Eyeworld

DEC 2012

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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24 EW CATARACT December 2012 Device focus Phakic IOLs and peripheral iridotomy by Michelle Dalton EyeWorld Contributing Writer The latest phakic IOLs don���t need PIs, but until those lenses are approved here, a PI is an integral part of the phakic IOL procedure P hakic IOLs may offer better refractive outcomes and better visual quality in some patients than laser vision correction; for example, phakic IOLs are viable options for patients with thin corneas or irregular topography who would otherwise be without a surgical option for their refractive error. In the U.S., there are two currently approved phakic IOLs���the anterior chamber, iris-supported Verisyse (Abbott Medical Optics, Santa Ana, Calif.) and the posterior chamber Visian ICL (STAAR Surgical, Monrovia, Calif.). Regardless of placement, all phakic IOLs have the potential to cause pupillary block, and the prophylactic placement of peripheral iridotomy (PI) prevents acute glaucoma. These can be placed with an Nd:YAG laser before surgery or can be created during the surgery itself. Several advantages of phakic IOLs are commonly cited, including predictable and stable results, a flat learning curve, and their ability to allow the crystalline lens to retain function and accommodation; among the disadvantages commonly cited are that implantation is an intraocular procedure and that pigment dispersion, pupillary block, and chronic uveitis are common complications. Outside the U.S., the latest iteration of the Visian lens (the V4c) and a third phakic lens, the anterior chamber angle-supported AcrySof Cachet (Alcon, Fort Worth, Texas), do not require PIs. The Cachet is under investigation in the U.S., and the Visian V4c has been submitted for regulatory approval. ���Once those lenses are approved in the U.S., where the need for a PI is eliminated, no one will use the older versions,��� said Neil J. Friedman, M.D., adjunct clinical associate professor, Stanford University School of Medicine, and director of cataract and lens implant surgery, Pacific Vision Institute, San Francisco. Dr. Friedman only uses the An eye with a Verisyse phakic IOL and a nuclear cataract Visian ICL Source: Kevin Miller, M.D. Visian currently, and typically restricts the lens for patients with ���5 D or higher (although for patients with thin corneas or dry eye, he will implant the lens in lower levels of myopia down to ���3 D). While PIs ���are not the major limiting determinant of phakic lens,��� they can be ���slightly inconvenient,��� said Sonia H. Yoo, M.D., professor of ophthalmology, Bascom Palmer Eye Institute, Miami. Dr. Yoo performs her PIs at the time of the patient���s pre-op visit, and said she prefers to create them ���at least 2 weeks prior to the procedure���I like to leave that much time to make sure inflammation has quieted down prior to placing phakic lens. I usually pretreat with argon laser and then I will take the patient to YAG laser and break through the pretreated area in the iris,��� she said. She places two PIs at 10 and 2 o���clock ���to make sure I don���t get pupillary block.��� Phakic IOL implantation pearls Dr. Yoo typically reserves phakic IOLs for patients with myopia greater than ���6 D. ���The more dilated the pupil, the easier it���s going to be for lens positioning,��� she said. Surgeons who are just beginning to implant phakic lenses should take ���extra measures to ensure proper dilation,��� she said. In some cases, that might include a cocktail of dilating drops on a sponge placed into the inferior fornix to ensure the pupil is big enough for easy lens implantation. Dr. Friedman also performs his PIs at the laser, but said that some surgeons have moved away from creating PIs with a laser and are creating a surgical iridectomy at the time of the ICL procedure, ���and they���ll usually just make one,��� he said. Surgical iridectomy tends to be ���a little bit larger��� than PIs created with a laser, Dr. Friedman said, ���but surgeons can be more confident in the patency when it���s created intraoperatively.��� Bigger PIs can cause visual issues if not created properly, he said. If the PI is occluded, for instance, angle-closure glaucoma can occur. ���When you���re doing a surgical iridectomy, you have to ensure you���re getting the pigment epithelium,��� he said. ���Sometimes with the laser, you���re not sure you���ve punched all the way through the pigment epithelium on the back surface of the iris. So it can appear like it���s open, but it���s not functional.��� That said, Dr. Friedman is still more comfortable using a laser (either YAG or argon) to create his PIs and prefers to make the recommended two. ���I���ve had a case where one PI was slightly obstructed and the other was patent, so it���s a good thing I had two,��� he said. ���But there are surgeons who are comfortable only making one and it���s worked fine for them.��� Several techniques exist for creating a PI, but one Dr. Friedman likes is to make a ���little stab incision, and with special forceps grab the peripheral iris, pull it out through the wound, and then snip a little piece off with scissors. The end goal is to make a small, patent PI.��� Dr. Yoo added that with thicker irides surgeons ���might have a harder time creating the patent PI. That���s why I like to pretreat with the argon.��� Using the argon laser also Source: STAAR Surgical allows her to reduce the amount of energy needed compared to using a YAG. ���I���ll pick a place where there���s a crypt in the iris and try to target the laser there so I don���t have to get through as much iris to get a patent opening,��� she said. ���I���m reasonably generous with the PI.��� If surgeons have access to a high-resolution ultrasonic biomicroscopy machine, they ���can measure directly what the sulcus length is to ensure that the length of the ICL is appropriate for the eye. Ideally, you���re going to have a vault in the ICL so that you have enough clearance from anterior lens capsule so as not to develop cataract over time,��� Dr. Yoo said. If no access to a UBM is possible, using the white-to-white as an estimation of the sulcus-to-sulcus diameter should suffice. Dr. Friedman advised surgeons to ensure the pupil is dilated enough ���to get the ICL footplates tucked underneath the iris,��� he said. ���If you start manipulating the iris, the pupil begins to constrict, making the procedure more difficult.��� Dr. Yoo said the main fear regarding phakic lenses from a patient���s perspective is ���that this is an intraocular procedure with a prosthesis, whereas LASIK is outside the eye. Some of the younger patients have some concern about what long-term ramifications the surgery will have for them.��� EW Editors��� note: Drs. Friedman and Yoo have no financial interests related to this article. Contact information Friedman: 415-922-9500, neil@paci���cvision.org Yoo: 305-326-6322, syoo@med.miami.edu

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