia but it remains a refractive challenge. Corneal procedures fall short of correcting high refractive errors because of low predictability, regression, deep ablation depth, smaller diameter ablation zones, poor quantitative and/or qualitative refractive results, iatrogenic corneal ectasia, and optical aberrations. Alternative surgical procedures that spare corneal tissue, such as clear lens extraction and phakic intraocular lens (PIOL) implantation, have been considered again after advances in technology and microsurgical techniques. Despite having excellent refractive results, clear lens extraction has been related to a high incidence of retinal detachment and loss of accommodation. To maintain predictability of lens surgery while avoiding loss of accommodation and minimizing vitreoretinal complications, implantation of PIOLs is a very attractive option. In addition, this corneal-spare refractive procedure preserves corneal asphericity, presents less reduction in contrast sensitivity, and usually results in potential gain in lines of vision if compared to keratorefractive surgeries. The gain in visual acuity is secondary to the magnification effect of myopic IOLs leading to an enlargement of the retinal image in these patients. Furthermore, these synthetic implant techniques are reversible, and corneal tissue–altering techniques are not. Implanting a PIOL in high myopic eyes has generated a renewed interest because it is one satisfactory surgical technique for correction of high refractive errors. Furthermore, a corneal refractive procedure may be added if there is any residual refractive error or if the patient develops more myopia in the long term.
The first PIOL, a minus power anterior chamber phakic intraocular lens (AC PIOL), was described by Strampelli shortly after the introduction of IOLs to correct aphakia in the early 1950s. Later, Barraquer published the first long-term series of high myopic patients who were implanted with an AC angle-fixated PIOL made of polymethylmethacrylate (PMMA). Both lenses were abandoned owing to high incidence of complications. PIOL implantation was reintroduced in 1986 by Fechner, van der Heijde, and Worst, who used a new biconcave iris-fixated IOL to correct high myopia based on modifications made in the iris-claw IOLs used in cataract surgery; by Baikoff and Joly, who modified the Kelman multiflex AC IOL used for aphakia; and by Fyodorov et al., who used a one-piece silicone collar button lens with 500 to 600 nm of Teflon coating implanted in the posterior chamber.
All of these models have undergone a series of design improvements to avoid complications related to corneal endothelium, iritis, and cataract formation.
Anterior Chamber IOLs
Historic Angle-Supported Models
The following lenses are no longer implanted. However, it is necessary to know the history and the complications associated with these models, as we still may find patients with these phakic IOLs implanted.
The main concerns with regard to long-term complications of AC PIOLs are related to glare, halos, pupil ovalization, pigment dispersion, and progressive loss of corneal endothelial cells.
Baikoff‘s Lens Models
Implantation of negative angle–supported AC PIOLs (ZB models, Chiron Domilens) was developed by Baikoff. There have been reports on progressive endothelial damage with consequent corneal decompensation secondary to intermittent contact with the thick edges of the first-generation angle-supported AC PIOLs. The haptic angulation was therefore lowered from 25 degrees to 20 degrees, the loops became more flexible, and the optic was thinned in the second-generation Baikoff ZB5M model (Bausch & Lomb/Chiron Vision), which was later named ZB5MF after adding a fluorine surface treatment to improve its biocompatibility. It was a single-piece, biconcave AC PIOL also based on a multiflex Kelman AC IOL. It was made of PMMA containing UV blocker, available in overall lengths of 12.5, 13.0, and 13.5 mm, and the optic was 5.0 mm in diameter with an effective optical diameter of 4.0 mm. It was available in 1-diopter (D) increments from −7.0 D to −20.0 D. Some preoperative parameters had to be considered before AC PIOL implantation. Patients had to have at least 2500 cells per mm 2 endothelial density and an anterior chamber depth of 3 mm or more.
In a series of 16 eyes with a follow-up of 1 year, Baikoff and Colin found little endothelial cell loss (4.2, 4.0, and 4.6%, at 3, 6, and 12 months, respectively) after ZB5M implantation. However, halos and glare were still reported; they seemed to be related to the small optic zone size of 4.0 mm combined with the physiologic eccentricity of the pupil. Pupillary ovalization could be discrete and stable, and sometimes reversing spontaneously, or progressive and irreversible, requiring additional surgery if goniosynechia did not allow iris contraction ( Fig. 32.1 ). Also, sporadic retinal detachment cases have been published related to ZB5M lenses. After including peripheral iridotomy in the surgical protocol, there was no more pupillary block glaucoma.
