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Implantable lenses may be a viable option for vision correction in patients with high myopia, and in those who have thin corneas or conditions that might predispose them to complications with LASIK.
Baltimore-Implantable lenses may be a viable option for vision correction in patients with high myopia, and in those who have thin corneas or conditions that might predispose them to complications with LASIK, said Kraig Scot Bower, MD, here at the 23rd annual Current Concepts in Ophthalmology meeting, held in association with Ophthalmology Times.
"In the past, 'do nothing' has been the primary option for these patients," said Dr. Bower, associate professor of ophthalmology, Johns Hopkins University School of Medicine, and director of refractive surgery, Wilmer Eye Institute, Baltimore. "We can now offer them implantable lenses."
Two primary phakic IOLs currently are available (Verisyse, Abbott Medical Optics; Visian Implantable Collamer Lens [ICL], STAAR Surgical). The Verisyse lens is an anterior chamber lens, while the Visian ICL is a posterior chamber lens that inserts behind the iris in front of the crystalline lens.
The ICL is approved by the FDA for the following indications:
Potential candidates for the ICL are between the ages of 21 and 45, with moderate-to-severe myopia. It is best if the patient has not had any previous eye surgery and has no previous history of eye disease such as glaucoma, iritis, or diabetic eye disease. Contraindications for ICL implantation include a shallow anterior chamber, narrow angles, pregnancy, nursing, or failure to meet endothelial cell densities.
"I personally don't do laser refractive surgery on anyone with greater than 10 D myopia," Dr. Bower said. "Patients with steep corneas and patients whose postoperative corneas would be overly flat may not be good candidates for laser surgery. Importantly, like any other refractive surgery, this procedure is for patients who have otherwise healthy eyes. It is particularly not appropriate for anyone with any lens changes such as early cataract."
Preoperative evaluation simple
Preoperative evaluation of these patients is similar to the standard exams done in LASIK candidates, and includes the refractive exam, pupil size, IOP measurement, and a comprehensive exam.
Candidates for ICL require only two additional exams, Dr. Bower said.
"Measure the bite-to-bite measurement to help calculate the diameter of this lens implant," he said. "I do an IOL measure to calculate the axial length, which also confirms the bite-to-bite measurement. Endothelial cell counts are also important in these [people], and I recommend that you do this via specular microscopy or confocal microscopy. Gonioscopy is another additional test that may be useful in these patients.
"If you've just started to do these, stick with the FDA-recommended guidelines for your first 20 to 40 cases," Dr. Bower added.
The company that manufactures the ICL has made a Web site (http://staarvision.com/) available to facilitate data collection and analysis.
"Once you've input the data, an ICL calculator will generate and calculate the diameter of the ICL and the power of the lens," he said. "It's pretty straightforward."
To prevent pupillary block, Dr. Bower places laser peripheral iridotomies (LPIs) superiorly in both eyes at two sites a minimum of 10 to 14 days before the surgery. It is important to make sure that inflammation and pigment dispersion from the LPIs have resolved prior to the ICL procedure, he said.