2. • B-scan or brightness modulation scan
provides two dimensional images of a series of
dots and lines.
• B-scan provides the topographic information of
shape, location, extension,mobility, and gross
estimation of thickness of the tissue.
3.
4. FREQUENCIES
• 1-2 MHZ : ABDOMINAL ULTRASOUND
• 8-10 MHZ : OPHTHALMIC ULTRASOUND
(B SCAN)
BEST FOR POSTERIOR SEGMENT
• 35- 80 MHZ : ULTRASOUND BIOMICROSCOPY
BEST FOR CORNEA &
ANTERIOR SEGMENT
7. TRANSDUCER
• Device which converts Electrical to Sound
energy [pulse ] and Sound to Electrical energy
[Echo]
• Basic Components –
Piezoelectric plate
Backing layer
Acoustic Matching layer
Acoustic lens
8. • Piezoelectric Element : essential part generates
ultrasonic waves . Coated on both sides with
electrodes to which a Voltage is applied.
Oscillation of Element with repeat expanding
and contraction generates a sound wave.
• Most common: Piezoelectric ceramic ( Lead
zirconate titanate).
9. • Backing layer : located behind the piezoelectric
element which dampens excessive vibrations
from probe thereby improves image resolution
• Acoustic matching layer : located in front of
piezoelectric element which reduces the
reflections from acoustic impedance between
probe and object thereby improves trasmission.
10. • Acoustic Lens : gray coloured rubber on tip
helps in focussing the ultrasonic waves as a slit
beam.
30. • Bell : Measurement of Sound Intensity
• Hertz : Frequency of transducer
• Acoustic impedence mismatch:
- Resistance of tissue to passage of Sound waves.
Difference of two tissues at the Interface.
- Homogeneous ( Vitreous)- Sound passes through
tissue with no returning signal.
-Heterogeneous (Orbital Fat) - Different levels of
Acousitc impedance mismatch within tissue.
31. • Echo – Reflected Sound wave.
• Anechoic – No Echo.
• Attenuation : Sound is absorbed ( Tumours)
• Shadowing : Sound is strongly reflected , nothing
passes through it.(Choroidal Osteoma
Drusen of Optic nerve head , Air bubble).
• Reverberation : Collection of Reflected sounds
bouncing back and forth between
tissue boundaries especially
( Foreign Body in Eyeball )
32. Ultrasound Velocity
• Normal Phakic eyes = 1555 m/s
• Aphakic eyes = 1532 m/s
• Pseudophakic eyes (PMMA) = 1556 m/s
(Acrylic )= 1549 m/s
• Silicon Oil filled eyes = 980 m/s
33. Normal Ultrasonography Characteristics
Lens :Oval highly reflective structure
Vitreous : Echolucent
Retina , Choroid , Sclera : Each is single highly
reflective structure.
Optic Nerve :Wedge shaped acoustic void in
Retrobulbar region
Extraocular muscles :Echolucent low reflective
fusiform structure.
Orbit : Highly reflective (Orbital fat)
36. Opaque Media (Anterior)
• Dense Cataract
• Miosis
• Hyphaema
• Hypopyon
• Corneal Opacity
• Plan for Penetrating keratoplasty with Opaque
Anterior segment.
37. Opaque Media (Posterior)
• Vitrous Haemorrhage
• Vitritis/ Endophthalmitis
• Pupillary or Retrolenticular membrane
38. Transparent Media
• Acquisition of Axial Length for Highly Myopic
surgical Candidates ( Caution for Posterior
Staphyloma)
• Inaccurate A – Scan data (Determination of
dimensions of Eye ball)
• Proptosis( Poorly represented Orbital Apex)
• Orbital tumours
• Carotico- cavernous fistula(Dilated Ophthalmic
vein)
39. • Cysticercosis of Extraocular Muscles
• Suspected Intra Orbital Foreign Body
• Orbital Cellulitis
• Iris & Ciliary body anomalies
• Optic Disc anomaly
• Retinal Detachment (Rhegmatogenous /Exudati
ve – shifting fluid)
• Choroidal Detachment.
41. 1. Examination of each quadrant
2. Look at each quadrant
- coronal
- sagital
3. Mentally assemble the Cross sections
4.Anticipate how it should look on
moving probe.
43. Multiple Fine Echo Opacities within the Vitreous Cavity suggestive of
Vitreous Haemorrhage .
44. Multiple, densely packed, homogeneously distributed echodense dots of
medium to high reflectivity with a Clear Preretinal space suggestive of
Asteroid Hyalosis
45. Moderately elevated thin smooth dome-shaped membrane
echo (arrow) located in the inferotemporal periphery suggestive of
Retinoschisis
47. • Smooth, dome shaped ,
• thick, less mobile with
• double high spike suggestive of
Choroidal Detachment
48. PVD RD CD
Topographic Smooth, with or
without disc insertion
Smooth or folded
with disc insertion
Smooth without
disc insertion
Quantitative < 100 % spike 100 % spike Double 100 % spike
Kinetic Marked Moderate None
49. PVD or RD ?
• RD attached to the OD
• RD is high reflective
• RD is less mobile
• Rd is 100% amplitude
• Reflectivity of the periphery
can differentiate between the
two in difficult situations like
trauma and inflammations .
50. Differentiating features of RD
Rhegmatogenous RD Tractional RD Exudative RD
Convex elevation ,
Undulating folds, PVR
Concave
elevation,Fibrous
tractional band
Convex elevation,
Shifting fluid
changes
Configuration
with postural
change