PRESENTER- DR BARUN GARG MODERATOR- DR SHUBHRA DAS RIO,GUWAHATI ULTRASONOGRAPHY IN OPHTHALMOLOGY
PRESENTER- DR BARUN GARGMODERATOR- DR SHUBHRA DAS
RIO,GUWAHATI
ULTRASONOGRAPHY IN OPHTHALMOLOGY
1. DIAGNOSTIC OPHTHALMOLOGY- NEMA2.AAO- RETINA AND VITREOUS(2012
EDITION)3. AIOS CME SERIES 20114.TEXTBOOK OF RETINA - RYAN
REFERENCES
Ultrasound Waves are acoustic waves that have frequencies greater than 20 KHz
The human ear can respond to minute pressure variations in the air if they are in the audible frequency range, roughly 20 Hz - 20 kHz
INTRODUCTION
First used in ocular diagnosis in 1956 by Mundt and Hughes- A scan technique
Baum and greenwood in 1950’s developed B scan using immersion method
In 1970’s A scan interpretation became more precise and standardise by Ossoing
Later Ossoing conceptualised standardised echography
HISTORY
Based on propagation, reflection and attenuation of sound waves
Acoustic interface- is created at the junction of two media which leads to production of echoes
Greater the difference in sound velocities of media at interface, greater the echo
Echo affected by- acoustic interface, angle of incidence, absorption. Scattering, reflection
Detected echo highest when incident beam is perpendicular to the interface
PHYSICS OF USG
A SCANB SCANCROSS VECTOR B SCAN3D B SCANULTRASOUND BIOMICROSCOPY
ULTRASONOGRAPHIC TYPES
The unit consists of four elements-PulserReceiverTransducer- located at tip of probeDisplay unit
INSTRUMENTATION A&B SCAN
MECHANISM
PIEZOELECTRIC EFFECT
The display may be in one of the two modesa) A mode( amplitude)- 1D display Time amplitude display Echoes represented as vertical spikes Spikes represents reflectivity, location and
size of anatomic structure X axis shows time elapsed( function of
tissue depth) Y axis- reflectivity in decibels
THREE MODES1) Orbita- for orbital examination, each
microsecond measures 1 mm on screen2) Bulbous- intraocular examination, each
microsecond measures approx 2 mm3) Varia – for axial length measurement
b) B mode( brightness)2D acoustic sectionEchoes represented as dotStrength of echo depicted by brightness of dotFocussed beam is used
Low frequency- orbital pathologyModerate frequency(7-10 mhz)- Globe examinationHigh frequency(30-50mhz)- Anterior segment examinationImmersion technique(10mhz)- Anterior chamber examination
TYPES OF B SCAN
A SCAN PROBESmall, pencil sized, easy
handling No mark presentBeam- parallel and non
focussed of 8 Mhzplaced at right angle to
the area of interestKept directly over the
globe after putting local anaesthetic
Thick
Mark present- indicates beam orientation
Focussed beam of 10 Mhz
Mostly kept transpalpebrum after slight increase of gain
PROBESB SCAN PROBE
A SCAN PROBE B SCAN PROBE
PROCEDURE- B SCANPatient in sitting/ reclining positionInstillation of anaesthetic dropsConductive gel is placed over the probeMarker acts as orientation point & corresponds to
upper portion of echogramPatient is asked to look away from probe to avoid
scanning through lens Ultrasound beam always kept perpendicular to
opposite retina
THREE BASIC PROBE POSITIONSA)Transverse section- marker kept parallel to limbusQuadrant examinationGives lateral extent of the lesionFor superior and inferior fundus- marker directed
towards nose nasal and temporal fundus- marker directed at
12o clock( vertical transverse)
B) Longitudinal section- marker is kept at right angle to the limbusOne clock hour per time examination determines the antero-posterior limit of the lesionBest for peripheral tears and documentation of
macula
C)Axial section- probe directly over cornea with patient
fixating in primary gaze
AXIAL LONGITUDNAL
TRANSVERSE
With contact type of scanning there is a dead zone of about 7.5mm adjacent to the probe, so that the lesions in this region are missed.