Alio et al. published a series of 263 eyes with a mean follow-up of 4.89 years (range 1.2 to 7.6 years) after implantation of different angle-supported AC PIOLs, including ZB5M, ZB5MF, and ZSAL-4 models. Only 10% of patients considered the night halos and glare significant at the 7-year follow-up. The authors also found acute postoperative anterior uveitis in 12 eyes (4.56%); increased intraocular pressure (IOP) in 19 cases (7.2%) with no correlation with pupil ovalization or acute anterior uveitis; retinal detachment in eight eyes (3%); and stabilization of endothelial cell loss over time after the second year (1.83% at 1 year, 1.37% at 2 years). Nonetheless, many patients were lost to follow-up, creating a significant bias for the conclusion about endothelial cell loss stabilization over time. Regarding significant pupil ovalization, defined as pupil border deviation reaching the edge of the optic, these authors noticed it to be present in 16 eyes (6.08%); two eyes required IOL explantation. Lesser degrees of variable ovalization were observed in another 27 eyes (10.3%). These authors postulated that the association of pupil ovalization, iris retraction, and atrophy might suggest the development of ischemic iridopathy and low-grade inflammation, possibly induced by haptic compression of the iris root vessels. In this series, 9 eyes (3.42%) required IOL explantation owing to cataract formation, which probably was age related. Surgery might increase the speed of cataract formation because of surgical trauma, postoperative inflammation, metabolic changes, and the use of postoperative topical steroids. However, other patients with high myopia and axial length greater than 30.0 mm did not develop a cataract, suggesting that surgery and AC PIOL were not the only factors involved in cataract development.
Baikoff et al. followed up on 134 eyes implanted with the ZB5M lens for 18 to 52 months (mean 35.8 months) and found endothelial cell loss of 3.3% at 6 months after surgery but declining by an additional 1% to 2% over the remaining follow-up. According to linear regression analysis, most of the observed reduction in endothelial cells over the course of the study was not from postoperative effects of the ZB5M model but was attributable to the acute effects of surgery. They also reported halos and glare in 27.8% of 133 eyes and iris retraction with pupillary ovalization in 22.6% of eyes. The latter increased in incidence over time. In this study, the lens was exchanged in 4 of 133 eyes (3.0%): rotation in two eyes, displacement in one eye, and because of a loop foot in the iridectomy in the fourth eye. It was removed in 3 of 133 eyes (2.3%): halos in one eye, and a flat anterior chamber with severe inflammation in two eyes. Late complications included implant rotation in six eyes (4.5%), and IOL displacement in two eyes (1.5%).
Based on this study, Baikoff created a third-generation lens to further reduce complications, the NuVita MA 20 model (Bausch & Lomb/Chiron Vision; Fig. 32.2 ).
Results published by Allemann et al. on 21 eyes implanted with the NuVita AC PIOL and followed up for 24 months showed pupil ovalization (difference between the smallest and largest diameters of at least 0.5 mm) in 40% of eyes (8 cases) in contrast to other series published, in which only severe cases of pupil ovalization were reported and IOL rotation of more than 15 degrees in 80% of eyes (16 cases). In 60% of eyes, IOL rotation occurred between the first and second year after surgery. A higher incidence of pupil ovalization was observed at 2-year follow-up ( Fig. 32.3 ). It seems to be related to improper position of footplates associated with an ischemic component ( Fig. 32.4 ).
ZSAL Models
Perez-Santonja et al. also developed a model (ZSAL) of angle-supported AC PIOL. The fourth-generation lens, the ZSAL-4 (Morcher GmbH), is a planoconcave lens made of single-piece PMMA and has Z-shaped haptics, like the NuVita. The optical zone diameter is 5.5 mm, with an effective optical zone diameter of 5.0 mm. The optic has a transitional edge with a three-sided design to reduce refracted glare. The overall length of the lens is 12.5 or 13.0 mm, and the lens power ranges from −6.0 D to −20.0 D in 1-D steps. Perez-Santonja et al. also confirmed the long-term endothelial tolerance for this lens. In addition, the rate of halos and glare was reduced compared to the angle-supported Baikoff models. However, this model did not prevent pupil ovalization, IOL rotation, or low-grade postoperative uveitis. A fifth-generation ZSAL-4/Plus lens (Morcher GmbH) was then designed, with larger effective (5.3-mm) and total (5.8-mm) optical zone diameters and a thinner connecting bridge between both footplates to increase flexibility and disperse compression forces against angle structures.
