Ophthalmic ultrasonography uses sound waves to evaluate the eye and orbit. It can assess tumors, retinal detachments, and foreign bodies when the eye is opaque. The A-scan provides one-dimensional measurements of internal structures. The B-scan gives a two-dimensional cross-section, displaying reflections as varying shades of gray. Together they characterize lesions by location, size, internal reflectivity, structure, and vascularity. Ultrasound is used preoperatively for cataract surgery planning and to evaluate intraocular tumors, accurately measuring their dimensions to guide treatment. Common indications also include opaque media evaluation and orbital disorders.

1. OPHTHALMIC
ULTRASONOGRAPHY
Dr. Nick Sargent

2. What are the indications for
ophthalmic ultrasonography?

3. Indications for ophthalmic US
 Evaluation of anterior and posterior segments in
the presence of opaque media
 Assessment of tumours:
 Dimensions
 Tissue characteristics (e.g. presence of calcium)
 Evaluation of orbital disorders
 Detection and location of IOFBs
 Biometry

4. What frequency is used for
standard ophthalmic
ultrasonography?

5.  US is an acoustic wave that consists of an
oscillation of particles within a medium.
 By definition, all US waves have a frequency
greater than 20kHz
 In standard ophthalmic US use 8-10 MHz
(higher than that used in abdominal US)
 Higher frequencies allow more precise
resolution of structures, but depth of penetration
is less)

6. What are the principles of
ultrasonography?

7. Based on the principles of
 Tissue-acoustic impedence mismatch
 Pulse-echo technology

8.  When sound waves moving in air or water
hit a solid surface, they are reflected off it.
This reflected sound is called an echo.

9.  By knowing the speed of sound in air or
water, the distance to the obstacle can be
calculated. To do this we must measure
the time taken for a pulse of sound to
travel to the object and back again:

10.  The distance to the object and back is
given by
distance = speed x time
 As this is the total distance that the sound
has travelled to the object and back, we
must divide by 2 to find the one-way
distance.

11.  As the wave moves through the tissues,
part of the wave maybe reflected toward
back toward the source of the emitted
wave (the probe); called the
REFLECTED WAVE

12.  Between different tissue interfaces, there
maybe a difference in the way that the
wave moves through it: i.e. there may be a
DIFFERENTIAL ACOUSTIC IMPEDENCE

13.  Where there is such differential acoustic
impedence, ECHOES are created.
 The greater the difference in impedence,
the stronger the echo

14.  E.g. strong echoes are produced between
the retina-vitreous interface
 E.g. weak echoes are produced between
vitreous gel and vitreous haemorrhage

15. Pulse-echo technology
 The acoustic wave is produced by
synthetic crystal transducers
 Echoes are retrieved, amplified,
electronically processed and electronically
displayed in visual format

16. How is the ultrasound used
in medicine produced?

17.  The frequencies of ultrasound required for
medical imaging are in the range 1 - 20
MHz. These frequencies can be obtained
by using piezoelectric materials.
 When an electric field is placed across a
slice of one of these materials, the
material contracts or expands.
 If the electric field is reversed, the effect
on the material is also reversed.

18.  If the electric field keeps reversing, the
crystal alternately contracts and expands.
 So a rapidly alternating electric field
causes the crystal to vibrate.

19.  The vibrations are then passed out as a
longitudinal wave. So, a sound wave is
produced.
 The piezoelectric effect occurs in a
number of natural crystals including
quartz, but the most commonly used
substance is a synthetic ceramic, lead
zirconate titanate.

20.  The crystal is cut into a slice with a
thickness equal to half a wavelength of the
desired ultrasound frequency, as this
thickness ensures most of the energy is
emitted at the fundamental frequency.

21. How is the
ultrasound reflected by the
body structures detected?

22.  The piezoelectric effect also works in
reverse.
 If the crystal is squeezed or stretched, an
electric field is produced across it.
 So if ultrasound hits the crystal from
outside, it will cause the crystal to vibrate
in and out, and this will produce an
alternating electric field.

23.  So if ultrasound hits the crystal from
outside, it will cause the crystal to vibrate
in and out, and this will produce an
alternating electric field.

24.  The resulting electrical signal can be
amplified and processed in a number of
ways. So a second crystal can be used to
detect any returning ultrasound which has
been reflected from an obstacle.

