spectral domain OCT by Hala Fathi Hannot
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This document discusses optical coherence tomography (OCT) and compares time domain OCT (TD-OCT) to spectral domain OCT (SD-OCT). TD-OCT measures reflections one pixel at a time by moving a reference mirror, limiting its speed, while SD-OCT measures all reflections simultaneously using a spectrometer without a moving reference mirror, making it 50 times faster than TD-OCT. SD-OCT provides higher resolution, definition, and signal than TD-OCT, enabling better visualization of retinal layers and small blood vessels. The document outlines various clinical applications of SD-OCT for imaging the retina, cornea, glaucoma, and its use in pediatrics and surgery. Commonly used commercial SD-OCT instruments are also listed
spectral domain OCT by Hala Fathi Hannot
- 2. • Evolution 1 • Optical principal 2 • TD vs SD 3 • Advantages 4 • Clinical Practice Applications 5 • Commercially available instruments 6 • Summary 7
- 3. • Evolution 1 • Optical principal 2 • TD vs SD 3 • Advantages 4 • Clinical Practice Applications 5 • Commercially available instruments 6 • Summary 7
- 4. OCT 1 & 2 1996 Stratus 2002 SD-OCT 2006 26,000 400 100 20 10 5 Speed (A-scans per sec) Resolution (mm) Time domain OCT
- 5. • Evolution 1 • Optical principal 2 • TD vs SD 3 • Advantages 4 • Clinical Practice Applications 5 • Commercially available instruments 6 • Summary 7
- 6. Time Domain OCT SLD Lens Detector Data Acquisition Processing The reference mirror must move one cycle for each axial scan-> limits speed of image acquisition. Reference mirror moves back and forth Scanning mirror directs SLD beam on retina Beam splitter Broadband Light Source Creates A-scan 1 pixel at a time Final A-scan Process repeated many times to create B-scan Reference beam sample beam Interferometer Combines light from reference with reflected light from retina + = +. . .
- 7. Spectral Domain OCT SLD Spectrometer analyzes signal by wavelength FFT Grating splits signal by wavelength Broadband Light Source Reference mirror stationary Combines light from reference with reflected light from retina Interferometer Spectral interferogram Fourier transform converts signal to typical A-scan Entire A-scan created at a single time Beam splitter SD measures all echoes of light simultaneously FFT :extracts the frequency content of a signal.
- 8. • Evolution 1 • Optical principal 2 • TD vs SD 3 • Advantages 4 • Clinical Practice Applications 5 • Commercially available instruments 6 • Summary 7
- 9. SD-OCT TD-OCT • SD-OCT is 50 times faster than TD-OCT • Faster than eye movements So less motion artifacts •Slower than eye movements 512 A-scans in 1.28 sec Motion artifact Higher speed, higher definition and higher signal. 1024 A-scans in 0.04 sec Small blood vessels IS/OS Choroidal vessels
- 10. SD-OCT TD-OCT SD-OCT and differ than my TD-OCT measurements. SD-OCT TD-OCT
- 11. • Clinical Practice Applications 5 • Commercially available instruments 6 • Summary 7
- 12. Improved sensitivity and speed of scanning 10 Folds improvement in sensitivity (it measures all of the reflected light at once) Improved Coverage of the Retina Dense raster pattern 50 times faster than TD
- 14. 3-D & video Imaging
- 15. Eye motion compensation LSO Image Transverse registration allows comparison between visits Eye tracking allows scans to be taken at the same place time after time.
- 16. Reproducibility Adaptive optics, media opacity Mid dilated or non dilated pupil is possible
- 17. Segmentation Segmentation techniques make it possible to view layers individually such as ILM and RPE.
- 18. • Evolution 1 • Optical principal 2 • TD vs SD 3 • Advantages 4 • Clinical Practice Applications 5 • Commercially available instruments 6 • Summary 7
- 19. Glaucoma Cornea & Anterior segment Retina Intraoperative uses Functional SD-OCT
- 20. Glaucoma Cornea & Anterior segment Intraoperative uses Functional SD-OCT
- 21. Recently intra operative imaging Monitors response to treatment Helps in decision of treatment Prediction of visual function or future disease progression Quantitative and objective method for follow up More understanding of diseases pathogenesis
- 22. Geographic atrophy Drusen PR nuclear layer
- 23. Choroidal neovascularization: • DD between type 1 and type 2 membranes • Detects small foci of fluid, PED and neurosensory detachment. • Confirms that it is classic or occult CNV o Monitors the response to treatment, o determines the frequency and duration of IVT injections • Provides quantitative measurement of activity • It is a reliable method to be used for fellow up after antiVEGF injections
- 24. Polypoidal Choroidal Vasculopathy (PCV)
- 26. Central Retinal Vein Occlusion
- 27. segmented surface maps of an ERM Epiretinal Membrane (ERM)
- 28. Vitreomacular Traction Syndrome SD-OCT showed that VMT could be sub-classified into two subgroups, focal and broad
- 29. Myopic traction maculopathy (MTM) retinal folding in the macular area SD-OCT clearly visualized macular pathology such as schisis , holes and myopic traction
- 30. Macular Hole The predictive value
- 32. Idiopathic central serous chorio-retinopathy Using SD-OCT findings, the degree of visual loss in CSR can be correlated with: 1. the extent of IS/OS band disruption (which indicates damage of the outer retinal layers), 2. presence of subfoveal defects in the IS/OS.
