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Fourier Domain OCT: The RTVue. Michael J. Sinai, PhD Director of Clinical Affairs Optovue, Inc. Rise of Structural Assessment with Scanning Lasers . Scanning lasers provide objective and quantitative information for numerous ocular pathologies

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fourier domain oct the rtvue

Fourier Domain OCT: The RTVue

Michael J. Sinai, PhD

Director of Clinical Affairs

Optovue, Inc.

rise of structural assessment with scanning lasers
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
role of imaging in clinical practice
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. 2005.
3 imaging technologies have been shown to be effective in detecting and managing ocular pathologies
3 Imaging technologies have been shown to be effective in detecting and managing ocular pathologies

Light

Polarizer

  • Scanning Laser Polarimetry (SLP)
  • Confocal Scanning Laser Ophthalmoscopy (CSLO)
  • Optical Coherence Tomography (OCT)

Two polarized components

Birefringent structure

(RNFL)

Retardation

slp gdx vcc
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

Normal

Glaucoma

Atypical

1. Bagga, Greenfield, Feuer. AJO, 2005: 139: 437.

2. Huang, Bagga, Greenfield, Knighton IOVS, 2004: 45: 3037.

cslo hrt 3
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
oct time domain stratus from czm and slo oct from oti
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
time domain oct susceptible to eye movements
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

scan location and eye movements affects results
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

Superior RNFL “Loss”

Inferior RNFL “Loss”

Normal Double Hump

time domain oct artifacts can be common
Time Domain OCT artifacts can be common
  • Sadda, Wu, et al. Ophthalmology 2006;113:285-293
  • Ray, Stinnett, Jaffe . Am J Ophth 2005; 139:18-29
  • Bartsch, Gong, et al. Proc. of SPIE Vol. 5370; 2140-2151
the future of oct
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

Anterior Chamber

Glaucoma

the evolution of oct technology
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

400

Zeiss Stratus 2002

100

16

7

5

10

Depth Resolution (mm)

comparison of oct images
Comparison of OCT Images

OCT 1 / 2

(Time Domain)

1996

Stratus OCT

(Time Domain)

2002

RTVue

(Fourier Domain)

2006

case 1 amd
Case 1: AMD

Stratus

(Time Domain)

RTVue

(Fourier Domain)

Drusen not visible in Stratus Time Domain OCT

case 2 dme
Case 2: DME

Stratus

(Time Domain)

RTVue

(Fourier Domain)

slide16

Case 3: PED

Stratus

(Time Domain)

RTVue

(Fourier Domain)

Same eye, PED missed by Stratus

slide17

Case 4: Macula Hole

Stratus

(Time Domain)

RTVue

(Fourier Domain)

slide18

Time Domain OCT vs Fourier Domain OCT

  • 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
  • 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
summary of fourier domain oct advantages
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
rtvue clinical applications
RTVue Clinical Applications

Anterior Chamber

Retina

Glaucoma

slide21

Retina Analysis with the RTVue: Line Scans

Cross Line Scan

  • Line Scan
  • Provides
  • vertical and horizontal 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)
  • 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
slide22

Courtesy: Michael Turano, CRA

Columbia University.

Line Scan: Cystoid Macula Edema

Courtesy: Michael Turano, CRA

Columbia University.

slide23

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
3 d view reveals extent of damage over large area
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)

slide25

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:

  • Outer retinal thickness
  • Innerretinal thickness

Surface Topography

Full retinal thickness

RPE/Choroid Elevation

ILM height

RPE height

IPL to RPE

ILM to IPL

ILM to RPE

slide26

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

slide27

Glaucoma Analysis with the RTVue:

Nerve Head Map Parameters

Optic Disc Parameters

RNFL Parameters

All parameters color-coded based on comparison to normative database

slide28

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
  • 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

the ganglion cell complex ilm ipl
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

normal vs glaucoma
Normal vs Glaucoma

Cup

Rim

NHM4

RNFL

Ganglion cell assessment with inner retinal layer map

GCC

Normal

Glaucoma

glaucoma cases
Glaucoma Cases

Optovue, RTVue

glaucoma patient case bk
Glaucoma Patient Case BK

64 year old

white male

Normal

Nerve Head Map on RTVue

24-2 white on white visual field

glaucoma patient case bk1
Glaucoma Patient Case BK

Macula Inner Retina Map on RTVue

Normal

10-2 white on white visual field

rtvue normative database
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
nerve head map nhm4 with database comparisons
Nerve Head Map (NHM4)with Database comparisons

Patient Information

RNFL Thickness Map

RNFL Sector Analysis

Optic Disc Analysis

Parameter Tables

TSNIT graph

Asymmetry Analysis

ganglion cell complex gcc with database comparisons
Ganglion Cell Complex (GCC)with Database comparisons

Patient Information

GCC Thickness Map

Deviation Map

Parameter Table

Significance Map

early glaucoma
Early Glaucoma

Borderline Sector results in Superior-temporal region

Abnormal parameters

OS Normal

TSNIT dips below normal

TSNIT shows significant Asymmetry

gcc analysis may detect damage before rnfl
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

glaucoma progression analysis nerve head map of stable eye
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

slide40

Glaucoma Progression Analysis(GCC of stable glaucomatous eye)

Thickness Maps

Deviation Maps

Significance Maps

GCC parameter change analysis

higher resolution allows better visualization of lasik flap
Higher resolution allows better visualization of LASIK flap

2 years after LASIK with mechanical microkeratome

Image enhanced by frame averaging

pachymetry maps
Pachymetry Maps

Inferotemporal thinning

Normal

Keratoconus

angle measurements
Angle Measurements

Normal

Narrow

narrow angle after peripheral iridotomy
Narrow angle after peripheral iridotomy

LD044, OS

Limbus

Angle Opening Distance500mm anterior to scleral spur

(AOD 500)

Scleral spur

normal angle
Normal Angle

MaTa, OD

Limbus

Trabecular meshwork-Iris Space 750mm anterior to scleral spur

(TISA750)

Scleral spur

advantages of the rtvue
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