Phakic 6 IOL
Phakic 6 IOL (Ophthalmic Innovations International) is a planoconcave, angle-supported AC PIOL, which is made of PMMA and has a 6.0-mm optical zone diameter. This model was also associated with postoperative pupil ovalization and endothelial cell loss, however.
Foldable Lenses
Other angle-supported AC PIOL models have been designed targeting the important issue of decreasing incision size for implantation. Foldable IOLs include the Duet Kelman, the Acrysof foldable AC PIOL (later known as Cachet), and the Baikoff foldable AC PIOL (Vivarte model). Foldable IOLs are more prone to vault and cause intermittent endothelial touch. Therefore long-term endothelial cell density assessment is mandatory.
Duet Kelman Lens
In a pilot study, involving only three eyes followed for 6 months, the Duet Kelman lens (Tekia Inc.) has confirmed its potential to solve pupil ovalization by selective postoperative haptic exchange of the PIOL. The haptic and the optic of the lens are separately implanted and then fixed together inside the eye. The rigid PMMA haptic can be implanted through 2.5-mm incisions and the 6-mm silicone optic is then implanted using an injector through the same incision. The haptic size (12.0, 12.5, and 13.0 mm) is chosen based on the white-to-white measurement.
Acrysof Phakic Implant (Cachet, Alcon)
It had a 6-mm optic, implantable with an injector through a 3-mm incision. Preliminary results showed excellent tolerance and minimal induction of pupil ovalization. However, the lens was retired from the market owing to several cases of accelerated endothelial cell loss in 2013.
GBR Vivarte Lens
The GBR Vivarte lens (CibaVision-IOLTech), designed by Baikoff and launched in Europe in 2001, is an angle-supported, one-piece hydrophilic acrylic lens with tripodal rigid haptics and a foldable optic that can be inserted in a 3.2-mm incision ( Fig. 32.5 ). As reported at the 2002 AAO meeting, Orlando, 2002, Tanaka et al. found pupil ovalization greater than 0.5 mm in only 1 eye out of 11 eyes with a follow-up of only 6 months. Lens sizing is not very accurate, and complications associated with undersized and oversized lenses are lens rotation and iris tucking, respectively ( Fig. 32.6 ).
Historic Angle-Supported Models
The following lenses are no longer implanted. However, it is necessary to know the history and the complications associated with these models, as we still may find patients with these phakic IOLs implanted.
The main concerns with regard to long-term complications of AC PIOLs are related to glare, halos, pupil ovalization, pigment dispersion, and progressive loss of corneal endothelial cells.
Baikoff‘s Lens Models
Implantation of negative angle–supported AC PIOLs (ZB models, Chiron Domilens) was developed by Baikoff. There have been reports on progressive endothelial damage with consequent corneal decompensation secondary to intermittent contact with the thick edges of the first-generation angle-supported AC PIOLs. The haptic angulation was therefore lowered from 25 degrees to 20 degrees, the loops became more flexible, and the optic was thinned in the second-generation Baikoff ZB5M model (Bausch & Lomb/Chiron Vision), which was later named ZB5MF after adding a fluorine surface treatment to improve its biocompatibility. It was a single-piece, biconcave AC PIOL also based on a multiflex Kelman AC IOL. It was made of PMMA containing UV blocker, available in overall lengths of 12.5, 13.0, and 13.5 mm, and the optic was 5.0 mm in diameter with an effective optical diameter of 4.0 mm. It was available in 1-diopter (D) increments from −7.0 D to −20.0 D. Some preoperative parameters had to be considered before AC PIOL implantation. Patients had to have at least 2500 cells per mm 2 endothelial density and an anterior chamber depth of 3 mm or more.