25.  Normally the transmitting and receiving
crystals are built into the same hand-held
unit, which is a called an ultrasonic
transducer
(generally, a transducer is any device to
convert energy from one form to another,
usually to or from electrical energy.)

26. PROBE

27. What is acoustic impendence?
How does acoustic impendence
affect the ultrasound scan?

28.  The exact fraction of the incident sound
which is transmitted or reflected depends
on how different the two materials on each
side of the boundary are.

29.  This is described by the acoustic
impedance of the materials, which is
related to the density of the material and
the speed of sound in the material.

30. The greater the difference in
impedance, the more sound will be
reflected rather than transmitted.

31. Some typical impedances are shown in
the table below:
Medium Impedance (in standard unit)
air 0.000429
water
1.50
blood
1.59
fat 1.38
muscle
1.70
bone
6.50

32.  Air and water have very different
impedances, so that a beam of ultrasound
hitting a water surface is almost entirely
reflected away, and only a small amount
enters the water.
 The same applies to a beam trying to
enter the eye from air.

33.  To obtain a reasonable image with good
resolution of an interface between two
layers, around 1% of a beam must be
reflected, leaving a substantial portion to
continue on to further reflections.

34.  Because of the impedance difference
between air and skin, a coupling medium
helps to match the impedance of the
crystal in the probe more closely to the the
impedance of the skin of the patient.

35.  The most common coupling medium is a
film of oil smeared on the patient's skin.
 The operator needs to ensure that the
probe is kept in continuous contact with
the oil, preventing air bubbles coming
between the probe and skin.

36. What is A-scan
ultrasonography?
A.k.a., the A-mode

37.  One dimensional, time versus amplitude
display
 ‘A’ stands for ‘Amplitude’ because
reflectivity (strength of the echo) is
displayed by the amplitude

38.  the distance is represented by the
horizontal baseline.
 This distance depends on the time
required for the sound beam to reach a
given interface and for its echo to return to
the probe

39. A-Scan
a = cornea spike
b = anterior lens spike
c = posterior lens spike
d = retinal spike
e = orbital spike

40.  The A-scan can be combined with a
simultaneous B-scan with a vector line to
demonstrate the position of the A-scan
information

41. What is the effect of
silicone oil on the A-scan?

42. The axial length value will be
longer than expected as
ultrasound travels slower in the
silicone oil than vitreous

43. Axial-length measurement
with the A-scan

44. Can judge if axial length measurements
are probably accurate by:
1) getting one retinal peak rather than
several peaks
2) if there is no significant differences
between the two eyes.

45. Note: the Guideline on Cataract Operation
from the Royal College of
Ophthalmologists finds that :
- 96% of axial lengths fall within the range
21.0 to 25.5 mm and
for 60% this is between 22.5 and 24.5 mm
- in the absence of pathology that might
affect eye size (eg, unilateral refractive error,
coloboma or staphyloma), most individuals
have similar axial lengths in each eye

46. What is B-scan
ultrasonography?
a.k.a., the B-mode

47.  2 dimensional, cross-sectional
display of the globe and orbit
 Image appears in shades of gray

48. ‘B’ stands for ‘Brightness’, because
the brightness (shade of gray)
depends on the echo strength
 Strong echoes appear white (e.g. retinal
tissue, sclera, calcification)
 Weak echoes appear gray (e.g. clotted
vitreous cells)

49. So a single pulse of ultrasound passing
into a series of tissues will give rise to a
series of spots,
The brightness of the spots correspond to
the amplitude of the reflection from
different layers.

50.  The largest amplitude gives rise to a spot with
the greatest brightness.
 The smallest amplitude gives rise to a spot
which is almost black.

51. The corneal spike and the retinal
spike have the biggest amplitude
and therefore appears nearly white.
The posterior lens spike has a
lower amplitude than the anterior
lens spike and therefore appears
darker.

52. The aqueous and the vitreous allow
the sound to pass through with
little impendence and therefore
appears black.
The lens substance offers some
resistance and therefore does not
appears as black.

