Introduction
In the 1950s, the pioneers Strampelli, Barraquer, and Choyce introduced the concept of intraocular lens (IOL) implantation in phakic eyes to correct high myopia. Since the 1980s, phakic IOL (PIOL) quality has improved and several PIOLs have been developed, either angle-supported or located in the posterior chamber. A completely different concept based on stabilization of the lens by an iris fixation was adopted by Worst. This approach was initially developed for pseudophakic patients ; in 1986, the concept of the claw lens was applied to correct myopia in phakic patients.
Lens Designs
Jan Worst developed the lens in 1978 under the name Iris Claw. Now built by Ophtec, it is available under four names: Artisan and Artiflex (distributed by Cristallens) and Verisyse and Veriflex (distributed by AMO). This lens has a convex–concave design to increase the distance between the PIOL and the corneal endothelium. Suppression of the prominent optical rim also reduced the prismatic effect possibly responsible for halos or glare. The vaulted design (0.5 mm) of the posterior face of the IOL allows it to ensure optimal space in front of the natural lens (about 0.8 mm) and prevents aqueous flow blockage. It also accounts for the forward displacement of the human lens during accommodation, which is at maximum about 0.6 mm. The optical part of the Verisyse myopic PIOL comes in two diameters: 5.0 mm and 6.0 mm (developed in 1997 to reduce phenomena such as glare and halos), with a power range of −5 to −20 diopters (D) for the 5-mm-diameter lens and 5 D to −15 D for the 6-mm-diameter lens, the power range increasing in 1.0 increments. It is a single-piece lens manufactured from ultraviolet light absorbing polymethylmethacrylate (PMMA).
In 1993, an iris-claw lens specially designed for the correction of hyperopia was introduced (5-mm diameter, power range of +1.0 D to +12.0 D).
Toric Verisyse IOL for the correction of astigmatism, which combines spherical anterior and spherocylindrical posterior surfaces, has been available since 2001.
To reduce surgically induced astigmatism, a foldable Verisyse IOL, Artiflex IOL, with a polysiloxane optic and PMMA haptics, has been developed. This is a lens with a polynomial design able to be injected in a 3.2-mm incision.
Indications and Contraindications
The following conditions must be fulfilled for phakic iris-claw lens implantation:
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Stable refraction.
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Periphery of the retina is healthy or adequately treated.
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No history of ocular disease, including glaucoma, cataract, uveitis, and macular disease.
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Endothelial cell density superior to 2000 cells/mm (specular microscopic examination of the cornea should be performed preoperatively).
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A pupil smaller than 8.0 mm in scotopic luminance (but the reactivity of the pupil seems to be as important as pupil size).
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A deep anterior chamber: the minimal central depth of the anterior chamber as measured by ultrasound should not be less than 3.2 mm.
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Lifelong close ophthalmologic follow-up will be possible.
Surgical Procedure
Preparation
IOL Power Calculation
The power of the IOL is calculated on the basis of the curvature of the cornea (K), the anterior chamber depth measured by ultrasonography and the spectacle correction, by applying a special mathematical formula (van der Heijde’s tables). Roughly, it will be about the same as the power of the spectacles at a vertex distance of 12 mm.
Preoperative Miosis
Preoperative application of topical myotics such as pilocarpine the day of the surgery is important. Miosis forms a protective shield for the natural lens during the insertion and fixation of the iris-claw lens.
Operative Technique ( and )
Incision Techniques
Various incision techniques can be used: clear corneal or scleral tunnel incision superiorly, or clear corneal incision temporally.
Incision Size
The incision should be 5.2 mm for the 5-mm lens and 6.2 mm for the 6-mm lens to avoid difficulties of IOL insertion. It could be 3.2 mm for the Artiflex and Veriflex.
Paracenteses
Two paracenteses are used for the introduction of the enclavation needles. These two small incisions of approximately 1 mm are located at 10 o’clock and 2 o’clock, when the main incision is superior.
Viscoelastic Material
The viscoelastic substance is injected through one of the puncture incisions to create a deep anterior chamber. It is mandatory to use high-viscosity sodium hyaluronate; material with lower viscosity (e.g., methylcellulose, hydroxypropylmethylcellulose) should be avoided. Before the entrapment of the haptics, some viscoelastic should be injected on top of the implant to protect the endothelium.
Introduction of the Phakic IOL Into the Anterior Chamber
The PIOL is introduced with the Verisyse fixation forceps into the anterior chamber by its smaller diameter ( Fig. 30.1 ). Then, the PIOL is rotated 90 degrees.
Guaranteeing Pupillary Miosis
Pupillary miosis should be guaranteed during the inserting and fixation procedure. The use of an intraocular myotic reduces the risk of lens touch.
Centration and Fixation of the IOL
Centration and fixation of the IOL is probably the most critical step of the procedure; its accuracy influences the postoperative results. The pupil is used as a reference for centration of the implant. Correct axial centration of the operating microscope will prevent postoperative parallactic errors.
