1. OPHTHALMIC ULTRASOUND
Dr. Yousaf Jamal
26/05/2012

2. Contents
• Introduction
• Instrumentation
• Indications
• Ultrasound Principles & physics
• B-scan, UBM, A-scan & techniques
• MCQs
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3. Objectives
• To create awareness about basics of US
• To emphasize on the importance of
ophthalmic US
• To create & follow standard operating
protocol while performing ophthalmic US
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4. Introduction
• Sound…
• Noise…
• Ultrasound…
• What is…
− Supersonic
− Hypersonic
− Transonic
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5. • Just for test of general knowledge
• Who was the first one to use ultrasound?
?
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6. Echolocation types
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7. TYPES
A – SCAN
B – SCAN

8. Instrumentation
• Pulsed-echo system
− Transducer
− Amplifier
− Display monitor
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9. Transducer function
ELECTRIC CURRENT
TRANDUCER
US WAVES
SURFACE
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10. Artist: Dr. Yousaf Jamal
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11. B-Scan
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12. B-scan
• Brightness mode scan
• OPD procedure
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13. Indications
• To examine intraocular structures with no
direct visualization of posterior segment
Or
• To confirm or differentiate between
pathologies in clear media
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14. Ultrasound physics & principles
• Parts of Sound wave
− Amplitude
− Wavelength (crest & trough)
− Frequency
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15. Frequency & its relations
With resolution
Image quality
With penetration
How much deep
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16. Frequency versus Resolution
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18. Frequency versus Penetration
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20. Medical Ultrasound frequencies
• Abdominal US
− 1-5 MHz
• Ophthalmic US (B-scan)
− 8-10 MHz
• Ultrasound Biomicroscopy (UBM)
− 20-50 MHz
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21. Ophthalmic US
• B-scan
− 10 MHz
− 40 mm
− 940 microns
• UBM
− 50 MHz
− 5-10 mm
− 40 microns
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22. Principles of US
• Velocity
• Reflectivity
• Angle of incidence
• Absorption
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23. Velocity
• Depends upon density of medium
• Distance = speed x time
− Thru air − Thru aqueous & vitreous
• 330 m/s • 1532 m/s
− Thru water − Thru cornea & lens
• 1500 m/s • 1641 m/s
− Thru metal − Thru silicon oil…1000 CS
• 5000 m/s • 980 m/s
− Thru blood − Thru silicon oil…5000 CS
• 1570 m/s • 1040 m/s
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24. Reflectivity (Echo)
• Follows law of Acoustic impedance
• A.I. = sound velocity x density of medium
Medium Acoustic impedance (x106) kgm-2 s-1
Fat 1.38
Human tissue 1.63
Blood 1.61
Muscle 1.70
Bone 5.6-7.8
Vitreous 1.52
Aqueous 1.50
Lens 1.84 24
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25. • Higher gain for weaker echoes
• Low gain for stronger echoes
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26. Angle of incidence
Transducer
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27. Absorption
• Dependent on density of medium
• Closed lids should be therefore avoided
but in children or open wound
• Shadowing occurs bcz of it
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28. Probe positioning
• Trans-ocular approach
− Transverse
− Longitudinal
− Axial
• Para-ocular approach
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29. Trans-ocular
Transverse position
− Most commonly used position
− Shows about 6 clock hours
− Used for basic screening
− Detects lateral extent of pathology
− Probe is placed opposite to the examined
meridian
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30. − Probe marker is tangential to limbus
− Mark is at nasal side when scanning 6 and
12 o’clock
− For the rest…marker is superior
− Limbus-to-fornix approach is used to
detect from posterior pole to periphery
Nasal
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31. Longitudinal positions
− Detects axial (AP) extent of pathology
− Useful for retinal tears detection
− Shows only 1 clock hour scan
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32. − Probe mark is perpendicular to limbus
− Pt looks towards the area of interest
− Optic nerve shadow is always at bottom of
scan
− Limbus-to-fornix approach can be used
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33. Axial positions
• Probe direct over the cornea
• Pt looks in primary gaze
• US waves pass thru center of lens and hit
optic nerve rather than macula
• Lens density affects the quality of image
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34. Positions of axial scan
• Horizontal
− Marker always nasal
• Vertical
− Marker always superior
• Oblique
− Marker always superior
Nasal
Bridge
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35. Basic screening technique
• Done for screening purpose in opaque
media
• Highest gain settings are used so weaker
signals shouldn’t be missed
• Any pathology found…further scanning is
required
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36. Technique
• 05 scans in different positions will detect
gross pathology
• Transverse position with limbus-to-fornix
approach in…
− 12, 3, 6 and 9 o'clock
• Horizontal axial scan…shows optic nerve
& macula in one image
• Print out of each position is taken with
labels
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37. If pathology found…
• Clock hour noted on transverse scan
• Patient is asked to look in the direction of
pathology
• Probe should be perpendicular
• Longitudinal scan, A-scan & change of
gains…adds further info of pathology
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38. Localization of macula
• 04 positions for macular detection
− Horizontal axial
− Vertical axial
− Transverse…probe placed nasally
− Longitudinal…probe placed nasally
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39. Anterior segment evaluation
Immersion technique
High resolution technique
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40. Immersion technique
• Cornea, anterior chamber & lens create
noise bcz of close contact with probe
• Shell or water bath is used to create
space
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41. High resolution technique
• Ultrasound biomicroscopy
• High resolution probes are used
• Scleral shell technique is used
• Image quality far superior to immersion
technique
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43. Common examples
Vitreoretinal disorders
• Most common indication for B-scan
− Vitreous hemorrhage
− Retinal detachment
− Intraocular tumors
− Intraocular foreign bodies
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44. Vitreous hemorrhage
• Fresh:
− Dot-like…Echolucent or low reflectivity
• Old:
− Membrane-like…varying reflectivity &
dense inferiorly
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45. Fresh VH Old VH
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47. Retinal detachment
• Rhegmatogenous R/D:
− Thin, continuous membrane anteriorly
separated from globe wall
− Echoes are of high amplitue-100% of
scleral spike
− Retinal cysts, subretinal hemorrhages may
be seen
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49. • Tractional R/D:
− Traction membranes are seen
− R/D usually doesn’t extend to ora serrata
− Lower mobility in contrast to Rheg. R/D
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52. • Exudative R/D:
− Smooth elevation of retina
− Shifting fluid
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53. Supine position
Erect position
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54. Intraocular tumors
• Retinoblastoma:
− Single or multiple mass lesions arising
from retina
− Highly refractile calcium seeding in
vitreous +/- orbital shadowing
− R/D may be found
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56. • Choroidal melanoma:
− Solid Dome shaped or mushroom shape
− High surface reflectivity with low to
medium internal reflectivity
− A scan flickering spikes…internal blood
flow
− Choroidal excavation
− Exudative R/D may be present
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57. 3/15/2013 Dome shape 57

