Ultrasound of Eye and Orbit

ULTRASOUND OF EYE AND ORBIT

Dr Surya Nandan PrasadMDRD(Std.)2010-2013

• The cystic structure & superficial position make the eye ideal for ultrasound exam.

• It is the most convenient & practical method for assessing the status of posterior segment, when light conducting media are opaque & also it is the most useful investigation prior to vitrectomy.

• Being realtime it provides opportunity to perform dynamic scan & also gives better spatial resolution.

• Non-invasive, lacks ionising radiation and inexpensive.

A Scan• One dimensional scan• Based on variations in echo amplitude from

tissue interfaces.B Scan• 2 dimensional image.• Displays ocular structures on gray scale

NORMAL ANATOMY

NORMAL ANATOMY

Eye Ball• Occupies anterior orbit & separated from

orbital fat by a membranous sac called Fascia Bulbi or Tenon’s capsule.

• Measures 24mm anteroposteriorly.• Wall of the eyeball composed of three layers –

Sclera, Choroid & Retina.

Sclera & Cornea• Outermost tough fibrous wall which are almost

avascular.• Sclera is cup like expansion of dural sheath of optic

nerve, thicker posteriorly (1mm) than anteriorly (0.6mm) or at the equator (0.5mm).

• Optic nerve pierces sclera posteriorly 3mm to the nasal side of the posterior pole & slightly above the horizontal meridian.

• Near the equator four vortex veins exit the eyeball, one from each posterior quadrant.

• Cornea is continuous with sclera but its laminae of fibrous tissue are transparent.

Choroid-Cilliary body-Iris• Middle coat of wall, formed by vascular tissue.• An extension of archnoid & piamater of optic nerve.• Choroid- Thin erectile vascular tissue upto 1mm in

thickness & is of lower echogenecity than sclera & retina.

• From sclera it is separated by Suprachoroidal space- a thin connective tissue layer across which the ciliary arteries, veins & nerves pass.

• Anteriorly ends at Orra Serrata & posteriorly firmly attached to the exit foramina of vortex veins & the point of entrance of optic nerve.

• Bruch’s membrane separates the vascular layer choroid from the pigmented layer of retina, to which it is firmly adherent.

Retina• Expansion of neural substance of optic nerve.• Basically composed of two layers- Outer Pigmented

layer attached to choroid, & Inner Nervous layer the retina proper in contact with vitreous body.

• Thickness- 0.4mm at the disc & 0.1mm at Orra Serrata.• Around optic disc & at the orra serrata, the retina is

more firmly adherent to the choroid than elsewhere.• Optic disc diameter- 1.5mm, situated about 3mm to the

nasal side & slightly above the level of posterior pole.• Macula- 4mm lateral to optic disc centre 1mm inferior.

Refracting Media• Aqueous humor-Lens-Vitreous body• Aqueous humor is dilute saline solution

secreted in posterior chamber from vessels of iris & ciliary processes.

• Lens- Transparent biconvex body enclosed in transparent elastic capsule-10mm in diameter, 3-4 mm in thickness. Posterior surface is more convex.

• The interior of normal lens is anechoic but echoes arise from central part of the posterior lens cortex as a fine curve.

Vitreous body• Transparent gel occupying posterior four-fifths

of the eyeball.• Composed of a collagenous matrix containing

mucopolysaccharides & water (98%) .• Adherent to ciliary processes behind the iris.• Also attached firmly to Pars plana, just in front

of orra serrata & optic disc margin. Elsewhere it lies free in contact with the retina.

EXAMINATION TECHNIQUE

B-Scan• Probe- 10-12Mhz high frequency, short focus.• Position- Patient lying supine- Vitreous

suspended from its base.• Both Static & Dynamic scans are performed in

primary as well as in all other directions of gaze.

• Scanning is done in both longitudinal and transverse planes.

Dynamic scan• During scan the patient is asked to move their

eyeball alternately in right & left directions & at the same time movement of ocular content observed.

• Structures of coats of eye (sclera, choroid & retina) resist deformation during these movements but vitreous being an elastic body which lies in free contact with retina over most of its areas deforms with each eye movement.

• Vitreous moves as a complete body & aftermovements observed for approximately a second but detached retina undulates as a membrane unless fixed by fibrosis.

• Thus dynamic scan helps to differentiate vitreous pathology from retinal detachment.