53. What clinical information is
provided by the A-scan and B-
scan?

54.  A-scan is used mainly for tissue
characterisation
 B-scan is used to obtain architectural
information
 A-scans used in IOL calculations

55.  Both may be needed and the information
they provide may overlap
 US interpretation is most helpful when
combined with clinical and radiographic
examination

56. What features of a lesion are
evaluated during the US
examination?

57. Features
1) Topography:
- location
- configuration
- extension
2) Quantitative features:
- reflectivity
- internal structure
- sound attenuation
3) Dynamic features
- Aftermovement
- Vascularity

58. Topography (location,
configuration, extension)
 Evaluated most often by the 2-dimensional
B-scan

59. REFLECTIVITY
 Evaluated by observing the:
 height of the spike on A-scan
 Signal brightness on B-scan
 INTERNAL REFLECTIVITY refers to the
amplitude of echoes within a lesion and
correlates with its histological architecture.

60. INTERNAL STRUCTURE
 Refers to the degree of variation in the histologic
architecture within a mass lesion.
 Regular internal structure: indicates a
homogenous architecture and is noted by
minimal or no variation in the height of spikes on
the A-scan and a uniform appearance of echoes
on the B-scan.
 Irregular internal structure: indicates a
heterogeneous architecture and is characterised
by variations in the echo appearance.

61. SOUND ATTENUATION
ATTENUATE: means to weaken
or become reduced

62. SOUND ATTENUATION
 Occurs when the acoustic wave is
scattered, reflected, or absorbed by a tissue
 It is indicated by a decrease in the strength
of echoes either within or posterior to a
lesion

63. SOUND ATTENUATION
 Occurs when the acoustic wave is
scattered, reflected, or absorbed by a
tissue
 It is indicated by a decrease in the
strength of echoes either within or
posterior to a lesion

64. SOUND ATTENUATION
See a decrease in spike height on A-scan or
a decrease in brightness of echoes on B-
scan

65. SOUND ATTENUATION
 Sound attenuation may produce
decreased signal strength and a void
posterior to the lesion = SHADOWING
 Examples: bone, calcium, foreign bodies

66. DYNAMIC FEATURES
detected on B-scan
1) Aftermovement
2) Vascularity

67. AFTERMOVEMENT
 Is evaluated by observing the motion of
lesion echoes after cessation of eye
movements.
 Example: the rapid movement of a
vitreous haemorrhage is distinguished
from the slower, undulating movement of
the retina in an acute rhegmatogenous
retinal detachment

68. VASCULARITY
 Is indicated by spontaneous motion of
echoes within a lesion and represents
blood flow within vessels

69. How is ocular ultrasound
performed?

70. Anterior segment
 Need to use an ‘IMMERSION TECHNIQUE’.
 A scleral shell is put between the lids and
filled with methylcellulose
 The probe is put in the methylcellose solution

71. Posterior segment
 Should not go through the lids, but should place
the probe directly on the globe = CONTACT
METHOD
 Each quadrant of the globe is scanned
systematically. Probe placed both horizontally
and vertically in each quadrant
 In each quadrant, start posteriorly and then
move anteriorly when probe orientated vertically.
Place in 3 positions in each quadrant like this.

72. Posterior segment
 In each quadrant, start superiorly and then
move inferiorly when probe orientated
horizontally. Place in 3 positions for each
quadrant like this.
 When probe placed in each position, pivot
the probe at the point of contact with the
globe from one side to the other whilst
observing the screen

73.  This method aims at minimising the
passage of waves through the lens that
cause artifacts.
 In practice, we often place the probe on
the closed lids. This will result in more
artefacts caused by the lens.

74. Printouts
 Frozen images only.
 Best for the clinician to observe the B-scan
at the time it is done so that can see the
dynamic properties.

75. HOW IS ULTRASOUND USED
IN THE PREOPERATIVE
CATARACT EVALUATION?

76.  A-scan: measure axial length required for
IOL power calculations
 B-scan: to look for co-morbidity if media
opaque

77. How is ultrasound used to
assess intraocular tumours?

78. 1) Diagnosis
2) Plan treatment
3) Evaluate tumour response to treatment
Specifically interested in:
 Shape
 Dimensions (thickness and basal diameter)
 Tissue characteristics
 Extraocular extension

79. CHOROIDAL MELANOMA

80. What are the characteristic
features of a choroidal
melanoma on ultrasound?

81.  Located in choroid and/or ciliary body
 Collar-button or mushroom shape
 Low-to-medium internal reflectivity
 Regular internal structure
 Internal blood flow (vascularity)

82. Describe the A-scan of a
choroidal melanoma.

83.  High initial spike produced by the strong
echo from the vitreoretinal interface
overlying the tumour.
 When the acoustic beam passes into the
tumour tissue, there is a rapid decline in
the amplitude of the echo, which is noted
as decreased height of the spike on A-
scan (low-to-medium internal reflectivity).