To visualize this area, probe kept on the opposite side at right angle or use immersion scan technique.
IMMERSION TECHNIQUE-Scleral shell filled with CMC inserted between
lids and probe placed on itCornea, anterior chamber, iris , lens, retro-
lental space and axial length can be measured
After screening the detected lesions examined under following headings-
1)Topographic echography-1. Size, shape and contour of the mass lesion2. Membranous opacity3. Discrete vitreous opacities (single or
multiple)4. Abnormalities in globe contourFindings are classified as point like, membrane
like or space occupying
2)Quantitative echography-Performed with A scan precisely to determine
reflectivitySPIKE HEIGHT LESIONS1.LOW(2-20%) SENILE VITREOUS
FLOATERS2.LOW MEDIUM (10-60) CHOROIDAL
MELANOMA3.MEDIUM(20-80) VITREOUS MEMBRANE
4.HIGH(80-100) ASTEROID HYALOSIS, METASTATIC CARCINOMA
5.VERY HIGH (100) RETINAL DETACHMENT, ORGANISED VITREOUS HAEMMAOHAGE, FOREIGN BODY
3) Kinetic Echography is required to determine the tissue mobility and vascularity in the lesion.
colour Doppler instruments may be used in conjunction with B scan.
Spontaneous movements indicate vascular lesion where as after movements indicate mobility( vertical motion of echo spikes)
INTERPRETATION OF NORMAL A SCAN
NORMAL B SCAN
EVALUATION OF VITREOUSHigh gain should be used, normally devoid of acoustic signalsa) Asteroid hyalosis- Bright round signals on b scan, medium amplitude spikes on A
scan
b)PVD-echogenic membrane concentric to the globe, in front of the
retinochoroido-scleral complex with clear subvitreal space.Low A scan reflectivity
COMMON PATHOLOGIES
c) Vitreous haemorrhageFor fresh vitreous haemorrhage, overall gain
can be increased by 10 db. They appear as multiple fine echo opacities
dusting the vitreous body not extending beyond the posterior vitreous border, low reflectivity on a scan
older haemorrhage, show denser echodots and higher reflectivity (up to 60%) on A scan.
In resolving vitreous haemorrhage, in comparison with older scans, echodots on Bscan show decrease in brightness and numbers.
Subhyaloid haemorrhage-typically at the posterior pole between the anterior surface of retina and posterior vitreous face.
old organized vitreous haemorrhage can result in vitreous-membrane formation (seen as echogenic lines on Bsan) mimicking RD
attachment of the echomembrane on/ upto the optic nerve head and Quantitative echography II(difference in decibel setting 6-15db for retina and >20 db for vitreous membrane) help in differentiation
Endophthalmitis/ vitritis – inflammatory cells seen as dot like on B scanmultiple, scattered diffusely or localised to a
segmentMembranes may be seenChoroidal thickeningA scan- low to medium reflectivity
POSTERIOR SCLERITIS- T SIGN
EVALUATION OF RETINA Normally dense membrane on b scan ,and cant
be differentiated from choroid A scan- typically 100% tall spike
Retinal detachment-On B scan, echogenic dense membrane,
biconvex or biconcave with 100% attachment ONH(except localised/peripheral) and 90-100% reflectivity on Ascan
Fresh RD characterised by mobile retina and translucent subretinal space
With settling of PVR- vitreous space becomes limited with debris dots or membrane formation
decreased mobility of retina cystic degeneration Funnel configuration- open and closed
Rhegmatogenous RD- Shows retinal tears especially operculated tears/ giant
tears trickle of vitreous haemorrhage from the break site
into the vitreous cavity may be picked up. Detached retina- convex
Funnel shaped
Cystic degeneration
Tractional RD-Fibrovascular frond in the vitreous →tent
like elevation/table top traction of the retina as an echogenic membrane
doesn't show after-movementDetached retina- concave
Exudative RD-Convex and bullous configuration
RetinoschisisSmooth, thin, dome shaped membrane not
inserting in the optic disc100% reflectivityMost commonly- inferotemporal fundus
EVALUATION OF MACULAFour Probe Positions-horizontal axialvertical transverselongitudinalvertical macula
EVALUATION OF CHOROID Retinochoroidal layer has smooth concave
configurationCHOROIDAL THICKENING- can be localised
or diffuseCHOROIDAL DETACHMENT-dome shaped elevation with clear sub
choroidal space on Bscan and 90-100% double peaked tall spike on Ascan.