• Also choroidal tumors differentiated from vitreous, retrohyaloid & subretinal hemorrhage. Choroidal tumors appear solid & attached to ocular wall, whereas vitreous, retrohyaloid or subretinal hemorrhages may swirl & sediment during eye movements.

Dopler study• Dopler study of ocular vessels help in

differentiating intraocular tumors from mimicking benign lesions.

• Intraocular tumors such as Melanoma, Metastases & Retinoblastoma, vessels show pulsating channels or lakes of colour.

• May also help in diagnosis of central retinal artery/vein occlusion by measuring flow velocities at optic nerve head.

INDICATIONS OF B-SCAN• Opacity of light conducting media, making

direct vision by opthalmoscopy difficult.• Suspected intraocular tumors.• Differentiation of serous & solid (caused by

tumor) retinal detachment.• Examination of the vitreous.• Localisation of foreign bodies.• Dopler investigation of orbital vascular disease

& tumor proptosis.

Also before vitreoretinal surgeries to know :• The state of the vitreous• Position & extent of any intraocular lesion

visible by ultrasound• The condition of retina & particularly the

macula• Mobility of content of globe• The relation between vitreous & retina &

presence of any vitreoretinal adhesions

PATHOLOGYLens• Cataract-Lens outline is well seen in subcapsularcataract.

• Ectopia lentisB/l lens subluxation in upward direction-

Marfan’s syndrome- also a cause of RD due to retinal degeneration.

Homocystinuria- downward displacement.

Retinal pathologies

Retinal Detachment• Rhegmatogenous- from degeneration or

trauma resulting in entry of fluid in subretinal space.

• Non-Rhegmatogenous- due to vitreoretinal traction from contracting membranes or subretinal exudate.

• Usg finding- detachments do not extend beyond firm anchoring points at orra serrata anteriorly & optic nerve head posteriorly- Funnel shaped in total RD.

• On dynamic scanning Recent rhegmatogenous detachment shows undulating, sinuous or whiplash motion of retinal membranes, whereas Old RDs become progressively immobile due to preretinal fibrosis. Retina then contracts to form a taut membrane streched between optic disc & periphery.

Aquired Retinoschisis• Seen in hypermetropes.• Sensory retina splits into 2 layers.• Inferotemporal periphery of both fundi

affected initially.• On scanning focal dome shaped membrane

which is thinner than a retinal or choroidal detachment.

Disciform lesions• Focal collection of subretinal exudate &

fibrosis a/w senile macular degn. (SMD)• Usually b/l but the severity & progression are

often asymmetric.• Usg- dome shaped, subretinal in location &

heterogeneous appearance. Serial scanning shows decrease in size which differentiate it from choroidal tumor.

Drusen (Hyaline bodies)• Congenital- hyaline calcific deposits within the

substance of optic nerve head. In children- lie below the surface of optic disc-

D/d Papilloedema. 2nd decade- visible on surface of optic disc as

bright, pearl like nodules.• Usually remain asymptomatic throughout life

but occasionally cause visual impairment due to hemorrhage or neovascularisation.

• Usg- collection of calcific material in the optic nerve head. May cast dense acaustic shadow.

• A/w AMD- small globular collection of hyaline material between basal lamina of retinal pigment epithelium & inner collagenous layer of Bruch’s membrane.

• Rare before 45 yrs of age.• Increase in size & number with advancing age

& also present with secondary calcifications.• Mostly asymptomatic.

CHOROIDAL DETACHMENT

• Usually in the periphery & may be Locallised or Total.

• Dome shaped convex elevation with fluid in suprachoroidal space.

• There may be 2 or more domes, limited posteriorly by exit foramina of vortex veins & may meet in the vitreous cavity to form ‘Kissing Choroidals’.

Kissing Choroids

CD with RD

VITREOUS

Persistent Hyperplastic Primary Vitreous (PHPV) • U/l developmental disorder of vitreous & a cause

of leucocoria.• Persistence of primary vitreous.2 Types-• Anterior- more common. There is presence of a

retrolental membrane & lens is thinner than normal.

• Posterior- less common. A dense membrane containing the hyaloid artrey extends from retrolental region to the optic disc. It may cause tractional RD.

