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