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entire eye "from the cornea to the retina," Dr. Fujimoto said. Imaging the optic nerve head At Massachusetts Eye and Ear, Dr. Shen is performing a research study using the DRI OCT-1 Atlantis 3D SS OCT in patients with glaucoma. "We want to determine if we can see more of the optic nerve head beyond what a clinician can see on slit lamp exam or beyond what the current commercially available tech- nology (SD-OCT) can do," she said. While her group has been able to see more structures of the optic nerve with the swept-source technology, "it has not been consistent." As she explained, "We're trying to image structures that are deep in the optic nerve head that are cov- ered by blood vessels and other non- transparent structures, which have made imaging more difficult in gen- eral. Swept-source OCT can theoreti- cally render those deep optic nerve structures in better resolution with- out much shadowing artifacts, com- pared to SD-OCT." Dr. Shen did stress, however, that requesting these high tech devices to image a structure that is only 1.5 mm to 2 mm in diameter is analogous to finding the proverbial needle in the haystack. Ideally, Dr. Shen hopes her group's research provides answers about who may be more vulnerable to glaucoma or to glaucomatous progression based on what the optic nerve head changes may be. In another study at the Univer- sity of Pittsburgh, 2 swept-source OCT was used to examine in vivo the three-dimensional microarchi- tecture features of the lamina cribrosa in both healthy and glaucomatous eyes. In that study, the device used has a 100,000 A- scan/second scanning rate, a 1050 nm light source, and a 5-micron axial resolution, the authors wrote. The study, the first to automatically quantify the lamina cribrosa mi- croarchitecture in 3D, found beam thickness to pore diameter ratio and pore diameter standard deviation were statistically significantly higher in glaucomatous eyes. The parame- ters were not statistically signifi- cantly associated with age (healthy eyes averaged 41 years old, while glaucomatous subject eyes averaged 71 years old). The authors wrote that because the microarchitecture differences are not readily apparent between glau- comatous and healthy eyes, "an automated quantification method is required in order to identify differ- ences that may not be obvious." The posterior lamina cribrosa "is the presumed site of optic nerve damage in glaucoma. Structural changes in that area are thought to impede flow within the axons," said Barry A. Schechter, MD, director of the cornea and cataract service, Florida Eye Microsurgical Institute, Boynton Beach, Fla. If swept-source OCT can discern details of more deeply located tissues, it might "pro- vide earlier and more detailed views to help clinicians better treat our glaucomatous patients," he said. In the anterior segment, Dr. Schechter said the technology might prove useful in visualization of synechiae and angle structures. An improved ability to ascertain where microinci- sional glaucoma surgery devices have been placed is a potential use as well, he said. For now, Dr. Shen said she's "cautiously optimistic" about the fu- ture of swept-source technology. EW References 1. Grulkowski I, Liu JJ, Potsaid B, et al. Retinal, anterior segment and full eye imaging using ultrahigh speed swept source OCT with vertical-cavity surface emitting lasers. Biomed Opt Express. 2012;3(11):2733-51. 2. Wang B, Nevins JE, Nadler Z, et al. In vivo lamina cribrosa microarchitecture in healthy and glaucomatous eyes as assessed by optical coherence tomography. Invest Ophthalmol Vis Sci. 2013;54:8270–8274. Editors' note: Dr. Fujimoto has finan- cial interests with Optovue (Fremont, Calif.) and Carl Zeiss Meditec (Jena, Germany). Drs. Schechter and Shen have no financial interests related to their comments. None of the swept- source devices mentioned in this article are commercially available in the United States. Contact information Fujimoto: jgfuji@mit.edu Schechter: bdsch77@aol.com Shen: Lucy_Shen@meei.harvard.edu April 2014

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