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Up Front | Feb 2010

Anterior Versus Posterior Phakic IOLs

What is the best lens?

Phakic IOLs have recently become a popular option for refractive correction. Some surgeons use them as in patients who are poor candidates for laser vision correction, and other surgeons introduce them to patients as a premium solution to refractive correction. The great debate of LASIK versus phakic IOLs will continue to surface; however, this article focuses on another debate surrounding the use of phakic IOLs: What is the best choice, anterior or posterior chamber phakic lenses?

Implanted in front of the crystalline lens, phakic IOLs may either be fixated in the anterior chamber angle or attached to the front of the iris (ie, anterior chamber) or sit between the back surface of the iris and the front surface of the crystalline lens (ie, posterior chamber). Each technique has its own pros and cons. In this article, CRST Europe has invited two surgeons to each present five reasons to defend his lens of choice.

ANTERIOR CHAMBER PHAKIC IOLS
By Jose L. Güell, MD
The following are five reasons to defend the use of anterior chamber phakic lenses. I would like to clarify that my defense focuses on the Artisan-Artiflex group (Ophtec BV; Groningen, Netherlands; distributed in the United States as Verisyse-Veriflex, Abbott Medical Optics Inc., Santa Ana, California) and under some circumstances on the AcrySof Cachet (Alcon Laboratories, Inc., Fort Worth, Texas).

Reason No. 1: Positive long-term safety data (5 to 10 years) is available and published for most of these lenses and models.1,2 Some of these studies are company driven; however, most originate from the retrospective or prospective experience of several investigators.

Reason No. 2: The main concern with anterior chamber phakic IOLs (almost the only one) is chronic endothelial cell loss. Once the loss is considered unacceptable (ie, higher than physiological), the lens may be explanted without the need for any additional treatment. This is an important difference from posterior chamber phakic IOLs, for which cataract and pigmentary glaucoma are the main concerns. With both of these conditions, additional treatment is necessary.

Reason No. 3: Especially with the iris–fixation-style phakic IOLs, we can perfectly centrate over the pupil (decentered pupils are common in ammetropic eyes) and fixate on the proper axis (for astigmatism correction), which provides obvious optical advantages.

Reason No. 4: In most cases, the higher the myopia, the deeper the anterior chamber, with the posterior chamber remaining a constant size. For this reason— although with a smaller optical zone—we have a disproportionate number of anterior chamber phakic IOLs for the higher conditions versus posterior chamber phakic IOLs.

Reason No. 5: Last but not least, I have had a positive experience with anterior chamber phakic IOLs for the past 15 years. Therefore, I have a lot of confidence in these lenses.

Jose L. Güell, MD, is the Director of the Cornea and Refractive Surgery Unit at the Instituto de Microcirugia Ocular, Barcelona, Spain, and an Associate Professor of Ophthalmology at the Universitat Autónoma de Barcelona. Dr. Güell states that he is a consultant to Carl Zeiss Meditec AG, Calhoun Vision, Visiometrics SL, and Ophtec. He may be reached at tel: +34 93 253 15 00; e-mail: guell@imo.es.

POSTERIOR CHAMBER PHAKIC IOLs
Roberto Zaldivar, MD

Reason No. 1: The surgical technique for implanting a posterior chamber phakic IOL allows an incision of 3 mm or slightly less. Such incision sizes induce only a small amount of corneal astigmatism. Once familiarized with the technique, implantation is easy in experienced hands.

Reason No. 2: After 20 years of experience with different types of phakic IOLs, I believe that posterior chamber phakic IOLs interact with the endothelium better than anterior chamber phakic IOLs.

Reason No. 3: This IOL is made of excellent material, thus allowing better intraocular tolerance and producing fewer cases of photic phenomena.

Reason No. 4: Because of its placement behind the iris, complications and visual side effects such as halos and glare are minimal. This coincides with the lens' material and its interaction with the endothelium.

Reason No. 5: The posterior chamber is the natural place for an IOL inside the eye. This position drastically reduces the amount of light reflection on the surface and any complication this may cause. It also helps to avoid the mirror effect of potential iris deformities, especially during the nighttime.

Roberto Zaldivar, MD, is the Scientific Director of the Instituto Zaldivar, Mendoza, Argentina. Dr. Zaldivar states that he is a consultant to STAAR Surgical. He may be reached at tel: +54 261 441 9999; e-mail: zaldivar@zaldivar. com.

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