Associated Features
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Early models of phakic IOLs were made of rigid polymethyl methacrylate (PMMA). Newer lenses are foldable, requiring a smaller incision and providing a faster visual recovery.
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Complications are IOL specific and include over- and undercorrection, glare and halos, endothelial cell loss, glaucoma, pigment dispersion, and cataract formation.
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Surgical peripheral iridectomy or preoperative YAG laser iridectomies are necessary to avoid postoperative pupillary-block glaucoma in most IOL models.
Introduction
If high ametropia occurs, laser corneal refractive surgery (photorefractive keratectomy [PRK] and laser-assisted in situ keratomileusis [LASIK]) is limited by decreased safety, predictability, and efficacy of postoperative results. Now a growing interest exists in the use of phakic intraocular lenses (IOLs) to correct these refractive errors. Phakic IOL implantation has the advantage of preserving the architecture of the cornea. Additionally, it may provide more predictable refractive results and better visual quality than surgical techniques that manipulate the corneal curvature.
History of Phakic Lenses
Clear lens extraction for the correction of myopia was a concept introduced in the early 1800s, becoming increasingly popular from 1850 to 1900. After the discovery of sterilization in 1889, a rush for myopia correction by clear lens extraction was started by Fukala in Austria/Germany (“Fukala surgery”) and Vacher in France. It was not until the end of the nineteenth century, however, that complications of this operation (e.g., retinal detachment and choroidal hemorrhage) began to be reported, and the technique largely fell out of favor.
In the 1950s, an emergence of the idea of correcting myopia by inserting a concave lens into the phakic eye was seen. At this time, Strampelli, Barraquer, and Choyce experimented with anterior chamber (AC) angle-fixed lenses, which they eventually abandoned because of corneal edema, chronic iritis with pupil ovalization, and iris atrophy. In the 1980s and 1990s several PMMA angle-supported AC phakic IOLs were introduced, but subsequently discontinued due to the same complications. The most important were the Baikoff lens, ZB and ZB5M models ( Fig. 3.7.1 ), which were based on the multiflex Kelman anterior chamber IOL and the ZSAL-4 (Morcher GmbH, Stuttgart, Germany). The ZB5M was later modified to implement thinner optics, greater effective optic diameter, flatter anterior face, and improved loop profile to reduce angle trauma. It was called NuVita MA20 (Bausch & Lomb, Rochester, NY) (see Fig. 3.7.1 ).
The first iris-fixated lenses were sutured to the iris stroma. The claw fixation method rendered iris stitching unnecessary. Worst introduced his final conceptual model of the midperipheral fixation iris-claw lens for secondary lens implantation. For many years, the iris-claw lens was used as a primary implant after intracapsular and extracapsular cataract extraction because of good tolerance and refractive results; it is still used today as a standby lens in cases of posterior capsule rupture. In 1986 Worst and Fechner modified this IOL to a biconcave AC lens for the correction of myopia. To increase the safety of this IOL and minimize the possibility of IOL–cornea contact, the biconcave design was changed in 1991 to a convex–concave model with a lower shoulder, a thinner periphery, and a larger optic diameter ( Fig. 3.7.2 ). This lens was called the Worst myopia claw lens. The name of the lens then was changed to the Artisan–Worst lens (Ophtec BV, Groningen, Netherlands) and Artisan–Verisyse lens (Abbott Medical Optics, Inc., Abbott Park, IL).
In the mid-1980s, the implantation of posterior chamber IOLs in phakic eyes was reported by Fyodorov. The original lens design was a “collar-button” type, with the optic located in the anterior chamber and the haptics behind the iris plane. The design, modified by Chiron-Adatomed to produce a silicone elastomer posterior chamber lens, was reported to have a high incidence of cataract formation. Further modification, the phakic refractive lens (PRL) (Ioltech/CIBA Vision, La Rochelle, France) ( Fig. 3.7.3 ), had a greater vaulting, decreasing the incidence of cataract but causing zonular lesions. Currently, the implantable collamer lens (ICL) (STAAR Surgical Co., Monrovia, CA) is the only posterior chamber phakic IOL available ( Fig. 3.7.4 ).
Indications of Phakic Lenses
Regardless of the type of phakic IOL, careful patient selection is critical for successful outcomes. General criteria should be followed ( Box 3.7.1 ).
