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Phakic IOL implantation has advantages as a method of refractive surgery. Enhancement may be needed to optimize the refractive result, but many issues should be considered before undertaking an enhancement and when offering this technology to potential candidates.
New Orleans-Implanting a phakic IOL and then adjusting residual refractive error using PRK or LASIK allows for predictably effective correction of large myopic refractive errors with or without astigmatism.
Although various enhancement techniques can be applied to optimize the refractive outcome if necessary, many issues must be considered regarding their use and when offering phakic IOL implantation to refractive surgery candidates, said Joseph Colin, MD, at the annual meeting of the American Academy of Ophthalmology.
"Rather than enhancement, the current hot topic relating to phakic IOL implantation is the risk of severe endothelial cell damage in eyes with an angle-supported phakic IOL," said Dr. Colin, chairman, Department of Ophthalmology, University of Bordeaux, France. "Very cautious follow-up is needed in these patients, and if there is evidence of progressive corneal endothelial cell loss, cataract, or other complications, the IOL will have to be removed. Therefore, it is important to keep all of the refractive data for later IOL power calculations."
High ametropia, particularly myopia exceeding the limits of excimer laser ablation, is one of the main indications for phakic IOL implantation, Dr. Colin said. It also might be considered as an alternative to laser vision correction in patients with thin corneas or suspicious topographic patterns.
Several factors limiting the accuracy of the refractive outcome after phakic IOL implantation contribute to a need for enhancement. Current methods for phakic IOL power calculation, which usually are based on use of the manufacturer's program, are one contributor. Depending on the IOL implanted and the patient's pre-existing level of myopia or astigmatism, residual refractive error and a need for enhancement may be anticipated.
Before undergoing an enhancement, patients must be evaluated for refractive stability. The time to achieve that endpoint will depend on the size of the incision used for IOL implantation. Alternative causes for refractive error, such as the anatomic position of the phakic IOL (i.e., whether it has decentered or was appropriately sized), also should be considered.
"Endothelial cell count should always be evaluated, whether or not IOL removal is being contemplated, to address residual refractive error," Dr. Colin said.
If the postoperative refractive error is high, then phakic IOL exchange represents the best solution, he said. Mild or moderate refractive errors can be adjusted with excimer laser surgery using LASIK or a surface ablation technique.
"In deciding between LASIK and surface ablation, surgeons might consider whether there are potential safety concerns associated with placing a suction ring on an eye with a phakic IOL," Dr. Colin said. "Although performing a customized treatment would be preferable, in our experience . . . it can be difficult to capture a good wavefront scan in patients with a phakic IOL."
Laser enhancement may be complicated further for surgeons who use a particular system (LADARVision, Alcon Laboratories), which has a tracker that requires the pupil to be dilated 7 mm, he said.
"In eyes with a phakic IOL, the ability to track the pupil edge may be affected by light reflected off the IOL," Dr. Colin concluded.