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Fourier Domain OCT: The RTVue Michael J. Sinai, PhD Director of Clinical Affairs Optovue, Inc.

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Presentation on theme: "Fourier Domain OCT: The RTVue Michael J. Sinai, PhD Director of Clinical Affairs Optovue, Inc."— Presentation transcript:

1 Fourier Domain OCT: The RTVue Michael J. Sinai, PhD Director of Clinical Affairs Optovue, Inc.

2 Rise of Structural Assessment with Scanning Lasers Scanning lasers provide objective and quantitative information for numerous ocular pathologies First appeared over 20 years ago as a research tool Today, structural assessment with retinal imaging devices has become an indispensable tool for clinicians

3 Role of imaging in clinical practice AAO preferred practice patterns recommends using scanning laser imaging in routine clinical exams In glaucoma, studies show imaging results can be as good as expert grading of high quality stereo-photographs 1 Pre-perimetric glaucoma is now commonly accepted In OHTS, most converted based on structural assessment only (not fields) 2 OHTS has shown that imaging results have a high positive and negative predictive power for detecting glaucoma 3 1.Wollstein et al. Ophthalmology Kass et al. Arch Ophthalmol Zangwill LM, Weinreb RN, et al. Archives of Ophthalmol

4 3 Imaging technologies have been shown to be effective in detecting and managing ocular pathologies Scanning Laser Polarimetry (SLP) Confocal Scanning Laser Ophthalmoscopy (CSLO) Optical Coherence Tomography (OCT) Retardation Light Polarizer Two polarized components Birefringent structure (RNFL)

5 SLP – GDx VCC Strengths Provides RNFL thickness Large database Easy to use/interpret (deviation map/automated classifier) Progression Weaknesses Atypical Pattern Birefringence (RNFL artifact) 1 Converts retardation to thickness assuming uniform birefringence (not true) 2 Only RNFL information (No Optic Disc info and no Retina info) Data not backwards compatible NormalGlaucomaAtypical 1. Bagga, Greenfield, Feuer. AJO, 2005: 139: Huang, Bagga, Greenfield, Knighton IOVS, 2004: 45: 3037.

6 CSLO – HRT 3 Strengths Provides Optic Disc morphology Sophisticated Progression Analysis Large ethnic Specific Database comparisons Automated classifier Data backwards compatible Some retinal capabilities Cornea microscope attachment Weaknesses Only Optic Disc assessment (poor RNFL) Manual Contour Line drawing Reference plane based on surface height (can change) Retina analysis confined to edema detection and sensitive to image quality Cornea scans very difficult and impractical

7 OCT – Time Domain (Stratus from CZM and SLO/OCT from OTI) Strengths Provides Cross Sectional images Useful to calculate RNFL thickness Cross section scans useful for retinal pathologies Database comparisons Weaknesses Slow scan speed (400 A scans / second) Limited data for glaucoma, 768 pixel (A-scan) ring for RNFL Limited data for retina, 6 radial lines with 128 A scans (pixels) each Macula maps 97% interpolated No progression analysis Location of scan ring affects RNFL results Prone to motion artifacts because of slow scan speed Poor optic disc measurements

8 Time Domain OCT susceptible to eye movements 1. Koozekanani, Boyer and Roberts. Tracking the Optic Nervehead in OCT Video Using Dual Eigenspaces and an Adaptive Vascular Distribution Model; IEEE Transactions on Medical Imaging, Vol. 22, No. 12, pixels (A-scans) captured in 1.92 seconds is slower than eye movements Stabilizing the retina reveals true scan path (white circles) 1

9 Scan location and eye movements affects results T S N I T Properly centered Normal Double Hump Poorly centered: too inferior Poorly centered: too superior Inferior RNFL Loss Superior RNFL Loss

10 Time Domain OCT artifacts can be common 1.Sadda, Wu, et al. Ophthalmology 2006;113: Ray, Stinnett, Jaffe. Am J Ophth 2005; 139: Bartsch, Gong, et al. Proc. of SPIE Vol. 5370;