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Age >21 years
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Stable refraction (less than 0.50 D change) for 1 year
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Clear crystalline lens
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Ametropia not suitable/appropriate for excimer laser surgery
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Unsatisfactory vision with/intolerance of contact lenses or spectacles
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Functional and occupational requirements
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Anterior chamber depth (measured from endothelium) *
* Güell JL, Morral M, Kook D, Kohnen T. J Cataract Refract Surg. 2010;36:1976–93.
Artisan–Verisyse / Artiflex–Veriflex: ≥2.7 mm
ICL: ≥2.8 mm for myopia, ≥3.0 mm for hyperopia
- •
A minimum endothelial cell density of:
≥3000 cells/mm 2 at 21 years of age
≥2600 cells/mm 2 at 31 years of age
≥2200 cells/mm 2 at 41 years of age
≥2000 cells/mm 2 at 45 years of age or more
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No ocular pathology (corneal disorders, iris or pupil anomaly, glaucoma, uveitis, maculopathy, etc.)
Moderate and High Myopia
Patients who are poor candidates for laser correction may be candidates for phakic IOL. Food and Drug Administration (FDA)–approved excimer lasers can treat myopia of up to −12.00 diopters (D). However, the higher the intended correction, the thinner and flatter the cornea will be postoperatively. For LASIK surgery, one must preserve a safe residual corneal stromal bed of at least 250 µm. A more conservative value would be 300 µm and a percentage of tissue altered (PTA) no more than 40%. There is a limit to the amount of central flattening one can induce in the cornea, which is usually around 35.00 to 36.00 D (final keratometry). Beyond these limits, there is an increased risk of developing corneal ectasia due to thin residual stromal bed and loss of visual quality and night vision problems due to excessive corneal flattening. It was shown that LASIK also induces significant spherical and coma aberrations compared with phakic IOLs for high myopia. Because of these risks, a current trend exists toward reducing the upper limits of LASIK and PRK to around −8.00 to −10.00 D. Above these limits, and in cases of keratoconus or keratoconus-suspect, or the cornea is too thin or too flat for laser surgery, phakic IOLs become the major alternative.
Most phakic IOLs for myopia can correct up to around −20.00 D ( Table 3.7.1 ). In 2004 the FDA approved the first phakic IOL designed to correct high myopia. The Verisyse (AMO/Ophtec, USA Inc.), also known as Artisan–Worst iris-claw lens, was approved for myopia ranging from −5.00 to −20.00 D with astigmatism less than or equal to 2.50 D. In 2005 a second phakic IOL was approved by the FDA. The Visian ICL was approved for myopia ranging from −3.00 to −20.00 D with astigmatism less than or equal to 2.50 D.
| Type of Lens | Name/Model | Power Range (D) | Optic Size (mm) | Length (mm) | Incision Size (mm) | Material | Manufacturer |
|---|---|---|---|---|---|---|---|
| AC Angle-Supported | Kelman Duet (two parts) | −8.00 to −20.00 | 5.5 | 12.5–13.5 (0.5 steps) | 2.0 (foldable) | Silicone optic PMMA haptic | TEKIA |
| Acrysof Cachet | −6.00 to −16.5 | 6.0 | 12.5–14.0 (0.5 steps) | 2.0 (foldable) | Hydrophobic Acrylic | Alcon | |
| AC Iris-Fixated | Artisan 202 Pediatric | −3.00 to −23.5 | 5.0 | 7.5 | 5.2 | PMMA | Ophtec/Abbott |
| Artisan 203 Hyperopia | +1.00 to +12.00 | 5.0 | 8.5 | 5.2 | PMMA | Ophtec/Abbott | |
| Artisan Toric | +6.5 to −23.00 Cyl +1.00 to +7.5 | 5.0 | 8.5 | 5.2 | PMMA | Ophtec/Abbott | |
| Artisan 204 Myopia | −1 to −15.5 | 6.0 | 8.5 | 6.2 | PMMA | Ophtec/Abbott | |
| Artisan 206 Myopia | −1.00 to −23.5 | 5.0 | 8.5 | 5.2 | PMMA | Ophtec/Abbott | |
| Artiflex/Veriflex | −2.00 to −14.5 | 6.0 | 8.5 | 3.2 (foldable) | Polysiloxane optic PMMA haptics | Ophtec/Abbott | |
| Artiflex/Veriflex Toric | −1.00 to −13.5 Cyl +1.00 to +5.00 | 6.0 | 8.5 | 3.2 (foldable) | Polysiloxane optic PMMA haptics | Ophtec/Abbott | |
| PC Sulcus-Supported | ICL | −23.00 to + 22.00 Cyl + 1.00 to + 6.00 | 4.65–5.5 | 11.0–13.0 (0.5 steps) | 3.0 (foldable) | Collamer | STAAR |
High Hyperopia
The upper limits for hyperopic laser surgery are around +5.00 to +6.00 D. Higher attempted corrections can cause excessive steepening of the cornea (above 50.00 D), usually with a small optical treatment zone, leading to induced aberrations, especially spherical and coma aberrations and degradation of optical quality. Phakic IOLs may be indicated for the correction of hyperopia up to +22.00 D (see Table 3.7.1 ). In many cases, however, these eyes have insufficient AC depth, limiting its implantation. For hyperopia, refractive lens exchange (refractive lensectomy) with IOL implantation is the main alternative for laser surgery in the presbyopic age group.
