Eyeworld

175 April 2017 EW MEETING REPORTER Ang and his colleagues are currently excited because it now provides the opportunity to study both structure and blood flow. Basically, he said, the OCT is used to take a series of images which are then compared in terms of speckle or intensity changes in OCT structural images (such as erythro- cytes tracked through vessels) and phase variance. Dr. Ang and his colleagues published the first anterior segment OCT angiography study in 2015. In their study, they found OCT angiog- raphy to be quite reproducible. They found OCT angiography to be a rap- id, noninvasive method for anterior segment angiography, with good repeatability and image quality. However, at the time, the software was not optimized for the cornea. Dr. Ang is currently conduct- ing clinical study comparing OCT angiography systems for the anterior segment. To date, he said, spectral domain and swept-source OCTs appear "quite comparable," with one limitation being that they don't really understand the differences between the algorithms used by vari- ous OCT machines. In terms of clinical applications, Dr. Ang and his colleagues are look- ing into the use of OCT angiography to delineate vessels, measure caliber, and potentially look at regression after treatment. He said that the sys- tem could be used to identify feeder vessels and assess the size of corneal pathology, depth of corneal scars, and disease progression. The gold standard to date re- mains indocyanine green angiogra- phy, but OCT angiography is already quite comparable. Comparing the two modalities, Dr. Ang said that OCT angiography is noninvasive, rapid, provides three-dimensional imaging, is static, and is not attend- ed by the risk of leakage. However, current OCT systems are still not optimized for cornea and have a limited field of view and some reso- lution issues. Clinically, in addition to delin- eating the corneal vasculature, OCT angiography could be used to guide fine-needle diathermy treatment, monitor response to angiogenic poor progression of the rhexis, and excessive lens mobility. There are modified phaco approaches and IOL considerations you can take in these cases, Dr. McGhee said, highlighting some of the options surgeons may use for these patients. He also highlighted key surgical management tools, including ophthalmic viscosurgi- cal devices, capsular stains, iris or capsule hooks, capsule tension rings, capsule segments, and appropriate sutures for rings and segments. Always anticipate zonular deficiency, he concluded. Carefully plan iris repairs. Understand con- temporary options, and be prepared and know the hardware, Dr. McGhee said. Techniques for corneal vasculature imaging, role of corneal imaging in systemic disease management highlighted Marcus Ang, MD, Singapore, de- scribed "Novel OCT Angiography Techniques for the Cornea" in a scientific symposium on "Clinical Applications of Anterior Segment Imaging." While OCT angiography has been in common use in retina and glaucoma clinics, the modality is relatively new in the cornea clinic. The potential is great given the clin- ical significance of corneal vascular- ization, being the leading cause of visual loss from corneal disease and a major risk factor for corneal graft failure. Dr. Ang took a moment to re- member the late Peter Watson, MD, who had passed away just the pre- vious week. Dr. Watson was one of the first few people to closely study the limbal vasculature and the blood supply of the anterior segment. More recently, Dr. Ang said that researchers have begun reviving interest in marginal corneal vascular arcades, for the study of which indo- cyanine green angiography remains the gold standard vascular imaging modality for the cornea. Optical coherence tomography has been around for a long time, used to take cross-sectional images of the anterior segment, but Dr. continued on page 176

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