Not inserting to optic nerve
FEATURES CHOROID DETACHMENT
RETINAL DETACHMENT
PVD
SHAPE DOME LINEAR V/U -LOCATION PERIPHERY VARIABLE VARIABLEATTACHMENT TO ONH
NO YES VARIABLE
OTHER FINDINGS
KISSING CHOROIDALS
FOLDS,BREAKS, PVR CHANGES
PROMINENT INFERIORLY
A SCAN SPIKE %
90-100 80-100 40-90
MOBILITY MINIMAL MODERATE MARKEDAFTER MOVEMENT
- MINIMAL MARKED
EVALUATION OF TRAUMATIZED EYE
VITREOUS HAEMMORHAGEDISLOCATED LENS- Round/globular structure in posterior vitreous
INTRAOCULAR FOREIGN BODY Can detect both metallic and non metallic FB Metallic foreign bodies- bright signals on low gain Round bodies classically- reverberation artifact behind
it High reflectivity
POSTERIOR GLOBE RUPTURE Breach of scleral and choroidal tissue Choroidal thickening
OPTIC NERVE AVULSION Peripapillary scleral break with vitreous
haemorrhage Chronic- proliferative tissue at disc
EVALUATION OF INTRAOCULAR TUMORSa) Melanoma- Solid, regular structured, vascular lesions of low to
medium reflectivity Most common shape- dome or collar
button(rupture of bruch’s membrane)
b) Choroidal haemangioma- Flat, echogenic, solid subretinal mass mostly at
posterior pole With or without exudative RD Very high reflectivity on a scan
c) retinoblastoma-solid tumor arising from the retinal layer
obliterating the vitreous cavity.Calcification within the tumor mass is typical
of retinoblastomashadowing effect behind the lesion in the
orbital mass. Concomitant RD may be present.A scan- high reflectivity, vascularity and
absence of after movements Increased axial length
STRUCTURAL ANOMALIESa)Pthisis bulbi- smaller globe with multiple
echogenic vitreous opacitiesChoroidal thickening, calcification of outer
coats
b)Atrophic bulbi- normal globe contour( normal axial length)
Calcification of outer coats
c)Posterior staphyloma-Shallow excavation of posterior poleSmooth edges, high myopic eyes
d)Choroidal coloboma- excavation of posterior poleSharp edgesMicrophthalmos, RD
e)Optic nerve drusenCalcified nodules at optic discHigh reflectivity
CT/MRI better optionsThe orbital examination comprises of(1) orbital soft tissue assessment(2) extraocular muscle evaluation(3) Retrobulbar optic nerve examination using
transocular (examination through the globe) or paraocular (examination next to the globe) approach.
ORBITAL USG
Indications of orbital ultrasonography :
• Proptosis and globe displacement• Abnormal lid positions and edema• Cases of motility disturbances• Some cases of ocular/orbital pain• Uniocular injection & rise in IOP• Cases of optic disc edema /atrophy and
vascular retinal occlusion• Orbital trauma
Vascular lesions of the orbit:These can be neoplasms or vascular malformations
as follows:
Neoplasms Cavernous hemangioma Capillary hemangioma Lymphangioma
Vascular malformations Carotid-cavernous sinus fistulaArteriovenous malformation Orbital aneurysm
Cavernous haemangioma-Round/oval, high reflectivity, abscence of
vascularity
Orbital varix: venous malformations which present as intermittent proptosis, exacerbated with bending of the head or performance of a Valsalva Maneuver.