High Astigmatism
LASIK is the treatment of choice for astigmatism of up to around 5.00–7.00 D. One may consider implanting toric phakic IOLs in cases of high degrees of astigmatism whether associated with myopia or hyperopia (see Table 3.7.1 ). Both spherical and cylindrical corrections can be combined in these lenses, which aims to correct the total refractive error, but to date, only spherical corrections are FDA approved. The sum of minus sphere and cylinder cannot exceed −14.50 D with Artiflex toric and −23.00 D with Artisan toric.
With irregular astigmatism or if toric models are not available, astigmatism can be reduced with relaxing procedures such as limbal relaxing incisions, arcuate keratotomy, intrastromal rings ( Fig. 3.7.5 ), and with toric pseudophakic IOLs in cases where the crystalline lens is opaque. LASIK or PRK could be performed after phakic IOLs to correct residual ametropia (myopia, hyperopia, and/or astigmatism), also called bioptics (discussed later in the chapter).
Moderate and High Myopia
Patients who are poor candidates for laser correction may be candidates for phakic IOL. Food and Drug Administration (FDA)–approved excimer lasers can treat myopia of up to −12.00 diopters (D). However, the higher the intended correction, the thinner and flatter the cornea will be postoperatively. For LASIK surgery, one must preserve a safe residual corneal stromal bed of at least 250 µm. A more conservative value would be 300 µm and a percentage of tissue altered (PTA) no more than 40%. There is a limit to the amount of central flattening one can induce in the cornea, which is usually around 35.00 to 36.00 D (final keratometry). Beyond these limits, there is an increased risk of developing corneal ectasia due to thin residual stromal bed and loss of visual quality and night vision problems due to excessive corneal flattening. It was shown that LASIK also induces significant spherical and coma aberrations compared with phakic IOLs for high myopia. Because of these risks, a current trend exists toward reducing the upper limits of LASIK and PRK to around −8.00 to −10.00 D. Above these limits, and in cases of keratoconus or keratoconus-suspect, or the cornea is too thin or too flat for laser surgery, phakic IOLs become the major alternative.
Most phakic IOLs for myopia can correct up to around −20.00 D ( Table 3.7.1 ). In 2004 the FDA approved the first phakic IOL designed to correct high myopia. The Verisyse (AMO/Ophtec, USA Inc.), also known as Artisan–Worst iris-claw lens, was approved for myopia ranging from −5.00 to −20.00 D with astigmatism less than or equal to 2.50 D. In 2005 a second phakic IOL was approved by the FDA. The Visian ICL was approved for myopia ranging from −3.00 to −20.00 D with astigmatism less than or equal to 2.50 D.