58. Collar stud shape
Arrowhead in A scan shows bruch’s membrane
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59. Intraocular foreign body
• Echodense signals with shadowing
• Persistence of signals at low gains
• Glass…reverberations
• Air bubble…may simulate IOFB
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61. Dislocated lens
• Signals depend on clarity of lens
• Clear lens…Echolucent globular structure
• Brunescent lens…highly reflective with
shadowing
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64. A-Scan
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65. A - scan
• Amplitude scan
• 10 MHz probe
• Measures axial length of eye and used for
diagnostic purposes when combined with
B-scan
• Follows law of acoustic impedance
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66. • X-axis…time
• Y-axis…amplitude
• Method
− Applanation technique
− Immersion technique
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67. A-scan by Applanation
• Cornea is anesthetized
• Patients should look directly at the red
fixation light
• Probe placed directly on cornea
• This causes a slight indentation (0.14 -
0.28 mm)

68. • Measurements vary slightly from each
other due to inconsistent corneal
compression
• Also, will have a shallower AC depth than
immersion
• Takes (20) readings
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69. • At least (4) of these should be within 0.02
mm of each other, and should look like
the previous slide
• This way the measurements will be made
to the center of the macula, giving the
refractive axial length, rather than
anatomical axial length

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73. A- Scan facts
• Average length of the eye: 23.5mm
• Average A/C depth: 3.24mm (but can
vary greatly)
• Average lens thickness: 4.63mm ( but can
vary with cataractous changes up to as
thick as 7.0mm in density)
• Average K’s : 43.00 – 44.00D

74. Summary
• Ophthalmic US…high frequency
• A & B scans mostly used
• Different pathologies can be diagnosed
easily when both scans are used
simultaneously
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75. Take home message
• Understanding of basic physics
• Proper standardized technique should be
applied in each case
• ‘Eyes do not see what mind does not
know’
• So background knowledge of pathologies
and experience count the yield of US
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77. MCQs / Cases
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78. MCQs / Cases
1. A patient presents with bilateral granulomatous
panuveitis with hazy fundus view due to cataract. No
Hx of trauma. B scan picture is given below:
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79. A. What is the probe position?
• Axial
B. What do the arrow head and arrow show?
• Retinal detachment
• Choroidal thickening
C. Probable diagnosis?
• V-K-H
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80. 2. A young patient with blunt ocular trauma comes to
your opd, complaining of floaters with normal visual
acuity. You order B scan which is given below
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81. • Describe the picture
• What is your probable diagnosis?
• How you differentiate it from retinal detachment?
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82. 3. An old patient complains of decreased vision after
trabeculectomy. There is large bleb but hypotonic
eye. B scan shows
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83. • Describe the picture
• Your probable diagnosis?
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84. 4. Describe the following A-scan
Ans… Immersion technique A-scan
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85. 5. What you say about these A-scans?
Ans… Artifacts By IOL (Reverberations)
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86. 6. Diagnosis?
Ans…Hypotonic eye with choroidal thickening
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87. NEXT
• Lecture
• Dr. Bilal… corneal topography
• Journal club
• Dr. Maooz
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