Tumors of orbitP s e u d o t u m o r a n d LymphomaRhabdomyosarcomaSchwannoma(Neurilemmoma)Neurofibroma
The commonly found cystic lesions in the orbit are dermoid cyst, epidermoid cyst,
dermolipoma,epithelial inclusion cyst, hematic cyst, microphthalmos
with cyst,congenital cystic eye, teratoma, lacrimal ductal cyst
and mucocele.
Extraocular muscle examination:The extraocular muscles may be thickened
due to Grave's disease, idiopathic orbital myositis, congestion, tumors (e.g. metastatic carcinoma), hematoma
Thirty degree testdeveloped by Ossoinig et al differentiates increased subarachnoid fluid from
thickening of optic nerve parenchyma or the perineural sheaths using A scan technique.
maximum thickness of the optic nerve is measured both anteriorly and posteriorly in primary gaze and with the patient fixating 30 or more towards theprobe.
The test is considered positive if the nerve pattern decreases by at least 10% at 30 gaze as compared to the primary gaze.
It is positive in patients with increased subarachnoid fluid.
Optic nerve lesionThe optic nerve is best displayed with the
probe placed on the globe temporally.
BIOMETRYMost commonly used function of A scan10 MHz solid probe with inbuilt fixation lightProbe aligned with optical axis
TWO TECHNIQUES-
a)Immersion technique
b)Contact technique-Probe hand held by examiner or attached to slit lamp/
applanation tonometreNo corneal indentationAligned along visual axis to optimise the five spikesLeading edge of each spike should be perpendicular to
baseline Gain changed according to density of cataract
CONTACT TECHNIQUE
Sitting position( more comfortable)
High variability due to corneal compression
Measured axial length is shorter by an average of 0.24mm
Supine or reclining
No variability
Closer to true value
IMMERSION TECHNIQUE
IN OCULAR PATHOLOGIES1)Congenital glaucoma- differentiates from
megalocorneaMonitors efficacy of treatmentImmersion method preferred 2)Myopia – Posterior staphyloma in high myopes- increased
axial lengthDifference with other eye of more than 1 mm/
comparision with previous records3)Nanopthalmos- globe less than 17mm with
thickening of retinochoroid and sclera4)Tumour height- distance between tumor height
and scleral height
Pathology viewed in 3DRegular B scan probe inserted in motorized
scanner- 200 pictures in 5 to 10 seconds
BENEFITS-Improved visualisationVolume measurementsProfile A scan analysis
THREE DIMENSIONAL USG
High frequency ultrasound imagingSelected anterior segment pathologiesGenerate images resolution upto depth of 4-
5mmFrequency used- 35 to 50 MhzResoltion of 60 microns
ULTRASOUND BIOMICROSCOPY
INSTRUMENTATION-3 main componentsTransducerSignal processorArticulated arm
Immersion technique is used
Cornea seen as multilayered structure with high reflective epithelium, bowman’s membrane and endothelium
Anterior chamber depth can be measured Measurement of angle is aided by definition of scleral spur
and corneoscleral junction Iris thickness can also be measured Ciliary body and processes, ciliary sulcus well distinguished Anterior lens surface and anterior zonules seen
Normal ocular structures
a)Corneal and scleral diseasesPrognosis and planning for keratoplastyDepth of involvement in scleritisb)Ocular surface tumorsDepth of tumor involvement in corneal and
conjunctival tumors
IN OCULAR DISEASES
c) Glaucoma Helped in understanding pathogenesis of PACGDeciding course of management in malignant
glaucomaPigment dispersion syndrome- diagnosisBleb details after filtering surgeries
d)Anterior segment cystic lesions and tumors-
Defines and characterises origin of cystsImages both surface of iris, so assesment
growth in follow upDefines extent of ciliary body tumors