| Type of Lens | Name/Model | Power Range (D) | Optic Size (mm) | Length (mm) | Incision Size (mm) | Material | Manufacturer |
|---|---|---|---|---|---|---|---|
| AC Angle-Supported | Kelman Duet (two parts) | −8.00 to −20.00 | 5.5 | 12.5–13.5 (0.5 steps) | 2.0 (foldable) | Silicone optic PMMA haptic | TEKIA |
| Acrysof Cachet | −6.00 to −16.5 | 6.0 | 12.5–14.0 (0.5 steps) | 2.0 (foldable) | Hydrophobic Acrylic | Alcon | |
| AC Iris-Fixated | Artisan 202 Pediatric | −3.00 to −23.5 | 5.0 | 7.5 | 5.2 | PMMA | Ophtec/Abbott |
| Artisan 203 Hyperopia | +1.00 to +12.00 | 5.0 | 8.5 | 5.2 | PMMA | Ophtec/Abbott | |
| Artisan Toric | +6.5 to −23.00 Cyl +1.00 to +7.5 | 5.0 | 8.5 | 5.2 | PMMA | Ophtec/Abbott | |
| Artisan 204 Myopia | −1 to −15.5 | 6.0 | 8.5 | 6.2 | PMMA | Ophtec/Abbott | |
| Artisan 206 Myopia | −1.00 to −23.5 | 5.0 | 8.5 | 5.2 | PMMA | Ophtec/Abbott | |
| Artiflex/Veriflex | −2.00 to −14.5 | 6.0 | 8.5 | 3.2 (foldable) | Polysiloxane optic PMMA haptics | Ophtec/Abbott | |
| Artiflex/Veriflex Toric | −1.00 to −13.5 Cyl +1.00 to +5.00 | 6.0 | 8.5 | 3.2 (foldable) | Polysiloxane optic PMMA haptics | Ophtec/Abbott | |
| PC Sulcus-Supported | ICL | −23.00 to + 22.00 Cyl + 1.00 to + 6.00 | 4.65–5.5 | 11.0–13.0 (0.5 steps) | 3.0 (foldable) | Collamer | STAAR |
High Hyperopia
The upper limits for hyperopic laser surgery are around +5.00 to +6.00 D. Higher attempted corrections can cause excessive steepening of the cornea (above 50.00 D), usually with a small optical treatment zone, leading to induced aberrations, especially spherical and coma aberrations and degradation of optical quality. Phakic IOLs may be indicated for the correction of hyperopia up to +22.00 D (see Table 3.7.1 ). In many cases, however, these eyes have insufficient AC depth, limiting its implantation. For hyperopia, refractive lens exchange (refractive lensectomy) with IOL implantation is the main alternative for laser surgery in the presbyopic age group.
High Astigmatism
LASIK is the treatment of choice for astigmatism of up to around 5.00–7.00 D. One may consider implanting toric phakic IOLs in cases of high degrees of astigmatism whether associated with myopia or hyperopia (see Table 3.7.1 ). Both spherical and cylindrical corrections can be combined in these lenses, which aims to correct the total refractive error, but to date, only spherical corrections are FDA approved. The sum of minus sphere and cylinder cannot exceed −14.50 D with Artiflex toric and −23.00 D with Artisan toric.
With irregular astigmatism or if toric models are not available, astigmatism can be reduced with relaxing procedures such as limbal relaxing incisions, arcuate keratotomy, intrastromal rings ( Fig. 3.7.5 ), and with toric pseudophakic IOLs in cases where the crystalline lens is opaque. LASIK or PRK could be performed after phakic IOLs to correct residual ametropia (myopia, hyperopia, and/or astigmatism), also called bioptics (discussed later in the chapter).
Advantages and Disadvantages of Phakic Iols
For the advantages and disadvantages of phakic IOLs, see Table 3.7.2 .
| Advantages | Disadvantages |
|---|---|
|
|
Intraocular Lens Power Calculation
Van der Heijde proposed the theoretical basis for IOL power calculations based on studies of patients implanted with a Worst and Fechner lens, which are directly applicable to other phakic IOLs. The power calculation is independent of the axial length of the eye. Instead it depends on: (1) central corneal curvature (power)−keratometry (K); (2) AC depth; and (3) patient refraction (preoperative spherical equivalent). With current IOL formulas and nomograms great accuracy occurs on IOL power calculations.
Sizing the Phakic IOLs
The eye’s anterior segment anatomy differs significantly among individuals, affecting the indications of phakic IOLs in different refractive errors. Most of the complications of these lenses are related to inappropriate sizing and inaccurate measurements of the AC dimensions.