84.  The low internal reflectivity is due to tissue
homogeneity within the tumour.
 The homogeneity is seen
histopathologically as tightly packed,
homogenous small cells.
 Finally, a high spike is created at the level
of the sclera and orbital fat.

85. The A-scan of a choroidal melanoma
typically shows low internal reflectivity.

86. What is choroidal
excavation?

87.  On B-scan, normal choroid tissue produces high
reflectivity
 choroidal excavation refers to a dark
appearance in the normally highly reflective
choroid, produced by invasion by a choroidal
melanoma.
 This can occur in other conditions of the choroid.

88. Choroidal melanoma (2)
• Surface orange pigment (lipofuscin) is
common
• Mushroom-shaped if breaks through
Bruch’s membrane
• Ultrasound - acoustic hollowness,
choroidal excavation and orbital
shadowing

89. Choroidal excavation

90. Describe the ultrasound patterns
in the differential diagnosis of
choroidal melanoma

91. Differential diagnosis (need to
combine US with clinical information)
 Choroidal haemangioma
 Metastatic carcinoma
 Choroidal naevus
 Choroidal haemorrhage
 Macular Disciform lesion
 Choroidal detachment
 Choroidal granuloma

92. Differential diagnosis of choroidal melanoma
Large choroidal naevus Metastatic tumour
Localized choroidal
haemangioma
Choroidal detachment Choroidal granuloma
Dense sub-retinal or
sub-RPE haemorrhage

93. Circumscribed choroidal haemangioma
• Presentation - adult life
• Dome-shaped or placoid,
red-orange mass
• Commonly at posterior
pole
• Between 3 and 9 mm in
diameter
• May blanch with external
globe pressure
• Surface cystoid retinal
degeneration
• Exudative retinal
detachment
• Treatment - radiotherapy
if vision threatened

94. Choroidal haemangioma
 Get internal acoustic heterogeneity
 the adjoining cell and tissue layers have marked differences in
acoustic impedence, which create large echo amplitudes at each
interface
 Usually there is a dense echo on the anterior surface of the mass
which is a phelbolith.
 No vascularity detectable on US
 A-scan: a high spike from the phelbolith, and high/irregular internal
reflections
 B-scan: tumour appears solid white

95. Choroidal haemangioma

96. Choroidal haemangioma

97. Choroidal haemangioma

98. Choroidal metastatic carcinoma
Most frequent primary site is breast in women and bronchus in both sexes
• Fast-growing, creamy-white,
placoid lesion
• Most frequently at posterior pole
• Deposits may be multiple
• Bilateral in 10-30%

99. Metastatic carcinoma
 Shape: diffuse and irregular
 Internal reflectivity: medium-to-high
 Irregular internal structure
 No vascularity on US

100. Metastatic carcinoma

101. Metastatic carcinoma

102. Choroidal naevus
 Shape: Dome or flat
 Internal reflectivity: high
 Internal structure: regular
 No vascularity on US

103. Choroidal naevus

104. Choroidal haemorrhage
 Dome-shaped
 Not attached to optic disc
 Internal reflectivity: variable (early on is dense and then
decreases), helps to judge timing of surgery
 Internal structure: variable
 No vascularity seen on US

105. Choroidal haemorrhage
(dense internal echoes seen)

106. Macular disciform lesion (e.g. AMD)
 Located at macula
 Shape: dome or irregular
 Internal reflectivity: high
 Variable internal structure
 No vascularity seen on US

107. Macular disciform lesion (e.g. AMD)

108. PAEDIATRIC
CONDITIONS

109. ROP
 Only type 4 & 5 ROP are seen on B-Scan
ultrasonography.

110. ROP
 There are dense retro-lental membranes.
 There is complete bullous retinal detachment with multiple
retinal loops.

