This document provides an overview of ophthalmic ultrasound including instrumentation, indications, principles, and techniques. It discusses B-scan, UBM, and A-scan ultrasound and how they are used to examine intraocular structures. Specific applications like detecting vitreous hemorrhage, retinal detachment, and intraocular tumors are covered. The document concludes with sample ultrasound images and multiple choice questions to test comprehension.

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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17. 3/15/2013 17

18. Frequency versus Penetration
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19. 3/15/2013 19

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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