For the iris-fixated phakic IOLs (i.e., Artisan and Artiflex), sizing is not an issue because these IOLs are fixated to the midperipheral iris, not the angle or sulcus, having the advantage of being one-size-fits-all length (8.5 mm).
For the sulcus-supported phakic IOLs (i.e., implantable collamer lens), different sizes of overall length are manufactured to suit normal variations in intraocular anatomy (e.g., 12.1, 12.6, 13.2, and 13.7 mm). The relationship of the selected overall diameter of the implanted lens to the dimensions of the posterior chamber represents an important determinant of the achieved postoperative vault, which is the term used to describe the measurable distance between the anterior capsule of the crystalline lens and the posterior surface of the ICL ( Fig. 3.7.6 ).
The white-to-white (WTW) diameter (external measurement from limbus to limbus) is the most important factor in determining the ICL size. It provides an approximate estimation of the AC (angle-to-angle [ATA]) and sulcus-to-sulcus (STS) diameters. The WTW is usually measured with the IOLMaster or the Lenstar biometers and checked with manual calipers between the 3 and 9 o’clock meridians. Alternative methods include tomographers such as the Galilei (Ziemer), Pentacam (Oculus), and the Orbscan IIz (Bausch & Lomb). Most studies have used the WTW measurement plus 0.5 mm, rounded to the nearest 0.5 mm increment.
The WTW measurement, however, is well known to suffer from significant inaccuracies. In a study comparing vertical and horizontal WTW measurements with direct anatomical measurements (postfixation) in postmortem eyes, there was no correlation between the horizontal WTW distance and the AC angle diameter; nor was there correlation between either technique of external measurement and the ciliary sulcus diameter.
High-frequency ultrasound biomicroscopy (35 to 60 MHz) has been used to directly measure the STS diameter. It was not until recently, however, that more adequate devices for imaging and measuring the anterior segment became available. The wide-angle high-frequency (50 MHz) ultrasound systems (Eye Cubed, Ellex; VuMAX II, Sonomed; Aviso, Quantel Medical; Artemis, Ultralink LLC; among others) ( Fig. 3.7.7 ) currently are the best tools to measure the STS distance. Although the FDA-approved technique for measurement remains WTW, growing evidence demonstrates that direct sulcus measurement using any of these methods is superior and minimizes the risk of incorrect ICL sizing.
Despite there being no consensus in the literature regarding the upper and lower limits of safe vault, the lens manufacturers suggest that an acceptable amount of vaulting of the lens optic over the crystalline lens is 1.00 ± 0.5 corneal thicknesses (approximately 250–750 µm). The clinical significance of vault outside of the range of safety resides in the risk of specific adverse events, including pupillary block, anterior subcapsular cataract, pigment dispersion, and glaucoma.
Sizing the Phakic IOLs
The eye’s anterior segment anatomy differs significantly among individuals, affecting the indications of phakic IOLs in different refractive errors. Most of the complications of these lenses are related to inappropriate sizing and inaccurate measurements of the AC dimensions.
For the iris-fixated phakic IOLs (i.e., Artisan and Artiflex), sizing is not an issue because these IOLs are fixated to the midperipheral iris, not the angle or sulcus, having the advantage of being one-size-fits-all length (8.5 mm).
For the sulcus-supported phakic IOLs (i.e., implantable collamer lens), different sizes of overall length are manufactured to suit normal variations in intraocular anatomy (e.g., 12.1, 12.6, 13.2, and 13.7 mm). The relationship of the selected overall diameter of the implanted lens to the dimensions of the posterior chamber represents an important determinant of the achieved postoperative vault, which is the term used to describe the measurable distance between the anterior capsule of the crystalline lens and the posterior surface of the ICL ( Fig. 3.7.6 ).
The white-to-white (WTW) diameter (external measurement from limbus to limbus) is the most important factor in determining the ICL size. It provides an approximate estimation of the AC (angle-to-angle [ATA]) and sulcus-to-sulcus (STS) diameters. The WTW is usually measured with the IOLMaster or the Lenstar biometers and checked with manual calipers between the 3 and 9 o’clock meridians. Alternative methods include tomographers such as the Galilei (Ziemer), Pentacam (Oculus), and the Orbscan IIz (Bausch & Lomb). Most studies have used the WTW measurement plus 0.5 mm, rounded to the nearest 0.5 mm increment.