111. RETINOBLASTOMA
 Irregular mass lesion in the
vitreous cavity with
calcification.
 Presence of calcification is
helpful in the diagnosis of
retinoblastoma, but absence
does not rule out
retinoblastoma.
 On A-Scan there is irregular
high reflectivity with distal
shadowing.

112. RETINOBLASTOMA

113. PHPV
 dense band extending
from the optic disc to
the posterior capsule.
 The axial length of the
eye is small.
 On A-Scan there is high
reflectivity from the
band.

114. PHPV

115. COAT’S DISEASE
 Bullous retinal
detachment with echoes
in the sub-retinal space
due to exudates.
 A-Scan: high reflectivity
from the retinal
detachment and low
reflectivity from echoes in
the sub-retinal space.

116. Describe the ultrasound
features of a retinal detachment

117.  B-scan:
-bright, continous, folded appearance.
-when total or extensive RD: the retina inserts into both
the optic nerve and the ora serrata.
-in acute rhegmatogenous RD, there is motion of the
detached retina with voluntary eye movements;
however, it is less mobile than a PVD
 A-scan:
-100% high spike when the sound beam is directed
perpendicular to the detached retina

118. Retinal detachment

119. Retinal detachment

120. Retinal detachment: one single extra
peak. The peak has the same height as
the last peak meaning that they have the
same acoustic impedence as the retina.

121. What features indicate a
chronic retinal detachment?

122.  Calcification
 Intraretinal cysts
 Cholesterol debris in the subretinal space

123. • Frequently inferior with small holes
• Very thin retina
• Secondary intraretinal cysts

124. Describe the ultrasound features that
differentiate retinal detachment, PVD,
and a choroidal detachment

125. Asteroid hyalosis with choroidal
naevus

126. Choroidal detachments

127. Choroidal detachments

128. Choroidal detachment. Characteristic
double peak at the tip of the extra peak

129. SURFACE
 RD: smooth or folded surface
 PVD: smooth surface
 Choroidal detachment: smooth, domed, or
flat surface

130. INSERTIONS
 RD:
-open or closed funnel with insertion into optic
nerve.
-inserts at ora serrata
 PVD:
-open funnel with or without disc or fundus insertion
-inserts at ora serata or ciliary body
 Choroidal detachment
-no disc insertion
-inserts at ora serrata or ciliary body

131. Quantitative evaluation with A-scan
 RD: steep 100% spike
 PVD: variable spike height that is <100%
 Choroidal detachment: steeply rising, thick,
double-peaked 100% high peak. The
echogenicity of the supra-choroidal space is
determined by its content namely : exudates,
serous or haemorrhage.

132. Mobility after eye movement
 RD: moderate to none
 PVD: marked to moderate
 Choroidal detachment: mild to none

133. Retinal detachment

134. Tractional Retinal detachment
Fibrosis radiating
from detachment

135. PVD with vitreous haemorrhage

136. PVD with vitreous opacities
(normal aging)

137. How is ultrasound used to evaluate
patients with proliferative diabetic
retinopathy and vitreous
haemorrhage?

138.  Detect tractional RD involving fovea when
visualisation is obscured by vitreous
haemorrhage
 Detect rhegmatogenous RD as a possible
cause of vitreous haemorrhage

139. Describe the ultrasound
findings in asteroid hyalosis

140.  Calcium soaps in the vitreous
 Bright echoes on B-scan that move with the
vitreous
 An area of clear vitreous gel is typically present
between the posterior boundary of the opacities
and the posterior hyaloid face
 A-scan: calcium soaps produce medium-to-high
reflective spikes

141. Asteroid hyalosis

143. Multiple echogenic substances in
the vitreous; differential diagnosis?
Asteroid hyalosis
Vitreous haemorrhage
Synchysis scintillans
Posterior uveitis
Amyloid

144. What is the appearance of
calcification on ultrasound?

145.  Calcium gives a strong acoustic interface
 A-scan: high-amplitude peak
 B-scan:
-white echoes
-Behind the area of calcification, there is usually
partial or complete shadowing of the sclera and
orbital fat

146. What ocular conditions may
demonstrate calcification on
ultrasound?

147.  Tumours (retinoblastoma, choroidal osteoma, optic nerve
sheath meningioma, choroidal haemangioma)
 Toxocara granuloma
 Chronic RD
 Optic nerve head drusen
 Disciform retinal lesion
 Vascular occlusive disease of the optic nerve
 Phthisis bulbi
 Intumescent cataractous lens

148. Choroidal osteoma

149. Optic nerve head drusen

150. What are the USS findings
in papilloedema?

151. Papilloedema
 Increased intracranial pressure (ICP) is
transmitted along the subdural space within the
optic nerve.
 When the ICP is mildly elevated, the optic nerve
is slightly widened.
 In severe cases, can see an echolucent circle
within the optic nerve sheath (separating the
sheath from the optic nerve). This is the so-
called crescent sign.