In a series of 16 eyes with a follow-up of 1 year, Baikoff and Colin found little endothelial cell loss (4.2, 4.0, and 4.6%, at 3, 6, and 12 months, respectively) after ZB5M implantation. However, halos and glare were still reported; they seemed to be related to the small optic zone size of 4.0 mm combined with the physiologic eccentricity of the pupil. Pupillary ovalization could be discrete and stable, and sometimes reversing spontaneously, or progressive and irreversible, requiring additional surgery if goniosynechia did not allow iris contraction ( Fig. 32.1 ). Also, sporadic retinal detachment cases have been published related to ZB5M lenses. After including peripheral iridotomy in the surgical protocol, there was no more pupillary block glaucoma.
Alio et al. published a series of 263 eyes with a mean follow-up of 4.89 years (range 1.2 to 7.6 years) after implantation of different angle-supported AC PIOLs, including ZB5M, ZB5MF, and ZSAL-4 models. Only 10% of patients considered the night halos and glare significant at the 7-year follow-up. The authors also found acute postoperative anterior uveitis in 12 eyes (4.56%); increased intraocular pressure (IOP) in 19 cases (7.2%) with no correlation with pupil ovalization or acute anterior uveitis; retinal detachment in eight eyes (3%); and stabilization of endothelial cell loss over time after the second year (1.83% at 1 year, 1.37% at 2 years). Nonetheless, many patients were lost to follow-up, creating a significant bias for the conclusion about endothelial cell loss stabilization over time. Regarding significant pupil ovalization, defined as pupil border deviation reaching the edge of the optic, these authors noticed it to be present in 16 eyes (6.08%); two eyes required IOL explantation. Lesser degrees of variable ovalization were observed in another 27 eyes (10.3%). These authors postulated that the association of pupil ovalization, iris retraction, and atrophy might suggest the development of ischemic iridopathy and low-grade inflammation, possibly induced by haptic compression of the iris root vessels. In this series, 9 eyes (3.42%) required IOL explantation owing to cataract formation, which probably was age related. Surgery might increase the speed of cataract formation because of surgical trauma, postoperative inflammation, metabolic changes, and the use of postoperative topical steroids. However, other patients with high myopia and axial length greater than 30.0 mm did not develop a cataract, suggesting that surgery and AC PIOL were not the only factors involved in cataract development.
Baikoff et al. followed up on 134 eyes implanted with the ZB5M lens for 18 to 52 months (mean 35.8 months) and found endothelial cell loss of 3.3% at 6 months after surgery but declining by an additional 1% to 2% over the remaining follow-up. According to linear regression analysis, most of the observed reduction in endothelial cells over the course of the study was not from postoperative effects of the ZB5M model but was attributable to the acute effects of surgery. They also reported halos and glare in 27.8% of 133 eyes and iris retraction with pupillary ovalization in 22.6% of eyes. The latter increased in incidence over time. In this study, the lens was exchanged in 4 of 133 eyes (3.0%): rotation in two eyes, displacement in one eye, and because of a loop foot in the iridectomy in the fourth eye. It was removed in 3 of 133 eyes (2.3%): halos in one eye, and a flat anterior chamber with severe inflammation in two eyes. Late complications included implant rotation in six eyes (4.5%), and IOL displacement in two eyes (1.5%).
Based on this study, Baikoff created a third-generation lens to further reduce complications, the NuVita MA 20 model (Bausch & Lomb/Chiron Vision; Fig. 32.2 ).
Results published by Allemann et al. on 21 eyes implanted with the NuVita AC PIOL and followed up for 24 months showed pupil ovalization (difference between the smallest and largest diameters of at least 0.5 mm) in 40% of eyes (8 cases) in contrast to other series published, in which only severe cases of pupil ovalization were reported and IOL rotation of more than 15 degrees in 80% of eyes (16 cases). In 60% of eyes, IOL rotation occurred between the first and second year after surgery. A higher incidence of pupil ovalization was observed at 2-year follow-up ( Fig. 32.3 ). It seems to be related to improper position of footplates associated with an ischemic component ( Fig. 32.4 ).