11 The Future of OCT RTVue Fourier Domain OCT overcomes limitations of Time Domain OCT Devices – Better resolution (5 micron VS 10 micron) – Faster scan speeds (26,000 A scans / sec VS 400) – 3-D data sets (wont miss pathology) – Large data maps (less interpolation) – Progression capabilities – Layer by layer assessment – Versatility (Anterior Chamber Imaging) Retina Glaucoma Anterior Chamber

12 The Evolution of OCT Technology Zeiss OCT 1 and 2, 1996 Zeiss Stratus 2002 RTVue , Speed (A-scans per sec) Depth Resolution (mm) Fourier domain OCT Time domain OCT ~ 65 x faster ~ 2 x resolution 7 40,000 20,000

13 Comparison of OCT Images OCT 1 / 2 (Time Domain) Stratus OCT (Time Domain) RTVue (Fourier Domain)

14 Case 1: AMD Stratus (Time Domain) RTVue (Fourier Domain) Drusen not visible in Stratus Time Domain OCT

15 Case 2: DME Stratus (Time Domain) RTVue (Fourier Domain)

16 Case 3: PED Stratus (Time Domain) RTVue (Fourier Domain) Same eye, PED missed by Stratus

17 Case 4: Macula Hole Stratus (Time Domain) RTVue (Fourier Domain)

18 Fourier Domain Entire A scan generated at once based on Fourier transform of spectrometer analysis Stationary reference mirror 26,000 A scans per second 5 micron depth resolution B scan (1024 A-scans) in 0.04 sec Faster than eye movements Time Domain OCT vs Fourier Domain OCT Time Domain A-scan generated sequentially one pixel at a time in depth Moving reference mirror 400 A scans per second 10 micron depth resolution B scan (512 A scans) in 1.28 sec Slower than eye movements

19 Summary of Fourier Domain OCT Advantages High speed reduces eye motion artifacts present in time domain OCT High resolution provides precise detail, allows more structures to visualized Layer by layer assessment Larger scanning areas allow data rich maps & accurate registration for change analysis 3-D scanning improves clinical utility

20 RTVue Clinical Applications Glaucoma Retina Anterior Chamber

21 Retina Analysis with the RTVue: Line Scans Line Scan Data Captured: 1024 A scans (pixels) Time: 39 msec Area covered: 6 mm line (adjustable 2-12 mm) Provides High resolution B scan Image averaging increases S/N Data Captured: 2048 A scans (pixels) Time: 78 msec Area covered: 2 x 6 mm lines (adjustable 2-12 mm) Provides vertical and horizontal high resolution B scan Image averaging increases S/N Cross Line Scan

22 Courtesy: Michael Turano, CRA Columbia University. Line Scan: Cystoid Macula Edema Courtesy: Michael Turano, CRA Columbia University.

23 Retina Analysis with the RTVue: 3-D Scans Data Captured: 51,712 A scans (pixels) Time: 2 seconds Area covered: 4 x 4 X 2 mm (adjustable) 101 B scans each 512 A scans Provides 3 D map Comprehensive assessment Fly through review C scan view SLO OCT image simultaneously captured

24 3-D view reveals extent of damage over large area Top Image: En face view of retinal surface from 3-D scan Bottom Image: B scan from corresponding location (green line)

25 Full retinal thickness Layer specific thickness maps Detailed B scans ETDRS thickness grid Outer retinal thickness RPE/Choroid Elevation Data Captured: 19,496 A scans (pixels) Time: 750 msec Area covered: 5 mm x 5 mm (grid pattern) Inner retinal thickness ILM to RPE ILM to IPL IPL to RPE RPE height Surface Topography ILM height Provides: Retina Analysis with the RTVue: Macula Maps (MM5)

26 Glaucoma Analysis with the RTVue: Nerve Head Map Provides Cup Area Rim Area RNFL Map TSNIT graph 16 sector analysis compares sector values to normative database and color codes result based on probability values (p values) Color shaded regions represent normative database ranges based on p-values

27 Glaucoma Analysis with the RTVue: Nerve Head Map Parameters RNFL Parameters All parameters color-coded based on comparison to normative database Optic Disc Parameters

