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4/23/2019
1
Introduction to OCT-Angiography
Gary Michalec, CRA
Sr. Regional Strategic Clinical Manager
North America
ZEISS Ophthalmic Devices
Carl Zeiss Meditec, Inc.
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What we’ll be covering
OCT Technology
Past, Present and Future
OCT Angiography
Advantages and Disadvantages
Clinical Cases
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How Did We Get From Here…
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…to here ?
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Puliafito,C.
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2 mm 2 mm1024
128-512 200-4096
Groups of A‐scans form to make the B‐scan
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Time Domain OCT• In TD‐OCT the depth information has to be subsequently probed by mechanically adjusting the length of the reference arm.
• This required motion limits the speed of the acquisition of an A‐Scan, (e.g. the STRATUS has a 400 Hz A‐Scan rate).
*Reference arm is mechanically adjusted to scan depth of eye
400‐500 A‐scans per second
Mechanical motion limits speed and precision of the acquisition
“outdated technology” slow and less precise
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Spectral Domain OCTHowever, instead of changing the length of the reference arm, it is equivalent to use a different wavelength of the light
When broadband laser diodes became available, SD‐OCT could use the different wavelengths to simultaneously obtain the depth information
Wide‐band source provides speed, but spectrometer causes signal loss w/depth, detector tech limits speed
27,000 A‐scans and up
“mature technology” speed/depth limitations
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TD vs. SD Comparison
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Swept Source OCTAdvances in the telecom industry provide narrow‐band lasers, where the wave‐length can be electronically tuned
Corresponding detectors are very sensitive with low noise.
Lack of a spectrometer allows improved imaging of deeper /wider structures
100,000 A‐scans and up
“developing technology” improvements vs. cost ?
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OCT Angiography• Algorithm detects red blood cells moving through vessels• Eye tracking, reduces motion artifact, negates blinks, and ensures precise
scan location on follow‐up scans
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• 245 B-Scans (cuts)• Each Repeated 4x
tracking
3 mm X 3 mm Angio
Total = 240,000 A‐scans, ~ 5.0 secs
• 245 axial A-Scans per B-Scan, e 1024 voxels deep
OCT Angiography
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OCTA vs FA
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Conventional IVFA shows dynamic phases of staining, leakage and pooling, OCTA does not.
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OCT‐A shows movement of red blood cells
Imagecaptured is equivalent to mid‐phase of FA
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• No NEEDLES, Less TIME, Less Complicated ‐ ‐ ‐ Lowered Risk• Single Scan ‐ in a few seconds
• Seeing hard‐to‐see pathology = Confidence/More informed Referrals
• Depth Color Coded for easy assessment
• Multiple layer segmentation • Deep Retina Plexus Layer not Clinically Visible before OCT‐A
• New Interpretation understanding necessary
OCTA vs FA
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2
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OCT – A are flattened 2D images of 3D vasculature. Color Represents Depth in Tissue
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Superficial Retina Deep Retina Avascular Retina
Color Depth Retina Map
Color Depth Map combines superficial, deep and avascular maps‐ allows for depth visualization of blood flow from the ILM to ONLY the RPE
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Normal 3x3 Angio Cube OD ‐ Full Retina (L) and Deep Plexus (R)
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Normal Pt, 6x6 Scans
Color Depth Encoded Superficial Deep Plexus
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00:14 FA AngioPlex – Retina Color Depth Map
Courtesy of S. Feldon, Flaum Eye Institute, University of Rochester, Rochester, NY, USA
PED with CNV 6x6 mm OCT‐A Scan
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Visual detail from OCT Angiography correlates very well with traditional fluorescein angiography
• Korobelnik J Fr Ophthalmol (2015)
Korobelnik J Fr Ophthalmol (2015)
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VRI – Vitreo Retina Interface Map
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BRVO3x3 mm OCT‐A Scan
OCT‐A – Retina Map
Courtesy of S. Lee, East Bay Retina Consultants, Oakland, California, USA
Late Phase FA
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FA of a CRVO
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SD‐OCT 3x3 images superimposed on FAOverlays for display effect
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FA of a CRVO
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SD‐OCT 3x3 images superimposed on FAOverlays for display effect, not a software feature
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PDR with NVD
FA (top) vs. OCT‐A (middle)
OCT‐A VRI interface (bottom)
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Another KNOWN DIABETIC – Looks Good, right?
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WRONGDeep Plexus, Superficial Retina
Eroded Deep Plexus Irregular FAZ, Peri‐macular Ischemia4/23/2019
…and the other eye…
Sup/Temporal Ischemia
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AMD/CNV OU Question: What is Projection Artifact/De‐Corellation Tails ?
OD OS
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AMD/CNV ODColor Retina Depth EncodingOCT‐A 3x3
Blue/Cool Color indicates flowin the Avascular Layer. But the coding is weak.
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AMD/CNV OD Custom RPE‐RPE slab OCT‐A 3x3
Feeder Vessel or Projection Artifact ?
Green Indicates Sub RPE Blood Flow
Red Indicates Pre RPE Blood Flow
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AMD/CNV OU (“faux feeder” projection artifact removed)3x3 AngioPlex™
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STAINING and POOLING? DOES IT MATTER ANYMORE?
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Classic or Occult?
Classic CNV is well‐defined on IVFA
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Regression of lesion over time
Idiopathic CNV
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Pt. 33: CSR – Central Serous Retinopathy
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7/22/16
11/23/15
11/9/15
CSR
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CSR: Last Visit – this would be missed my MOST docs at ALL LEVELSCNV despite < SRF. REFER THIS PT TO A RETINA SPECIALIST !
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Analytics and Metrics
Superficial Deep Perfusion Density
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Analytics and Metrics
5Agemy S, et al. Retinal Vascular Perfusion Density mapping using OCTA in Normals and DR Patients. Retina. 35(11):2353‐2363, November 2015.
Superficial
Angio
Flow Den
sity
Carolyn Majcher OD FAAO, Rosenberg School of Optometry4/23/2019
Additional Resources
• https://www.laboratoires‐thea.com/medias/ouvrage_practical_angiography.pdf
• https://www.optovue.com/case‐studies
• https://business‐lounge.heidelbergengineering.com/gb/en/products/spectralis/oct‐angiography‐module/#product‐details
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