Fixation of the IOL is performed by gently creating an iris fold under the claw and, consequently, entrapping the iris fold into the claw. Specially designed iris entrapment needles are used. They are blunt and can create a fold of midperipheral iris tissue. The IOL claws are then pressed over the fold ( Fig. 30.2 ).
Iridectomy/Iridotomy
Although a prophylactic iridectomy or iridotomy as a standard procedure is theoretically unnecessary (the Verisyse lens is vaulted to encourage natural fluid flow), experience has shown that it can prevent pupil block glaucoma in certain cases. A slit iridotomy, which is more elegant, is usually used.
Wound Closure
Watertight wound closure is of paramount importance to prevent a shallow anterior chamber leading to IOL endothelial contact in the immediate postoperative period.
Particularities of the Toric and Foldable Models
The Toric Lens
In this case, it is particularly important to position the lens accurately in the correct axis. A careful preoperative biomicroscopic examination of the iris with the patient sitting up (to avoid rotation of the globe) is necessary.
The Artiflex Lens ( )
The Artiflex foldable lens is inserted using a spatula through a small (3.2-mm) incision ( Fig. 30.3 ). For the enclavation, special curved forceps are used, which hold the base of the PMMA haptic. The incision is usually watertight and suturing is not necessary.
Removal of the Viscoelastic Material
Once the wound has been closed almost completely, the viscoelastic material should be entirely removed to prevent a shallow anterior chamber and a touch between the IOL and the cornea.
Preparation
IOL Power Calculation
The power of the IOL is calculated on the basis of the curvature of the cornea (K), the anterior chamber depth measured by ultrasonography and the spectacle correction, by applying a special mathematical formula (van der Heijde’s tables). Roughly, it will be about the same as the power of the spectacles at a vertex distance of 12 mm.
Preoperative Miosis
Preoperative application of topical myotics such as pilocarpine the day of the surgery is important. Miosis forms a protective shield for the natural lens during the insertion and fixation of the iris-claw lens.
IOL Power Calculation
The power of the IOL is calculated on the basis of the curvature of the cornea (K), the anterior chamber depth measured by ultrasonography and the spectacle correction, by applying a special mathematical formula (van der Heijde’s tables). Roughly, it will be about the same as the power of the spectacles at a vertex distance of 12 mm.
Operative Technique ( and )
Incision Techniques
Various incision techniques can be used: clear corneal or scleral tunnel incision superiorly, or clear corneal incision temporally.
Incision Size
The incision should be 5.2 mm for the 5-mm lens and 6.2 mm for the 6-mm lens to avoid difficulties of IOL insertion. It could be 3.2 mm for the Artiflex and Veriflex.
Paracenteses
Two paracenteses are used for the introduction of the enclavation needles. These two small incisions of approximately 1 mm are located at 10 o’clock and 2 o’clock, when the main incision is superior.
Viscoelastic Material
The viscoelastic substance is injected through one of the puncture incisions to create a deep anterior chamber. It is mandatory to use high-viscosity sodium hyaluronate; material with lower viscosity (e.g., methylcellulose, hydroxypropylmethylcellulose) should be avoided. Before the entrapment of the haptics, some viscoelastic should be injected on top of the implant to protect the endothelium.
Introduction of the Phakic IOL Into the Anterior Chamber
The PIOL is introduced with the Verisyse fixation forceps into the anterior chamber by its smaller diameter ( Fig. 30.1 ). Then, the PIOL is rotated 90 degrees.
Guaranteeing Pupillary Miosis
Pupillary miosis should be guaranteed during the inserting and fixation procedure. The use of an intraocular myotic reduces the risk of lens touch.
Centration and Fixation of the IOL
Centration and fixation of the IOL is probably the most critical step of the procedure; its accuracy influences the postoperative results. The pupil is used as a reference for centration of the implant. Correct axial centration of the operating microscope will prevent postoperative parallactic errors.
Fixation of the IOL is performed by gently creating an iris fold under the claw and, consequently, entrapping the iris fold into the claw. Specially designed iris entrapment needles are used. They are blunt and can create a fold of midperipheral iris tissue. The IOL claws are then pressed over the fold ( Fig. 30.2 ).
Iridectomy/Iridotomy
Although a prophylactic iridectomy or iridotomy as a standard procedure is theoretically unnecessary (the Verisyse lens is vaulted to encourage natural fluid flow), experience has shown that it can prevent pupil block glaucoma in certain cases. A slit iridotomy, which is more elegant, is usually used.
Wound Closure
Watertight wound closure is of paramount importance to prevent a shallow anterior chamber leading to IOL endothelial contact in the immediate postoperative period.
Particularities of the Toric and Foldable Models
The Toric Lens
In this case, it is particularly important to position the lens accurately in the correct axis. A careful preoperative biomicroscopic examination of the iris with the patient sitting up (to avoid rotation of the globe) is necessary.
The Artiflex Lens ( )
The Artiflex foldable lens is inserted using a spatula through a small (3.2-mm) incision ( Fig. 30.3 ). For the enclavation, special curved forceps are used, which hold the base of the PMMA haptic. The incision is usually watertight and suturing is not necessary.