PHPV

PHPV

PHPV & RD

Vitreous haemorrhage • May be Intravitreal, Subvitreal (Retrohyaloid)

or both.Causes:• Tearing from vitreoretinal traction• Diabetic retinopathy• Vasculitis• Retinal vein thrombosis• Subarchnoid hemorrhage(Terson’s syndrome)• Blunt trauma

• Usg- Intravitreal hemorrhage appears as multiple fine echodensities dusting the vitreous body, which do not extend beyond the posterior vitreous border. They show marked movement on dynamic scanning.

Subvitreal hemorrhage is situated typically at the posterior pole between anterior surface of retina & posterior vitreous face. They may sediment to form a fluid level behind the collapsing gel.

VH

VH & Melanoma

Asteroid hyalosis• Senile degenerative disorder of unknown origin,

occurring in otherwise healthy eyes.• Uniocular in 75% cases.• They are calcium crystals embeded in an

amorphous matrix (calcium soaps).• Not reduce visual acuity.• Usg- multiple densely packed, suspended

homogenously distributed echodense dots of medium to high reflectivity, usually locallised to the core of vitreous body.

One may find clear retrovitreal space.

Asteroid Hyalosis

Synchysis scintillans • Degenerative condition & does not reduce

visual acuity.• Frequently b/l, occurring after long standing

uveitis or following VH.• Vitreous is liquified & contains cholesterol

crystals, which sink under the action of gravity.• When still, cholesterol crystals sediment

leaving an echofree vitreous & on dynamic scanning the crystals stir up.

Posterior Vitreous Detachment (PVD) Complete : old age- alteration in micromlecular

structure of vitreous- gel liquifaction (synchysis senilis)- liquified fluid enters subvitreal space- detachment of vitreous upto vitreous base.

Also this lead to decreased vitreal volume & increased mobility of gel suspended from vitreous base & surrounded by synchitic fluid.

• Most cases- uncomplicated cataractous eyes.

• However when vitreous traction causes retinal tear or avulsion of a peripheral blood vessel- intragel or subvitreal hemorrhage results, which causes marked mobility & elasticity of detached vitreous. On dynamic scan the gel assume mirror image configurations, when the eye is deviated to one side & then the other.

PVD Mirror imaging

Incomplete:• Normally vitreous attached loosely to sensory

retina.• In abnormal eye strong vitreoretinal adhesion

may occur at posterior border of retinal lattice degeneration, congenital cystic retinal tufts, retinal pigment clumps, vitreous base anomalies or at the impaction site of foreign body.

• Also association seen with diabetic proliferative vitreoretinopathy & retinal vein occlusion.

VR adhesion & Intravit. Hem.

INTRAOCULAR TUMORS

Choroidal Metstases:• Commoner than primaries• Frequently b/l• Usually located posteriorly in the fundus

appearing as diffuse lesion with mild to moderate elevation.

• Usual primaries- Breast in females, Bronchus in males. Others- testis, kidney, GIT.

• Usg- diffuse choroidal thickening with high or medium amplitude echoes.

Ch. Mets

Choroidal Melanoma:• Malignant melanoma of choroid is the

commonest primary intraocular tumor in adults.• Peak age: 50-60 yrs.• Rare below 30 & after 80 yrs.• Rare in black population.• Usg- typically a lenticular shaped mass deeply

embeded in & arising from the choroid. Usually moderately reflective. Some have a

Collar button or Mushroom shaped appearance, caused by waisting as they break through Bruch’s membrane. If memb is intact, the tumor is Lenticular or Dome shaped.

Melanoma bursting through Bruch’s memb

• Colour Dopler may be used to demonstrate flow within the tumor, which shows pulsating channels or lakes of colour, though tumors less than 3mm size may not show vascularity.

• Dynamic scan helps in differentiating melanoma from subretinal hemorrhage & VH.

Tumor fixed to the wall of the eye, whereas VH or subretinal hemorrhage show some movement & sedimentation.

• Usg aids in m/m as it reveals the location of tomor in relation to macula & optic disc, size of the tumor, extension to extraocular substance, elevation & base diameter.

Melanoma with extraocular extension

Osseous choristoma (choroidal osteoma)• Rare benign tumors• Young women, rarely b/l• Mostly focal, u/l, slightly elevated lesions with

well defined borders situated in peripapillary region.

• Usg- dense highly reflective lesion due to bone formation with marked acaustic shadowing.