ZSAL Models
Perez-Santonja et al. also developed a model (ZSAL) of angle-supported AC PIOL. The fourth-generation lens, the ZSAL-4 (Morcher GmbH), is a planoconcave lens made of single-piece PMMA and has Z-shaped haptics, like the NuVita. The optical zone diameter is 5.5 mm, with an effective optical zone diameter of 5.0 mm. The optic has a transitional edge with a three-sided design to reduce refracted glare. The overall length of the lens is 12.5 or 13.0 mm, and the lens power ranges from −6.0 D to −20.0 D in 1-D steps. Perez-Santonja et al. also confirmed the long-term endothelial tolerance for this lens. In addition, the rate of halos and glare was reduced compared to the angle-supported Baikoff models. However, this model did not prevent pupil ovalization, IOL rotation, or low-grade postoperative uveitis. A fifth-generation ZSAL-4/Plus lens (Morcher GmbH) was then designed, with larger effective (5.3-mm) and total (5.8-mm) optical zone diameters and a thinner connecting bridge between both footplates to increase flexibility and disperse compression forces against angle structures.
Phakic 6 IOL
Phakic 6 IOL (Ophthalmic Innovations International) is a planoconcave, angle-supported AC PIOL, which is made of PMMA and has a 6.0-mm optical zone diameter. This model was also associated with postoperative pupil ovalization and endothelial cell loss, however.
Foldable Lenses
Other angle-supported AC PIOL models have been designed targeting the important issue of decreasing incision size for implantation. Foldable IOLs include the Duet Kelman, the Acrysof foldable AC PIOL (later known as Cachet), and the Baikoff foldable AC PIOL (Vivarte model). Foldable IOLs are more prone to vault and cause intermittent endothelial touch. Therefore long-term endothelial cell density assessment is mandatory.
Duet Kelman Lens
In a pilot study, involving only three eyes followed for 6 months, the Duet Kelman lens (Tekia Inc.) has confirmed its potential to solve pupil ovalization by selective postoperative haptic exchange of the PIOL. The haptic and the optic of the lens are separately implanted and then fixed together inside the eye. The rigid PMMA haptic can be implanted through 2.5-mm incisions and the 6-mm silicone optic is then implanted using an injector through the same incision. The haptic size (12.0, 12.5, and 13.0 mm) is chosen based on the white-to-white measurement.
Acrysof Phakic Implant (Cachet, Alcon)
It had a 6-mm optic, implantable with an injector through a 3-mm incision. Preliminary results showed excellent tolerance and minimal induction of pupil ovalization. However, the lens was retired from the market owing to several cases of accelerated endothelial cell loss in 2013.
GBR Vivarte Lens
The GBR Vivarte lens (CibaVision-IOLTech), designed by Baikoff and launched in Europe in 2001, is an angle-supported, one-piece hydrophilic acrylic lens with tripodal rigid haptics and a foldable optic that can be inserted in a 3.2-mm incision ( Fig. 32.5 ). As reported at the 2002 AAO meeting, Orlando, 2002, Tanaka et al. found pupil ovalization greater than 0.5 mm in only 1 eye out of 11 eyes with a follow-up of only 6 months. Lens sizing is not very accurate, and complications associated with undersized and oversized lenses are lens rotation and iris tucking, respectively ( Fig. 32.6 ).
Baikoff‘s Lens Models
Implantation of negative angle–supported AC PIOLs (ZB models, Chiron Domilens) was developed by Baikoff. There have been reports on progressive endothelial damage with consequent corneal decompensation secondary to intermittent contact with the thick edges of the first-generation angle-supported AC PIOLs. The haptic angulation was therefore lowered from 25 degrees to 20 degrees, the loops became more flexible, and the optic was thinned in the second-generation Baikoff ZB5M model (Bausch & Lomb/Chiron Vision), which was later named ZB5MF after adding a fluorine surface treatment to improve its biocompatibility. It was a single-piece, biconcave AC PIOL also based on a multiflex Kelman AC IOL. It was made of PMMA containing UV blocker, available in overall lengths of 12.5, 13.0, and 13.5 mm, and the optic was 5.0 mm in diameter with an effective optical diameter of 4.0 mm. It was available in 1-diopter (D) increments from −7.0 D to −20.0 D. Some preoperative parameters had to be considered before AC PIOL implantation. Patients had to have at least 2500 cells per mm 2 endothelial density and an anterior chamber depth of 3 mm or more.