28 Glaucoma Analysis with the RTVue: Nerve Head Map Nerve Head Map (NHM) Ganglion Cell Map (MM7) 3-D Optic Disc Data Captured: 9,510 A scans (pixels) Time: 370 msec Area covered: 4 mm diameter circle Provides Cup Area Rim Area RNFL Map Data Captured: 14,810 A scans (pixels) Time: 570 msec Area covered: 7 x 7 mm Provides Ganglion cell complex assessment in macula Inner retina thickness is: NFL Ganglion cell body Dendrites Data Captured: 51,712 A scans (pixels) Time: 2 seconds Area covered: 4 x 4 X 2 mm Provides 3 D map Comprehensive assessment TSNIT graph

29 The ganglion cell complex (ILM – IPL) Inner retinal layers provide complete Ganglion cell assessment: Nerve fiber layer (g-cell axons) Ganglion cell layer (g-cell body) Inner plexiform layer (g-cell dendrites ) Images courtesy of Dr. Ou Tan, USC

30 Normal vs Glaucoma Normal Glaucoma Cup Rim RNFL Ganglion cell assessment with inner retinal layer map NHM4 GCC

31 Glaucoma Cases Optovue, RTVue

32 Glaucoma Patient Case BK 64 year old white male 24-2 white on white visual field Nerve Head Map on RTVue Normal

33 Glaucoma Patient Case BK 10-2 white on white visual field Macula Inner Retina Map on RTVue Normal

34 RTVue Normative Database 34 Age Adjusted comparisons for more accurate comparisons Age and Optic Disc adjusted comparisons for Nerve Head Map scans Over 300 eyes, ethnically mixed, collected at 8 clinical sites worldwide IRB approved study from independent agency

35 Nerve Head Map (NHM4) with Database comparisons Patient Information RNFL Thickness Map RNFL Sector Analysis Optic Disc Analysis Parameter Tables TSNIT graph Asymmetry Analysis

36 Ganglion Cell Complex (GCC) with Database comparisons Patient Information GCC Thickness Map Deviation Map Parameter Table Significance Map

37 Early Glaucoma OS Normal Borderline Sector results in Superior- temporal region Abnormal parameters TSNIT dips below normal TSNIT shows significant Asymmetry

38 GCC Analysis may detect damage before RNFL GCC and RNFL analysis will be correlated, however GCC analysis may be more sensitive for detecting early damage

39 Glaucoma Progression Analysis (Nerve Head Map of stable eye) Thickness Maps Change in optic disc parameters TSNIT graph comparisons RNFL trend analysis Change in RNFL parameters

40 Glaucoma Progression Analysis (GCC of stable glaucomatous eye) Thickness Maps Deviation Maps GCC parameter change analysis Significance Maps

41 Versatility: Scanning the Anterior Chamber with the same device Cornea Adapter Module (CAM)

42 Higher resolution allows better visualization of LASIK flap 2 years after LASIK with mechanical microkeratome Image enhanced by frame averaging

43 Post-LASIK interface fluid & epithelial ingrowth 056-CP Fibrosis Epithelial ingrowth Fluid

44 Higher resolution helps visualize pathogens Acanthamoeba in 0.25% agar

45 Pachymetry Maps Inferotemporal thinning Normal Keratoconus

46 Angle Measurements Normal Narrow

47 Narrow angle after peripheral iridotomy LD044, OS Angle Opening Distance 500 m anterior to scleral spur (AOD 500) Scleral spur Limbus

48 Normal Angle MaTa, OD Trabecular meshwork- Iris Space 750 m anterior to scleral spur (TISA750) Scleral spur Limbus

49 Advantages of the RTVue 5 micron resolution allows more structures and detail to be visualized High speed allows larger areas to be scanned Layer by layer assessment Data-rich maps Volumetric analysis Comprehensive glaucoma assessment (Cup, Rim, RNFL, ganglion cell complex) Normative Database Progression Analysis Anterior Chamber imaging

50 Thank You!

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