Optical coherence tomography

1. OPTICAL COHERENCE TOMOGRAPHY
PART-1
OPTOM FASLU MUHAMMED
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2. Optical: relating or involving light and
optics
Coherence: Constant phase
difference in 2 or more waves
overtime
Tomography: imaging by sectioning or
slicing
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3. INTRODUCTION
 OCT is the new diagnostic tool that can perform
cross- sectional images of biological tissues
within less than 10 micron axial resolution.
 It provide non contact, real time, high resolution,
cross- sectional imaging of the eye
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4. PRINCIPLE
 interferometry and low coherence light in near
infrared range (820nm)
 probe beam
 Reflected light from each structures are according
to their optical property
 Based on interferometry
 involves interference between the
reflected light and the reference
beam
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5. 5
L.S
REFERENS
E MIRROR
BEAM
SPLITTE
R
DETECTORE
EYE
REFLECTED
MEASSURE
MENT BEAM

6.  The echo time delay of the light reflected from various
layers of retina is compared with echo time delay of the
light reflected form the reference mirror
 positive interference - light reflected from the retina and
the reference mirror- within short coherence length of
each other.
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7.  photo detector -range of time delays for comparison
 Different colors represent light backscattering from
different depths of retina.
 The low- coherence light source determines the axial
resolution.
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8. OCT SYSTEM COMPRISES
 Fundus viewing unit
 Interferometry unit
 Computer display
 Control panel
 Color printer
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9. • Resolution 10 m
• 2 dimensional images
• Low coherence
interferometry
 using fixed wavelength
• Lower speed
 Upto 512 A scan/sec
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• Resolution 3m
• 2 or 3 dimensional images
• Low coherence
interferometry
• using broad wavelenth
spectrum
• High speed –
• Upto 16000A scan/sec
TIME DOMAIN OCT SPECTRAL DOMAIN OCT
2 TYPE OCT

10. SPECTRAL 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
• 3-D scanning improves clinical utility
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11. PROCEDURE
Activation of the machine and entering of patient data is
the first step.
Patient position: Patient is asked to look in to the internal
fixation target light.
Protocol for scan is selected as per the case requirement.
The scanning beam is placed on the area of interest and
scans are obtained.
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12. 12
Advantages Disadvantages
Non contact Media
clarity
Easy tolerance skill of operator
Quantitative retinal pt. cooperation
Information
Teaching tool non-centered scans-
inaccurate
measurements.

13. NORMAL OCT SCAN OF RETINA
 The OCT scan of retina allows cross-sectional
study of the macular ,peripapillary region including
RNFL and ONH region
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14. PHOTORECEPTORSRPE
CHORIOCAPILLARIS
NFL
FOVEOLA
GCL
ELM
ONL
OPL
INL
IPL

15. NORMAL OCT
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•High reflective (Red) - NFL & RPE
• Medium reflective (yellow / Green) - Plexiform >Nuclear
• Low reflective (Blue-Black) - photoreceptors
• Photoreceptor layer - thickest at fovea
• NFL- increased thickness nasally

16. OCT SCANS
 Line scan:
 It gives an option of acquiring multiple line scans
without returning to main window.
 . Default angle is 0* and length of scan is 5mm
 The length of the scan and angle can be altered to
acquire multiple scans of different parameter.
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17. 17

18.  Radial line:
 Consists 6-24 equally spaced line scans that pass
through a central common axis; the length of these line
scans can be changed by adjusting the size of aiming
circle
 The radial lines are useful for acquiring macular scan
and retinal thickness /volume analysis.
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20.  Macular thickness map ;
 same as radial lines except that the aiming circle has a
fixed diameter of 6mm .
 protocol helps in measuring macular thickness
 Fast macular thickness map
 a quick protocol that takes only 1.92 seconds to acquire
six scan of 6mm length each , when done in both the
eyes
 used for comparative retinal thickness / volume analysis
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21. EMM5 (MACULAR THICKNESS SCAN)
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22. THICKNESS MAP
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23.  Raster lines ;
 it provides options of acquiring series of lines that are
parallel , equally spaced and are 6-24 in number
 This scan is especially useful in choroidal neovascular
membrane where one wishes to obtain scan at multiple
level.
 Not only CNVM to scan ,all macular disease
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24. RASTER LINE SCAN
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25. CROSS LINE SCAN
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26.  Optic disc scan:
 Consits of equally placed line scans 4 mm length ,at 30*
intervals and centered on disc
 Accurate assessment of size ,area ,C:D ratio ,volume of cup
can be meassured
 RNFL scan:
 Circular scan of 1.34mm radius centered on ONH
 The mean RNFL Thickness meassured using age adjusted
RNFL thickness average analysis protocol
 In case of glaucoma progression, neuro ophthalmic diseases.
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27. OCT SCANS
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28. TO BE CONTINUED…
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29. ANY DOUBTS ????
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30. REFERENCE
 Ophthalmology investigation and examination
techniques –bruce james larry benjamin-pg no.232-
239
 RTVue users manual OF OCT
 Diabeticeye disease-Alejandro espaillat-pg.75
 www.opsm.com
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31. PROFICIENCY TEST
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32. 1.BASIC PRINCIPLE OF OCT ?
A. SCATTERING
B. POLARIZATION
C. INTERFERENCE
D. DIFFRACTION
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33. 2.IN NORMAL OCT ,NERVE FIBER LAYER
INCREASED THICKNESS AT WHICH AREA?
A. NASALLY
B. TEMPORAL
C. SUPERIOR
D. INFERIOR
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34. 3. RNFL SCAN CIRCULAR SCAN OF
………..RADIUS CENTERED ON ONH
A. 3.5 mm
B. 2mm
C. 3mm
D. 1.34mm
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35. 4.RADIAL LINE CONSISTS OF EQUALLY SPACED LINE
SCANS OF ……….
A. 6-24 line scan
B. 1-20 line scan
C. 1-6 line scan
D. None of the above
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36. 5.IDENTIFY THE SCAN?
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A.Line scan
B.Cross line scan
C.RNFL Scan
D.None of the
above

37. THANK UUUUU…
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