OC

Retinoblastoma • Commonest primary malignant intraocular tumor

of childhood.• Incidence 1 in 20,000 live births, Both sexes

affected equally. B/l in 1/3rd cases.• Most present before 3 yrs of age & average age at

diagnosis is 18 months.• 94% sporadic, 6% inherited as AD with incomplete

penetrance.• Usg- heteroechoic mass locallised to one area of

globe. Dome shaped or irregular outline. Calcium deposits commonly present.

• D/d- Coat’s dis, ROP, Toxocariasis & PHPV.

RB

Trauma

• Can lead to a combination of usg findings, which include VH, lens dislocation, retinal tearing (dialysis), subretinal & subhyaloid hemorrhage & even rupture of globe or avulsion of extraocular muscles.

• Usg- distortion of normal shape with loss of ocular volume, intravitreal hemorrhage & intraocular air may be seen particularly if there is communication with ethmoid sinus.

Lens disloction

Foreign bodies• Dense material like metal, glass, stone are

highly reflective & can be readily identified by usg.

• Following penetration by a foreign body, a track of hemorrhage may be seen crossing the vitreous, outlining the trajectory of the object & indicating position.

• The entry or exit sites of foreign body may cause vitreous incarceration & some injuries allow entry of air into the globe.

FB

Orbit • Though orbit better delineated in CT & MRI studies,

usg can give some insight into the orbital pathologies.

Thyroid opthalmopathy • Grave’s disease- commonest cause of extraocular

muscle enlargement.• Typically b/l.• Mid & post. Portion of muscle belly is enlarged, but

tendon remains normal.• Involved muscles have medium to high reflectivity

due to separation of muscle fibers by inflammatory cells & edema.

• All the extraocular muscles may be enlarged, but severity of involvement is assesed by usg measurement of medial rectus width, that should not be more than 4mm, when scanned in real time.

• Sometimes inferior rectus muscle is selectively enlarged.

• Also increased orbital fat & edema may be noticed.

Inflammatory orbital disease (Pseudotumor)

• A group of relatively rare, idiopathic, non neoplastic orbital lesions & includes myositis, dacroadenitis, periscleritis, perineuritis & the diffuse condition.

• Majority patients are middle aged.• Onset is usually acute & u/l, mimicking the

presence of an orbital tumor, hence called pseudotumor.

• Usually respond well to antibiotics.

Locallised form• Discrete inflammatory mass• Usg- mass is low reflective, hypoechoic,

smooth or more commonly irregular in outline.

• Myositis- enlargement extraocular muscle including origin & insertion, differing from selective muscle belly enlargement of thyroid opthalmopathy.

Diffuse form• Orbital fat involved causing a mottled

appearance on scanning.

Oedema in the retrobulbar fascia (Tenon’s capsule) tracks along the optic nerve sheath to form the ‘T-sign”

Orbital Tumors Lymphoma • Usually Non-Hodgkin’s type• Usg- an elongated low reflective oval mass

typically affecting patients above the age of 60 yrs.

• May occur in any part of orbit, sometimes b/l, & occasionally exclusively involve the lacrymal gland.

• Histopathological study needed to differentiate from inflammatory conditions.

Lymphoma cupping globe

Rhabdomyosarcoma • Commonest primary malignant tumor of

childhood.• Usually present around 7 yrs of age with

rapidly progressing proptosis• Arises from extraocular muscle, mostly in

superonasal quadrant.• Usg- hypoechoic mass arising from extraocular

muscle. D/d- Metastatic neuroblastoma.

Orbital rhabdomyosarcoma

Rhabdomyosarcoma & RD

Metastases • Children- orbital mets occur in 40% children

with neuroblastoma- causes rapid onset proptosis & may be b/l.

Other primaries- Ewing sarcoma of bone, Wilm’s tumor, Leukemia.

• Adults- primaries from Bronchus, Breast, Prostate, Kidney & GIT.

• Usg- heteroechoic deposits.

Optic nerve tumors

• Neurilemmoma- ronded masses showing low to medium amplitude echoes and occasionally cystic areas

• Glioma- benign congenital hamartoma, presents between 4-8 yrs of age.

More than 50% patients have neurofibromatosis.

Usg- Fusiform or irregular expansion of optic nerve.

• Meningioma- arises from archnoid villi & presents with u/l slowly developing impairment of vision due to optic nerve compression, as the tumor within the dural sheath.

When tumor enlarges- rupture through the dura- forms intraconal mass- proptosis.

Usg- dffuse or focal broadening of optic nerve with high reflectivity.

Orbital Meningioma

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