Eyeworld

75 EW RETINA July 2015 are investigating this technology's potential. Dr. Khurana said a potential ad- vantage of swept source will be the improved resolution of choroidal thickness, which many believe has a role in numerous retinal disorders. Enhanced depth imaging (EDI) on SD-OCT devices is beginning to be adapted by retina specialists, Dr. Khurana said, and is showing promise in imaging the sclera and choroid. EDI SD-OCT captures a higher resolution image of the choroid and allows visualization of the scleral-choroidal junction, Dr. Hsu said. "Some diseases have a simi- lar fundus appearance but may be distinguished based on choroidal thickness. Improving our diagnostic accuracy allows us to provide better patient care," he said, citing chronic central serous retinopathy and wet macular degeneration as 2 such dis- orders with very different treatment algorithms. Another potential major ad- vance is OCT angiography, although the technology is still in early stages of investigation in both SD-OCT and swept source OCT. "Our group and others are currently evaluating OCT angiog- raphy. I suspect it will be a novel imaging modality that provides different information from both standard SD-OCT and fluorescein angiography," Dr. Ehlers said. "It's more like a structural reconstruction of the vascular network that has active flow," and has the potential to help clinicians and researchers better understand retinal diseases at a different level. "The images are spectacular," he said. EW Editor's note: Dr. Ehlers has financial interests with Bioptigen (Morrisville, N.C.), Carl Zeiss Meditec (Jena, Germany), and Alcon (Fort Worth, Texas). Dr. Hsu has financial interests with Optovue (Fremont, Calif.). Dr. Khurana has no financial interests related to this article. Contact information Ehlers: EHLERSJ@ccf.org Hsu: jhsu@midatlanticretina.com Khurana: rnkhurana@gmail.com difficult to manage and screen, but in 2011 the American Academy of Ophthalmology issued guidelines specifically mentioning SD-OCT screening. Rheumatologists and general practitioners put their patients with rheumatoid arthritis and lupus (and other autoimmune disorders) on hy- droxychloroquine because "it's such a generally well tolerated drug with few systemic side effects," Dr. Hsu said. "But it can cause toxicity to the retinal pigment epithelium, which then can lead to bull's eye maculop- athy and vision loss." Still being developed Dr. Khurana said when SD-OCT came to market, resolution im- proved to 5 microns. Newer tech- nology that uses adaptive optics "allows you to get near cellular scale of resolution, which in my mind is absolutely amazing." The technolo- gy is being used in Europe, but has not entered clinical practice here in the U.S., he added. Another potential development is swept source technology, he said. "It uses different light sources that have longer wavelengths to get deeper penetration into the eye." It's also faster—about twice as quick as SD-OCT, which can take about 50,000 A-scans per second. Swept source can capture closer to 100,000 per second. "It's about a two-fold increase and that allows you to get a better resolution, up to 1 micron," he said. By being able to take more A-scans per second, swept source "allows faster image acquisition and more scans through a given section," Dr. Hsu said. "By scanning more times through the same sec- tion of retina, you can also average the images and further improve image quality." Dr. Ehlers said an additional potential benefit of swept source technology is the range it can image —for example, from the cornea to the posterior capsule, or from the mid-vitreous to the choroid in one scan. "The jury is still out on this technology—there's no system commercially available in the U.S., although Topcon [Oakland, N.J.] does have one approved outside the U.S.," Dr. Ehlers said, adding "multi- ple companies and research groups"

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