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Today's Practice | Apr 2010

Classification of Phakic IOLs

These lenses can be categorized based on their position in the eye.

Phakic IOL technology has significantly improved over the past 25 years in terms of safety and efficacy. The risk-to-benefit ratio becomes acceptable to the individual desiring refractive surgery when proper attention to details and postoperative care are considered and implemented. Generally, ophthalmologists approach postoperative care for phakic IOL implantation in the same fashion that they approach postoperative care for cataract patients. Clinical results have confirmed that phakic IOLs are a promising treatment option for patients with high refractive errors with or without thin corneas who cannot undergo keratorefractive procedures. The main advantages of these lenses are that they correct high levels of myopia and hyperopia and are reversible.

TYPES
The idea of implanting an anterior chamber IOL in a phakic eye to correct high myopia was proposed and then abandoned by Strampelli1 and Barraquer2 in the 1950s. Interest has more recently been revived by Fechner, van der Heijde, and Worst in the 1970s and 1980s,3 who used iris-fixated lenses, and by Joly, Baïkoff, and Bonnet in the late 1980s,4 who used angle-supported lenses that resembled the Kelman-style anterior chamber lens. Many phakic IOL designs have since emerged, and, today, the designs can be classified according to the way that they are fixated in the eye: posterior chamber, irisfixated, or angle-fixated.

Posterior chamber. The Visian ICL is a posterior chamber lens based on the original design introduced by Svyatoslav Fyodorov, MD, and further developed by STAAR Surgical (Monrovia, California).5,6 The first ICLs made by STAAR were implanted in human eyes in Europe in 1993, and its design has been further developed in subsequent years. The Visian ICL is a one-piece plate-haptic lens made of a porcine collagen/hydroxymethacrylate copolymer (34% water, <0.1% collagen). This lens, which has a refractive index of 1.45, has provided safe, effective, predictable, and stable visual and refractive outcomes with minimal intraoperative and postoperative complications for myopia, hyperopia, and astigmatism correction.7-13

Development of the Phakic Refractive Lens (PRL; IOLTech/Carl Zeiss Meditec AG, Jena, Germany) began in 1987. The PRL is a one-piece plate-haptic design lens made of silicone. Like the ICL, the PRL is designed for implantation in the posterior chamber for the correction of myopia and hyperopia. Its distinction is that it floats in the aqueous humor instead of resting on the sulcus because there are no feet on its plate haptics.

Iris-fixated. Jan G.F. Worst, MD, of Holland, developed the original iris-claw lens in the 1970s for the correction of secondary aphakia after cataract surgery. The Artisan lens (Ophtec BV, Groningen, Netherlands) is a one-piece IOL made of ultraviolet-blocking PMMA. The lens corrects spherical and cylindrical errors. In 2003, a foldable model of the Artisan, the Artiflex phakic IOL (Ophtec BV), was released in Europe. This lens can be inserted through a smaller incision than the Artisan.

Angle-fixated. The AcrySof Cachet (Alcon Laboratories, Inc., Fort Worth, Texas), is a foldable, angle-supported phakic lens with flexible and adaptable haptics designed to be implanted in the anterior chamber angle for the correction of moderate to high myopia. It is made of the same soft, flexible hydrophobic acrylic material as other AcrySof IOLs, which allows the lens to be folded and inserted through a small incision of 2.6 mm with the Monarch II IOL Delivery System (Alcon Laboratories, Inc.). The lens has an optic diameter of 6.0 mm, an overall length of 12.5 to 14.0 mm, and a dioptric range of -6.00 to -16.50 D in 0.50 D increments.

For additional information on phakic IOLs, please see the cover stories in CRST Europe's February 2010 issue.

José F. Alfonso, MD, PhD, practices at the Fernández- Vega Ophthalmological Institute, Surgery Department, School of Medicine, University of Oviedo, Spain. Dr. Alfonso states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +34 985245533; fax: +34 985233288; e-mail: j.alfonso@fernandez- vega.com.

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