In a series of 16 eyes with a follow-up of 1 year, Baikoff and Colin found little endothelial cell loss (4.2, 4.0, and 4.6%, at 3, 6, and 12 months, respectively) after ZB5M implantation. However, halos and glare were still reported; they seemed to be related to the small optic zone size of 4.0 mm combined with the physiologic eccentricity of the pupil. Pupillary ovalization could be discrete and stable, and sometimes reversing spontaneously, or progressive and irreversible, requiring additional surgery if goniosynechia did not allow iris contraction ( Fig. 32.1 ). Also, sporadic retinal detachment cases have been published related to ZB5M lenses. After including peripheral iridotomy in the surgical protocol, there was no more pupillary block glaucoma.
Alio et al. published a series of 263 eyes with a mean follow-up of 4.89 years (range 1.2 to 7.6 years) after implantation of different angle-supported AC PIOLs, including ZB5M, ZB5MF, and ZSAL-4 models. Only 10% of patients considered the night halos and glare significant at the 7-year follow-up. The authors also found acute postoperative anterior uveitis in 12 eyes (4.56%); increased intraocular pressure (IOP) in 19 cases (7.2%) with no correlation with pupil ovalization or acute anterior uveitis; retinal detachment in eight eyes (3%); and stabilization of endothelial cell loss over time after the second year (1.83% at 1 year, 1.37% at 2 years). Nonetheless, many patients were lost to follow-up, creating a significant bias for the conclusion about endothelial cell loss stabilization over time. Regarding significant pupil ovalization, defined as pupil border deviation reaching the edge of the optic, these authors noticed it to be present in 16 eyes (6.08%); two eyes required IOL explantation. Lesser degrees of variable ovalization were observed in another 27 eyes (10.3%). These authors postulated that the association of pupil ovalization, iris retraction, and atrophy might suggest the development of ischemic iridopathy and low-grade inflammation, possibly induced by haptic compression of the iris root vessels. In this series, 9 eyes (3.42%) required IOL explantation owing to cataract formation, which probably was age related. Surgery might increase the speed of cataract formation because of surgical trauma, postoperative inflammation, metabolic changes, and the use of postoperative topical steroids. However, other patients with high myopia and axial length greater than 30.0 mm did not develop a cataract, suggesting that surgery and AC PIOL were not the only factors involved in cataract development.
Baikoff et al. followed up on 134 eyes implanted with the ZB5M lens for 18 to 52 months (mean 35.8 months) and found endothelial cell loss of 3.3% at 6 months after surgery but declining by an additional 1% to 2% over the remaining follow-up. According to linear regression analysis, most of the observed reduction in endothelial cells over the course of the study was not from postoperative effects of the ZB5M model but was attributable to the acute effects of surgery. They also reported halos and glare in 27.8% of 133 eyes and iris retraction with pupillary ovalization in 22.6% of eyes. The latter increased in incidence over time. In this study, the lens was exchanged in 4 of 133 eyes (3.0%): rotation in two eyes, displacement in one eye, and because of a loop foot in the iridectomy in the fourth eye. It was removed in 3 of 133 eyes (2.3%): halos in one eye, and a flat anterior chamber with severe inflammation in two eyes. Late complications included implant rotation in six eyes (4.5%), and IOL displacement in two eyes (1.5%).
Based on this study, Baikoff created a third-generation lens to further reduce complications, the NuVita MA 20 model (Bausch & Lomb/Chiron Vision; Fig. 32.2 ).
Results published by Allemann et al. on 21 eyes implanted with the NuVita AC PIOL and followed up for 24 months showed pupil ovalization (difference between the smallest and largest diameters of at least 0.5 mm) in 40% of eyes (8 cases) in contrast to other series published, in which only severe cases of pupil ovalization were reported and IOL rotation of more than 15 degrees in 80% of eyes (16 cases). In 60% of eyes, IOL rotation occurred between the first and second year after surgery. A higher incidence of pupil ovalization was observed at 2-year follow-up ( Fig. 32.3 ). It seems to be related to improper position of footplates associated with an ischemic component ( Fig. 32.4 ).