The WTW measurement, however, is well known to suffer from significant inaccuracies. In a study comparing vertical and horizontal WTW measurements with direct anatomical measurements (postfixation) in postmortem eyes, there was no correlation between the horizontal WTW distance and the AC angle diameter; nor was there correlation between either technique of external measurement and the ciliary sulcus diameter.
High-frequency ultrasound biomicroscopy (35 to 60 MHz) has been used to directly measure the STS diameter. It was not until recently, however, that more adequate devices for imaging and measuring the anterior segment became available. The wide-angle high-frequency (50 MHz) ultrasound systems (Eye Cubed, Ellex; VuMAX II, Sonomed; Aviso, Quantel Medical; Artemis, Ultralink LLC; among others) ( Fig. 3.7.7 ) currently are the best tools to measure the STS distance. Although the FDA-approved technique for measurement remains WTW, growing evidence demonstrates that direct sulcus measurement using any of these methods is superior and minimizes the risk of incorrect ICL sizing.
Despite there being no consensus in the literature regarding the upper and lower limits of safe vault, the lens manufacturers suggest that an acceptable amount of vaulting of the lens optic over the crystalline lens is 1.00 ± 0.5 corneal thicknesses (approximately 250–750 µm). The clinical significance of vault outside of the range of safety resides in the risk of specific adverse events, including pupillary block, anterior subcapsular cataract, pigment dispersion, and glaucoma.
Visual Outcomes
Phakic IOLs are the most predictable and stable of the refractive methods for preserving the crystalline lens in high myopia. New improved designs and current methods for sizing and power determination are providing increasing safety and efficacy for the correction of severe ametropias.
In high myopia correction, significant postoperative gain of best-corrected visual acuity (BCVA) over the preoperative levels likely occurs as a result of a reduction in the image—the minimization that is present with spectacle correction of high myopia. A loss of BCVA is uncommon. The loss of contrast sensitivity observed after LASIK for high myopia does not occur after phakic IOL. In fact, with phakic IOLs an increase in contrast sensitivity occurs in all spatial frequencies compared with preoperative levels with best spectacle correction. Even for moderate myopia (between −6.00 and −9.00D) phakic IOLs provide better CDVA, contrast sensitivity at high spatial frequencies, and higher percentage of eyes gaining lines of CDVA compared with femtosecond laser-assisted LASIK.
Anterior Chamber Angle-Supported Phakic Intraocular Lenses
After the development of foldable AC angle-supported phakic IOLs, the rigid PMMA IOLs were almost abandoned, including the NuVita MA20, ZSAL-4 (Morcher GmbH) and Phakic 6 H2 (Ophthalmic Innovations International). Later, due to safety concerns related to endothelial cell loss, the NewLife and Vivarte (both from IOLTech–Zeiss Meditec) ( Fig. 3.7.8 ) and the Icare (Corneal Inc.) were also withdrawn from the market.
A few years ago the AcrySof Cachet (Alcon Laboratories, Inc., Fort Worth, TX) phakic lens was approved by the FDA. The Cachet is a single-piece, foldable, soft hydrophobic acrylic phakic IOL ( Fig. 3.7.9 ). Four models were available, each with a different overall length. The haptics were designed to allow compression within the angle for IOL stability without creating excessive force that could cause angle tissue damage or pupil ovalization. The vault of the IOL was designed to provide optimal central clearance distance between the IOL and the cornea and the natural crystalline lens ( ) ( Figs. 3.7.10 and 3.7.11 ). The 3-year findings from pooled global studies (United States, Canada, and the European Union) showed favorable refractive results and acceptable safety in patients with moderate to high myopia. Recently, however, its distribution was placed on hold due to a significant late-term endothelial cell loss (ECL) in a subset of patients, especially in those with small eyes and patients self-identified to be of Asian race. Data predict that eyes need to be monitored frequently because ~30% of eyes are at risk of early explantation based on the observed ECL rates, and 5% have loss rates higher than 3.9% per year. These rates can accelerate suddenly.
