Ultrasound in Ophthalmology

1. DR KRIPESH LAMICHHANE
1ST YEAR RESIDENT
CMC
Ultrasonography in
opthalmology

2. Introduction
 Ultrasound is sound that is beyond the range of human hearing
 Ultrasound is an acoustic wave that consist of an oscillation of
particles within a medium
 By definition ultrasound waves have frequencies greater than
20kHZ(20,000 oscillations/sec)

3.  Ultrasound uses high frequency sound waves to produce echoes
as they strike interface between acoustically distinct structures

4. HISTORY
 1956-mundt and hughes –first use of industrial ultrasound to
examine enucleated normal eye with intraocular tumor
 1957-oksala of finland -1st clinical use of A scan
 1958-Baum and greenwood developed the B scan using the
immersion methods, but the image was quite poor
 Purnell and sokallu described orbital B scan evaluation and
classification of orbital disease with its help.

5.  1960- Jansson( Sweden) used USG to measure distance between
structures in the eye.
 1970- Coleman and associates – 1st commercially available
immersion B- scan.
 Later Bronson introduced a contact B-scan machine.

6. History continues…
 Original mask and water
bath immersion
technique described by
Baum.

7. History continues..
 Simplified immersion standoff system
devised by Purnell, which allowed
automatically spaced horizontal scanning
as used in Baum’s method, which also
allowed a smaller, more easily controlled
volume of water to be used and reduced
the problems of face mask adaptation.

8. PHYSICS OF ULTRASOUND
 Audible sound frequency- 20 to 20,000 Hz
 Ophthalmic Ultrasound = 8-10 MHz( 1 MHz= 1,000,000 cycles
/sec) – Short wavelength( < 0.2 mm) have small penetration
(6cm at 7.5MHz) but excellent resolution of small structures
 Propogated as longitudinal wave consisting of compressions &
rarefactions of molecules as the wave passes through the
medium, that can propagate within fluid & solid substances.

9. Physics
 The behaviour of longitudinal waves produced by ultrasound
energy is similar to that of light rays in that these longitudinal
waves can be refracted and reflected predictably.
 It is this property that makes ultrasound useful for diagnostic
purposes.

10. echo
 When sound travels from one medium to another medium of
different density, part of the sound is reflected from the
interface between those media back into the probe. This is
known as an echo; the greater the density difference at that
interface, the stronger the echo, or the higher the reflectivity.

11.  The returning echoes are affected by many factors
1. absorption and refraction
2. Angle of sound incidence
3. Size
4. Shape
5. Smoothness of acoustic interfaces

12. Angle of incidence
 When the beam strikes interfaces in perpendicular manner ,the
echo is reflected back towards its origination
 When obligue beam strikes some of the reflected energy is
diverted away from direction of origin

14. Acoustic impedence
 Acoustic impedence is determined by its sound velocity and
density
 acoustic impedence = sound velocity* density
 The greater the difference the stronger the reflection of
ultrasound wave.

15. Acoustic interfaces
 Echoes are created by acoustic interfaces
created at the junction of two media that
have different acoustic impedence.
 The size, shape and smoothness of an
interface play roles in returning echoes.

16. Pulse echo system
 Emits ultrasound wave –detects and processes and displays
returning wave.
 The basis of pulse echo system is peizoelectric elements made
up of ceramic crystals or quartz.
 Peizoelectric crystals-mechanical vibration-longitudinal
ultrasound wave –pause of several sec-allows transducer rime to
receive and process returning echoes

17. Schematic diagram of an ultrasound system

18. Signal processing
 An instrument must have four components
1. A pulser
2. A transducer
3. A receiver
4. Display screen

19. Gain
 It helps to adjust the amplifications of the echo signal that is
displaced in the instrument screen.
 Higher the gain level ,the spike height and the sensitivity of
display screen is maximized, enabling visualization of weaker
signals, but resolution is affected adversely and vice versa.

20. Gain
 Represent relative units of ultrasound intensity(db)
 In high gain retina and sclera appears as one thickened spike

21. A scan
 One dimensional acoustic display
 Echoes are presented as vertical spikes
from a baseline
 Spikes represents reflectivity, location &
size of anatomic structure
 The ht. of the spikes corresponds to the
strength (amplitude) of the echo.

22. B scan
 2 dimensional
 An echo representes as dot rather than
a spike
 Strenght of echo shown by brightness
and coalescence of multiple dots on
screen
 A section of tissue is examined by an
oscillating transducer that emits a sound
beam that slices through tissue.