152. Crescent Sign

153. When is ultrasound used to
evaluate ocular trauma?

154.  Evaluate position of lens
 Evaluate retinal status
 Diagnose a posterior rupture site in the
globe
 Diagnose an IOFB

155. o Avoid undue pressure.
o Use sterile methylcellulose if applying probe
directly on globe
o Maybe contraindicated if globe integrity to
badly disrupted.
o Think about doing radiographs and CT-scan
first.

157. What are the ultrasound
findings with an IOFB?

158. Usefulness of US
 US is not sufficient to exclude an IOFB
 Useful for non-metalic IOFBs that may not
be seen with radiography
 Although CT is often used for localisation,
it may not be able to define the exact
position of a FB that lies close to the
ocular wall

159. Findings with IOFB
 High reflectivity when probe beam perpendicular to the
reflective surface
 B-scan: metallic FB gives a bright echo that persists
when the gain of the US output is decreased
 Small FBs may produce ‘RINGING’: a string of
reflections that extends posterior to the FB (produced by
reflections of the acoustic wave within the FB)
 Shadowing often present due to almost complete
reflection of waves from the probe

160. List the structures and
disorders that can be
evaluated by orbital US

161. The orbit, extraocular muscles, optic
Nerve can be assessed for:
- Tumours
- Vascular lesions
- Infection
- Inflammation
- Effects of trauma
- Orbital FBs

162. What are the ultrasound
findings in thyroid orbitopathy?

163. Involvement of extraocular musles
can be seen on B-scan
 Thickening of EOM bellies (sparing of tendinous
insertions)
 Medium to high internal reflectivity of the
thickened muscle because of the tissue
interfaces created within the muscle lamella by
oedema and inflammation
 Changes maybe seen before clinical signs
apparent

164. Other findings in TED
 Enlargement of lacrimal gland
 Thickening of periorbital tissues
 Enlargement of the superior ophthalmic
vein
 Thickening of the optic nerve sheath if the
optic nerve is compressed

165. What are the features of
phthisis bulbi?

166.  Shrunken, irregular globe
 Normal ocular structures may not be able to be
identified
 May not be possible to exclude a small
intraocular tumour
 Extensive calcification of the posterior ocular
coats
 Subretinal space maybe filled with dense
opacities
 Often a total, funnel-shaped retinal detachment

167. The B-scan of the left eye (A) shows a shrunken globe with extensive
calcification and loss of the normal shape. There was a history of trauma.
The normal right eyeball (B) is shown for comparison

168. Sclera

169. Imaging in posterior scleritis
Ultrasound
a - Thickening of posterior sclera
b -Fluid in Tenon space (‘T’ sign)
Axial CT
Posterior scleral thickening
a
b
a
b

170. Posterior scleritis
T-sign is caused by the
spread of inflammation
along the Tenon’s space
into the optic nerve
sheath.

171. Nodular posterior scleritis with fluid in the Tenon capsule.
The scan on the right demonstrates a positive T-sign at the
insertion of the optic nerve.

172. Posterior staphyloma
 Patients who are myopic may have focal
areas of thinning sclera.
 These areas can form staphylomas, or
out-pouching.
 Ultrasound is the best imaging modality for
staphylomatous changes.

173. Posterior staphyloma

174. Staphyloma

175. Lens

176. Aphakia: there are only 2 peaks, the
corneal peak and the retina peak. The
lens peak is absent

177. LUXED CRYSTALLINE LENS

178. What is ultrasound
biomicroscopy?

179. UBM
 Uses high frequencies (50-100MHz)
 Depth of penetration: 5-7mm
 Gives high resolution images of anterior
segment structures
 Useful for evaluation secondary
glaucomas and angle closure

180. THE END

181. Choroidal melanoma