The Kelman Duet (Tekia, Inc., Irvine, CA) consists of a duet of an independent PMMA tripod haptic and a silicone optic ( Fig. 3.7.12 ). The haptic is implanted first in the AC through a 2.5-mm incision. The optic is then inserted using an injector system. Finally, the optic is fixated in the AC by the optic eyelets and haptic tabs using a Sinskey hook. At 12 months, 17% of eyes had more than 15% ECL. No mid- or long-term data of endothelial cell loss have been reported to date. The Duet is not FDA approved.
Complications
Pupillary Ovalization
Ovalization of the pupil, one of the most prevalent complications of angle-supported phakic IOLs, has a reported incidence of between 7% and 22%. Pupillary abnormalities tend to be progressive, being more frequent with longer follow-up visits. The most accepted mechanism is related to haptic compression of the angle structure due to an oversized lens causing inflammation of the angle, peripheral synechia formation, and pupillary ovalization. This mechanism was believed to be associated with iris ischemia. Iris hypoperfusion was confirmed using indocyanine green angiography (ICGA).
Another associated complication is iris retraction and atrophy ; the atrophy usually occurs in the iris sector affected by ovalization. Total sector iris atrophy can occur after progressive pupil ovalization in long-standing cases ( Fig. 3.7.13 ).
Endothelial Damage
Endothelial damage was the main reason for recalling several AC phakic IOLs from the market.
Two different mechanisms have been proposed to explain the ECL: the excessive proximity of the IOL parts to the corneal endothelium, which may intermittently or permanently be in contact with the posterior cornea or the presence of inflammatory cytokines in the aqueous humor produced by trauma to uveal structures. A follow-up study of more than 15 years of an angle-supported phakic intraocular lens model (ZB5M) for high myopia found a median coefficient of ECL of 17.5% with a rate of 0.97% every year, twice the physiological loss. Careful long-term follow-up of each patient with an AC phakic IOL is necessary to identify patients who may need explants of the IOL.
Elevation of Intraocular Pressure
Elevation of intraocular pressure (IOP) usually occurs transiently during the early postoperative period but may become chronic due to peripheral synechiae, which affects 2%–18% of patients. Another risk is acute glaucoma secondary to pupillary block in the absence of adequate iridectomies.
Uveitis
Chronic uveitis can be observed after angle-supported IOLs, with rates from 1% to 5%. An oversized lens can be a potential cause, compressing the angle structures and altering the blood–aqueous barrier (BAB) permeability. The chronic inflammation may continue for several years, inducing pupil ovalization, iris atrophy, and other complications, such as glaucoma, cataract, or anterior synechiae.
Cataract
Cataract after an AC lens—less common than with posterior chamber IOLs—can still occur, mainly due to chronic uveitis and other complications. A meta-analysis of cataract development after AC phakic IOL implantation found an incidence of 1.29%.
Complications
Pupillary Ovalization
Ovalization of the pupil, one of the most prevalent complications of angle-supported phakic IOLs, has a reported incidence of between 7% and 22%. Pupillary abnormalities tend to be progressive, being more frequent with longer follow-up visits. The most accepted mechanism is related to haptic compression of the angle structure due to an oversized lens causing inflammation of the angle, peripheral synechia formation, and pupillary ovalization. This mechanism was believed to be associated with iris ischemia. Iris hypoperfusion was confirmed using indocyanine green angiography (ICGA).
Another associated complication is iris retraction and atrophy ; the atrophy usually occurs in the iris sector affected by ovalization. Total sector iris atrophy can occur after progressive pupil ovalization in long-standing cases ( Fig. 3.7.13 ).
Endothelial Damage
Endothelial damage was the main reason for recalling several AC phakic IOLs from the market.
Two different mechanisms have been proposed to explain the ECL: the excessive proximity of the IOL parts to the corneal endothelium, which may intermittently or permanently be in contact with the posterior cornea or the presence of inflammatory cytokines in the aqueous humor produced by trauma to uveal structures. A follow-up study of more than 15 years of an angle-supported phakic intraocular lens model (ZB5M) for high myopia found a median coefficient of ECL of 17.5% with a rate of 0.97% every year, twice the physiological loss. Careful long-term follow-up of each patient with an AC phakic IOL is necessary to identify patients who may need explants of the IOL.
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