EyeWorld Asia-Pacific June 2014 Issue

29 EWAP CAtArACt/IOL Pseudophakic dysphotopsia June 2014 by Michelle Dalton EyeWorld Contributing Writer Understanding positive dysphotopsia The visual disturbances exacerbated by ocular surgery can range from annoying to disabling P ositive dysphotopsia— the unwanted images including rings, arcs, and central flashes that become bothersome after IOL implantation—have been associated with everything from the patient’s ability to recognize the edge of the implanted IOL to corneal disease to multifocal IOLs to an oversized peripheral iridotomy (PI) that allows too much light scatter in the back of the retina. Like most visual anomalies post-surgery, it’s nearly impossible to determine who will be affected and who will not beyond a generalized “anyone who is at risk for glare or halo postop.” Numbers may not bear it out, as positive dysphotopsia may not result in an IOL exchange but will result in substantial additional chair time after uneventful cataract surgery. In short, these patients are unhappy, and the wrong approach to take is to reinforce the surgery was “perfect”. “Square-edge IOLs that reduce posterior capsule opacification (PCO) and have higher index of refractions (acrylic) will have an initial result of about 15% who notice positive and negative dysphotopsia that decreases to less than 5% by one year,” said Jack Holladay, MD , professor of ophthalmology, Baylor College of Medicine, Houston, Texas, U.S. It’s not just the IOL, added William Trattler, MD , in practice at the Center for Excellence in Eye Care, Miami, Fla., U.S. “If someone is on tamsulosin and the iris is not managed well intraoperatively, you can damage the iris,” he said. “Iris defects can lead to glare and/or halo that can result in positive dysphotopsia.” Simple under or overcorrection can also lead to the unwanted aberrations, although this can be managed with spectacles, he said. Jeremy Kieval, MD , in practice at Lexington Eye, Mass., U.S., added the cornea and ocular surface can adversely impact vision postop, and while the IOL’s optics and the design of the optic edge have been implicated in numerous studies, he cautions surgeons against excluding other potential causes. “I usually think about the implant, but you can’t forget about the surface of the eye, the iris, and the capsule,” he said. “Multifocal IOLs will cause positive dysphotopsia, due to the edge of the optic as well as the concentric rings.” But severe dry eye and other corneal disease “can have some induced aberrations just from the ocular surface that they are perceiving as positive dysphotopsia,” he said. Treating the surface issues before surgery will substantially reduce the potential for aberrations postop, he added. “You want to avoid aberrations that are induced by the cornea and not the implant,” he said. Irregular topography should be considered before lens selection to minimize the risk as well. Frosting or texturing the edge of the IOL can help reduce—but not eliminate—the occurrence of positive dysphotopsia, Dr. Holladay said. “ Marie-Jose Tassignon, MD , developed an IOL with flanges that has totally eliminated the problem, but it is not available in the U.S. and requires a posterior capsulorhexis,” Dr. Holladay said. Piggybacking an IOL can help to stave off dysphotopsia. Source: : Samuel Masket, MD continued on page 32 AT A GLANCE • Negative dysphotopsia can occur after cataract surgery, even if the surgery was perfect. • Surgeons cannot predict who will experience negative dysphotopsia. • It’s best to observe patients for a few months before providing treatment, as many cases will resolve on their own. • Treatment options include Nd:YAG laser capsulectomy, a piggyback lens, and lens exchange.