- 33. Retinal dystrophies Visualization of Lipofuscin Early stage of RP Cone-rod dystrophy Stargardt disease Recent studies using SD-OCT showed that foveomacular retinoschisis in XLRS does not appear to occur in the NFL X-linked retinoschisis
- 34. Previtelliform & vitelliform stage vitelliform macular dystrophy
- 35. Glaucoma Cornea & Anterior segment Intraoperative uses Functional SD-OCT Retina
- 36. Structural changes precedes Functional changes
- 37. only surface topography pp NFL thickness
- 39. • Neural retinal rim • Cup area Normal Glaucoma ONH parameters & RNFL thickness maps • RNFL TSNIT graph • RNFL Thickness Map 3-D Imaging of the ONH true optic nerve topography
- 41. Anterior segment SD-OCT imaging was able to show fine superficial features in the bleb wall.
- 42. Glaucoma Intraoperative uses Functional SD-OCT Retina Cornea & Anterior segment
- 43. • OCT could provide more accurately map corneal thickness, epithelial thickness, and corneal curvatures Corneal mapping over 8 meridians (8 x 1019 a-scans) in 0.31 second • High-resolution 2mm scan Stroma /Epithelium/Endothelium assessment Cornea Pachymetry
- 44. Lasik Keratoconus detection Guiding PTK IOL calculation Glaucoma surgery Tear meniscus assessment
- 46. PK needed .. Not A Candidate for PTK Full thickness scar It precisely measures the opacity size It helps in proper management decision o When to peel. o How deep to ablate. o When to use transepithelial ablation. o When keratoplasty is needed. o When to do nothing. A Candidate for PTK After PTK Before PTK
- 47. Normal reference pachymetry map Keratoconus pachymetry map Inverse normalized pachymetry map Cone is revealed
- 49. Fuchs corneal dystrophy with corneal guttae on the posterior corneal surface. . macular corneal dystrophy with irregularity of Bowman layer
- 51. dry eye soft contact lens
- 53. Glaucoma Intraoperative uses Functional SD-OCT Retina Cornea & Anterior segment
- 54. Portable unit Non-contact imaging Intraoperative use Sedated or non- sedated infant in the supine position
- 55. 1 For Pediatric use 1 Oculocutaneous Albinism Retinopathy of Prematurity shaken baby syndrome elevation of the optic nerve Pre macular fold By SD-OCT we can image premature infants, without the risk of general anesthesia
- 56. 2 For Intraoperative use • before and after internal limiting membrane removal (before fluid-gas exchange) 3D En face image B scan •to assess the donor- host interface • to find interface fluid that was clinically undetectable under the microscope removal of the trabecular meshwork using the trabeculotome. the placement of transcanalicular shunts to guide the needle during pharmacotherapeutic injections into Schlemm’s canal such as gene transfer. Before and after membrane peel Posterior segment Cornea Glaucoma
- 57. Glaucoma Intraoperative uses Functional SD-OCT Retina Cornea & Anterior segment
- 58. Doppler • Recently SD-OCT allows imaging of • That has a value in Glaucoma (assess that may help in more accurate RNFL thickness determinations ).
- 59. • Evolution 1 • Optical principal 2 • TD vs SD 3 • Advantages 4 • Clinical Practice Applications 5 • Commercially available instruments 6 • Summary 7
- 60. Topcon –3D OCT1000 Cirrus HD OCT Spectralis (Heidelberg) Bioptogen - SDOCT Copernicus HR (Optopo OCT SLO (OPKO/OTI) RTVue (Optovue)
- 61. Topcon –3D OCT1000 Cirrus HD OCT Spectralis (Heidelberg) Bioptogen - SDOCT Copernicus HR (Optopo OCT SLO (OPKO/OTI) RTVue (Optovue)
- 62. • Evolution 1 • Optical principal 2 • TD vs SD 3 • Advantages 4 • Clinical Practice Applications 5 • Commercially available instruments 6 • Summary 7
- 63. SD-OCT has many advantages over TD-OCT SD-OCT can yield information similar to and even more than TD-OCT, RTA, GDx and HRT. Quantitative assessment of retinal diseases True retinal thickness (not comparable with RT measured by TD instrument ) objective, quantitative, and reproducible images of the ONH and RNFL and recently ganglion cell complex loss Map corneal thickness, epithelial thickness, and corneal curvatures Hand held pediatric and intra operative OCT is now available New developments; Doppler will be promising