23. Indication of ultrasound
Clear ocular media
Anterior segment
 Iris lesion
 Ciliary body lesions
Posterior segment
 Tumors
 Choroidal detachment: serous versus exudative
 Optic disc abnormalities
 Intraocular foreign bodies: detection and localization
Biometry
 Axial length of eyeball
 Anterior chamber depth
 lens thickness
 tumor measurements
Determining the extraocular muscle thickness

24. Indication of ultrasound
Opaque ocular media
Anterior segment
• Corneal opacification
• Hyphema or hypopyon
• Miosis
• Cataract
• Pupillary or retrolenticular membrane.
Posterior segment
• Vitreous hemorrhage
• Endophthalmitis

25. Examination techniques for the globe
 B scan probe has a marker usually dot, line or logo that indicates
the side of the probe that is represented on upper portion of B
scan screen display.
3 basic B scan probe orientation
1. Transverse
2. Longitudinal
3. Axial

26. Transverse scan
1. The probe is placed on the globe so that back and forth
movement of the transducer occurs parallel to limbus.
2. The orientation appropriate for showing lateral extensions

27. Transverse scan
 Horizontal transverse: Evaluate
superior and inferior fundus and
marker is kept towards nose.
 Vertical transverse: Evaluate the
nasal and temporal fundus and
marker is kept towards 12 o’clock
 Oblique transverse: Evaluate the
pathology not located at major
meridians(3,6,9,12 o’clock)

28. Longitudinal scan
1. Probe face rotated 90 deg from transverse scan position
2. The back and forth movement of transducer is oriented
perpendicular.

29. Longitudinal B scan
1. The optic disc and posterior aspect of globe along the meridian
are displayed on lower portion of screen.
2. Provides anterior or posterior view of meridian being
examined.

30. Axial B scan
1. The sound beam directed through center of lens
2. It is easier to understand but sound attenuation and refraction
from the lens often hinder resolution of posterior portion of
globe.
3. In horizontal axial scan macular region is just below the optic
disc

31. Interpretation of normal B scan
 At high gain reveals 2 echographic areas separated by an echo
free area
 Echographic area at beginning of scan-reverberations at tip of
probe
 If good resolution- posterior convex structure of crystalline lens.
 Large echo free area –vitreous cavity
 Echogenic area after vitreous- retina, choroid, sclera & orbital
tissues
 Retina seen as a concave surface proximally
 Optic nerve shadow –triangular shadow within orbital fat

32. Contact technique

33. Special examination technique
1. Topographic echography
2. Quantitative echography
3. Kinetic echography

34. Topographic echography
1. Useful for shape, location and
extension
2. Transverse B scan probe is placed
exactly opposite the lesion,shift
from limbus to fornix
3. In longitidinal approach sound
beam is oriented laterally
4. Axial appraoch

35. Quantitative echography
1. Reflectivity estimate : according to size, configuration
,thickness ,density.
comparision of spike height on A scan and signal brightness in
B scan
2 Internal structure : useful for histological
architecture.character of cellular substance. Also determines
number size and distribution of cell aggragates
3 Sound attenuation :absorption scattered or reflected

36. Kinetic echography
1. Assess the motion of or within
a lesions
 Aftermovement-non solids
show aftermovement
 Vascularity –fast spontaneous
motion of echoes on screen
 Convection-slow spontaneous
motion of echoes
seen(cholesterol debris)

37. Briefly ultrasound findings of different
vitreoretinal disease
 Vitreous haemorrhage
1. Pattern depends upon density location &fibrous changes
2. A scan
 in fresh –mild with dispersed RBC –chain of low amplitute
spikes
 More dense-high reflectivity; if blood organizes larger interface
–even higher reflectivity( 60-100%)

38.  B-scan:
- Appears as small white echoes
• With greater density of vitreous haemorrhage - greater
opacities
• Fresh, diffuse & unclotted haemorrhage - very little or no
echoes
 - Vitreous haemorrhage may be confined- within PVD, pre &
post hyaloid, diffusely dispersed, old clotted or fresh
 Thick inferiorly –thin superiorly

39. Vitreous haemorrhage

40.  A-scan -
 multiple echo spikes with medium
to high reflectivity
 B-scan -
 Bright round signals
 opacities exhibit distinct movement
on movement of the eye

41.  B-scan:
• Appears as an undulating membrane in front of the
retinochoroidal layer
• May remain attached to optic disc or separated completely
from the post. pole
• Height of A-scan spike & brightness of B-scan of PVD reduces
as gain is reduced
 Kinetic echography typically shows a very fluid ,undulating after
movement pf PVD-this characteristics differencites PVD from
retinal and choroidal detachment .

43.  A-scan:
 Tall single spike but not as tall as in RD
 Reflectivity is low(5-10%) if post. vitreous layer is thin &
high(80-90%) if thick or lined by RBC

44. Retinal detachment
 B SCAN
 appears tall (100%)spike separated from chorio scleral layer
 Attach to optic nerve and ora serrata
 Recent RD –mobile with translucent subretinal space

45. A-scan :
 Single, steeply rising, extremely high(100%) & moderately
thick retinal spike when sound beam is perpendicular to
retinal surface
 Lower & wider spikes with 2 or more peaks - oblique beam
 Long chain of low to medium high spikes -tangential beam
 Distance between the retinal spikes and the ocular wall
spikes in a given beam direction is equal to the degree of
elevation.
 Presence of signals between retinal & scleral spike- indicative
of exudative or hemorrhagic RD

