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OCT is taking glaucoma diagnosis to new levels

Dr Joel S Schuman highlighted the successes of the technology during the recent 6th Annual Glaucoma 360 New Horizon’s Forum in San Francisco and said over the past decade OCT had become one of the vital ancillary tests in ophthalmic practice.“It’s the most rapidly adopted ophthalmic technology in history,” he told the conference.Among the key advances of OCT is its role in understanding the relationship between nerve fibre thinning of the retina and vessel density to visual loss field.{{quote-A:R-W:450-I:2-Q: It’s the most rapidly adopted ophthalmic technology in history, -WHO:Dr Joel S Schuman, Chairman of the Department of Ophthalmology}}The non-invasive approach of OCT provides real-time images of tissue microstructure without having to rove tissue samples for processing.The applied technologies of OCT have been far-reaching, and include the 3D imaging capabilities that provide ophthalmologists with a multi-dimensional view of the retina and a real-time snapshot of the histology of conditions – particularly glaucoma.According to Schuman, spectral-domain OCT– which measures wavelengths of back-reflected light – is replacing time-domain OCT, which measures time-of-flight light, because it is 50-1,000 times faster.Meanwhile another technique, OCT angiography, is also uncovering important information about glaucoma.During his presentation, Schuman, who is also the chairman of the Department of Ophthalmology at the New York University Langone Medical Center, described a recent discovery where the macular superficial vascular complex low-perfusion area matches ganglion cell complex thinning and visual field defects.{{quote-A:L-W:450-Q: These revelations, and many more are just the tip of the iceberg regarding knowledge and information brought to light by OCT. }}He went on to say these revelations, and many more are just the tip of the iceberg regarding knowledge and information brought to light by OCT.OCT was developed using near-infrared light in a Michelson-type interferometer that adopted the principle of time gating, which is a syst that isolates a segment of a time record for viewing and analysis.Schuman explained that time gating roves unwanted scattered light and partially recovers the image.The idea for OCT started when Schuman, then working for his fellowship at the Massachusetts Eye and Ear Laser Laboratory, was studying the possibility of using optical coherence domain reflectometry (OCDR) to measure the thickness of the retina in glaucoma and macular disease cases.What started out as a scientific hunch did not interest his supervisor, but Schuman was allowed to take his thoughts to the Massachusetts Institute of Technology (MIT), where he met and collaborated with co-inventor Dr David Huang, who was then a PhD student.Huang came up with the idea of a tomogram, after they moved the OCDR beam traversely to generate a B-scan which could be interpolated with an original A-scan.They did this while studying the cross-sections of calf eyes for their study on retinal nerve fibres and nerve responses to light exposure.Published in 1991, the discovery sparked the interest of the scientific community and in 1994, Schuman and Huang created a prototype device at the New England Eye Care Centre.

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