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-photographs1
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
Wollstein et al. Ophthalmology 2000
Kass et al. Arch Ophthalmol 2001
Zangwill LM, Weinreb RN, et al. Archives of Ophthalmol

4. Birefringent structure
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 Weaknesses 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
Normal
Glaucoma
Atypical
1. Bagga, Greenfield, Feuer. AJO, 2005: 139: 437.
2. Huang, Bagga, Greenfield, Knighton IOVS, 2004: 45: 3037.

6. CSLO – HRT 3 Strengths Weaknesses 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
768 pixels (A-scans) captured in 1.92 seconds is slower than eye movements
Stabilizing the retina reveals true scan path (white circles)1
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, 2003

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

10. Time Domain OCT artifacts can be common
Sadda, Wu, et al. Ophthalmology 2006;113:
Ray, Stinnett, Jaffe . Am J Ophth 2005; 139:18-29
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 (won’t 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
40,000
RTVue
2006
26,000
20,000
Speed
(A-scans
per sec)
Time domain OCT
Fourier domain OCT
~ 65 x faster
~ 2 x resolution
Zeiss OCT 1 and 2, 1996
Zeiss OCT1 debuted at 100 axial scans per second. The Stratus quadrupled the speed in axial scans per second was sufficient to make OCT a standard for the diagnosis of many retinal diseases and glaucoma. By using the new Fourier-domain technology, OptoVue is introducing the RTVue OCT system at an amazing 26,000 axial scans per second, a whopping 65-fold advance over the Stratus. This generational leap in speed is greater than the difference between a 1920 biplane and the latest Boeing jet airliner. The RTVue also offer a 2-fold advance in resolution to 5 micron, close to the “ultrahigh-resolution” level.
400
Zeiss Stratus 2002
100 16 10 7 5
Depth Resolution (mm)

13. Comparison of OCT Images
(Time Domain)
1996
Stratus OCT
(Time Domain)
2002
RTVue
(Fourier Domain)
2006

14. Drusen not visible in Stratus Time Domain OCT
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. Same eye, PED missed by Stratus
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. Time Domain OCT vs Fourier Domain OCT
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
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
FD OCT can capture 2000 pixels simultaneously, while TD OCT captures one pixel at a time. So in the time it take TD OCT to form one single axial scan, FD OCT can capture an entire image. The higher speed and resolution of FD-OCT allows higher definition, or more pixels per image. As anyone familiar with high definition TV know, this makes the picture much sharper. Details such as small blood vessels and the photoreceptore inner and outer segment boundary become clearly visible. Because the FD OCT picture is captured in a small fraction of a second, there is no motion artifact that is commonly seen in conventional OCT images. Finally, because of the efficiency of simultaneous signal acquisition, FD OCT actually has higher signal, or appear brighter and cleaner, than TD OCT. Even deep choroidal vessels can be visible in normal eyes.

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
Anterior Chamber
Retina
Glaucoma

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

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

23. Retina Analysis with the RTVue: 3-D Scans
Provides
3 D map
Comprehensive assessment
Fly through review
C scan view
SLO OCT image simultaneously captured
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

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

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

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

28. Glaucoma Analysis with the RTVue: Nerve Head Map
Nerve Head Map (NHM) Ganglion Cell Map (MM7) D Optic Disc
Data Captured: 9,510 A scans (pixels)
Time: 370 msec
Area covered: 4 mm diameter circle
Data Captured: 51,712 A scans (pixels)
Time: 2 seconds
Area covered: 4 x 4 X 2 mm
Data Captured: 14,810 A scans (pixels)
Time: 570 msec
Area covered: 7 x 7 mm
Provides
Cup Area
Rim Area
RNFL Map
Provides
Ganglion cell complex assessment in macula
Inner retina thickness is:
NFL
Ganglion cell body
Dendrites
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)
The speed and resolution of the RTVue is also very useful in glaucoma diagnosis. In the Advanced Imaging for Glaucoma study, we use the RTVue to measure the ganglion cells over a wide macular area.
Images courtesy of Dr. Ou Tan, USC

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

31. Glaucoma Cases
Optovue, RTVue

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

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

34. RTVue Normative Database
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 Borderline Sector results in Superior-temporal region
Abnormal parameters
OS Normal
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
Change in RNFL parameters
RNFL trend analysis

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

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
Post-LASIK interface fluid & epithelial ingrowth
Epithelial ingrowth
Fluid
Fibrosis

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
Narrow angle after peripheral iridotomy
Limbus
Angle Opening Distance 500 mm anterior to scleral spur
(AOD 500)
Scleral spur 47

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

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!