46. A scan of RD

47. Tractional retinal detachment
1. Common in vascular retinopathies
2. Caused by strong adhesion of vitreous membrane bands, past
hyaloid face to retina and subsequent traction
3. Adhesion could be tent like or broad causing table top traction

49. Choriodal detachment
 B-scan:
. Usually in periphery
 Smooth, dome-shaped, thick membranous structure not
inserted to the optic nerve
 localized or involve entire fundus- kissing choroidal
detachment
 little or no after movement on kinetic scanning
 Nature of Suprachoroidal fluid
▪ In serous detachment- echolucent
▪ Haemorrhagic - echodense

50.  In 360 deg highly elevated charoidal detachments apposition of
temporal and nasal detachment may aoocur in centre giving
appearance of kissing choroidal detachment

51.  A-scan:
 A thick steeply rising 100% high spike just behind the retinal
spike
 On lowering the gain the spike is double peaked
 If choroidal haemorrhage- low to medium spikes in
subchoroidal space
 If choroidal effusion- echofree space

52. Choroidal melanoma
 Few characteristics features
1. Solid
2. Collar buttom ie mushroom tumor( means tumor has broken
through brich’s membrane)
3. Low to medium internal reflectivity
4. Internal blood flow

53. . A-scan pattern typical of melanoma, with the high
retinal spike on the surface of the lesion but low-to-
medium internal reflectivity within the lesion. The
sclera and orbital tissues are seen as spikes to the
right of the lesion.
No after movement of spikes- solid consistency
Low reflective spikes behind the sclera.

54. Choroidal hemangioma with an associated exudative
retinal detachment. This lesion is composed of tightly
compacted blood vessels and, therefore,
demonstrates high, regular internal reflectivity on
both B-scan and diagnostic A-scan

55. Metastatic choroidal lesion
 Metastatic choroidal lesion from the breast. The lesion has
rather irregular borders, with medium-high, irregular internal
reflectivity on both B-scan and diagnostic A-scan(high internal
reflectivity-60 to 80%)

56. Optic disc drusen
 Calcified nodules seen echographically with high reflectivity at or
within the optic nerve head
 Best seen with - transverse or longitudinal B-scan approach
which bypasses the lens

57. Retinoblastoma
 A-scan:
 Irregular acoustic structure with high internal reflectivity(70-
100%)
 Spontaneous movement of lesion spikes – evidence of
vascularity
 Axial length measured - normal or decreased
 Depends upon size, degree of tumors, calcification & necrosis

58.  B-scan
 If large- irregular echogenic mass involving vitreous, retina,
subretinal space
 Area of calcification - high echogenicity- strong sound
attenuation- area of echolucency behind calcification- sound
totally reflected by calcification

59. Endopthalmitis
 A-scan:
 Multiple echospikes with low to medium reflectivity(10-60%)
 With organization & membrane formation reflectivity
increases
 Chain of low ampliyude spikes

60. endopthalmitis
 B-scan:
 Opacities are seen
 Membrane formation - in severe cases
 Choroidal thickening,choroidal detachment, RD, retained IOFB
- possible associated findings

61. Posterior scleritis
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

62. Limitations of USG
1. Multiple reduplication-calcified lens, itraocular implants, FB
,scleral buckles ,air bubbles
2. Attenuation artifects- silicone oil disperses the ultrasound
beam difficult to perform

63. 3 .refraction artefacts- tumor formation or thickening of choroid.
4 Absorption /shadowing effect
5 Insufficient fluid coupling-entrapment of air between probe and
eye, displays bright echoes that represents multiple signals
between probe and entrapped air

64. 6 To detect the acoustic structure its thickness should at least be
2mm
7 Tumors located at the orbital apex are difficult to recognize
because of the attenuation of the sound and confluence of Optic
Nerve and Muscles that are inseparable ultrasonically.
8 dispersed vitreous cell ar haemorrhage may be missed initially
due to low reflectivity
9 IOFB less tha 1 mm2 difficult to detect
10 small air bubble may mimic IOFB but they usually disappear
within a day or two

65. Ultrasound biomicroscopy
 New method of producing high resolution images of anterior
segment with high frequency ultrasound
Ranging from 50-100MHz
Depth penetration is in the range of 5-7mm
Imaging eye at microscopic resolution
 In 1990 Pavlin and colleagues described the first high
frequency ultrasound .

66. Ultrasound biomicroscopy

67. Ultrasound biomicroscopy
Uses
 To evaluate ant. segment anatomy in eyes with corneal scars
before penetrating keratoplasty
 To delineate the extent of iris & ciliary body tumors
 To understand the pathology - mechanism of various types of
glaucoma
 To locate ant. segment FB
 Measures anterior chamber depth.
 Measures corneal thickness

68. Doppler B scan
 Use of B-scan with color Doppler
 Non-invasive approach to
measure and visualize blood flow
in orbital vessels and tumors.
 To evaluate many ocular
disorders including glaucoma,
hypertension & ocular ischemia

69. Thank You