investigative ophthalmology

1. ULTRASONOGRAPHY
(B-SCAN)
VASIUR RAHMAN
Dr R. P. Centre, AIIMS

2. HISTORY
 1793: Lazzaro Spallanzani (Italy) discovered that bats orient
themselves with the help of sound whistles while flying in
darkness. This was the basis of modern ultrasound application
Bats use ultrasounds to navigate in the darkness

3. INTRODUCTION
 first used in the field of ophthalmology
by MUNDT and HUGHES.
 Oksala et al report the sound velocities
in the various compartment of eye.
 Contact Bscan was introduced by
Bronson and it being portable, become a
part of everyday use in ophthalmology.

4. physics
 Ultrasound
○ Longitudinal wave
○ Alternating compressions and rarefactions of
molecules
 >20khz (20,000 oscillations /sec) Ultrasound
 Similar to sound waves
 Reflected
 Refracted

5. Low
frequency (1
to 5 MHz)
Longer
wavelength
Lower
Resolution
(abdominal and
pelvic
structure)
Abdominal ultrasound Ophthalmic ultrasound
High
frequency
(8 to 10 MHz)
Short
wavelength
(< 0.2mm)
Higher
Resolution of
minute ocular
and orbital
structure

6.  By karl ossoing
Sound Wave Velocities
Medium Velocity (m/sec)
Water 1,480
Aqueous / vitreous 1,532
Soft tissue 1,550
Crystalline lens 1,641
Bone 3,500

7.  based on physical principles of pulse-echo
technology
 Echoes are generated at adjoining tissue
interfaces greater the difference, the
stronger the echo

8.  having frequency greater than 20khz for
imaging the posterior segment-8 to 25 MHz
 for imaging the anterior segment-50 MHz
 Rule-greater the frequency lesser will be
penetration

9. Probe
 thick, with a mark
 emit focussed sound beam at frequency
10mhz
 mark on the Bscan probe indicates beam
orientation-area towards which mark is
directed appears at the top of the
echogram on display screen

10. ULTRASOUND PRINCIPLES AND PHYSICS
Angle of incidence:
 Perpendicularity to the
area of interest always
should be maintained to
achieve the strongest
echo.

11. A scan (amplitude) -
single dimensional
display of spikes through
the eye.
The spikes on A scan
represent amplitude /
reflectivity of an echo
A-Scan

12.  Transverse scan
 Longitudinal
 Axial
B-scan Probe Orientations

13.  Transverse scan
 Movement of transducer is parallel to limbus
 Produces a circumferential slice through several
meridians
 Lateral extent of a lesion
Transverse Scan

14.  Longitudinal scan
 Transducer - perpendicular to
the limbus
 Probe marker - towards centre
of cornea
 Antero posterior extent of the
lesion
 Optic disc and posterior aspect
of the globe –lower portion of
screen
 Best – demonstrating the
insertion of membranes to optic
disc

15.  Axial scan
 Probe centered on the cornea
 Easiest to understand (displays lens & optic nerve)
 Documenting lesions & membranes in relation to optic disc
 Evaluates macular region
 Hinder resolution of posterior portion of globe (Sound attenuation
and refraction )
AXIAL SCAN

16. CLOCK HOUR
PROBE POSITION
CLOCK AREA
SCREENED
3-limbus 9-posterior
3-equator 9-equator
3-firnix 9-anterior
6-limbus 12-posterior
6-equator 12-equator
6-fornix 12-anterior

17. Why we need B-scan..????
 Evaluation of intraocular details
 Evaluation of retrochoroidal lesions
especially tumors
 Examination of retrobulbar soft tissue
masses
 Identification, localization and
measurement of foreign bodies
 Assessment of damage in trauma cases

18. PROCEDURE
 mostly the Bscanning is done
transpalpebrum
 Lesions must place at the centre of scanning
beam
 Lowest possible decibel gain consistent with
the maintenance of adequate intensity
should be used

19.  Measured in decibels
 Higher gain –
 Display weaker echos like
vitreous opacities
 Lower gain
 Stronger echoes (retina and
sclera)
 Better resolution
Gain

20.  Dot like lesions – vitreous floaters, vitreous
hge, vitreous exudates.
 Membranous lesions – vitreous membranes,
PVD, RD
 Mass lesions – choroidal or retinal tumors
Echotexture of Lesion

21. VITREOUS HAEMORRHAGE
To detect extent, density,
location and cause
Fresh haemorrhage shows
dots or lines
Old haemorrhage the dots
gets brighter

25. CHOROIDAL DETACHMENT KISSING CHOROIDS

27. POSTERIORLY DISLOCATED LENS

28. INTRAOCULAR FOREIGN BODY

29. SILICON OIL FILLED VITREOUS

30. Complete PVD

31. Choroidal melanoma

32. Endophthalmitis

33. Intra ocular foreign body

34.  Non invasive
 Performed in an office setting
 Does not expose to radiation
 High resolution echography provides
reliable and accurate assessment
 Ideal for follow up of lesion
Advantages:

35. Disadvantages
 High frequency sounds waves have
limited penetration

36. THANK YOU